A State-of-the-Art Review on Recently Developed Sustainable and Green Cooling/Lubrication Technologies in Machining Metal Matrix Composites (MMCs)

Metal matrix composites (MMCs) are lightweight, hard materials applied in heavy-duty applications such as automobile, aerospace, and electronics, as well as sports equipment. MMCs reveal exceptional physical and mechanical properties, including high strength, corrosion, wear resistance, higher stiffness, and toughness. However, owing to poor surface finish, accelerated tool wear, and high material removal cost, MMCs are categorized as difficult-to-cut composites. This article reviews sustainable machining under different lubrication and cooling approaches and the economics of the operation for MMCs. The study focuses on optimizing machinability factors, such as surface integrity, chip formation, tool wear, and sustainability analysis. To attain this goal, the review evaluates suitable cutting parameters for Aluminum, Titanium, Magnesium, and Copper-based metal matrix composites, which hitherto have not been explored or summarized comprehensively. This study provides strong guidance regarding selection of precise cutting parameters for MMCs. The findings of this review suggest that different cooling/lubrication technologies can optimize and improve the sustainability and machinability characteristics, extend tool life and surface quality, during the cutting operation.


Introduction
With the continuous development and progress of technology in heavy industries and the continuous improvement of products, material, and cultural levels [1], modern manufacturing is moving towards miniaturization, flexibility, and lightweight equipment and products [2].Today, lightweight materials such as metal matrix composites (MMCs) have become the preferred composite material [3] because of their various mechanical and physical properties such as strengt-to-weight ratio, specific stiffness, high modulus of elasticity, excellent thermal conductivity [4], good corrosion resistance and high specific strength [5].MMCs are the combination of reinforcement Al 2 O 3 and Silicon and matrix components such as Al [6], Mg, Ti and Ni.However, Copper are the most enthusiastic components of MMCs [7]. Figure 1 presents the application and type of MMCs, mechanical properties, tool wear, and applications [8].
Due to an elevated cutting heat during machining of MMCs, severe tool wear occurs during cutting, and it becomes a bottleneck by restricting the development of cutting technology [9][10][11].There are various forms of friction in the cutting process such as tool-chip friction [12,13].Among them, the tool-workpiece friction mainly leads to diffusion and adhesion type of wear at the flank, which affects the surface quality, work hardening, stresses, and surface morphology [14,15].The tool-chip friction mainly causes the rake face to wear, so it is the main source of cutting heat and high cutting forces [16,17].Therefore, it is important to control the friction and heat generation at primary cutting zone while machining MMCs.These days, the research on the machining of MMCs is particularly important from the perspective of a sustainable cooling/lubrication approaches [18].Figure 2 shows the detailed systematic representation of various lubrication/cooling in the machining process [19].Application of different cooling/lubrication are studied by several authors, while focusing on environmentally-friendly strategies for MMCs [20,21].Therefore, this paper examines the economics of sustainable machining for MMCs under a variety of lubrication and cooling scenarios.Surface integrity, chip formation, tool wear, and sustainability analysis are some of the machinability issues that have been examined and optimized in this work.To this end, the review assesses cutting parameters that have not been previously investigated or summarised thoroughly for MMCs based on Aluminium, Titanium, Magnesium, and Copper.The details are provided in the following sections.

Purpose and Significance of the Research
This review article is consisting of the cooling/lubrication approaches to obtain the sustainable machining process which is focusing on common descriptions of conventional machining.In this review mostly turning, milling,  drilling, and grinding of MMCs are studied under different techniques such as dry cutting [22][23][24], minimum quantity lubrication (MQL) [25,26], flood cooling [27,28], cryogenic [29], high-pressure cooling and hybrid lubri-cooling etc. Considering the sustainable factors for improving the machining characteristics such as tool wear, surface quality, heat generation, cutting forces, and chip formation during machining are focused.Finally, the future scope and directions are suggested about the MMCs that could lead to optimum cutting conditions and improve machinability of MMC composites.The optimization in the machining process is achieved through smooth machining operation during the metal removal process, which is considered a good cutting process for obtaining sustainable machining goals [22,28,30,31].Figure 3 depicts the predetermined goal only by varying the cutting parameters, tool materials, geometry or changes in the cutting process.The machining of MMC exhibits challenges beyond that.Therefore, the different choices of lubrication/cooling methods need to be studied in the cutting process [32][33][34][35].The MMCs family is a typical aging-strengthened composite material, it has got worse characteristics under certain temperature conditions, cutting techniques, and lubricating/cooling machining conditions [23,36,37].At different approaches of physical properties at different ambient temperatures, it has a great influence through cooling and lubrication mechanism such as oil-water-gas flow in machining MMCs [38,39].Furthermore, this research focuses on understanding the behavior of the machinability characteristics under different lubrication methods in extreme environments (low temperature, room temperature, and high temperature) [25][26][27][28].
In addition, the researchers are in pursuit of optimizing solutions for extracting a higher amount of productivity at economic conditions and lower environmental degradations.Therefore, this work focuses on the several results from the researchers in the field of sustainable machining, manufacturing process, cooling/lubrication for energy savings and achieving the machinability of difficult machine metal matrix composite materials.Furthermore, this work is arranged in such a manner which classifies the work under a specified framework.Therefore, this work is useful for the identification of the obstacles to the development of technologies and identifies the upcoming challenges concerning energy consumption based on available literature.

