Achieving compressive plasticity in CrMoNb multi-principal element alloy by Ti addition for excellent strength-plasticity synergy at room and high temperatures

Compressive plasticity is successfully introduced into brittle CrMoNb multi-principal element alloys (MPEAs) by Ti addition. This endows the MPEA family exceptional mechanical properties across a broad temperature spectrum. Ti modifies C14 and C15 Laves phases in the MPEAs and lowers the Peierls-Nabarro stress for dislocation movement in the hybrid BCC matrix, leading to remarkable plastic deformation enhancement. The fracture mode of the MPEAs under compression, as the Ti content increases, evolves from completely brittle fracture to cleavage fracture, and eventually to cleavage and ductile combined fracture. Both characterization and thermodynamic calculation confirm the microstructural evolution of the MPEAs with increasing Ti content. Excellent strength-plasticity synergy is achieved by equiatomic CrMoNbTi. It exhibits a room temperature yield strength of 1717 MPa coupled with a fracture strain of 9.7%. Notably, CrMoNbTi shows outstanding resistance to thermal softening outperforming traditional superalloys; it demonstrates an impressive yield strength of 1093 MPa at 1073 K facilitated by the presence of Laves phases. Systematic investigation into the deformation behavior of CrMoNbTi reveals diverse deformation mechanisms, including the slip and cross-slip of mixed dislocations and the formation of kink bands within deformed grains. CrMoNbTi exhibits superior mechanical properties to a wide range of MPEAs at both room and elevated temperatures, making it a promising candidate for demanding application environments.