On the Twist Effect of V-h Alloys Associated with the Precipitation of Hydrides

A vanadium wire containing hydrogen begins to twist by itself, when cooled, at the onset of hydride precipitation. The magnitude of the twist is greatly increased, if the specimen is plastically deformed in torsion prior to observations. The effect of the elastic stress is systematically studied by observing the zero point drift on cooling and heating under the applied torque; both the precipitation and the dissolution processes are found to be affected by the external stress. Hydrides in vanadium is known to precipitate in the form of platelets along particular crystallographic planes. The twist effect can be interpreted as the preferential precipitation (dissolution) of one type of platelets over others under the effect of external or internal stresses.