Structure and mechanical properties of the AlCrxNbTiV (x = 0, 0.5, 1, 1.5) high entropy alloys

Abstract

The AlCrxNbTiV (x = 0, 0.5, 1, 1.5) high entropy alloys were produced by vacuum arc melting. The crystal structure, microstructure, density and compression mechanical properties at 22°C–1000 °C of the AlCrxNbTiV alloys after homogenization annealing at 1200 °C for 24 h are reported. After homogenization the AlNbTiV and AlCr0.5NbTiV alloys consist from single bcc solid solution phase, while the AlCrNbTiV and AlCr1.5NbTiV alloys contain bcc phase and respectively 13% and 35% of hexagonal (C14) Laves phase. The density of alloys increases with increase of Cr content from 5590 kg m−3 of the AlNbTiV alloy to 5900 kg m−3 of the AlCr1.5NbTiV alloy. The strength of the AlCrxNbTiV alloys increases with increase of Cr concentration at temperatures from room to 800 °C. The yield strength of the AlNbTiV and AlCr1.5NbTiV alloys is 1000 MPa and 1700 MPa respectively at room temperature and 560 MPa and 970 MPa at 800 °C. Strengthening of the AlCrxNbTiV alloys with increase of Cr content is accompanied by decrease of ductility. Phase composition of the alloys was affected by deformation at 800 °C and 1000 °C. In the AlNbTiV and AlCr0.5NbTiV alloys Nb2Al-type phase precipitated predominantly on grain boundaries, while in the AlCrNbTiV and AlCr1.5NbTiV alloys additional amounts of Laves phase appeared inside grains of bcc matrix. The experimentally observed phase composition of the AlCrxNbTiV alloys is compared with results of thermodynamical modeling of equilibrium phases in the alloys. The effect of phase composition of the alloys on mechanical properties is discussed and possibilities for properties optimization of the Al–Cr–Nb–Ti–V high entropy alloys are suggested.