Different Cooling/Lubrication Methods
Used in Machining of MMCs

Dry Cutting
In the machining process, the dry cutting condition is a kind of cutting condition that excludes the use of lubricants or coolants [40,41].There are several advantages of dry machining conditions including the reduction of environmental hazards, lower amount of machining costs, and improve operator health conditions ascending from the utilization of different lubricants and coolants [42,43].The dry machining condition in the industry can provide encouraging conditions such as the elimination of the hazards associated with cutting fluids for the production process and other associated costs of handling cutting fluids supply, use, and disposal, etc. as shown in Fig. 4.However, there are some disadvantages of dry cutting includes the higher cutting temperature due to friction generation compared to machining under cooling/lubrication.Furthermore, the dry-cutting process does not release toxic and health-hazard chemicals [44,45] as utilized in emulsion cooling.The dry condition hinders the machinability of the metals by increasing the tool wear, higher energy consumptions, forces, and poor surface quality.The dry-cutting conditions have a high cost for cutting tools, but in some cases, it provides relatively good results by decreasing thermal shocks, which helps in increasing tool life [46,47].The machining of MMC produces lower cutting forces and temperatures compared to the Al alloys due to ease in chip evacuation and increases the cutting tool life in highspeed machining [49].Barnes et al. [50] show the phenomena of the thin chips arising in the dry machining condition of MMC at high parameters, owning to higher thermal expansion and reduced heat capacity.The high-speed machining in dry-cutting conditions produce chip eruption practice during the machining operation, which is hazardous for the worker's health and environment.These kinds of issues can be resolved with the implementation of lubricantions/cooling conditions.The heat produced during the cutting process of such kinds of materials reduces the machinability characteristics [51].Usually, in the machining process of MMCs with hard cutting tools and inserts are used at moderate cutting parameters along with lubrication/cooling for improved machinability and efficiency of the machining process [25][26][27].To avoid such drawbacks and hindrance to the machining operation nowadays the interest of several researchers is increasing toward different approaches.The PVD or CVD coated tools with textured are employed in dry cutting [52,53].Dry machining is a better option at moderate parameters as well as application of environmentally friendly cooling/lubrication methods is also important to consider during machining [54][55][56][57]

Minimum Quantity Lubrication (MQL)
In the cutting processes, MQL technique has achieved excellent results, in perspective of advancing the machinability of metals, alloys and metal-based composites.Lubrication gained much attention and attracted by several researchers [58][59][60][61].The lubrication technique in the machining process will also go through different changes, and experienced various alterations, which include cold air cutting, and MQL methods [62].Lubrication in cutting process provides help in reduction of heating process and friction during tool-work contact friction and tool-chip contact [63].The extrusive existence of friction causes several hindrances and malfunction during the cutting process which includes tool wear, lower surface integrity and higher forces, and residual stress problems.The implementation of the lubrication/cooling method can provide help in the reduction of friction and heat generation and provide ease in the cutting process to perform smoothly material removal method, therefore improving the machinability characteristics of difficult-to-cut MMCs [64,65].Figure 5 represents the main motivation for using sustainable cooling and lubrication approaches for MMCs, using MQL.Therefore, MQL method possesses an ability to use a lower amount of cutting fluid which is economical and sustainable for environments as well as gives proper lubrication effect during the machining process.
While reviewing literature based on experimental investigations at MQL machining performance of composite materials to identify the cutting characteristic at high-speed machining experiments.It was found that the lubrication  effects provide better results in terms of machining MMCs.Furthermore, it is also revealed from the study that the cutting parameters along with MQL performance and suitability of operation [66].MQL effect on temperature and cutting force at high-speed machining provides relatively good results compared to dry machining by reducing temperature and cutting force significantly

