On effect of damage on superplastic formability of LY12CZ aluminum alloy and H62 brass sheet

The authors present the results of their experimental research on superplastic forming limit under different strain states of two alloys: (1) LY12CZ aluminium alloy (corresponding to ASTM 2024; sheet thickness is 2mm; hardness HB is 131; grain size is 18.3 μm); (2) half-hardened H62 brass (corresponding to ASTM 280; sheet thickness is 1.5mm; hardness HB is 60; grain size is 14.2 μm). The experimental findings are given. Considering two experimental findings, the authors make the following deduction with confidence: during the process of superplastic deformation, cavity damage makes continuity of transfer of strain worse and worse, thus accelerating the drift of externally applied strain state toward plane strain state with lowering of superplastic forming limit of sheet as the natural result.