EVALUATION OF SUPERPLASTIC PROPERTIES OF AA7075 ALUMINUM ALLOY SHEET FABRICATED BY THERMOMECHANICAL PROCESSING

The superplastic forming (SPF) process is the large plastic deformation ability of metals and alloys. However, SPF ability can only be achieved under certain conditions including ultrafine grain (UFG) microstructure, high temperature, and very small strain rate. In this work, the high-strength aluminum alloy AA7075 was selected for the experimental process due to its outstanding industrial application. First, thermomechanical processing (TMP) is performed to create a fine stable grain size for the studied alloy. The UFG microstructure was obtained after TMP with an average grain size of about 10 μm. Subsequently, the tensile test method and the bulging free-forming (BFF) method were used to evaluate the superplastic properties of the AA7075 aluminum alloy sheet fabricated by TMP. These two methods are performed at temperatures of 500º C and 530º C with strain rates from 10-4 (s-1) to 10-3 (s-1). The relative elongation and the strain rate sensitivity are the evaluation criteria. At the temperature of 530ºC and strain rate of 10-3 (s-1), the maximum relative elongation and flow stress were achieved at 280 and 7.6 MPa, respectively. The value of the coefficient m ranges from 0.3 to 0.6. The obtained results confirm the SPF properties of the aluminum alloy sheet AA7075. 2024 © International Journal of Modern Manufacturing Technologies.