Effect of stress state on cavitation and hot forming limits of a coarse-grained Al5052 alloy

Effect of stress state on cavitation and deformation behaviour of superplastic or superplastic-like materials has less been investigated. A coarse-grained Al5052 alloy was deformed at its optimal temperature of 873 K under different biaxial stress states. A superplastic gas forming tester with die aspect ratios of 1, 0.75, 0.5 and 0.375 was used. It is observed that the amount of cavities increases with increasing strain level. More and larger cavities were observed at higher strain levels for all stress states. It is also found that an increase in stress ratio will slightly increase the cavity growth rate. An experimental forming limit curve of the alloy was constructed, and an analytical model based on M-K model and damage mechanics approach has been applied to predict limit strains of the alloy based on experimental cavitation data. It is found that the limit strain increases with increasing f0and decreases with increasing DB0/DA0. The prediction is in reasonable agreement with the experimental limit strains.