EUROPEAN CONGRESS AND EXHIBITION ON ADVANCED MATERIALS AND PROCESSES - EUROMAT 2021

Two parallels of tensile tests at room temperature and at 650 °C were performed on the AlCoCrFeNi2.1 eutectic high-entropy alloy (EHEA) in as-cast and aged conditions. The as-cast AlCoCrFeNi2.1 has a eutectic microstructure with B2-type NiAl lamellae inside the L12-type Ni3Al matrix in a ratio of 35% and 65%, respectively. Isothermal aging at 800 °C for 100 h was performed in order to induce the precipitation of a B2 (BCC) micro-phase of ellipsoid shape inside the L12 (FCC) matrix. Fractography was performed on all samples in order to study the failure mechanisms at different material conditions. In addition, longitudinal sections of fractured specimens were prepared for metallographic analysis. Tensile-test results of parallel samples do not deviate much from each-other even at the as-cast condition and show lower values as compared to the aged samples, both at room- and elevated temperatures. This is mainly due to the precipitation strengthening effect from the B2 micro-phase inside the ductile L12 matrix. Fractography reveals that the fracture of the room-temperature tested samples generally occurs inside the more brittle B2 phase and propagates toward the more ductile L12 matrix. In contrast, in the high-temperature tested samples, the fracture initiates and propagates mainly along the semi-coherent B2-L12 interface and along the grain boundaries.