The variation of lattice parameter, saturation magnetization, and Curie temperature on the addition of Ti4+, Zr4+, and Sn4+ to some Ni-Zn ferrite compositions are reported and the results are explained on the basis of the movement of the substituting ions first to the tetrahedral and finally to the octahedral sites of the spinel lattice.

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The effect of plastic strain on the deformation microstructure has been investigated in polycrystalline copper rolled at room temperature to 5,10,20, and 30% reduction in thickness (equivalent strain 0'06-0'42). Resultsfrom transmission electron microscopy (TEM) observations show that dense dislocation walls (DDWs) and cells develop during the initial stages of cold rolling. Grains having a high density of DDWs are described as high wall density (HWD) structures, and grains having a low density of DDWs are described as low wall density (LWD) structures. These structures are characterised by cell size, misorientation across the cell walls, and the crystallographic orientation of the grains in which they appear. The DDWs in the HWD structures have special characteristics, extending along several cells and having a misorientation across them greater than that across ordinary cell boundaries at the same strain. The DDWs appear to have a macroscopically determined orientation. Analysis of their crystallographic orientation shows that they are not, asfrequently reported in the literature, parallel to {111} planes. It is suggested that the DDWs separate regions of the crystal having different operating slip systems. Two generations of microbands are found to develop with increasing deformation. The first generation microbands are related to a continuous development of the structure according to the principle of grain subdivision, whereas the second generation microbands relate to localised shear on {ill}. Finally, the evolution of the deformation microstructure in copper is compared with that observed in other face centred cubic metals, especially aluminium.MST/1273

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