Effect of alloying elements on interfacial properties and mechanical behavior of Mg/WC systems: A first-principles study

Alloying elements play a key role in the interfacial stability and mechanical properties of WC reinforced Mg matrix composites while their influence is complex and unclear. In this work, the segregation energy, adhesion work, interface energy and tensile strength of Mg(0001)/WC(0001) interface alloying with Al, Si, Zn, Zr, Ca, La, Mn, Sc, Y and Sn were calculated by first-principles method and the strengthening and fracture mechanism of the interface were clarified. The results show that alloying elements such as Al, Si, Zr, Ca, La, Mn, Sc and Y increase the adhesion work and reduce the interface energy, thereby improving the interface stability. Meanwhile, the addition of Sn and Zn shows the opposite effect. Multiple regression analysis indicates that the valence electrons and electronegativity of alloying elements have the most significant effect on the thermodynamic parameter and a high-accuracy prediction regression equation is put forward. The fracture of the Mg/WC interface occurs in the Mg matrix side but not on the exact interface. This may result from the strong M−C (M = Al, Si) bonds at the interface and weak Mg-Mg bond in the bulk according to COHP analysis.