The effects of mixing non-metal atoms in the B1 structured transition metal carbo-nitrides on their structure and mechanical properties: HfC1-xNx

Abstract

In this paper, we utilize density functional theory to explore how alloying the carbide and nitride of a group IVB transition metal affects the phase stability and mechanical properties; we place an emphasis on elastic and dislocation properties, taking the HfC-HfN system as an example. An evolutionary algorithm is used to identify the ordered carbonitrides and the enthalpies of formation are compared with special quasi-random structures to identify this system's tendency to order and form a solid solution. The variation of elastic constants with composition is examined, and the computed elastic constants are used to predict the theoretical hardness. The GSF curves for various compositions are computed to determine how alloying would affect dislocation behavior. These results show that while there may be a modest peak in elastic response, the resistance to dislocation motion does not particularly show a peak. Furthermore, the alloying of HfC with HfN reduces the resistance to slip almost universally, and helps stabilize dislocations on {111} planes through the stabilization of an intrinsic stacking fault. These results are compared to previous in-depth analysis of the HfC-TaC system, allowing for comparisons between metal and non-metal alloying strategies.

Keywords

• Ultrahigh temperature ceramics
• Carbides
• Nitrides
• Modeling
• Theory
• Mechanical properties