Micromechanical study of strengthening mechanisms for Ti65(AlCrNb)35 medium-entropy alloy

Abstract

Metal solutions, such as high- and medium-entropy alloys, exhibit extraordinary mechanical performance in comparison to regular alloys. In this study, we employ a crystal plasticity finite element model (CPFEM) to study the strengthening mechanisms of a new medium-entropy alloy, Ti65(AlCrNb)35. A 3D representative model is constructed by processing experimental results for Ti65(AlCrNb)35, such as average grain size, grain size distribution, and initial texture, using the open-source software Dream.3D. The constitutive law for the grains is described by the crystal plasticity and implemented in Abaqus user-defined material (UMAT). The results of uniaxial tensile tests are utilized to calibrate the required parameters in the CPFEM. Strengthening effects resulting from the grain size, strain rate, and cyclic loading for Ti65(AlCrNb)35 are investigated by performing numerical simulations based on the proposed computational framework. Numerical simulation results show that the yield strength increases with decreasing initial grain size, which agrees well with experimental observations of the Hall–Petch effect. In addition, the rate-dependent yield stress increases as the applied strain rate increases in the tensile tests. Moreover, the cyclic loading results demonstrate the isotropic hardening behaviors and the saturation of yielding strength when the maximum strain reaches 10%. Finally, we discuss the contributions of different strengthening mechanisms on the yield strength of Ti65(AlCrNb)35 under different load conditions.