Strain-hardening properties of the high-entropy alloy MoNbTaTiVZr processed by high-pressure torsion
Chuyi Duan, Marius Reiberg, Peter Kutleša, Xiaohu Li, Reinhard Pıppan, Ewald Werner
Abstract
Abstract An equiatomic MoNbTaTiVZr refractory high-entropy alloy (HEA) produced by arc melting was processed by high-pressure torsion (HPT) at room temperature. Thermodynamic calculations and experimental results indicated a dual-phase microstructure composed of about 85% BCC Zr-depleted and 15% BCC Zr-rich phase in the as-cast condition. HPT causes grain refinement and an increase in dislocation density without the formation of new phases. After four revolutions, the Zr-depleted phase was hardened to $$\sim $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> </mml:math> 540 HV, while the Zr-rich phase exhibited softening with a decrease in hardness to $$\sim $$ <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mo>∼</mml:mo> </mml:math> 480 HV. The occurrence of a vortex-like microstructure and the analysis of elemental concentrations indicated a shear-induced mechanical homogenization, which was supposed to be the cause of the observed softening.