First principles study on the structural, electronic and magnetic properties of Ni4C

AbstractThe first-principles calculations were performed based on density functional theory to study the structural, electronic and magnetic properties of Ni4C resulting from carbon atom diffusion in a conventional Ni unit cell. Firstly, geometry optimization was performed to reach the equilibrium state of Ni4C. The lattice constant of the stable Ni4C crystal structure was larger than that of the Ni unit cell. Then the electronic and magnetic properties of Ni4C were determined, and the results showed that the magnetic moment was 0.46 μB per unit cell, and the calculated local magnetic moment of carbon atoms was 0. There were two occupied sites for Ni atoms with different local magnetic moments, which was about 0.64 μB (close to that of nickel unit cell) for Nia atoms at the top corners and a negative value of −0.06 μB for Nib atoms at the face center. The magnetic moment increased abruptly to 1.89 μB at 3.79 Å due to the changes of lattice parameters with external factors, and fluctuated slowly from 3.5 Å to 3.78 Å

Effect of TiC Content on Microstructures and Properties of Laser Cladding TiC/Ti Based Composite Coatings

To improve the corrosion resistance and load-bearing performance of titanium alloy, the TiC/Ti based composite coating with good metallurgical quality was prepared on the surface of TC4 titanium alloy by using Diode laser, and the effect of TiC content on the microstructures and properties of TiC/TC4 cladding was studied. The microstructure and phase constitution of the coating were characterized by scanning electron microscope (SEM) and X-ray diffraction (XRD), the micro-hardness, corrosion resistance and the load-bearing performance of the coatings were evaluated. The results show that the cladding consists of TiC, TiC0.95, NiTi2 and α'-Ti, and the overall hardness of the coating fluctuates greatly. The micro-hardness in hard phases and in the heat affected zone are 1000-1500HV and about 437HV respectively. While the mass fraction of Ni coated TiC is not higher than 60%, higher corrosion resistance of claddings can be obtained with the increase of the mass fraction of Ni coated TiC, reaching a maximum at 60%; while the mass fraction of Ni coated TiC is not higher than 50%, the load-bearing capacity of claddings can be improved with the increase of the mass fraction of TiC, reaching a maximum at 50%