7075铝合金在复杂触变挤压过程中的显微组织和力学性能

Microstructure and mechanical properties of 7075 aluminum alloy during complex thixoextrusion

采用复杂触变挤压技术制备7075铝合金弯头零件,随后采用SEM、TEM等分析方法研究材料在复杂触变挤压过程中显微组织和力学性能的变化。研究结果表明:7075铝合金弯头各部分的显微组织存在较大差异。反向挤压形成的薄壁部位的显微组织出现分层现象,而角挤压形成的零件底部表现为明显的变形组织,且剪切力可以促进晶粒和粗大第二相的破碎。材料中主要的强化相为η相和E相。在坯料加热至半固态和触变挤压的过程中,η相和E相会大量减少。经过热处理后η相和E相均匀析出,可提高材料的力学性能。经过触变挤压和热处理后,弯头零件的平均抗拉强度为485.49 MPa,平均伸长率为5.49%。

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 areηphase 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%.