Twinning-dominated microstructure evolution and deformation mechanism during cold rolling in pure rhenium

Abstract

The extremely high work hardening rate and the high cracking propensity were the main challenges that limit the successful deformation processing of rhenium. Rolling tests to 82% thickness reduction were conducted at room temperature, and three-stage twining evolution behavior was revealed. At 10% rolling reduction, primary {112¯1} tension twins were activated and dislocation accumulation appeared near the twin boundary. As the rolling reduction increases to 45%, twin-twin interactions prevailed and abundant GNDs accumulated around {112¯1} twin boundaries and {112¯1} twin- {112¯1} twin interactions. More importantly, A new twinning sequence behavior in rhenium, secondary {112¯1} twins within primary {112¯1} twins, was investigated. After twinning saturation, shear bands were formed due to the promoted local plastic deformation by the twin lamellar structure and submicron-scale isolated twins, which brought pronounced strengthening of rhenium. The extremely high work hardening rate of rhenium was found to mainly originate from the twin lamellar structure and twin-twin interactions. High temperature annealing released the stored strain energy, achieving a synergistic effect of high tensile strength and ductility. This study provides a systematic investigation into the deformation structure during the large reduction cold rolling in rhenium and provides insights into unique twinning evolution and shear bands.