HIGH-TEMPERATURE DEFORMATION-BEHAVIOR OF TITANIUM SAMPLES WITH SUPERPLASTIC LAYER

The progress of high temperature deformation in samples of two commerc ial titanium alloys with superplastic (SP) structure, non-SP structure , and with an SP layer sandwiched between the non-SP regions has been studied on the scale of the entire deformed volume and on the scale of grain groups. The results of mechanical behavior showed that samples with SP layer exhibit higher stress level than those with completely S P structure and higher strain rate sensitivity than those with complet ely non-SP structure. Samples with SP layer demonstrate a more pronoun ced decrease in strain rate sensitivity with the increase of strain th an samples with completely SP structure, Deformation in the SP layer p roceeds as grain shear in a layer-by-layer manner, The deformation of SP layer through the operation of cooperative grain boundary sliding, i.e,, sliding of grain groups as an entity along certain grain boundar y surfaces, provides the main contribution to the total strain.