Improvement of fatigue crack growth resistance by controlled overaging in 2024-T3 aluminium alloy

Abstract

A controlled overaging process is proposed to increase region II fatigue crack propagation resistance of 2024-T3 aluminium alloy. Overaging was achieved by subjecting the material from the initial T3 state to heat treatment at specific aging temperatures resulting in substantial reduction in hardness. Fatigue crack growth tests were subsequently performed in the intermediate region to assess the influence of aging treatment on fatigue crack propagation rate. The experimental results showed that overaging at high temperatures enhances the fatigue crack growth resistance of the material with regard to initial T3 state. Fatigue crack growth rates were found to decrease with increasing overaging temperature. Cyclic stress strain tests were performed to assess the impact of the performed overaging on cyclic behaviour. The results revealed that cyclic strain hardening is enhanced in the overaged material, contributing to increased fatigue crack closure levels.