The effect of interstitial solutes on the twinning stress of b.c.c. metals

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Abstract
Flow stress measurements at −196°C on Fe-4.8 at. % Sn-C alloys demonstrate that the presence of interstitial carbon markedly increases the stress for deformation by twinning. The flow stress for an alloy with 0.09 at. % carbon is 12.6 Kg/mm2 higher than the flow stress for a carbon-free alloy. This behaviour, which is an exception to the rule that twinning stresses are relatively invariant to solute content, was anticipated because the normal twinning mode in ferrite does not shear all interstitial atoms to proper octahedral sites. In confirmation of this viewpoint, the experimental results were found to be in reasonable agreement with a theoretical estimate of the change in twinning stress that should result from this crystallographic restraint.