r-values of Ti–6Al–4V sheet after superplastic strain

Abstract

The plastic strain ratio r of Ti–6Al–4 V sheet was measured after superplastic strain at 925°C and the effects of sheet thickness and testpiece shape on r were investigated. The r-values were related to directionality in the microstructure and increased with superplastic strain towards unity, representing increasingly isotropic behaviour, as the microstructure became more equiaxed. The r-values were also influenced by the constraining effect of the testpiece heads on the width strain in the gauge length. This effect was reduced as the length-to-width ratio of the undeformed gauge length was increased.

MST/465