Effect of temperature rise on microstructural evolution during high-pressure torsion

Dynamic recrystallization occurs at room temperature during high-pressure torsion (HPT) leading to the formation of ultrafine grains with high angles of misorientation. There are questions concerning whether dynamic recrystallization occurs due to the temperature rise during severe plastic deformation or due to the effect of lattice defects. In this study, the real temperature rise was measured by directly placing a thermocouple separately on disc samples of tin, aluminum, silver, copper and titanium. The measurements, which are consistent with finite element simulations, show that the temperature rise is of minor significance in initiating dynamic recrystallization. A relationship is developed to predict the temperature rise in HPT.