Metallurgical Abstracts on Light Metals and Alloys vol.54
Effect of Die Coating on Tearing of Hot Extrusion of 7075 Aluminum Alloy
Tatsuya Funazukaa*, Norio Takatsujia, Kuniaki Dohdab and Ngernbamrung Sukunthakanc
aGraduate School of Science and Engineering for Research., University of Toyama, Toyama, 930-8555, Japan
bDepartment of Mechanical Engineering, Northwestern University, Evanston, 60201, USA
cMetal and Manufacturing Process Research Group National Metal and Materials Technology Center, Pathumthani, 12120, Thailand
[Published in International Conference on Tribology in Manufacturing Processes Joining Technologies (9th ICTMP2021), November 24–26, Chennai, India]
Keywords: hot extrusion, 7075 aluminum alloy, die coating, Tearing
Abstract
7000 series aluminum alloy is a high-strength alloy and is used in a wide variety of products for the purpose of weight reduction in the field of transportation equipment and aerospace. In particular, A7075 alloy has the highest strength and is expected to be further applied in a wide range of fields such as aircraft parts and sports equipment. However, it has high deformation resistance and is prone to surface defects called tearing on the product surface. Low productivity is a problem because of shortness. Tearing is likely to occur under high temperature and high speed conditions, and it is thought to be caused by local melting due to heat generated by the processing of Zn, an additive element. In this study, in order to improve the productivity of the A7075 alloy, attention was paid to the die surface properties to prevent the effect of friction during molding and recrystallization of the extruded material surface crystal grains due to processing heat generation and adhesion to the tool surface. The AlCrN coating was adopted for the. Compared to Nitriding, which is a conventional surface treatment, it was found that the tearing size and heat generated by AlCrN coating were small. In addition, it was found that the recrystallization region on the product surface, which is the tearing generation region, was reduced. From the above results, the coating on the die reduces the effect of friction during molding, and has the effect of preventing recrystallization of the extruded surface crystal grains and local melting of Zn due to processing heat generation.