High-temperature tensile behavior and high-cycle fatigue properties of Mg-7Li-1Zn alloy

Abstract The use of light steels such as magnesium alloys is increasing due to their suitable mechanical behavior in various industries (e.g., automotive, aerospace, and electronic engineering). In this regard, pure magnesium is one of the most earth-abundant metals and has unique properties such as high strength-to-weight ratio and very high recyclability. Among magnesium alloys, magnesium compounds and various percentages of lithium are known as one of the most popular engineering metals due to their high formulation capability. Also, significant features of magnesium-lithium alloy include its high elongation beside the low density. The results of previous studies indicate that annealing at 350 °C for 3 h leads to the same physical properties in different directions for Mg-7Li-1Zn alloy. The main aim of this research is to investigate the static properties at different temperatures and the high-cycle fatigue behavior of this alloy. To this end, Optical Microscopy (OM) observations and X-ray Diffraction (XRD) analysis were employed to determine the metallurgical properties of the material. Next, tensile and fatigue test specimens were fabricated according to ASTM E21 and ASTM E466 standards, respectively. Tensile tests were performed at the temperature of the room, 150, 200, and 300 °C. The key parameters were extracted and compared to that of pure Mg. Eventually, force-controlled axial fatigue tests were carried out on pure Mg and Mg-7Li-1Zn specimens under a loading frequency of 10 Hz and fully reversed loading. The experimental results reveal that fatigue strength of Mg-7Li-1Zn alloy is much higher than pure magnesium (i.e., the fatigue life improvement of 400% occurs by utilizing Mg-7Li-1Zn in compared with fatigue life of pure Mg at the maximum loading of 50 MPa).