Anisotropic microstructure and thixo-compression deformation behavior of extruded 7075 aluminum alloy in semi-solid state

In order to examine the micro-mechanism behind the thixotropic behavior of semi-solid alloys, microstructural effects on the compression deformation of semi-solid 7075 aluminum alloy prepared by recrystallization and partial melting (RAP) method were investigated. The fibrous and deformed microstructure of as-extruded 7075 aluminum alloy can transform into elongated and globular grains via reheating to semi-solid states, and exhibiting dominated {100}<001> recrystallization texture and preferred crystal growth in extrusion direction. The anisotropic microstructure of semi-solid alloys depends on the remelting temperatures to a great degree. Correspondingly, the initial peak stress of compression stress-strain curves also demonstrated as anisotropic behavior. It was analyzed that the crystallographic texture caused orientation dependent Young's modulus and a corresponding elastic response, and the disagglometation of the saturated solid skeleton led to an increase of viscoplastic stress, which relates to the amount of bonds between solid grains.