Secondary Recrystallization in High-Purity 49% Ni-Fe

Abstract

In 1962 Benford and Lindsay showed that secondary recrystallization temperature in a 49% Ni‐Fe alloy of commercial purity depends upon the degree of texture developed as a function of penultimate grain size (PGS) and percent of last cold reduction. The objective of this investigation was to determine the effect of these variables in a 49% Ni‐Fe alloy of high purity. An electrode, prepared from Fe and Ni powders, was vacuum‐consumable melted, forged, and hot‐rolled. Cold rolling was done with intermediate anneals to produce two penultimate grain sizes followed by reductions of 86.6%, 90.0%, and 93.0% to 0.014 in. thick. Permeability measurements, magnetic anisotropy measurements, macrostructure examinations, and Laue transmission patterns were made on samples annealed at different temperatures in dry hydrogen. The results show that both PGS and percent cold‐reduction influence sharpness of the primary recrystallized texture, which agrees with the earlier work. This study, however, indicates that sharp primary textures result in higher secondary recrystallization temperatures. It is concluded that high initial permeability, after annealing at moderate temperatures, requires a large PGS and lesser percent final cold reduction. The results further suggest that for square hysteresis loop characteristics over a relatively broad annealing range, one should start with a small PGS and greater percent cold reductions.