Phase transformation and microstructure evolution in ultrahard carbon-doped AlTiFeCoNi high-entropy alloy by high-pressure torsion

Mechanical properties of high-entropy alloys (HEAs) have received significant attention, while there are still attempts to find new strategies to further improve their properties. In this study, to produce an ultrahard HEA, an FCC carbide was introduced in a BCC-based AlTiFeCoNi alloy by the assistance of CALPHAD thermodynamic calculations. The alloy was synthesized by arc melting and processed by severe plastic deformation via the highpressure torsion (HPT) method to generate defects. The material showed nanograin formation, dislocation accumulation, carbide fragmentation, L21 -> BCC ordered-to-disordered phase transformation, and accordingly an ultrahigh hardness of 950 Hv after HPT processing.

Automated summary

By introducing an FCC carbide into a BCC-based AlTiFeCoNi alloy with the assistance of CALPHAD thermodynamic calculations, an ultrahard HEA was produced and processed through severe plastic deformation via the high-pressure torsion method, resulting in nanograin formation, dislocation accumulation, carbide fragmentation, L21 -> BCC ordered-to-disordered phase transformation, and achieving an ultrahigh hardness of 950 Hv.