Abstract
The α– β titanium alloy with fine grained equiaxed microstructure exhibits structural superplasticity. The characterisation of the constitutive behaviour of the α+ β titanium alloy Ti–6.4Mo–1.5Cr–0.4Fe–0.3Si in the temperature–strain rate domain of superplasticity revealed an increase in grain size exponent p with the temperature of deformation. This increase in p was attributed to the decrease in the Widmanstatten content in β grains. As Widmanstatten content decreased with increase in temperature, the volume fraction of α in the mantle region and the fraction of α–α boundary decreased. This results in a decrease in the contribution of the non-superplastic deformation in the core and an increase in the contribution of the superplastic mechanism in the mantle. Since p is high (2 to 3) for the superplastic mechanism, p increases with the increase in temperature.
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