The grain-size dependence of tensile properties in hydrogenated vanadium

Abstract

A transition from ductile to brittle behaviour has been observed as a consequence of increasing the grain size in unnotched tensile testpieces of vanadium containing 12 ppm (by weight) of hydrogen when tested at 195 K with a strain rate of 10⁻¹s⁻¹. Application of the Cottrell relationship σ_yk_yd^½ = βμγ for the ductile→brittle transition to the results gives a value of 1.32 J m⁻² for the surface energy of the hydrogenated V. This value is well below that reported for hydrogen-free V and is attributed to the effect of H in solid solution which also increases the dislocation locking strength.