Mechanical properties of low-density, refractory multi-principal element alloys of the Cr–Nb–Ti–V–Zr system

Abstract

Room temperature and elevated temperature mechanical properties of four multi-principal element alloys, NbTiVZr, NbTiV2Zr, CrNbTiZr and CrNbTiVZr, are reported. The alloys were prepared by vacuum arc melting followed by hot isostatic pressing and homogenization. Disordered BCC solid solution phases are the major phases in these alloys. The Cr-containing alloys additionally contain an ordered FCC Laves phase. The NbTiVZr and NbTiV2Zr alloys showed good compressive ductility at all studied temperatures while the Cr-containing alloys showed brittle-to-ductile transition occurring somewhere between 298 and 873K. Strong work hardening was observed in the NbTiVZr and NbTiV2Zr alloys during deformation at room temperature. The alloys had yield strengths of 1105MPa and 918MPa, respectively, and their strength continuously increased, exceeding 2000MPa after ∼40% compression strain. The CrNbTiZr and CrNbTiVZr alloys showed high yield strength (1260MPa and 1298MPa, respectively) but low ductility (6% and 3% compression strain) at room temperature. Strain softening and steady state flow were typical during compression deformation of these alloys at temperatures above 873K. In these conditions, the alloys survived 50% compression strain without fracture and their yield strength continuously decreased with an increase in temperature. During deformation at 1273K, the NbTiVZr, NbTiV2Zr, CrNbTIZr, and CrNbTiVZr alloys showed yield strengths of 58MPa, 72MPa, 115MPa and 259MPa, respectively.