Superplastic Behavior of Ti–6Al–4V–0.1B Alloy

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The superplastic behavior of Ti–6Al–4V–0.1B sheet was evaluated. The strain rate sensitivity (m) is ≥0.47 in the temperature range 775–900 °C and at strain rate, ε˙ = 10−5 to 10−3 s−1. The material exhibits tensile elongations > 200% in the temperature range 725–950 °C at ε˙ = 3 × 10−4 s−1. The optimum superplastic forming temperature is 900 °C, which is similar to conventional Ti–6Al–4V. However, a lower flow stress is needed in the case of Ti–6Al–4V–0.1B. The superplastic deformation mechanism is suggested from estimates of activation energy to be grain boundary sliding (GBS) accommodated by dislocation motion along grain boundaries at ε˙ = 10−4 s−1 and is diffusion-controlled dislocation climb at ε˙ = 10−3 s−1. Microstructural observations also confirm that GBS is the operating deformation mechanism at 900 °C and ε˙ = 3 × 10−4 s−1.