Strain-Rate Dependence of Tensile Behavior in Commercial-Grade Tungsten-Effect of Recrystallization Condition.

The tensile deformation behavior of double-forged (DF-W) and recrystallized (RX-W) commercial-grade tungsten was investigated at 700 °C. With increasing strain rate, the dominant dynamic recrystallization (DRX) mechanism changes from continuous dynamic recrystallization (CDRX) to discontinuous dynamic recrystallization (DDRX). For DF-W, pre-existing sub-grains promote CDRX and associated a high-DRX fraction, resulting in reduced post-necking strain under a static condition. With increasing strain rate, a shift in the restoration mechanism from CDRX to DDRX contributes to the enhanced ductility in DF-W, while RX-W shows enhanced flow hardening without a loss of ductility. These results suggest that the strain-rate dependence of mechanical behavior depends on the initial microstructure.