Elevated temperature deformation: Hot working amplifies creep

Because creep research is motivated by restricting strain at high temperature, it generally considers rates below 10−4/s and failure in tension. Hot working studies aim to reduce hot strength and raise ductility at 10−2 to 10+2/s, applying similar dependence of stress and substructure on dynamic recovery. Deformation extending far into steady state permits evolution unrecognized in creep, to the extent of geometrically refining the grains and developing intense textures. The higher rates lead to higher misorientations so that multistage processing gives rise to static recrystallization, yielding refined microstructure. Although grain boundary sliding, much diminished at high rates, initiates failure, accommodation at triple junctions by recovery enhanced grain flow provides torsional strain >50 in metals with high stacking fault energy. In other metals, dynamic recrystallization refines grains and lowers strength while boundary migration retards cracking. In thermomechanical processing, substructures are developed for strength with toughness, for creep resistance, or for superplastic behavior.