First-principles Study On Interfacial Structural Properties Of TiC/Mg Magnesium Matrix Composites

TiC/Mg magnesium matrix composites have broad application prospects in automotive,electronic communications,aerospace and military industries,due to light weight,high specific rigidity and specific strength,easy cutting,excellent damping performance and anti-electromagnetic interference ability.For metal matrix composites,its performance is mainly determined by the interface bonding between the reinforcement phase and the matrix.The interface can effectively transfer the load from the relatively fragile matrix to the reinforced phase with high strength and high modulus,so that the mechanical properties of the composite material are significantly improved.In addition,the bonding strength of the interface will be affected by many factors,such as interface wettability,interface orientation relationship,interface defects and the incorporation of other alloying elements.Therefore,it is important to systematically study the interfacial structures and properties of TiC/Mg magnesium matrix composites.In this paper,the electronic configuration and bonding methods of Mg and TiC bluk and the surface energy of their representative surfaces were stuied by First-principles calculation method,it revealed the microscopic mechanism of Mg and TiC internal atom bonding and its surface stability,and the ideal TiC/Mg interface was established according to the existing micro-topography of TiC/Mg composite interface and the characteristics of Mg and TiC interfaces.By introducing point vacancy defects and alloy elements into the ideal TiC（111）/Mg（0001）interface,the effects of point vacancy defects and alloy elements on the wettability and bonding strength of TiC（111）/Mg（0001）interface were studied.The research results are summarized as follows:Firstly,for the study on the electronic structure and bonding method of ideal Mg bulk and TiC bulk and its representative surfaces,it can be see that,there are mainly metallic bonds contributed by 2p electron orbitals in the ideal Mg bluk,while in the ideal TiC bluk,the main bonding types are the strong covalent bonds formed by the hybridization of C-2p and Ti-3d and a small amount of metallic bonds formed between Ti-3d and Ti-3d.For the representative surfaces of Mg,the surface energy of the Mg（0001）plane is the smallest and Mg（0001）plane is the most stable.For the non-polar surfaces of TiC,the surface energy of TiC（100）surface is the smallest,while for the polar surfaces of TiC,the surface energy of C-terminated TiC（111）plane is larger,the surface activity is higher,and the surface energy starts to converge after the number of atomic layers reaches 6.Secondly,for the study on the bonding state of 4 ideal TiC（111）/Mg（0001）interfaces and TiC（111）/Mg（0001）interfaces with point defects V_Mgand V_C,it can be see that,the structures of Ti-terminated interface cannot exist stably,and the ideal work of adhesion of the C-terminated center-site interface is amaximum（4.842 J/m²）,the interface spacing is minimum（1.39（?））,the wettability is good,and the interface is the most stable.For the the C-terminated center-site interface and the C-terminated top-site interface,the bonding methods on both sides of the interface are mainly covalent bonds and ionic bonds,while in the Ti-terminated center-site interface,the bonding methods at the interface are mainly metallic bonds.In addition,the interfacial point defects V_Mgand V_C are not conducive to the combination of the TiC（111）/Mg（0001）interface,and point defects V_C are more likely to form.Finally,for the study of effect of doping alloy elements（Al,Zn and Cu）on TiC（111）/Mg（0001）interfacial property,it can be see that,when the doped atoms are in the interface layer,the effect on TiC（111）/Mg（0001）interface is the most obvious,and the doped Al atoms and Cu is beneficial to improve the wettability of TiC（111）/Mg（0001）interface and the effect of Al atom is the best.However,due to doped Zn atoms do not participate in the formation of interfacial covalent bonds,they mainly combine with other atoms through metallic bonds,which leads to a decrease in the adhesion work of the interface,which is not conducive to improving the interface wettability.