Microstructure Development during Extrusion of Mechanically Alloyed Powder

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Microstructure Development during Extrusion of Mechanically Alloyed Powder

Sections from partially extruded bars of iron-base MA956 and nickel-base MA758 were studied using acombination of microscopy and heat treating methods. It was found that the mechanically alloyed powder,prior to extrusion , had a heavily deformied microstructure with hardness higher than the extrusion pro -ducts, and there was no dynamic recrystallization during the mechanical alloying process. Clear evidencerevealed dynamic primary recrystallization during extrusion in the nickel-base alloy, but not in the steel,inaccord with earlier observations of fully extruded materials. In MA758, primary recrystallization which normally happens during extrusion process can indeed be induced by simple high temperature heat treatment of the mechanically alloyed powder.