Mechanism of Secondary Recrystallization in 50% Nickel-Iron Alloys

Abstract

Secondary recrystallization in 50% nickel‐iron alloys results predominantly in {112} and {120} textural components. The beneficial effects of {120} textures on the magnetic properties of toroidal wound cores have been reported, and the effects of impurities and surface energies in promoting {120} growth have been discussed in the technical literature. Therefore, an understanding of the mechanism of secondary recrystallization in these alloys is pertinent. A strong {100}〈001〉 texture is developed by the primary recrystallization of cold rolled 50% nickel‐iron. It is demonstrated in the present study that during heat treatment the non‐coherent boundaries of {221} first order annealing twins partially or completely sweep adjacent grains in the {100}〈001〉 textured matrix to produce enlarged grain segments in the {221} orientation, and it is proposed that the {221} grains are the nuclei for secondary recrystallization. On further annealing an incubation period occurs during which essentially no growth of the {221} grains is observed. During eventual secondary recrystallization the {221} grains, after some growth, twin massively to form the predominant secondary orientations, {112} and {120}. The {112} and {120} secondaries, therefore, bear a second order twin relationship with the {100}〈001〉 primary matrix. The boundaries of the {112} and {120} twins are not coherent with the matrix and consequently migrate very rapidly.