FRACTURE BEHAVIOUR OF A MEDIUM STRENGTH Al-Zn-Mg ALLOY.

The fracture behavior of 60 mm thick plate of an Al-5. 16Zn-1. 19Mg-Mn-Zr-Si-Fe alloy was investigated after a variety of heat treatments as a function of orientation with respect to the rolling direction. Emphasis is on the critical parameters controlling the magnitude of energy absorption both in shear fracture and intergranular fracture. Simple models were developed to describe these modes of failure which point out the importance of the residual as-cast structure and the rate of work hardening in determining the fracture resistance. In addition, results are described which indicate the improvements in fracture resistance which can be developed by modification of the grain structure.