Skip to main content

Microstructure and mechanical properties of melt-grown alumina-mullite/glass composites fabricated by directed laser deposition


Melt-grown alumina-based composites are receiving increasing attention due to their potential for aerospace applications; however, the rapid preparation of high-performance components remains a challenge. Herein, a novel route for 3D printing dense (< 99.4%) high-performance melt-grown alumina-mullite/glass composites using directed laser deposition (DLD) is proposed. Key issues on the composites, including phase composition, microstructure formation/evolution, densification, and mechanical properties, are systematically investigated. The toughening and strengthening mechanisms are analyzed using classical fracture mechanics, Griffith strength theory, and solid/glass interface infiltration theory. It is demonstrated that the composites are composed of corundum, mullite, and glass, or corundum and glass. With the increase of alumina content in the initial powder, corundum grains gradually evolve from near-equiaxed dendrite to columnar dendrite and cellular structures due to the weakening of constitutional undercooling and small nucleation undercooling. The microhardness and fracture toughness are the highest at 92.5 mol% alumina, with 18.39±0.38 GPa and 3.07±0.13 MPa·m1/2, respectively. The maximum strength is 310.1±36.5 MPa at 95 mol% alumina. Strength enhancement is attributed to the improved densification due to the trace silica doping and the relief of residual stresses. The method unravels the potential of preparing dense high-performance melt-grown alumina-based composites by the DLD technology.


  1. [1]

    Armani CJ, Ruggles-Wrenn MB, Hay RS, et al. Creep and microstructure of Nextel™ 720 fiber at elevated temperature in air and in steam. Acta Mater 2013, 61: 6114–6124.

    CAS  Google Scholar 

  2. [2]

    Chen Z, Sun XH, Shang YP, et al. Dense ceramics with complex shape fabricated by 3D printing: A review. J Adv Ceram 2021, 10: 195–218.

    CAS  Google Scholar 

  3. [3]

    Van Roode M, Bhattacharya AK. Durability of oxide/oxide ceramic matrix composites in gas turbine combustors. J Eng Gas Turbines Power 2013, 135: 051301.

    Google Scholar 

  4. [4]

    Vasechko V, Flucht F, Rahner N. Mechanical investigation of weak regions in a wound oxide-oxide ceramic matrix composite. J Eur Ceram Soc 2018, 38: 5192–5199.

    CAS  Google Scholar 

  5. [5]

    Wang X, Zhang W, Xian QG, et al. Preparation and microstructure of large-sized directionally solidified Al2O3/Y3Al5O12 eutectics with the seeding technique. J Eur Ceram Soc 2018, 38: 5625–5631.

    CAS  Google Scholar 

  6. [6]

    Su HJ, Ren Q, Zhang J, et al. Microstructures and mechanical properties of directionally solidified Al2O3/GdAlO3 eutectic ceramic by laser floating zone melting with high temperature gradient. J Eur Ceram Soc 2017, 37: 1617–1626.

    CAS  Google Scholar 

  7. [7]

    Mesa MC, Serrano-Zabaleta S, Oliete PB, et al. Microstructural stability and orientation relationships of directionally solidified Al2O3-Er3Al5O12-ZrO2 eutectic ceramics up to 1600 °C. J Eur Ceram Soc 2014, 34: 2071–2080.

    CAS  Google Scholar 

  8. [8]

    Krishnarao RV, Bhanuprasad VV, Madhusudhan Reddy G. ZrB2-SiC based composites for thermal protection by reaction sintering of ZrO2+B4C+Si. J Adv Ceram 2017, 6: 320–329.

    CAS  Google Scholar 

  9. [9]

    Liu GW, Zhang XZ, Yang J, et al. Recent advances in joining of SiC-based materials (monolithic SiC and SiCf/SiC composites): Joining processes, joint strength, and interfacial behavior. J Adv Ceram 2019, 8: 19–38.

