Deformation mechanisms and remarkable strain hardening in a lightweight high-temperature eutectic high-entropy alloy

Abstract

The utilization of lightweight high entropy alloys (LWHEAs) in aerospace materials hold significant potential. However, addressing the urgent challenge of enhancing mechanical properties such as specific strength and compressive strain equilibrium at room temperature and high temperature remains a crucial problem in developing new, cost-effective structural materials. In this work, Al_1.0CrVNi_x (x = 1.3, 1.5, 1.7, 2.0 and 2.5) and Al_yCrVNi_1.5 (y = 0.75, 1.25, 1.3, 1.37 and 1.5) LWHEA systems with low densities of 5.6–6.6 g cm⁻³, have been proposed. Two eutectic LWHEAs with B2/BCC and L2₁/BCC structures are obtained in Al_1.0CrVNi_1.7 and Al_1.37CrVNi_1.5, respectively. The alloys show excellent specific yield strengths of 311 and 277 MPa (g cm⁻³)⁻¹, respectively (typically ∼ 220 MPa (g cm⁻³)⁻¹ in conventional Ti- and Ni-based alloys at room temperature), and hardness of 648 and 568 HV, respectively (typically ∼ 480 HV in conventional Ti- and Ni-based alloys), while keeping the compressive strain over 30 %. Furthermore, Al_1.37CrVNi_1.5 and Al_1.5CrVNi_1.5 LWHEAs possess excellent mechanical properties at high temperature, whose specific yield strengths are as high as 177 and 161 MPa (g cm⁻³)⁻¹ respectively at 800 °C, far exceeding those currently reported LWHEAs. The alloys exhibit significant strain hardening capability, resulting from the interaction between ordered and disordered phases with semi-coherent interfaces, along with the presence of coherent nano-precipitates dispersed throughout the eutectic phases.