2016 Volume 57 Issue 11 Pages 1859-1867
The coercive force of an iron powder core decreases with an increase in the circularity of the base iron powder. Microstructural observation reveals that the crystal grain size of the iron powder core is reduced by recrystallization during stress relief annealing after powder compaction. An analysis of the work hardening behavior during the compaction process shows that a rounder particle shape leads to smaller particle deformation, resulting in a reduced grain refinement effect during recrystallization. A grain boundary pinning model convincingly describes the reduction of coercive force with the increase in the eventual grain size.
This Paper was Originally Published in Japanese in J. Japan Inst. Met. Mater. 79 (2015) 315–323.