STABILITY OF THE DISLOCATION SUBSTRUCTURE OF ALPHA-TITANIUM AGAINST DEFORMATION TEMPERATURE-VARIATION IN THE RANGE 4.2-293-K

The dislocation substructure of polycrystalline alpha-Ti of commercial purity after tension with the test temperature changed in various sequences between 4.2, 77 and 293 K has been studied by the TEM method. The stability of elements of the substructure characteristic of certain deformation temperatures to the deformation temperature changes has been studied. It has been found that reorientation bands (RB's) arising from predeformation at 293 K during subsequent deformation at 4.2 and 77 K gradually degrade and are subject to fragmentation by low-temperature twins for which they are not insurmountable obstacles. If the temperature is changed in the reverse sequence, formation of RB's is impeded or even suppressed and low-temperature twins become insurmountable obstacles for RB's. Processes of nucleation, development of new substructures and their interaction with initial ones are discussed.