The Utility of Torsion in Hot Workability Testing of Metallic Materials

Abstract

The hot torsion test has proven very versatile in determining high temperature (> 0.5 T_m) characteristics at constant strain rates of l0^-3 to 10² s^-1.The stress-strain and strain hardening curves are suitable bases for constitutive equations giving temperature and strain rate dependencies. Critical points in the above curves in association with metallography clarify the progress of the restoration mechanism and the influence of solutes, precipitates and inclusions. The ductility is related to how the softening mechanisms delay the fracture mechanisms ssmming from the alloy structure. The rate of static softening after hot deformation is determined by comparing the yield stress on reloading after an interval to that before it; many measurements for different times can be carried out on a single specimen by recrystallizing it between each stage in the torsion apparatus. The physical simulation of rolling schedules having many passes with declining temperature and rising strain rate is possible on computerized machines