An investigation of the strain rate and temperature effects on the plastic flow stress and ductile failure strain of aluminum alloys 5083-H116, 6082-T6 and a 5183 weld metal

Abstract

This article presents a comprehensive experimental and numerical study to investigate the effects of strain rate and temperature on flow stress and ductile failure strain of three aluminum alloys. The test matrix includes smooth and notched round tensile specimens tested at room temperature (24 ℃) and two elevated temperatures (66 ℃ and 149 ℃), and under different strain rates. For 5083-H116, three loading rates are considered at 24 ℃ and it is found that the flow stress and failure strain are lowest at the intermediate strain rate. At high strain rate, the flow stresses of 5083-H116 and 6082-T6 are higher than the quasi-static loading while the flow stress of the 5183 weld metal remains unchanged; the ductility of the 5XXX alloys shows a significant increase compared to the quasi-static loading while the ductility of 6082-T6 does not change much. The study indicates that the Johnson–Cook plasticity and fracture models can be used to describe the temperature dependencies of the flow stress and the failure strain for 6082-T6 but not the 5XXX alloys. At 66 ℃ the 5XXX alloys do not display temperature softening compared to 24 ℃ while their ductility is reduced. As temperature is elevated to 149 ℃, the flow stress of the 5XXX alloys decreases while the ductility increases. The unconventional behavior of the 5XXX alloys in certain temperature and strain rate ranges has been attributed to the dynamic strain aging effect. The study also suggests that the dependency of the failure strain on stress triaxiality can be described by the Johnson–Cook fracture model for all three materials under quasi-static loading at room temperature and the model parameters are calibrated using an inverse method combining experimental results with finite element analysis.