Strain effect on grain refinement and thermal stability of ultrafine-grained molybdenum processed by severe plastic deformation

摘要

Ultrafine-grained molybdenum was obtained by equal channel angular pressing and high-pressure torsion at 673 K. Microstructure evolution and thermal stability were investigated by electron backscatter diffraction, transmission electron microscopy and heat treatment. The generation of ultrafine grains is strain dependent. The influence of dislocation cells on grain refinement saturates to a constant level with the increasing strain, and then the grain refinement mechanism turns into continuous dynamic recrystallization. The ultrafine-grained microstructure after heating consists of homogeneous fine grains with high microhardness due to continuous static recrystallization, which demonstrates the nobler thermal stability.