Microstructural, mechanical and thermodynamic properties ınvestigation of the novel rare earth-free multicomponent Mg-15Al-8Ca-3Zn-2Ba alloy

Abstract

There has been a significant increase in research and development efforts to meet the growing demand for environmentally friendly magnesium (Mg) alloys. Studies are currently exploring various alloying element combinations to meet demanding specifications. In this study, it was aimed to examine the usability of aluminum (Al), calcium (Ca), and zinc (Zn) elements together with barium (Ba), and to investigate the mechanical and thermodynamic properties of the obtained multicomponent alloy system. SEM and hardness tests were used to examine the microstructural and mechanical features of Mg alloys. In the SEM analysis, the alloy was determined to consist of an ?-Mg matrix, a blocky compact structure containing Ba (Mg17Ba2), a regional eutectic structure (Ca2Mg6Zn3), and independently growing lamellae (Al2Ca). The general hardness analysis results of the alloy, measured with Brinell and Vickers tests, were determined to be ~77 and ~82, respectively. The indentation test also revealed that stress transfer to the Al2Ca laves phase is possible, depending on the orientation of the slip plane between the matrix and the Al2Ca phase. It was also observed that cracks developed in the indentation test on the Mg17Ba2 intermetallic phase were only formed in the high-stress regions of the structure, and their propagation was limited. According to thermodynamic analysis, the ?Hmix value is -2.73 kJ/mol, the ?Smix value is 5.95 J/molK, the ? value is 34%, the ?? value is 0.14, and the ? value is 2.03. The obtained thermodynamic data were found to be compatible with the microstructural development of the alloy.