First principle predictions of anomalous yield strength in L1₂ materials

Abstract

By using previous energy based arguments for screw dislocation cross-slip from (111) to (001) now combined with verifying antiphase boundary (111) stability and the width of subsegment complex stacking fault, we construct a simple plot that predicts the existence of yield strength anomaly and its relative strength. We construct the plot from calculating planar-fault energies, i.e. antiphase boundary (APB), complex and superlattice intrinsic stacking faults (CSF and SISF) and their stability for a range of L1₂ based intermetallics using ab initio electronic structure methods. Our plot reproduces the relative order of observed values of anomalous peak temperatures. The importance of determining the stability of APB(111) and the role of chemical (thermal antisite) disorder is also discussed.

Keywords:

• First principle calculations
• Defects
• Yield phenomena
• Intermetallic

Acknowledgements

The authors are grateful for the financial support from the Key Laboratory of Advanced Materials, and the National Natural Science Foundation of China (50971072, 51131003), the Ministry of Science and Technology of China (973 Program 2011CB606301, 2012CB825700) and the Administration of Tsinghua University.