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

The progress of high temperature deformation in samples of two commercial 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 SP structure and higher strain rate sensitivity than those with completely non-SP structure. Samples with SP layer demonstrate a more pronounced decrease in strain rate sensitivity with the increase of strain than samples with completely SP structure, Deformation in the SP layer proceeds 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 boundary surfaces, provides the main contribution to the total strain.