Lattice Distortion in Nickel-Iron

Abstract

RECENT investigations of W. A. Wood¹ on the broadening of high-order Debye-Scherrer lines of copper and -brass have shown that the lattice distortion may be accompanied by changes in the spacings of various lattice-planes, pointing to a change in shape and (perhaps) size of the unit cell. The occurrence of such an effect can be very clearly shown for nickel-iron. For an alloy with 53 atomic per cent Fe, the side-length of the unit-cube a is 3.58 A., so that the (400)-reflections with cobalt K₁ and K₂ radiation occur at about 85° and 87° respectively, and thus show extremely large dispersion (the distance of the _{1 2}-lines for a specimen to film distance of 12 cm. being about 7 mm.). Back-reflection photographs of discs, cut from recrystallised cold-rolled band, show these reflections with great intensity, as the recrystallisation texture is a very pronounced cube-texture (Würfellage), all crystals lying with a cube-face and side within ±10° parallel to the plane and direction of rolling². The effect of compression-deformation is shown in Fig. 1, where a relates to the original disc, b to the same disc after compressing it to about 10 per cent (the discs were rotated about an axis parallel to the X-ray beam). The shift of the ₁₂-lines amounts to about one sixth of their distance apart, corresponding to a decrease in spacing of about 0.04 per cent.