Influence of pre-straining and heating on strain-rate sensitivity of AA5182-O

Abstract

The manufacturing process of auto-body parts usually includes forming (i.e., pre-straining) and baking (i.e., heating), which could alter mechanical properties of the substrate materials. The present study clarifies the influence of pre-straining and heating on the strain-rate dependent mechanical performance of aluminum alloy 5182-O (AA5182-O). Quasi-static and intermediate strain-rate tensile tests were conducted with either AA5182-O material as received or processed by different combinations of pre-straining and heating. The quasi-static test results show that the yield strength is enhanced by pre-straining and weakened by heating, while the ultimate strength is less affected. The test results at different strain-rates show a transition of negative to positive strain-rate sensitivity (SRS) at a critical rate below 100 s−1, and it is revealed that pre-straining enhances the negative effect and heating mainly enhances the positive effect. A modified Khan-Liu model that incorporates the non-monotonic SRS is employed to characterize the influence of pre-straining and heating, and electron backscatter diffraction (EBSD) analysis is performed to address the mechanism behind the SRS variation.