The plastic deformation of non-cubic metals by heating and cooling

Several pure metals were subjected to cyclic thermal treatment between 30 and 150° C. Specimens of zinc, cadmium and tin showed signs of plastic deformation which were evident after a small number of cycles, and which became more pronounced as the number of cycles increased. On the other hand, the phenomenon was not observed in lead. Evidence is brought forward to show that this deformation is due to the anisotropy of thermal expansion in the crystals of non-cubic metals. The persistence of the lattice distortions is shown by X -ray photographs, and also by recrystallization subsequent to the cyclic treatment. In certain metals, grain boundary migration is associated with the deformation. The implications of the phenomenon are particularly exemplified in a comparison of certain tin-base and lead-base bearing alloys. Some possible theoretical and practical implications of the phenomenon are discussed.