Comparative investigations of superplastic behavior and processing properties (formability an solid state weldability) of commercial sheets with microcrystalline (MC, a grain size of 3 µm), nanocrystalline and submicrocrystalline (NC and SMC, a grain size of 0.1…0.8 µm) structure out of titanium Ti-6Al-4V alloy have been performed. It is shown that the decrease in the grain size leads to a significant decrease in the temperature of superplastic deformation to 500-650°C, or to a shift of superplasticity optimum to higher strain rates at temperatures above 600-650°C. The process of superplastic forming (SPF) and pressure welding (PW) of sheet samples out of Ti-6Al-4V alloy with NC and SMC structure at the temperatures 600-800°C was investigated. Unlike commercial sheets, the sheets with NC and SMC structure are characterized by isotropy of mechanical properties and isotropic formability. Nanocrystalline and submicrocrystalline processed Ti-6AL-4V sheet can be successfully used in SPF/PW processes. The temperature range of superplastic forming and pressure welding can be between at 600 and 800°C.
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