The Effects Of Hydrogen On The Mechanical Properties And Fracture Of Zr And Refractory Metals

The effect of hydrogen on the mechanical properties of zirconium and the refractory metals is reviewed with particular attention to the effects on fracture and ductility. The various mechanisms proposed for the hydrogen embrittlement of these metals is reviewed. Both the effects of hydrogen in solution and in the surrounding gas phase is considered. New results on the embrittlement of Nb and Nb-N alloys obtained using a variety of experimental techniques is presented and discussed relative to the generic embrittlement phenomena in these metals. The relation of the crack propagation mechanism to stress and temperature induced phase changes is discussed and a model of hydrogen embrittlement is put forth. (Modified author abstract).