Microstructure and mechanical properties of 7075 aluminum alloy during complex thixoextrusion
(1. National Key Laboratory for Precision Hot Processing of Metal, Harbin Institute of Technology, Harbin 150001, China;
2. KaShui Technology (Huizhou) Co., Ltd., Huizhou 516000, China)
2. KaShui Technology (Huizhou) Co., Ltd., Huizhou 516000, China)
Abstract: 7075 aluminum alloy was used to obtain elbow parts by complex thixoextrusion and the microstructure evolution and mechanical properties during this process were studied by SEM, TEM and other analytical methods. The results show that different parts in 7075 aluminum alloy show quite different microstructures. The microstructure of the thin walls formed by back-extrusion is stratified, and the bottom of the parts formed by angular extrusion is obviously deformed. Shear forces contribute to the crushing of grains and the coarse second phase. The main strengthening phases in the material are η phase and E phase, whose amounts greatly decrease during heating to semi-solid and thixoextrusion. After heat treatment, they can precipitate evenly to improve the mechanical properties of the material. The average tensile strength of whole part after thixoextrusion and heat treatment is 485.49 MPa, while the average elongation is 5.49%.
Key words: 7075 aluminum alloy; thixoextrusion; semi-solid forming; elbow parts; mechanical properties