Abstract
The effect of hydrogen on the ductility of tantalum single crystal was investigated in the temperature range of 77-396K using a variety of techniques including observation by the S.E.M., tensile testing, X-ray radiography, and electric resistivity methods. The solid solution of hydrogen in tantalum was shown to be highly ductile at temperatures above 300K. The ductility of the solid solutions decreased rapidly at temperatures below 300K, and was minimum at about 200K. The fracture mode was cleavage at the temperatures in the region of ductility minimum, while it was ductile at temperatures near 77K. The factors affecting the above embrittlement are considered to be inhomogeneous distribution of hydrogen in the specimen and formation of stress induced hydrides. The ductility near 77K may be caused by very slow diffusion of hydrogen at that temperature.
