Effect of cryogenic temperature equal channel angular pressing on microstructure, bulk texture and tensile properties of AA1050

Plastic deformation of metallic materials at cryogenic temperature is believed to be able to suppress the dynamic recrystallization and further refine their microstructures compared to that at room temperature. This paper investigates the microstructure, bulk texture as well as the tensile properties of commercially pure aluminum AA1050 processed by equal channel angular pressing (ECAP) at both cryogenic temperature (CT-ECAP) and room temperature (RT-ECAP). The experimental results suggest that CT-ECAP process is more effective than RT-CAP in grain refinement and strength enhancement for the studied material. As for the bulk texture, a significant difference is observed between the 1-pass CT-ECAP and RT-ECAP samples, which is attributed to the suppression of texture development at cryogenic temperature. After 2 or more passes CT-ECAP, the texture obtained is similar to RT-ECAP and can be interpreted by the ideal ECAP texture for FCC metals. It can be concluded that CT-ECAP suppresses the dislocation sliding and dynamic recovery as well as texture evolution, thus it has the capability to fabricate materials with higher strength. The CT-ECAP process induced higher strengths than RT-ECAP can be explained by two main mechanisms, namely the grain boundary strengthening and dislocation strengthening. It has also been found that the grain boundary strengthening mechanism plays the dominant role.