Abstract
The aluminum alloys belonging to the 7000 series are high-strength alloys used in a wide variety of products for weight reduction. They are primarily used in the field of transportation and aerospace. Among these, the A7075 alloy has the highest strength and is expected to be applicable in a wide range of fields, such as aircraft components and sports equipment. However, it has high deformation resistance and is prone to surface defects, which is called tearing. Tearing typically occurs at high temperatures and high ram speeds, and adversely affects productivity. The localized melting of Zn and additive compounds, due to the heat generated during the process, is considered to cause tearing. In this study, the effect of friction, heat, and tearing at the tool—metal interface was mitigated by improving the die surface quality. The reduced friction eliminated recrystallization by preventing the temperature from increasing to recrystallization temperature. In addition, an AlCrN coating was adopted instead of nitriding to improve the die surface quality. The tearing size and heat generated when using the AlCrN coating were found to be limited. Moreover, the grain size observed in the tearing region on the extruded surface was small. The simulations using the shear friction coefficient m observed from friction tests indicate that the use of the AlCrN coating improved the material flow. Thus, the AlCrN coating is considered effective for reducing friction at the interface and preventing the recrystallization of the extruded surface. From the aforementioned results, it can be inferred that a die coating can reduce the tearing sensitivity and increase the productivity of the A7075 alloy.
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Abbreviations
- h f :
-
Forward extrusion length (mm)
- h b :
-
Backward extrusion length (mm)
- m :
-
Shear friction coefficient
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We would like to thank https://www.editage.com/ for English language editing. We would like to thank Keishi OKAMOTO of Toyo Advanced Technologies Co. Ltd. for applying coating.
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Tatsuya FUNAZUKA. He is an assistant professor of the Department of Mechanical Engineering, University of Toyama, Japan. His research interests include working towards understanding the hot extrusion and forging of aluminum alloy, and tribology in metal forming and micro-manufacturing.
Kuniaki DOHDA. He is the Dr. of Eng. (Nagoya University, Japan) and a professor of the Department of Mechanical Engineering, Northwestern University, USA. His main research interests are in the interrelated area of metal forming, process tribology, surface engineering, and micro-manufacturing. Currently, he is the president of International Research Group of Tribology Manufacturing, International Forum on Micro Manufacturing, and Global Research Group on Light Metal Manufacturing. He is a fellow of American Society of Mechanical Engineers, Japan Society of Mechanical Engineers, and Japan Society for Technology of Plasticity.
Norio TAKATSUJI. He is a professor of the Faculty of Engineering, University of Toyama, Japan. His main research interests are in the hot extrusion of aluminum alloy, die design, and micro-manufacturing.
Chengliang HU. He is a professor in the Institute of Forming Technology and Equipment, Shanghai Jiao Tong University, China. He is part of the National Engineering Research Center of Die and Mold CAD, China. He has more than 10 years’ research experience working in areas of precision forging processing technologies. As the leader, he has managed 20 research projects sponsored by NSFC, MIIT, and industrial companies.
Sukunthakan NGERNBAMRUNG. He is currently doing research at National Metal and Materials Technology Center (MTEC), Thailand. His research interests are in the fields of design and manufacturing, metal forming, metal joining. He utilizes the fundamental and advanced understandings of materials, microstructure and process conditions in order to control and optimize manufacturing processes.
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Funazuka, T., Dohda, K., Takatsuji, N. et al. Effect of die coating on surface crack depth of hot extruded 7075 aluminum alloy. Friction 11, 1212–1224 (2023). https://doi.org/10.1007/s40544-022-0649-y
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DOI: https://doi.org/10.1007/s40544-022-0649-y