| AVS 55th International Symposium & Exhibition | |
| Thin Film | Wednesday Sessions |
| Session TF-WeA |
| Session: | Computational and Experimental Studies of Thin Films |
| Presenter: | V. Chirita, Linköping University, Sweden |
| Authors: | D.G. Sangiovanni, Linköping University, Sweden V. Chirita, Linköping University, Sweden L. Hultman, Linköping University, Sweden |
| Correspondent: | Click to Email |
TiN-based thin films, such as Ti1-xAlxN and their alloys, are known to have excellent mechanical and thermal properties. In this paper we report the initial results of our ab-initio investigations of two novel ternary compounds, Ti1-xWxN and Ti1-xMoxN, obtained by alloying TiN with W, respectively Mo, in concentrations of up to 50%. The elastic constants as well as the bulk, shear and Young’s moduli of these compounds were evaluated using density functional theory calculations within the generalized gradient approximation, and compared with the corresponding properties of TiN and Ti1-xAlxN. Significantly, we found that the addition of W and Mo resulted in substantial increases in bulk modulus values compared to TiN (up to 15%) and Ti1-xAlxN (up to 30%). At the same time, we observed a dramatic decrease (up to 50%) in the values of C44, and a reversal of the Cauchy pressure, C12-C44, from negative to positive, results indicative of significantly increased ductility in these compounds. Both of these trends are in total contrast to what is known for Ti1-xAlxN, which exhibits increased C44/brittleness and lower bulk modulus values as the Al content is increased. We also investigated, in the same manner, the effects of alloying Ti0.5Al0.5N with W and Mo, in concentrations of up to 6% and observed a similar trend in increasing hardness and ductility. However, in the case of quarternary TiAl(W/Mo)N, the impact of W and Mo addition was considerably more moderate, as the increase in bulk modulus, respectively decrease in C44, were in the 5% range. As it will be shown, these results demonstrate and help understanding the mechanisms through which W and/or Mo additions modify the atomic bonding in these compounds, from a strong angular/directional character, towards a more metallic type of bonding. This type of electronic structure information is essential in designing compounds with different mechanical properties and tailoring them to a variety of applications.