Hot rolling and superplastic forming response of net shape processed Ti-6Al-4V produced by centrifugal spray deposition

摘要

The hot rolling and superplastic forming response of Ti-6A1-4 V deposits, produced using a unique low pressure centrifugal spray deposition (LPCSD) facility, have been examined. Fundamental information has been generated relating to the parameters which govern microstructural development (porosity distribution, grain size, andα/β phase volume fraction) both during the deposition process and following post-spray thermomechanical processing. As sprayed deposits were characterised by relativelycoarse transformedβ microstructures, withα lath and priorβ grain sizes varying from about 0.6 to 1.1μm and from 70 to 400μm respectively, depending on the spray forming environment (Ar or vacuum) and the position within the preform. Despite thesecoarse microstructural features, and relatively high levels of porosity, single and multi pass hot rolling reductions of up to 80% were successfully achieved, yielding microstructures and strain rate sensitivity factors (m values) compatible withsuperplastic forming grade sheet specifications.