Cryogenic Cooling
The machining process embedded with the cryogenic cooling method is used to provide excellent machinability of the materials; it is an environment-friendly and easy-to-use method.The cryogenic cooling technique is used to reduce the substantial amount of generated heat in machining operation and produce help in removing debris and chips during the material removal process [58,74,75].Cryogenic methods are consisting of various liquids including the carbon dioxide and nitrogen which possess lower temperatures near to − 200 °C [76].The main motivation for using sustainable cooling and lubrication approaches for MMCs is that cryogenic coolants engross the machining heat with their ability of lower temperatures and provide protection to the cutting tools.Cryogenic coolant is supplied through the nozzles or with the cutting tools and stored on the cylinders or tanks [19,77,78].In the recent work, Değirmenci et al.
[79] performed the machining operation on Aluminum based hybrid composites under cryogenic and MQL conditions.Figure 6 shows the cooling/lubrication strategies.The authors claim that the cutting temperature was decreased by 69.5%, flank wear was decreased by 18.5%, and surface roughness was decreased by 34.9% under the cryo-LN 2 environment compared to the dry medium.
The cryogenic LN 2 provided much decline in surface quality, heat generation, and tool flank wear relative to conventional cooling [80, 81].In addition, the applications of CO 2 -snow under machining of MMCs were investigated to understand and analyze the flank wear.Furthermore, studies are compared at different lubri-cooling approaches during cutting process of MMCs for identifying the machinability, and energy consumption during operation.It's found from the results of the lubri-cooling approaches that are playing an excellent role in reducing cutting heat and improve the surface quality and reducing the significant amount of energy consumption [82,83].Liquid nitrogen a cryogenic technique is usually used for the improvement of the machining Al7075 composite and shows a significant reduction of force and temperature up to 20% and 29% respectively [84].While discussing the cryogenic cooling method for Mg-based materials such as AZ31B Mg show 56% of great improvement in surface quality, and expressively lowers the temperature compared to the dry cutting process [85,86].

High-Pressure cooling (HPC)
The high-pressure cooling (HPC) technique is used to reduce the cutting zone temperature and clean the workpiece by removing debris and chips during cutting.The tool chip contact generates a higher amount of cutting temperature which is needed to be in a particular range for different cutting tools and materials to reduce the tool wear [87,88].HPC is a superior cooling technique to avoid extreme heat generation compared to the dry, and it helps in the chip removal process and built-up edge formation during materials removal process with the assistance of specially designed nozzles for showering of the powerful fluid jet [89].The pressures of liquids are showering at the pressure range of 5.5-35 MPa along with the speed up to 500 km/h [90].The advantage of the HPC is that it gives excellent assistance in the cutting operation enhancement; however, the higher consumption of the coolant can impact the economics of the machining operation and environmental degradations [91][92][93].Application of HPC machining process in machining titanium are found very usual with great performance in the machining process [94] but the Al and Mg-based composites are found in very limited studies.The Binder-less CBN cutting tool performance is found more favorable at the HPC machining process for titanium-based composites and alloys with higher tool life, excellent surface quality, and less force than dry or flood cooling methods.However, the cutting tools materials such CBN and ceramics show the extreme tool wear and damages mechanisms at HPC machining process [95,96].Muthuraman et al. [97] extensively demonstrated the machinability characteristics of the Al/SiC metal matrix composites at both techniques such as higher pressure coolant liquids and lower pressure coolant liquids at a pressure.It is depicted from the results that both coolants are favorable for improving tool life at the notable level and the built-up edge is seen decreasing significantly for PCD cutting tool insert during machining process of SiCp/Al metal matrix composites.Similar research work was performed by Barnes et al. [98] in their respective work shows that the high-pressure coolant implemented from double sides of the cutting tool for cutting aluminum/SiC MMC reduces the cutting forces significantly and increases tool life compared to dry conditions.Even though flood cooling is mostly considered a sufficient cooling for cutting aluminum/SiC MMC, however, the HPC method for the machining process is preferred in research [99].Bleicher et al. [100] concentrated on the internally and externally cooled cutting tool for the machining process of aluminum-based composite materials at different flow rates such as (240, 385, 540, 680 mL/min).

Conventional Flood Cooling
Along with the different lubrication/cooling cutting conditions, conventional flood cooling plays a unique role in the machining process of MMCs [101].Several manufacturing industries adopted the flood-cooling machining process to remove cutting heat, debris, and chips for acquiring a smooth machining process [102,103].The most important job of any cutting fluid is to improve the machining factors by dealing with frictional phenomena and reducing the heat generation and making ensure a smooth machining process by removing chips.Therefore, the fluids which utilize synthetic-based lubricants, and semi-synthetic, available minerals, for lubrication/cooling are most appropriate to handle the heat and thermal conductivity of the tool and workpiece during chip-tool contact [104].There are different kinds of conventional flood cooling methods one of the key methods is the oilin-water during machining with certain nozzles.Although the water is both economical in cost and environment friendly compared to the other lubrication/cooling conditions.The disadvantage to the water as cutting flood is due to its lower lubrication properties and corrosion problems for workpiece and machines, for avoiding such hurdles some additives are mixed with the water to make it more lubricant, such features includes the semi-synthetic and synthetic oils and fluids [96,105].Flood cooling assisted machining process is used to remove cutting zone heat partially, which is also enough for the machining process to have longer tool life, however, the chemical additives in the cutting fluids lead to health issues for the operator and environmental hazardous [106][107][108][109]. Cutting fluid also possesses the ability to reduce the buildup of edge formation and provide a smooth material removal process.Therefore at lower cutting parameters, there is less machining performance of cutting fluids, and at lower cutting parameters better to prefer the dry machining conditions [105].Cutting fluids are preferred in machining, due to their ability to reduce the build-up edge formation and provide a smooth material removal process.Therefore, at lower cutting parameters, there is less machining performance of cutting fluids, and at lower cutting parameters, better to prefer the dry machining conditions [110].The machining application of coolant on metal matrix composites shows improved tool life and surface roughness and the workpiece materials adhesion on the cutting tool was found minimum compared to other machining conditions such as dry cutting [111].

