AbstractThe 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 onrwere investigated. Ther-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. Ther-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