First-principles study on the effects of the alloying elements on the structural stability and mechanical properties of [formula omitted] (X = Al, Hf, Zr) interfaces

Abstract

Pt-based alloys are promising materials for high-temperature and special applications. The introduction of γ/γ' microstructures is an effective way to improve the high-temperature mechanical properties of Pt-based alloys. Due to the instability of the γ/γ' two-phase microstructures, the addition of alloying elements is necessary. However, systematic studies of alloying effects on γ/γ' interfaces in Pt-based alloys are still lacking. In this work, the first-principles calculations are performed to investigate the γ-Pt/γ'-Pt3X (X = Al, Hf, Zr) interface properties, and the effects of the six alloying elements (Ni, Cr, Ru, Re, Ti and Ta) on the structural stability and mechanical properties of the interface are further explored. The results show that the alloying elements investigated in this work all prefer to partition to γ-Pt matrix due to the lower formation energies. The negative interface energy of the unalloyed Pt/Pt3Al, Pt/Pt3Hf and Pt/Pt3Zr interfaces indicates the instability of the interface. By changing the interface energy, Ti and Ta tend to increase the stability of Pt/Pt3Al interface, while Ni has the potential to increase the stability of Pt/Pt3Hf interface and Pt/Pt3Zr interface. Moreover, the alloying elements increase the bonding strength of the γ-Pt/γ'-Pt3X interfaces in the order of Ni < Ru < Cr < Re < Ti < Ta. The analysis of the electronic structure shows that the strong covalent interaction between Pt atom and X atom may be the reason for precipitates strengthening, and the strengthening effect of the alloying elements is closely related to the distribution of their density of states around Fermi level. Our systematical analysis of the alloying effects on γ/γ' interfaces is expected to provide guidance for the design of high performance Pt-based alloys.