Hybrid Cooling/Lubrication Techniques
The hybrid cooling/lubrication technique is a kind of method where two or more cooling or lubrication approaches are mingled or synthesized in such a manner that accomplishes improved results for the machining process [112][113][114].This approach of mixing different lubricants and coolants together increases the machining efficiency to a greater extent compared to conventional cooling and lubrication techniques for enlarging the tool life and producing subsequent improvement in surface quality [115][116][117].Furthermore, Park et al. [118] investigated the hybrid cooling approach while mixing the MQL through exfoliated graphite nanoparticles and liquid nitrogen together for improving the characteristic of machinability of Ti alloy.Results of the machining experiments with the implementation of hybrid approach found optimization of machining characteristics including lower cutting forces and tool wear compared to the normal conventional cooling and lubrication approaches.The hybrid MQL-LN 2 was found more promising compared to individual cryogenic or MQL environment, however, outcomes of the study discovered that it could be an alternative to MQL rather than the conventional cooling methods [63,119].Hybrid cooling method is most efficient for improving machining performance, because hybrid nanofluids with a concentration of 0.3% reduced cutting power, friction coefficient and surface roughness [120].In latest work, Sivalingam et al., [121] analysed the environmental and machining performance of an aluminium hybrid composite (AA6082 + 3wt%SiC + 1wt%MoS 2 ) using dry, MQL, LCO 2 , and MQL + LCO 2 cooling methods.The author studied the wide range of social, economic, and environmental sustainability variables, including Total cycle time (TTCT), productivity, Total machining cost (CT), Energy consumption (Ec), Carbon emission analysis (Cee), Cutting force (CF), and Surface Roughness (Ra), as shown in Fig. 7.They prove that the maximum overall equipment effectiveness (OEE) was achieved with a hybrid (CO 2 + MQL) setup, while the lowest carbon emission (0.6 kg-CO 2 ) was achieved at a higher cutting speed of 120 m/min with a feed rate of 0.1 mm/rev and a depth of cut of 1 mm.