    CAS  Google Scholar 

  10. [10]

    Zhang FC, Luo HH, Roberts SG. Mechanical properties and microstructure of Al2O3/mullite composite. J Mater Sci 2007, 42: 6798–6802.

    CAS  Google Scholar 

  11. [11]

    Burgos-Montes O, Moreno R, Baudín C. Effect of mullite additions on the fracture mode of alumina. J Eur Ceram Soc 2010, 30: 857–863.

    CAS  Google Scholar 

  12. [12]

    Aksel C. The effect of mullite on the mechanical properties and thermal shock behaviour of alumina-mullite refractory materials. Ceram Int 2003, 29: 183–188.

    CAS  Google Scholar 

  13. [13]

    Medvedovski E. Alumina-mullite ceramics for structural applications. Ceram Int 2006, 32: 369–375.

    CAS  Google Scholar 

  14. [14]

    Sadik C, El Amrani IE, Albizane A. Recent advances in silica-alumina refractory: A review. J Asian Ceram Soc 2014, 2: 83–96.

    Google Scholar 

  15. [15]

    Peretz I, Bradt RC. Linear thermal expansion coefficients of mullite-matrix aluminosilicate refractory bodies. J Am Ceram Soc 1983, 66: 823–829.

    CAS  Google Scholar 

  16. [16]

    Fan SH, Zheng H, Gao QC, et al. Preparation of Al2O3-mullite thermal insulation materials with AlF3 and SiC as aids by microwave sintering. Int J Appl Ceram Technol 2020, 17: 2250–2258.

    CAS  Google Scholar 

  17. [17]

    Nečina V, Pabst W. Influence of the heating rate on grain size of alumina ceramics prepared via spark plasma sintering (SPS). J Eur Ceram Soc 2020, 40: 3656–3662.

    Google Scholar 

  18. [18]

    Heinrich JG, Gahler A, Günster J, et al. Microstructural evolution during direct laser sintering in the Al2O3-SiO2 system. J Mater Sci 2007, 42: 5307–5311.

    CAS  Google Scholar 

  19. [19]

    Zhang X, Wang F, Wu ZP, et al. Direct selective laser sintering of hexagonal Barium titanate ceramics. J Am Ceram Soc 2021, 104: 1271–1280.

    CAS  Google Scholar 

  20. [20]

    Gahler A, Heinrich JG, Günster J. Direct laser sintering of Al2O3-SiO2 dental ceramic components by layer-wise slurry deposition. J Am Ceram Soc 2006, 89: 3076–3080.

    CAS  Google Scholar 

  21. [21]

    Mazerolles L, Perriere L, Lartigue-Korinek S, et al. Microstructures, crystallography of interfaces, and creep behavior of melt-growth composites. J Eur Ceram Soc 2008, 28: 2301–2308.

    CAS  Google Scholar 

  22. [22]

    Wang X, Zhang N, Zhong YJ, et al. Microstructure evolution and crystallography of directionally solidified Al2O3/Y3Al5O12 eutectic ceramics prepared by the modified Bridgman method. J Mater Sci Technol 2019, 35: 1982–1988.

    Google Scholar 

  23. [23]

    Lee JH, Yoshikawa A, Kaiden H, et al. Microstructure of Y2O3 doped Al2O3/ZrO2 eutectic fibers grown by the micro-pulling-down method. J Cryst Growth 2001, 231: 179–185.

    CAS  Google Scholar 

  24. [24]

    Hu YB, Wang H, Cong WL, et al. Directed energy deposition of zirconia-toughened alumina ceramic: Novel microstructure formation and mechanical performance. J Manuf Sci Eng 2020, 142: 1–10

    Google Scholar 

  25. [25]

    Wei C, Zhang ZZ, Cheng DX, et al. An overview of laser-based multiple metallic material additive manufacturing: From macro- to micro-scales. Int J Extrem Manuf 2020, 3: 012003.

