The superplastic behaviour of gas atomised and mechanically milled Ti-6Al-4V powder

摘要

Superplastic forming of conventional titanium alloy sheet is limited commercially by the relatively long cycle times imposed by the high temperatures and slow strain rates required for forming. In order to minimise cycle times material with a fine grain size is required to enable increases in the forming rate and/or reductions in the deformation temperature. This study details an investigation of the production of fine grained Ti-6Al-4V. Ti-6Al-4V powder with nanocrystalline grains was produced by mechanical milling (MM). However, the grain size coarsened rapidly during hot isostatic pressing (HIPing). Superplastic testing revealed cavitation formation and low elongations to failure in comparison with conventional wrought material. This behaviour is discussed in terms of the microstructural development and potential argon entrapment.