Tool Wear Phenomenon and Wear Mechanism
The machining of MMCs is always special; it is usually separated from the common and conventional kinds of metals and alloys [122,123].MMCs are fabricated with the reinforced hard particles SiC, Al 2 O 3 , etc., with a soft matrix such as Mg, Al, Ni, C, Ti, etc., to put emphasis on the natural progression of the material removal process and affect the productivity of manufacturing process [124].Tool damage, sudden breakage, extreme wear mechanism, a poor surface, and workpiece quality degradation are the usual phenomena [125] in machining MMCs.The high heat generation is the consequence of the extreme plastic deformation rate during the material removal process [126][127][128].Due to the uncertain structural integrity of MMCs exposed to the adaptability of different approaches and variables for smooth material removal process.Hence, the reinforcement distribution for MMCs part during the fabrication process shows a key role in the developed structure and characteristics of the composite material, according to the cutting parameters, choice of lubrication/cooling process needs to be considered [129,130].Several authors adopted the sustainable machining process for such hard to cut materials are performed in [131,132].Such an experimental example from the machining operation can be observed while performing the milling process on high-density composite materials.The dense reinforcement in the workpiece possesses the ability Fig. 7 Overall performance under different cooling conditions (Copyrights reserved) [121] to cause fracture and damage to the cutting tool and cracks at the surface during the material removal process [133].
The combination of soft matrix materials and abrasive hard additives in composite materials change the cutting process dynamics, therefore for balancing such hindrances there is a need to adopt different machining approaches, dry, MQL, cryogenic, flood, or high-pressure flood machining methods [134].Tool wear mechanisms in MMCs machining have four basic kinds of wear patterns [135,136], Fig. 8 shows the different wear mechanisms, types, and consequences of wear, which is including (a) adhesion mechanism, which formed due to the addition of the soft matrix or other materials at prominent temperatures, which can also prompt build-upedge generation on the cutting tools [137,138], (b) while cutting tool form the oxidation wear mechanism [139,140], (c) Cutting tool possesses abrasive wear due to the accumulation of SiC, Al 2 O 3 harsh particles, which directly affect the flank wear [141], (d) the mechanism of diffusion wear is emerging on the rake face and elevating the crater wear.These phenomena are observed during the milling process of hybrid composite materials [142][143][144].
While studying the performance of different tool materials such as PCD, CVD, and PCBN, it is found that PCD cutting tool materials are supreme for performing the cutting operation.Several studies exhibit that the PCD cutting tool is able to give longer tool life and excellent surface quality of MMC part, and are generally used for the finishing process.Furthermore, while studying the performance of the CVD thin film diamond, it is depicted from the literature that the CVD cutting tool is excellent in forming complex-shaped tools, but it has high machining cost and rapid shedding of the diamond film during processing limits its various industrial application.The CVD thick film diamond cutting tools have also presented a long tool life similar to the PCD cutting tools, however, the CVD cutting tools are very expensive to manufacture when compared to the manufacturing cost of the PCD cutting tools, furthermore, the employment of lubrication/cooling method during material removal method can prolong the tool life and reduce the energy consumptions [145,146].The manufacturing cost of PCBN tools is equivalent to that of PCD tools, while the machining performance of the PCBN cutting tool is poor comparing to the PCD cutting tools for MMCs.Study performed on the behavior of coated tools such as TiN and TiC for analyzing the machinability characteristics, it is found that these cutting tools have not been significantly improved compared with their base materials, and chipping and coating peeling conditions of these tools are serious [124,147].
The cutting tool wear mechanism and type of different cooling approaches were performed by Sap et al. [119] at different selected parameters such as feed rates from 0.2 mm/rev to 0.3 mm/rev and cutting speeds from 200 to 300 m/min at Dry, MQL and cryogenic.For measuring and understanding the tool life criteria, the flank wear is considered at a certain limit of wear to address the tool life.Furthermore, Fig. 9 represents the flank faces respectively, for understanding the wear behavior of composite materials in different cooling environments and machining performance by following sustainable goals.Furthermore, the authors found that flank wear is happening either from worn land Fig. 8 Different tool wear mechanisms, types and consequences of wear in machining of nickel-based super-alloys (Copyrights reserved) [142] which grows from the main cutting edge to downwards and other is the growth of worn land is steady all over at the cutting edge.Such results can be found below that at reducing cutting speed and feed rate doesn't affect the cooling conditions.The cutting performance of dry machining conditions at different feed rates shows lower performance compare to cryogenic and MQL.The wear of cutting tool increases at increasing cutting speeds even on extensive implementation of lubrication/cooling approaches.It is due to the fact that the extreme plastic deformation at dry cutting compared to the cutting process under lubri-cooling which gives excellent performance in tool life and lower wear mechanism, and excellent surface quality [119,138].According to the findings of Saikrupa [148] during turning of Al-MMC as rise in cutting speed using the different cooling and lubrication methods in machining process an excellent results are obtained because of the cooling and lubrication is additional operative compared to the pressurized mist oil.However, the pressured oil is putting more impasses comparing cryogenic for perpetrating the deformation zone on reduced cutting speeds with the assistance of air.In some ways, surpassing these values creates an easy environment for the cooling and lubrication machining approaches to penetrate the deformation zone.Furthermore, several studies from the literature have mentioned such findings that the lubri-cooling approaches are delivering excellent results at higher cutting speed under the cryogenic condition possesses an ability to defend the tool cutting edge effectively [149][150][151].

Surface Quality
In the machining process, the obtained trends of the surface quality are the most intuitive physical quantity to evaluate the performance of the cutting operations and related machining characteristics.The measurement of different machining characteristics is of great importance for evaluating and analyzing the surface integrity, and machining vibrations [152][153][154].Implementation of coolant and lubrication methods ensures the sustainable manufacturing process and reduce the energy consumption and increase the machining efficiency and improve the machinability characteristics [155][156][157][158]. Today, the metal cutting technology has become a mainstream technology in the manufacturing industry, which provides the required size, and shape.For further understanding, research on the surface integrity of components during the machining process was carried out by the researchers [159,160].It is depicted that the higher amount of cutting speed possesses ability to progressively softened the workpiece material and thereby improve the quality of the finished surface effectively.The increasing amount of feed rate can fluctuate the chattering phenomena which is causing higher surface roughness as found by [161].Furthermore, the mist cooling machining approaches also result in a higher amount of surface roughness when comparing the flood machining process during higher cutting speed.During the MQL machining process, it is extensively found that the heat generation reduces extensively at lower cutting speeds due to effective lubrication.However, Fig. 9 Tool wear under cryo, MQL and dry conditions while machining aluminium based composites (Copyrights reserved) [119] the higher cutting speeds possess lower lubrication due to the lower absorption of oil droplets during the cutting process in the cutting zone [162].The surface optical, 3D, and 2D topographies of milled Al-Gr hybrid composite samples under various cooling techniques are displayed in Fig. 10.Mountains9® was used to generate the topographic 3D models of the surfaces.Due to the creation of indentations and protrusions, the heights of the peaks and valleys in the 3D surface topography have a negative impact on the surface quality.Even though the surface quality of the MQL-milled sample is higher than that of dry machining, the cooling may not be adequate.Cryo-LN 2 milled samples resulted in smoother surfaces [79].An experimental examination of dry, lubrication, and cooling impact on machining process, hybrid composites was performed results show the dry cutting degraded the surface quality in higher amount while comparing to the MQL and cooling method as shown in Fig. 11 [119].
Furthermore, the implementation of the Hybrid cooling and lubrication method in machining applications possesses an excellent position that not only provides lubrication in the cutting region but also enables a cooling effect which results in a higher surface finish.The influence of different cooling and lubrication approaches along with hybrid approaches and their impact on temperature generation, and smaller ridges formation presented.