    Google Scholar 

  26. [26]

    Fan ZQ, Zhao YT, Tan QY, et al. Nanostructured Al2O3-YAG-ZrO2 ternary eutectic components prepared by laser engineered net shaping. Acta Mater 2019, 170: 24–37.

    CAS  Google Scholar 

  27. [27]

    Lakhdar Y, Tuck C, Binner J, et al. Additive manufacturing of advanced ceramic materials. Prog Mater Sci 2021, 116: 100736.

    CAS  Google Scholar 

  28. [28]

    Mishra GK, Paul CP, Rai AK, et al. Experimental investigation on Laser Directed Energy Deposition based additive manufacturing of Al2O3 bulk structures. Ceram Int 2021, 47: 5708–5720.

    CAS  Google Scholar 

  29. [29]

    Pappas JM, Dong X. Direct 3D printing of silica doped transparent magnesium aluminate spinel ceramics. Materials 2020, 13: 4810.

    CAS  Google Scholar 

  30. [30]

    Balla VK, Bose S, Bandyopadhyay A. Processing of bulk alumina ceramics using laser engineered net shaping. Int J Appl Ceram Technol 2008, 5: 234–242.

    CAS  Google Scholar 

  31. [31]

    Niu FY, Wu DJ, Ma GY, et al. Nanosized microstructure of Al2O3-ZrO2(Y2O3) eutectics fabricated by laser engineered net shaping. Scripta Mater 2015, 95: 39–11.

    CAS  Google Scholar 

  32. [32]

    Yan S, Huang YF, Zhao DK, et al. 3D printing of nano-scale Al2O3-ZrO2 eutectic ceramic: Principle analysis and process optimization of pores. Addit Manuf 2019, 28: 120–126.

    CAS  Google Scholar 

  33. [33]

    Hu YB, Ning FD, Cong WL, et al. Ultrasonic vibration-assisted laser engineering net shaping of ZrO2-Al2O3 bulk parts: Effects on crack suppression, microstructure, and mechanical properties. Ceram Int 2018, 44: 2752–2760.

    CAS  Google Scholar 

  34. [34]

    Wu DJ, San JD, Niu FY, et al. Directed laser deposition of Al2O3-ZrO2 melt-grown composite ceramics with multiple composition ratios. J Mater Sci 2020, 55: 6794–6809.

    CAS  Google Scholar 

  35. [35]

    Li FZ, Zhang XW, Sui CY, et al. Microstructure and mechanical properties of Al2O3-ZrO2 ceramic deposited by laser direct material deposition. Ceram Int 2018, 44: 18960–18968.

    CAS  Google Scholar 

  36. [36]

    Pappas JM, Thakur AR, Dong XY. Effects of zirconia doping on additively manufactured alumina ceramics by laser direct deposition. Mater Des 2020, 192: 108711.

    CAS  Google Scholar 

  37. [37]

    Wu DJ, Zhao DK, Niu FY, et al. In situ synthesis of melt-grown mullite ceramics using directed laser deposition. J Mater Sci 2020, 55: 12761–12775.

    CAS  Google Scholar 

  38. [38]

    ASTM International. ASTM E112-13, Standard test methods for determining average grain size. ASTM International, West Conshohocken, USA, 2013.

    Google Scholar 

  39. [39]

    Dittmer M, Ritzberger C, Schweiger M, et al. Phase and microstructure formation and their influence on the strength of two types of glass-ceramics. J Non-Cryst Solids 2014, 384: 55–60.

    CAS  Google Scholar 

  40. [40]

    Sanei SHR, Fertig RSIII. Uncorrelated volume element for stochastic modeling of microstructures based on local fiber volume fraction variation. Compos Sci Technol 2015, 117: 191–198.

    CAS  Google Scholar 

  41. [41]

    Waterbury MC, Drzal LT. Determination of fiber volume fractions by optical numeric volume fraction analysis. J Reinf Plast Compos 1989, 8: 627–636.

