CAJ | 학술논문

7075 aluminum alloy thick-plates were produced by three processing routines: commercial hot-rolling followed by heat treatment of quenching and ageing (HR+QA), combination of large deformation processing of multi-directional warm forging and subsequent warm rolling followed by heat treatment of quenching and ageing (LD+QA), and that followed by annealing at moderate temperature (LD+AN). Tensile strength, yield strength and elongation were measured by tension test, and the metallographic structures were examined by optical microscopy (OM) and transmission electron microscopy (TEM), also the fracture morphologies were observed by scanning electron microscopy (SEM). It is shown that higher tensile strength and yield strength are obtained from (LD+QA) processing in comparison with those from (HR+QA) and (LD+AN) processings. Tensile strength and yield strength obtained from (LD+QA) processing are 9.9% and 8.6% higher respectively than those from (HR+QA) processing, and 48.6% and 57.7% higher respectively than those from (LD+AN) processing; while the elongations of all the samples show no significant difference and keep 10%-12%. Analyses of OM and TEM reveal that the mechanical behaviors are deeply associated with the formation of refined structures with fine grains and very fine precipitates, leading to fine-grained hardening and excellent age hardening.