Spall failure of aluminum materials with different microstructures

• Influence of microstructure on spall behavior of aluminums was explored.
• Al HP exhibits the higher spall strength than the low-porosity pure aluminum.
• 2024-T4 alloy exhibits a stronger spall failure resistance than the 7075-T6 alloy.
• Correlations between microstructures and the continuum measurements were discussed.

The effects of microstructure on the spall failure were studied for four aluminum materials by a series of plate-impact spall experiments, including the real-time measurements of the free surface velocity profiles and the microscopic postimpact examination of the soft-recovered samples. Spall strength values are calculated by using the free surface velocity measurements. The high density high purity aluminum (Al HP) exhibits a higher spall strength than the low-porosity pure aluminum. The metallographic examination revealed that it could be attributed to the less impurity in the grain boundaries in the Al HP samples, having a better resistance for void nucleation. The 2024-T4 aluminum alloy exhibits a stronger spall failure resistance than the 7075-T6 aluminum alloy, which is associated with the stronger plastic strain hardening behavior. Comparison among the Al HP, 2024-T4 and 7075-T6 alloys indicates that the differences observed in the rise rate of pull-back are linked with the different active mechanism and growth rate of damage evolution.