Stacking fault, dislocation dissociation, and twinning in Pt3Hf compounds: a DFT study

The Pt3Hf compound plays a decisive role in strengthening Pt-Hf alloy systems. Evaluating the stacking fault, dislocation dissociation, and twinning mechanisms in Pt3Hf is the first step in understanding its plastic behavior. In this work, the generalized stacking fault energies (GSFE), including the complex stacking fault (CSF), the superlattice intrinsic stacking fault (SISF), and the antiphase boundary (APB) energies, are calculated using firstprinciples calculations. The dislocation dissociation, deformation twinning, and yield behavior of Pt3Hf are discussed based on GSFE after their incorporation into the Peierls-Nabarro model. We found that the unstable stacking fault energy (gamma(us)) of (111)APB is lower than that of SISF and (010) APB, implying that the energy barrier and critical stress required for (111)APB generation are lower than those required for (010)APB formation. This result indicates that the a < 1 (1) over bar0 > superdislocation will dissociate into two collinear a/2 < 1 (1) over bar0 > superpartial dislocations. The a/2 < 11 (1) over bar0 > dislocation could further dissociate into a a/6 < 1 (1) over bar2 > Shockley dislocation and a a/3 < 2 (1) over bar(1) over bar > superShockley dislocation connected by a SISF, which results in an APB -> SISF transformation. The study also discovered that Pt3Hf exhibits normal yield behavior, although the cross-slip of a a/2 < 1 (1) over bar0 > dislocation is not forbidden, and the anomalous yield criterion is satisfied. Moreover, it is observed that the energy barrier and critical stress for APB formation increases with increasing pressure and decreases as the temperature is elevated. When the temperature rises above 1400 K, the a/2 < 1 (1) over bar0 > dislocation slipping may change from the {111} planes to the {100} planes.

Automated summary

In this study, the role of Pt3Hf compound in strengthening Pt-Hf alloy systems was investigated through first-principles calculations of stacking fault energies. It was found that Pt3Hf exhibits normal yield behavior, and the energy barrier for APB formation increases with temperature. Additionally, the study revealed that the slip behavior of a/2 < 1 (1) over bar0 > dislocation may change with temperature elevation.