Features of Mechanical Behaviour and Structure Evolution of Submicrocrystalline Titanium under Cold Deformation

Summary

Essential technology progress in the methods of severe plastic deformation (SPD) that was reached at last time let to receive structures with submicrocrystalline (SMC) grain sizes (0.1–1 m) in massive billets. Experimental study of their deformation behaviour showed, that SMC materials possess not ordinary combination of physics-mechanical properties. In one aspect it was noted changes of density, modulus of elasticity, diffusion activity and deviation from Hall–Petch law [1]. These cases (in combination with considerable boundaries extent increasing and their «unequilibrium» state) let authors [2] to assume about qualitative change: together with dislocation gliding in grains interior the activation of grain boundary sliding (GBS) took place, even during cold deformation. At the same time, it was found considerable strength increasing [1], presence of high dislocation density [3] and essential internal stress [1, 4], forming of crystallographic and metallographic texture [3]. All of these facts together evidence of intensive dislocation gliding in grains interior and it can be explained in frame of ordinary conceptions about grain size effect on mechanical behaviour.