Influences of thermo-mechanical treatment process on the microstructure evolution and tensile properties of 7075 Al alloy

Three types of 7075 Al alloys with average grain sizes of 11.6 mu m, 26.7 mu m and 49.8 mu m were successfully fabricated through a thermo-mechanical treatment (TMT) process. Systematic room-temperature tensile tests were conducted on those alloys with different grain sizes and aging states. Regardless of the grain size, the relationship between strength and plasticity followed a "barb" trend with increasing aging time. At the under aged (UA) state, it has the best matching, with the highest strength-plasticity product. Grain refinement improved the matching at the over aging (OA) state, and microstructure regulation did not alter the tensile fracture mode. At the OA state, grain refinement reduced the strain-hardening exponent. Both grain refinement and aging influenced the work hardening rate, attributed to the high density of mobile dislocations at the UA state. As aging progressed, slip characteristics transformed from planar to cross-slip mode. This study clarifies the relationship between microstructure and mechanical properties, providing insights for optimizing the mechanical performance of high-strength Al alloys with better plasticity.