An electron microscopy examination of primary recrystallization in TD-nickel

Abstract

Primary recrystallization in TD-nickel 1 in. bar has previously been regarded as the process by which the initial fine grain structure (1μ average grain radius) is converted to a coarse grain size (increases in grain size by 500 times) under suitable deformation and annealing conditions. This process is dependent on deformation mode. While it occurs readily after rolling transverse to the bar axis and annealing (800°C), it is completely inhibited by longitudinal rolling and swaging deformations, even for very high (1320°C) annealing temperatures. A transmission electron microscopy examination of deformation and annealing substructures indicates that primary recrystallization in TD-nickel 1 in. bar actually occurs on the sub-light optical level, to produce a grain structure similar in size to the initial fine grained state. Coarse grain formation is the result of abnormal grain growth (or secondary recrystallization), which follows primary recrystallization.