Heat Generation
During the cutting process, heat is generated due to tool particle integration, this phenomenon occurs during the plastic deformation [163].Heat generation is usual, it is dissolute with the workpiece, cutting tool, chips, and cutting fluids.Several researchers reported the summary of dissolved heat such as much of the heat passing by the chips, and some amount to the workpiece [18,138,164].This proportion of heat varies with the material removal rate, such as lower removal of material and smaller shear zone angles use to produce higher heat, however, the increasing material removal can produce lower heat [38,165].O'Sullivan and Cotterell employed the thermocouple to measure the cutting temperature for the Al-based6082-T6 composite.Results from the thermocouple embedded experiment show that the higher cutting speed impact by reducing the cutting temperature, due to the higher material removal of the cutting process.The higher removal possesses the ability to remove more materials in the form of chips which carry out a higher amount of generated heat [166].The key areas where heat generates at a higher amount during the orthogonal machining process are depicted in Fig. 12.
It represents the core zones where the rise of cutting temperature can be seen during the orthogonal machining.Heat produces in the machining while plastic deformation happened and workpiece materials remove in some amount by cutting the tool, it is due to the friction component during tool-work interfaces, represented in Fig. 13.[168].It is found from several studies that of the amount of heat transferred to the formed chips while a proportion is performed with the workpiece.These proportions are depending on the rate of materials removal but proportions were seen as smaller for higher rates of metal removal [169].
During the cutting process, heat is generated due to tool particle integration.This phenomenon occurs during plastic deformation.Heat generation is usual, it is dissolute with the workpiece, cutting tool, chips, and cutting fluids.Several researchers have reported the summary of dissolved heat during the cutting process such as much of the heat passes into the chips and some amount to the workpiece [170].This proportion of heat varies with the material removal rate, such as lower removal of material and smaller shear zone angles use to produce higher heat however, increasing material removal can produce lower heat [171].The different techniques used to describe the heat distribution and generation during machining processes such as FEM-based models are vital techniques to identify the cutting temperature distribution during the cutting operation.The FEM model developed by the Majumdar et al. shows that the heat generation phenomena at the tool-chip interface of composite Fig. 11 Surface quality images adopted on different cutting conditions including Dry, MQL, and cryogenic (Copyrights reserved) [119] Fig. 12 Heat generation phenomena in machining process (Copyrights reserved) [167] materials [172].Furthermore, while identifying the other temperature measuring devices such as the infrared pyrometer, thermocouple, the FEM modeling is an efficient methods for measuring the amount of temperature for machining of hardened steel and AISI H13 with PCBN cutting.The study depicted that the PCBN cutting tools with higher temperatures generation [173].The properties of the composite materials and cutting tool materials are playing a key role in heat generation in both primary and secondary cutting zones other factors which influence heat generation.The machinability is influenced by the choice of the coolant or lubrication such as the air and water used during the machining process as a coolant decreased [174,175].The most influencing factor for higher cutting temperature for the cutting tool is the amount of contact length, and it is used to define the temperature in the operation it was observed that the higher contact length [169].

