T6处理对Al-Sr中间合金变质的A356铝合金组织与性能的影响

Influences of T6 Heat Treatment on Microstructure and Mechanical Properties of A356 Alloy Modified by Al-Sr Master Alloy

在传统的A356铝合金中加入Al-10Sr中间合金压铸成型制备新型的铝合金轮毂材料,通过光学显微镜和扫描电镜研究了铸态及T6热处理态A356铝合金的组织及其性能,分析了合金的断裂机制。结果表明:铸态A356合金中铁基化合物主要为β相(Al5FeSi);经T6工艺处理后,共晶Si粒子的边角更加圆润,Mg2Si完全固溶于铝基体中,合金组织得到改善;铸态及热处理态A356铝合金试样的拉伸断口均有大量韧窝存在,合金呈现较好的塑性;但T6热处理态A356铝合金的断口处韧窝与铸态相比更加均匀,合金的塑性提高;合金的断裂机制为韧窝+解理断裂的复合断裂机制。

A356 Al alloy modified by Al-10Sr master alloy was die-casted.The tensile properties of the alloy before and afterT6 heat treatment were tested,and the fracture morphology was observed.Then the fracture mechanism was determined by OM and SEM.The results show that the iron-based particle in A356 alloy is mainly β phase（Al5FeSi）,the cornea of Si eutectic particle is more round after T6 heat treatment,and the particle of Mg2Si completely solubles in Al matrix,the microstructure is improved;a large amount of dimples appear in the tensile fracture of both as-cast and heat-treated A356 alloy,which reveals a good ductility.But there are more uniform dimples distribution in the tensile fracture of T6-treated A356 alloy than those of as-cast alloy.The tensile fracture morphology of as-cast A356 Al alloy is occupied by dimples,showing a good ductility.And the tensile fracture mechanism is dimple fracture and cleavage fracture.