The high strain rate and high temperature properties of as cast and aged 7075 aluminium alloy were examined by metallographic observation and by means of a split Hopkinson bar test at temperatures between 25 and 300°C and at strain rates of 1.3 × 103 and 3.1 × 103 s-1. The effect of aging, as well as strain rate and temperature, on the dynamic mechanical response, microstructure evolution, and fracture characteristics are presented. The compressive stress-strain response of as cast and aged 7075 alloy is found to depend strongly on both the applied strain rate and the test temperature. However, the aged material is generally found to be stronger than the as cast material. The work hardening rate is seen to decrease with increasing strain, strain rate, and temperature, and its value is higher in the aged material than in the as cast material. Microscopic observation shows that aging, strain rate, and temperature have a significant influence on the microstructural evolution and the changes in grain morphologies. The average grain size can be expressed by a Hall-Petch type relationship after impact deformation. Fracture surface examination revealed that a high strain rate favours the formation of deformed shear bands that are precursors to crack formation and fracture. The aged material has a better ductility owing to the higher percentage of transgranular fracture and an increased density of microdimples.
All Science Journal Classification (ASJC) codes
- Materials Science(all)
- Condensed Matter Physics
- Mechanics of Materials
- Mechanical Engineering