Fatigue response of a cast Al-Cu-Mg-Ag-TiB2 (A205) alloy: Stress relieved and aged

Abstract

The purpose of this study is to assess the influence of heat treatment on the fatigue behavior of cast A205 alloy (i.e., Al-Cu-Mg-Ag-TiB2 nanocomposite). To do so, A205 samples were heat-treated and divided into two categories (i) stress-relieved (SR) and (ii) T7 stabilizing over-aged. This research delves further into the microstructure, mechanical properties, and fatigue performance of A205 alloy in SR and T7 heat-treated (i.e., T7 aged) conditions. After production and post-heat treatments, the samples underwent force-controlled fatigue experiments, tensile and depth-sensing indentation testing, and advanced microstructural characterizations (using electron backscattered diffraction and transmission electron microscopy). Microstructural characterization revealed exceptionally equiaxed, texture-free microstructure with uniform grain distribution and the existence of Al2Cu precipitates and TiB2 particles. The T7 heat treatment did not change grain size significantly (grain size: 46.4 ± 13.5 µm for SR and 48.5 ± 13.7 µm for T7 material). The T7 heat treatment was found to be very effective in improving the fatigue resistance of A205. The higher fatigue resistance of cast T7 material is attributed to the accelerated precipitation of Al2Cu along with different habit planes. The results of this study offer a critical understanding for choosing the optimum heat treatment parameters to control the fatigue behavior of cast A205, which is crucial considering their applications in the aerospace industry.