Energy of Lattice Distortion in Cold Worked Permalloy

Abstract

The lattice distortion produced by severe cold working of permalloy of 70 percent Ni content has been studied by measuring the broadenin of the reflection of the Fe $K\ensuremath{\alpha}$ doublet by the (311) planes, with a focusing camera. The broadening decreases upon annealing and recovery is complete at 650\ifmmode^\circ\else\textdegree\fi{}C, when the breadth of the x-ray intensity curve at half-maximum is as small as that obtained by use of the two-crystal spectrometer. The mean square distortion in the lattice spacing due to cold work is derived from the x-ray measurements after photo-metering the x-ray film, converting the curve into an x-ray intensity curve, fitting the latter with an empirical equation and using an analysis worked out by S. O. Rice. The energy of the distortion is then calculated by using an equation derived by G. R. Stibitz. The root-mean-square distortion was found to be 0.31 percent of the lattice spacing after the material had been reduced 96 percent in cross-sectional area by cold working. The energy of distortion in the hard worked condition is thus found to be 23\ifmmode\times\else\texttimes\fi{}${10}^{6}$ ergs/${\mathrm{cm}}^{3}$ or 0.065 calorie/gram.