Interface structure characterization and elements doping on interface bonding strength and tensile failure mechanism of NiCo coating/Cu matrix

Abstract

The interface bonding strength is one of the most important properties of coatings, which is significantly affected by the interface microstructure. By electron backscatter diffraction technology, it was determined that the grain orientation relationship of coating and matrix at interface is dominated by Cu 〈101〉/NiCo 〈101〉, some of Cu 〈101〉/NiCo 〈101〉 grains contain a certain twist angle, range of 0 to 63.5°. On this basis, using the first principles calculation to predict the Cr, Os, and Ir doping on the interface bonding strength and the tensile failure mechanism of NiCo coating. Heat of segregation shows that the doping elements have no tendency to diffuse to the matrix and interface. Work of separation reveals that the Cu(101)/NiCo(101) interface has good bonding strength (3.758 eV), stronger than Cu (2.203 eV), weaker than NiCo (4.860 eV) and the Cr doping at Co2 site and Os doping at Ni3 site can improve the interface bonding strength. The ideal tensile test reveals that Cr and Os doping can increase the max tensile strength of NiCo coating (along the 〈101〉 direction), and Cr doping increased by 34%. The analysis of atomic position and bond length shows that the tensile failure occurs inside the Cu atom layers. By the electron properties, the strengthening effect is attributed to the enhanced covalent properties between the Cr-Ni or Co atoms. The electron location function and charge density map intuitively reflect the origin of crack of interface structure in the stretching process. In summary, the Cr and Os doping not only strengthen the tensile strength of NiCo coating itself, but also improve the interface bonding strength, which is worthy of further study.

Keywords

• EBSD
• Texture
• Interface
• First principles
• Tensile