چكيده به لاتين
In this work the effects of severe plastic deformation by equal channel angular pressing (ECAP) on microstructure evolution, mechanical behavior and texture development was investigated in AA5052 alloy. ECAP was carried out via route A and C for 2,4 and 6 passes in room temperature. In order to investigate detailed microstructure and texture development in ECAPed samples, these specimens were characterized by scanning electron microscopy (SEM) equipped with electron back scattered diffraction (EBSD) system. EBSD-color maps showed that the grain size reduced significantly after 2 passes of ECAP. Furthermore, dislocation cells were formed after 2 passes of ECAP. By proceeding ECAP process to 6 passes, average grain size and average cell size reduced relative to 2 passes ECAPed samples. After 6 passes of ECAP via route A and C, the grain size reduced up to 471 nm and 371 nm, respectively. Pole figures were constructed in order to investigate texture development in ECAPed samples. Pole figures showed that no significant texture developed after 2 passes of ECAP. By proceeding ECAP process to 6 passes B/B ̅ component of {hlk}<110> fiber was developed. Phase analysis was performed using XRD patterns. Only α-Aluminum Phase was detected in this alloy. Furthermore, dislocation densities were calculated by Williamson-Hall method using XRD patterns. The maximum dislocation density was achieved after 4 passes of ECAP, and by proceeding ECAp to 6 passes dislocation density reduced due to dynamic recovery during deformation. After 2 passes of ECAP Vickers hardness (Hv) increased significantly. The hardness increased by 102% and 110% for 2 passes ECAPed samples via route A and C, respectively. Further increase in hardness was observed with for deformation in 4 passes ECAPed samples. By proceeding ECAP to 6 passes via route A the hardness remains constant, and reduced for that deformed via route C. Some of tensile properties .i.e., yield strength (YS), ultimate tensile strength (UTS) and work hardening properties was studied using stress-strain curves. After 2 and 4 passes of ECAP via route A the YS increased by 158% and 229%, and for that via rout C increased by 188% abd 202%, respectively. By proceeding the deformation to 6 passes via route A the YS remains constant relative to 4 passes ECAPed sample, however it was reduced for that ECAPed for 6 passes via route C. Grain size, dislocation density and crystallographic texture were investigated as the factors which influence the YS. UTS was increased continuously up to 6 passes of ECAP via both of routes A and C. Work hardening properties investigations showed that work hardenability of AA5052 alloy decreased significantly after ECAP. The decrease in work hardenability was due to increase in dislocation density and decreasing the grain size.
