Structure and mechanical properties of FeAlCrV and FeAlCrMo medium-entropy alloys

Abstract

In this work, the evolution of microstructure and mechanical properties of FeAlCrV and FeAlCrMo medium-entropy alloys were studied. In both FeAlCrV and FeAlCrMo alloys, the as-cast sample is a body centered cubic (BCC)-ordered solid solution. In FeAlCrMo, it exhibits a dendritic structure, whereas in FeAlCrV, two types of particles are present. The first one is the solid solution VxCr1-x (0.8 < x < 1) with the BCC structure and the second one is the V2C carbide with orthogonal symmetry. In FeAlCrV, the structure of the investigated material remains stable even after annealing at 800 °C for 15 days. Nevertheless, vanadium starts to redistribute, and the lattice parameter slightly changes at a temperature of 500 °C. Furthermore, a new solid solution enriched in vanadium forms. In FeAlCrMo, a lengthy annealing at a high temperature (800 °C/15 days) results in decomposition into a two-phase material composed of a BCC solid solution and a Mo3Al phase with a primitive cubic (PC) structure. Differential scanning calorimetry and dilatometry revealed that decomposition already starts at the temperature of approximately 400 °C. Compression deformation tests were performed at various temperatures starting from room temperature (RT) up to 800 °C. The results showed that both materials exhibit excellent values of yield stress, especially at high temperatures (965 MPa and 898 MPa at 800 °C for FeAlCrV and FeAlCrMo, respectively). The plasticity reaches 5–12% and 3–9%, respectively.