Generalized stacking fault energies and ideal strengths of MC systems (M = Ti, Zr, Hf) doped with Si/Al using first principles calculations

Highlights: • The effects of Si/Al impurities on deformation behaviors of carbides are studied. • Dislocation glide may be turn to twinning with the increase of Si/Al impurities. • Compared with MC, the ideal strengths of M₃(Si/Al)C₂ decreases obviously. • M₃SiC₂ systems possess better mechanical properties than M₃AlC₂. The IVB transition metal carbides, MC, (M = Ti, Zr and Hf, respectively) and the synthesis of M₃(Si/Al)C₂ have been extensively studied due to their excellent mechanical, thermal and electrical properties. In this work, the effects of solute atoms (Si/Al) on the deformation mechanism and ideal strengths in various MC (M = Ti, Zr, Hf) systems are investigated systematically using first principle calculations. The deformation mechanisms of MC may vary from the glide of perfect dislocation to twinning once Si/Al solute atom concentration (η) in the glide plane reaches some critical value, indicating that the stacking faults and twin structures may appear in the region with high solute concentration, such as grain boundary, which agrees with the experimental results. Compared with MC, the ideal tensile/shear strengths of M₃(Si/Al)C₂ decreases obviously, which can be attributed to weak M–(Si/Al) bonds in contrast to M–C bonds.