Mechanisms of Submicrocrystalline Structure Formation in Titanium and Two-phase Titanium Alloy during Warm Severe Processing

摘要

Mechanisms of Ti and Ti-6Al-4V titanium alloy microstructure refinement to submicron range during warm "abc" deformation have been studied. The "abc" deformation was consisted of successive compression of sample along three orthogonal directions. Microstructure refinement in titanium was found to be a result of high angle boundaries formation within initial grains. Those boundaries were produced by both rearrangement and accumulation of dislocation and twinning. Appearance of new boundaries was associated with strengthening of titanium. However, a steady state flow was observed at the last stages of deformation due to accommodation of microstructure under strain path changing. In two-phase Ti-6Al-4V alloy the initial lamellar structure has been transformed into the submicron globular one during "abc" deformation. Globularization of the alloy microstructure was associated with softening and superplastic flow.