    Google Scholar 

  42. [42]

    ISO Standard 18754. Fine ceramics (advanced ceramics, advanced technical ceramics)—Determination of density and apparent porosity. International Organization for Standardization, Geneva, Switzerland, 2020.

    Google Scholar 

  43. [43]

    Tian S, Wang W-m, Zhang F, et al. Testing method of density and porosity of dense ceramic materials. J Physical Testing and Chemical Analysis (Part A: Physical Testing) 2011, 47: 476–479. (in Chinese)

    Google Scholar 

  44. [44]

    Botero CA, Jiménez-Piqué E, Baudín C, et al. Nanoindentation of Al2O3/Al2TiO5 composites: Small-scale mechanical properties of Al2TiO5 as reinforcement phase. J Eur Ceram Soc 2012, 32: 3723–3731.

    CAS  Google Scholar 

  45. [45]

    Kim HS. On the rule of mixtures for the hardness of particle reinforced composites. Mater Sci Eng: A 2000, 289: 30–33.

    Google Scholar 

  46. [46]

    Voigt W. Ueber Die Beziehung zwischen den beiden Elasticitätsconstanten isotroper Körper. Ann Der Physik 2006, 274: 573–587.

    Google Scholar 

  47. [47]

    Reuss A. Berechnung der Fließgrenze von Mischkristallen auf Grund der Plastizitätsbedingung für Einkristalle. Z Angew Math Mech 1929, 9: 49–58.

    CAS  Google Scholar 

  48. [48]

    Chawla KK. Fibrous Materials. Cambridge, UK: Cambridge University Press, 1998.

    Google Scholar 

  49. [49]

    Chawla KK, Coffin C, Xu ZR. Interface engineering in oxide fibre/oxide matrix composites. Int Mater Rev 2000, 45: 165–189.

    CAS  Google Scholar 

  50. [50]

    Schneider H, Fischer RX, Schreuer J. Mullite: Crystal structure and related properties. J Am Ceram Soc 2015, 98: 2948–2967.

    CAS  Google Scholar 

  51. [51]

    Niihara K. A fracture mechanics analysis of indentation-induced Palmqvist crack in ceramics. J Mater Sci Lett 1983, 2: 221–223.

    CAS  Google Scholar 

  52. [52]

    Kriven WM, Pask JA. Solid solution range and microstructures of melt-grown mullite. J Am Ceram Soc 1983, 66: 649–654.

    CAS  Google Scholar 

  53. [53]

    Wang JT. Process and mechanism of laser engineered net shaping thin-wallen Al2O3-YAG ceramic. M.D. Thesis. Dalian, China: Dalian University of Technology, 2015. (in Chinese)

    Google Scholar 

  54. [54]

    Haynes WM. CRC Handbook of Chemistry and Physics, 97th edn. Boca Raton, USA: CRC Press, 2016.

    Google Scholar 

  55. [55]

    Hornberger H, Marquis PM, Christiansen S, et al. Microstructure of a high strength alumina glass composite. J Mater Res 1996, 11: 855–858.

    CAS  Google Scholar 

  56. [56]

    De Paris A, Robin M, Fantozzi G. Welding of ceramics SiO2-Al2O3 by laser beam. J Phys IV France 1991, 1: C7–1275–C7–129.

    Google Scholar 

  57. [57]

    Shieh YN, Rawlings RD, West DRF. Laser processing of ceramics of the SiO2-Al2O3 system. J Mater Sci 1994, 29: 5285–5292.

    CAS  Google Scholar 

  58. [58]

    Li MJ, Nagashio K, Kuribayashi K. Microstructure formation and phase selection in the solidification of Al2O3-5 at% SiO2 melts by splat quenching. J Mater Res 2002, 17: 2026–2032.

    CAS  Google Scholar 

  59. [59]

    Lawrence J, Li L. Effect of laser induced rapid solidification structures on adhesion and bonding characteristics of alumina/silica based oxide to vitreous enamel. Mater Sci Technol 2000, 16: 220–226.

