Processing properties of nano- and submicro-crystalline Ti–6Al–4V titanium alloy

This paper reports the results of experiments on superplastic forming (SPF) and pressure welding (PW) performed with sheets of nano- and submicro-crystalline Ti–6Al–4V alloy. The decrease in the mean grain size of Ti–6Al–4V alloy sheets from 0.4 to 0.2 μm allows the decrease of the SPF temperature from 750 to 600 °C and the fabrication of cylindrical samples with appropriate shape, bending radius and thickness distribution. Due to the low temperature superplasticity flow stress, sound solid state joint (SSJ) for nanostructured Ti–6Al–4V alloy was obtained at 600 °C. The decrease of the mean grain size to nano- and submicro-crystalline sizes allows the application of the “low temperature superplasticity” for processing hollow components out of Ti–6Al–4V alloy by combining SPF and PW.