The Influence of Hydrogen on the Multiaxial Fracture Behavior of Titanium Alloy Sheets.
MICHIGAN TECHNOLOGICAL UNIV HOUGHTON DEPT OF METALLURGICAL ENGINEERING
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The influence of hydrogen on the deformation and fracture of three Ti alloys in the form of sheet has been examined as a function of the state of stress. Unnotched sheet specimens of alpha-phase Ti -60, 630, and 980 ppm H, Beta-phase Ti-30V -40 and 2000 ppm H, and alpha-Beta Ti-6Al-4V 30, 240, and 500 ppm H have been investigated over deformation paths ranging from uniaxial to equibiaxial tension. Based on the measurements of the local fracture strains, the alpha-Ti data show a decrease in ductility with increasing hydrogen content as the degree of biaxiality of the tensile strain increases. Thus hydrogen embrittlement of Ti sheet is most severe under equibiaxial straining. In contrast, there is no pronounced effect of stress state on the localized necking and fracture behavior of either the Ti-30V or the Ti-6Al-4V at any of the hydrogen levelsmicrostructures examined. The results indicate that, even in equibiaxial tension, Ti alloys in the form of sheet are immune to hydrogen embrittlement if hydrides do not form. If hydrides are present, the embrittlement is most pronounced under those state of stress e.g., plane strain and equibiaxial tension which are characterized by large normal stresses.
- Properties of Metals and Alloys