    CAS  Google Scholar 

  60. [60]

    Deng BH, Luo J, Harris JT, et al. Molecular dynamics simulations on fracture toughness of Al2O3-SiO2 glass-ceramics. Scripta Mater 2019, 162: 277–280.

    CAS  Google Scholar 

  61. [61]

    Klug FJ, Prochazka S, Doremus RH. Alumina-silica phase diagram in the mollite region. J Am Ceram Soc 1987, 70: 750–759.

    CAS  Google Scholar 

  62. [62]

    Fu ZH, Guo JJ, Liu L, et al. Directional Solidification and Processing of Advanced Materials. Beijing, China: Science Press, 1998. (in Chinese)

    Google Scholar 

  63. [63]

    Kurz W, Bezençon C, Gäumann M. Columnar to equiaxed transition in solidification processing. Sci Technol Adv Mater 2001, 2: 185–191.

    CAS  Google Scholar 

  64. [64]

    Choi JY, Lee HG. Wetting of solid Al2O3 with molten CaO-Al2O3-SiO2. ISIJ Int 2003, 43: 1348–1355.

    CAS  Google Scholar 

  65. [65]

    Tiller WA, Jackson KA, Rutter JW, et al. The redistribution of solute atoms during the solidification of metals. Acta Metall 1953, 1: 428–437.

    CAS  Google Scholar 

  66. [66]

    Viswabaskaran V, Gnanam FD, Balasubramanian M. Mullite from clay-reactive alumina for insulating substrate application. Appl Clay Sci 2004, 25: 29–35.

    CAS  Google Scholar 

  67. [67]

    Cascales A, Tabares N, Bartolomé JF, et al. Processing and mechanical properties of mullite and mullite-alumina composites reinforced with carbon nanofibers. J Eur Ceram Soc 2015, 35: 3613–3621.

    CAS  Google Scholar 

  68. [68]

    Niu FY. Cracking mechanism and suppressing methods for laser melting deposition of Al2O3 ceramic. Ph.D. Thesis. Dalian, China: Dalian University of Technology, 2017. (in Chinese)

    Google Scholar 

  69. [69]

    Meng B, Peng JH. Effects of in situ synthesized mullite whiskers on flexural strength and fracture toughness of corundum-mullite refractory materials. Ceram Int 2013, 39: 1525–1531.

    CAS  Google Scholar 

  70. [70]

    Maldhure AV, Tripathi HS, Ghosh A. Mechanical properties of mullite-corundum composites prepared from bauxite. Int J Appl Ceram Technol 2015, 12: 860–866.

    CAS  Google Scholar 

  71. [71]

    Xu XH, Li JW, Wu JF, et al. Preparation and thermal shock resistance of corundum-mullite composite ceramics from andalusite. Ceram Int 2017, 43: 1762–1767.

    CAS  Google Scholar 

  72. [72]

    Chen YQ, Liu GQ, Gu Q, et al. Preparation of corundum-mullite refractories with lightweight, high strength and high thermal shock resistance. Materialia 2019, 8: 100517.

    CAS  Google Scholar 

  73. [73]

    Anderson TL. Fracture Mechanics: Fundamentals and Applications, 3rd edn. Boca Raton (USA): Taylor & Francis Group, 2005.

    Google Scholar 

  74. [74]

    Serbena FC, Mathias I, Foerster CE, et al. Crystallization toughening of a model glass-ceramic. Acta Mater 2015, 86: 216–228.

    CAS  Google Scholar 

  75. [75]

    Faber KT, Evans AG. Crack deflection processes—I. Theory. Acta Metall 1983, 31: 565–576.

    Google Scholar 

  76. [76]

    Khan A, Chan HM, Harmer MP, et al. Toughening of an alumina-mullite composite by unbroken bridging elements. J Am Ceram Soc 2000, 83: 833–840.

