Low-Temperature Mechanical Properties of AA 6063-T6 and 7075-T6: Tests and Full-Range Constitutive Models

Aluminum alloys (AAs) are potential alternative constructional materials for low-temperature infrastructures in cold regions and liquefied natural gas (LNG) storage tanks. This study investigated the mechanical properties of AA 6063-T6/7075-T6 materials through tension tests on 32 AA coupons at low temperatures ranging from 20°C to −165°C. All the AA 6063-T6 coupons exhibited ductile failure modes, and AA 7075-T6 coupons failed in brittle modes at 20°C to −165°C. The experimental results showed that decreasing the temperature from 20°C to −165°C, respectively, increased the yield, ultimate, and fracture strengths of AA 6063-T6 (or 7075-T6) by 26.8% (8.5%), 21.2% (6.5%), and 27.6% (9.7%), but their ductility was not compromised. Furthermore, regression analyses were performed to establish prediction equations for the low-temperature mechanical indexes of AAs. Finally, a full-range constitutive model was proposed to estimate the stress–strain behaviors of AA 6063-T6 and 7075-T6. The validation results confirmed that the proposed constitutive models accurately described the stress–strain behaviors of AA 6063-T6 and 7075-T6 within the temperature range of 20°C to −165°C.