Influence of heat treatment on phase evolution, microstructure, tensile properties, and low-cycle fatigue behaviour of WE54 magnesium alloy: An experimental investigation

WE series magnesium alloys offer attractive properties for the aerospace, aviation, and automotive industries. The microstructure and mechanical properties of the WE54 Mg alloy under different processing conditions, such as as-cast, T4-treated, conventional age-hardening (C.A), and step age-hardening (S.A), were studied. The microstructure of the processed alloy was analyzed using a Field Emission Scanning Electron Microscope (FE-SEM) equipped with Energy-Dispersive Spectroscopy (EDS), a High-Resolution Transmission Electron Microscope (HR-TEM), and X-ray Diffraction (XRD). The microhardness, modulus, and tensile strength of the as-cast sample are 95.5±3.99 HV 0.1 , 68.20±4 GPa, and 139.75±3.3 MPa, respectively. The results indicate the formation of the β’ phase (Mg12RE) along the grain boundaries and the β1 phase (Mg3RE) as cuboidal particles within the grains after age-hardening. The age-hardened samples (C.A and S.A) reach the runout cycles (10,000) without failure at a strain amplitude of 0.1%. The S.A samples exhibit better tensile and fatigue behaviour than those from the other processing conditions. Based on microstructural observations, the improved mechanical properties are attributed to the formation of the β’ and β1 phases. The fracture mechanism in the tensile and LCF test samples was quasi-cleavage, characterized by a predominant cleavage plane, tear ridges, and transgranular cracks.