    CAS  Google Scholar 

  77. [77]

    Bae SI, Baik S. Determination of critical concentrations of silica and/or calcia for abnormal grain growth in alumina. J Am Ceram Soc 1993, 76: 1065–1067.

    CAS  Google Scholar 

  78. [78]

    Rice RW. Grain size and porosity dependence of ceramic fracture energy and toughness at 22 °C. J Mater Sci 1996, 31: 1969–1983.

    CAS  Google Scholar 

  79. [79]

    Niu FY, Wu DJ, Lu F, et al. Microstructure and macro properties of Al2O3 ceramics prepared by laser engineered net shaping. Ceram Int 2018, 44: 14303–14310.

    CAS  Google Scholar 

  80. [80]

    Niu FY, Wu DJ, Huang YF, et al. Direct additive manufacturing of large-sized crack-free alumina/aluminum titanate composite ceramics by directed laser deposition. Rapid Prototyp J 2019, 25: 1370–1378.

    Google Scholar 

  81. [81]

    Fu Q, Saiz E, Rahaman MN, et al. Toward strong and tough glass and ceramic scaffolds for bone repair. Adv Funct Mater 2013, 23: 5461–5476.

    CAS  Google Scholar 

  82. [82]

    Knudsen FP. Dependence of mechanical strength of brittle polycrystalline specimens on porosity and grain size. J Am Ceram Soc 1959, 42: 376–387.

    CAS  Google Scholar 

  83. [83]

    Rice RW. Evaluating porosity parameters for porosity-property relations. J Am Ceram Soc 1993, 76: 1801–1808.

    CAS  Google Scholar 

  84. [84]

    Danzer R, Lube T, Supancic P, et al. Fracture of ceramics. Adv Eng Mater 2008, 10: 275–298.

    CAS  Google Scholar 

  85. [85]

    Schlacher J, Lube T, Harrer W, et al. Strength of additive manufactured alumina. J Eur Ceram Soc 2020, 40: 4737–4745.

    CAS  Google Scholar 

  86. [86]

    Ashizuka M, Ishida E, Matsushita T, et al. Elastic modulus, strength and fracture toughness of alumina ceramics containing pores. J Ceram Soc Japan 2002, 110: 554–559.

    CAS  Google Scholar 

  87. [87]

    Wachtman JB, Cannon WR, Matthewson MJ. Mechanical Properties of Ceramics. Hoboken, USA: John Wiley & Sons, Inc., 2009.

    Google Scholar 

  88. [88]

    Sglavo VM, Paternoster M, Bertoldi M. Tailored residual stresses in high reliability alumina-mullite ceramic laminates. J Am Ceram Soc 2005, 88: 2826–2832.

    CAS  Google Scholar 

  89. [89]

    Zhang FC, Luo HH, Wang TS, et al. Stress state and fracture behavior of alumina-mullite intragranular particulate composites. Compos Sci Technol 2008, 68: 3245–3250.

    CAS  Google Scholar 

  90. [90]

    Selsing J. Internal stresses in ceramics. J Am Ceram Soc 1961, 44: 419.

    Google Scholar 

Download references


This work was supported by the National Natural Science Foundation of China (51805070 and 51790172), the Natural Science Foundation of Liaoning Province (2019-ZD-0010, 2020-BS-057), and the Basic Scientific Research Program for the Central Universities (DUT19RC (3) 060).

Author information



Corresponding author

Correspondence to Fangyong Niu.

Rights and permissions

Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made.

The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder.

To view a copy of this licence, visit

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Zhao, D., Wu, D., Shi, J. et al. Microstructure and mechanical properties of melt-grown alumina-mullite/glass composites fabricated by directed laser deposition. J Adv Ceram 11, 75–93 (2022).

Download citation

  • Received:

  • Revised:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:


  • laser
  • additive manufacturing
  • alumina
  • mullite
  • microstructure
  • mechanical properties