Change in the structure of hot-worked austenite in nickel steels during post-deformation holding
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Hot deformation and brief (<2 sec) holding at high (900\dg) temperatures is accompanied by softening processes in nickel steels 60N20 and 80N18 \3- polygonization and recrystallization of austenite \3- which leads to irregularities in the substructure through the volume.
With increasing deformation, and with the same deformation but increasing carbon concentrations, the volume recrystallized and the volume of polygonized substructure in the deformed matrix increase.
With post-deformation isothermal holding the polygonized substructure is rebuilt, static polygonization occurs, and also static recrystallization. The rate of these softening processes increases with increasing deformation, decreasing size of the original austenite grains, and increasing carbon concentrations.
Under the deformation conditions selected the final structure of the steels investigated depends on the development of recrystallization. Up until completion of primary recrystallization the size of the recrystallized grains remains \s<10 μ and the dislocation density remains high.
KeywordsNickel Austenite Recrystallization Final Structure Dislocation Density
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