Abstract
The lattice misfit of small Miller indices crystal faces between Mg and TiC is calculated based on Bramfitt two-dimensional lattice misfit theory. The electronic structure, adhesion energy and interfacial energy of Mg(001)/TiC(111) interface are investigated by first-principle calculation. The bond characteristics between interfacial atoms are analyzed by charge density difference and electron localization function. The calculation shows that the two-dimensional lattice misfit of Mg(001)/TiC(111) interface is 4.9%, which indicates TiC is suitable to act as an effective heterogenous nucleation substrate for Mg. The band structure and density of states calculations prove that the chemical bonds in Mg bulk structure are mainly metallic bonds, while that in TiC bulk structure are mixed bonds composed of polar covalent bonds and metallic ones. At the Mg-C interface, the electrons between Mg atoms and C atoms are shared to form covalent bonds, and the charge accumulation is obvious. The bonds in the Mg-Ti interface are metallic bonds, and the charge density between Mg atom and Ti atom is uniformly distributed. Compared with the Mg-Ti interface, the Mg-C interface has a larger adhesion energy (Wad = 6.96 J/m2) and a smaller interfacial energy (γ = 1.41 J/m2). Therefore, the crystallographic orientation most likely to produce a heterogeneous nucleation is Mg(001)//TiC(111), and the interface structure is optimally formed as the Mg-C type model.
Highlights
As one of the most promising structural materials, magnesium alloy has the advantages of high strength-to-weight ratio, good shock absorption, good heat dissipation and easy to recycle, which has been widely used in automobile, aviation, aerospace and other machinery manufacturing industries
Wang et al.7 observed and analyzed the Mg/Al8Mn5 interface by high resolution transmission electron microscope, it is found that there is no crystallographic orientation or coherent relation between them, and they inferred that Al8Mn5 particles in Mg-Al alloy are unlikely to serve as effective heterogeneous nucleation substrate for Mg phase
In order to analyze the properties of TiC strengthening phase and Mg matrix phase in Mg alloy, the density of states (DOS) and the band structure of Mg and TiC bulk structures were calculated
Summary
As one of the most promising structural materials, magnesium alloy has the advantages of high strength-to-weight ratio, good shock absorption, good heat dissipation and easy to recycle, which has been widely used in automobile, aviation, aerospace and other machinery manufacturing industries. with the development of science and technology, various industrial fields put forward higher requirements for the properties of magnesium alloys. Theoretically explanations about the mechanism of TiC act as heterogeneous nucleation substrate of Mg phase, as well as the crystallographic orientation between TiC/Mg, the interface coherent relationship and the interface properties have not been reported. The first principles calculation is used to theoretically calculate the interface atomic structure, crystallographic orientation, adhesion energy and the stability of Mg/TiC interface structures with different terminations and stacking modes, and analyze the mechanism of TiC act as the heterogeneous nucleation substrate of Mg phase. Some theoretical basis can be provided for studying the bond strength, stability and heterogeneous nucleation mechanism between TiC strengthening phase and Mg matrix phase in TiC reinforced Mg alloy. The energy change in the process of structural optimization converges to 1.0×10-5 eV/atom, and the maximum stress converges to 0.02 eV/Å
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