Sustainability in Machining
Recently the concept of sustainability is extensively adopted by industries due to the increasing demands of customers to implement the new regulations of the manufacturing process to compete with the rising features of product demands in the modern world [176].A sustainable economy is guided and constrained by ecological, social, and economic principles.In other words, to achieve sustainable development, there must be economic progress, social justice, and preservation of the environment.Therefore, sustainability is made up of three pillars: economy, society, and the environment.These principles are also informally referred to as profit, people, and planet.Sustainable machining events are briefly discussed in this section.At the beginning of the sustainability concept, it is only associated with environmental concerns, now it has included several activities such as Triple Bottom Line (TBL) which impacts different perspectives of social dimensions, and economic and environmental points of view as shown in Fig. 14 [177].The amalgamations of all these concepts give birth to the new approach known as life cycle sustainability assessment (LCSA).The LCSA is an approach that is used to evaluate the environmental impact of manufactured components from different materials conditions to the final disposal [178].
These are the models which emphasize the whole manufacturing process including the design and product life cycle as well.Therefore, the whole attention is toward the analysis and improvements of the existing manufacturing process, because the traditional processing steps consume more energy and resource and emit carbon and health hazards and risks to the operators and environment [179].In the sustainable manufacturing process, the machinability of materials is a vital part to be considered during adopting the concept of TBL in manufacturing industries for understanding the social, economic, and environmental impact.There is extensive research work developing for the sustainability to control the machining cost, energy consumption, operator health, and carbon emission-related issues.The dry cutting conditions are frequently used as a sustainable process but it is not feasible for all kinds of materials to be machined at improved machining characteristics and cost [180].While machining light-weight Ti, Al, and Mg based MMCs under dry cutting conditions usually ascends with several issues such as cutting temperature, surface quality, and tool life problems.Figure 15 shows the concept of sustainable manufacturing [121].The overarching goal of sustainable manufacturing is to reduce negative effects on the environment during the production of goods and services; an EMS compliant with ISO 14001:2015 is recommended for this purpose.The input parameters, production procedures, and final products all play a role in how well a machining process works.To protect the environment and the health of workers, it is important to adhere to the rules set forth by the occupational health and safety management systems [OHSMS -ISO 45001:2018] on the use of metalworking fluids.
Thus Fig. 16 presents the ring of sustainable cutting technologies [181].While focusing on the energy consumption and efficiency of machining operations in sustainable Fig. 13 Modes of heat transfer from coated carbide insert (Copyrights reserved) [168] 1 3 machining process, it is found that the energy consumption of the manufacturing sector accounts for the highest energy consumers compared to the other sectors in the world, which is 33% of primary energy use and 38% of CO 2 gas [182,183].
The machining of different materials in the manufacturing-related sectors is the vital factor that consumes the Fig. 14 Sustainable manufacturing: strategies, targets and pillars (Copyrights reserved) [177] Fig. 15 Concept of sustainable manufacturing (Copyrights reserved) [121] majority of the energy for the material removal process to provide proper shape and size to the product.Machining of materials is found to be the major energy consumption source; therefore, machining is the major target for the reduction of energy-related activities and costs in recent years.Figure 17 presents the machining experimental setup for measuring machining responses and energy consumption during the machining process using nano-fluids [184].

Discussions
While performing the literature review for the machining process of particle-reinforced aluminum-based composite materials several authors have put focused on the selection of cutting tools materials, cutting parameters, and machining [185,186].Studies on the selection of tool materials and their wear mechanisms mainly focused on using dry machining at moderate parameters are the limitations of several research works performed [187,188].The advantages of performing the literature review of different other techniques such as implantation of lubrication/cooling approach for researching the selection of tool materials in the machining of particle-reinforced aluminum-based composite materials, analyzing and observing the life and wear of tools of different materials, surface quality, cutting force, chip formation show excellent results [103,189,190].Furthermore, this review found that tool materials such as PCD tools are ideal for processing particle-reinforced metal-based composites, with long tool life and high processing quality, and are generally used for finishing.CVD thin film diamond has advantages in manufacturing complex-shaped tools, but its high cost and rapid shedding of the diamond film during processing limit its application.CVD thick film diamond tools have similar life and cutting performance as PCD tools, but they are expensive to manufacture compared to the PCD tools, however, the employment of lubrication/cooling method can enlarge the tool life and reduce the energy consumption [145,146].The manufacturing cost of PCBN tools is equivalent to that of PCD tools, but the cutting performance is far less than that of PCD tools during the machining of particle-reinforced aluminum-based composite materials.The cutting performance of coated tools such as TiN and TiC has not been significantly improved compared with their Fig.16 Sustainable cutting technologies (Copyrights reserved) [181] Fig. 17 Power vs cycle time along with energy consumption profiles of a machine tool to produce a machining routine (Copyrights reserved) [184] base materials, and chipping and coating peeling are serious [124,147].Carbide tool wear is severe during cutting, but its manufacturing cost is relatively low, and it has certain applications in the rough machining of particle-reinforced metal matrix composites.Studies on machining of particlereinforced aluminum-based composite materials have found various mechanisms of tool wear; it is generally believed that the cutting tool has several types of wear such as abrasive wear, bond wear, and chemical wear during cutting.Among them, abrasive wear is the main form [31,124,147].The combination of soft matrix materials and abrasive hard additives in composite materials change the cutting process dynamics, therefore for balancing such hindrances there is a need to adopt different machining approaches, such as dry, MQL, [191] SQCL [192], Nano-fluid based MQL [193][194][195][196], Solid lubrication [197,198], Oil-on Water (OoW) based cooling method [102], Cryogenic Machining [58,76], MQL hybrid with Cryogenic lubri-cooling [63], for adopting sustainable concepts.Tool wear mechanisms in MMCs machining have four basic kinds of wear patterns [135,136], including (a) adhesion mechanism, which formed due to the addition of the soft matrix or other materials at prominent temperatures, which can also prompt build-up-edge generation on the cutting tools.Different studies proposed the friction characteristic equation with close contact as the main feature; it found that the adhesive wear is mainly in the small area near the tooltip.Besides the adhesive wear, the distance from the tooltip is obviously affected by the abrasive wear.Table 1 presents the advantages and disadvantages of each cooling/lubrication strategy on different machining factors such as heat generation, lubrication, lubrication coolant cost per unit production, the environmental effect of coolant application, operator health, tool life, surface quality, and (CO2 emission) environmental burden due to coolant production.

Conclusions and Future Scope
The present review demonstrates the machinability of metal matrix composite materials on different lubri-cooling approaches including MQL, cryogenic, flooding, and dry cutting conditions.The sustainability of the machining and energy consumption was studied and analyzed from the literature to obtain a smooth and cost-effective machining process.The machining process of Al, Mg, and Ti-based lightweight composite materials was considered in this study.From this extensive literature review is following concluding remarks are drawn: • The literature presented on the dry machining process is shown that it is preferred for some cases and avoided for materials so there are advantages and disadvantages of dry cutting conditions.For avoiding the environmental, operator health hazards, and other related costs of lubrications, the dry machining process is preferred, however, some materials produce a lot cutting temperature which increases tool wear, surface degradation and higher cutting force for that dry machining should be avoided because it doesn't help in improving machinability and eliminate related issues.• The machining process assisted with the cooling/lubrication approach has its own advantages and disadvantages, it is reported for the last several years that the application of the cooling/lubrication process for improvement of machinability of lightweight hard-to-cut composite materials, however, it is not found sustainable in perspective of environment and economics concerned but it shows better results in improving the machining characteristics such improve tool life, surface integrity and reduction cutting force compare to the dry cutting process.• In literature, it is extensively reported that it is better to use a cooling/lubrication approach for titanium and aluminum-based composites and alloys because due to Table 1 Advantages and disadvantages of each cooling/ lubrication [58,63,76,102,[191][192][193][194][195][196][197][198] The lower thermal conductivity and excellent mechanical properties of these materials produce a higher amount of heat during cutting operation.Additionally, during the material removal of aluminum alloys, the adhesion and built-up-edge the formation is very common in dry machining conditions due to such kind issues the lubrication/cooling conditions are preferred during the cutting process of Ti and Al-based composites and alloys.• The cryogenic machining approach is found as a favorable machining approach for obtaining the sustainable machining process for composite materials due to its application of lowering the cutting temperature and providing help in chip formation.However, the economic feasibility of the method is needed to be investigated.• The hybrid lubri-cooling method is getting more consideration by researchers these days dues to the perspective of sustainable machining process such as the implementation of nano-fluids, neat oil MQL advancement (RHVT, ionic-liquids, cryogenic) for cutting lightweight materials.The hybrid lubri-cooling method is still needed to be researched more because there is not much literature available on this method for the machining process of Al and Ti-based composite materials.• This review has provided a novel contribution to advance techniques and their sustainable contributions to the machining process of composite materials which were rarely reviewed before.It is well-meant here to mention the limitations and machinability characteristics of each cutting condition such as dry MQL, cryogenic, and floodbased approaches.It is vital to substitute the traditional combination of cooling methods which might be the poorest approach while focusing on the sustainability of the cutting process.• In the perspective of future recommendations and suggestions it is necessary for the sustainable machining process of MMCs is requiring more investigation, which needed to be performed for advanced cooling techniques to grab the attention of the global manufacturing sectors toward the net and clean manufacturing approach.In future research, the target should be not only the effectiveness of the different methods for machinability taken into consideration but also the economic sustainability, health hazards of the operator and overall environmental impact should be assessed.In precise, there is a lack of availability of studies investigating social sustainability, which needs to be focused on in the future.

Fig. 1
Fig. 1 Application and type of MMCs with physical and mechanical properties

Fig. 2
Fig. 2 Systematic representation of different lubrication/cooling techniques

Fig. 3
Fig. 3 Role of cooling and lubrication method for machinability and sustainability of MMCs

Fig. 5
Fig. 5 Minimum Quantity Lubrication (MQL) approaches for MMCs [67, 68].Kouam et al. [69] performed the high-speed machining experiments on microlubrication mechanisms for Al-based MMCs.The microlubrication mechanism projected a control mechanism for the residual stresses' generation on workpiece surface.The analysis of MQL cutting operation influencing the cemented carbide tool wear during drilling MMCs is thoroughly studied.The effect of overall machining performance through MQL conditions and temperature distribution under MQL conditions are forced and multi-objective optimization of MQL parameters was carried out through experimental research [70].MQL provides dramatic results for surface quality, tool life improvements compared to dry cutting conditions at moderate cutting parameters.It has ability to significantly reduce the built-up edge formation on the rake face and flush the sticky chips on the cutting tool and machined surface to enhance the surface quality and tool life [71].Li Jilin et al. [72] performed the cutting operation using the cold air MQL method.The influence of cutting parameters and cold air MQL was investigated through machinability experiments on Al-based composite materials.The influence of MQL condition on the residual stresses is of great importance during the machining of Aluminum composites.In a similar study, Liu et al. [73] accomplished a study to measure the effect of multi-medium mixed MQL on high-speed cutting process on Al-composite materials, which emphasizes the influence of the existence of oil and water on the cutting forces, surface quality, and cutting temperatures.The mechanism of micro-lubrication with water droplets attached to the oil film was proposed [73].