Influence of stress field of expanding and contracting plate shaped precipitate on hydride embrittlement of Zr-alloys

Influence of loading rate and hydrogen content on fracture toughness of Zr-2.5Nb pressure tube material

“…Singh et al [16], made an attempt to explain the susceptibility of Zr-alloys to hydride embrittlement in regards to the stress field imposed on the matrix by the hydrides. A Finite element method was used to compute the stress field for the expanding (precipitation) and the contracting (dissolution) hydrides for the fully constrained case.…”

“…Plots of S 22 as a function of distance (Arbitrary units e AU) for partially dissolving hydride along a line passing though hydride and matrix for (a) plane strain and (b) axisymmetric fully constrained cases[16].…”

Effect of direction of approach of test temperature on fracture toughness of Zr–2.5Nb pressure tube material

“…Singh et al [11] argued that increase in matrix ductility, solid solubility of hydrogen in matrix and toughness of hydride with increase in temperature could possibly explain the reduced susceptibility of this alloy to hydride embrittlement at higher temperature. However, it was also pointed out that the gross tensile ductility of this alloy is reportedly unaffected by temperature(s) up to 300 1C [12,13] and the hydride of this alloy reportedly fails in brittle manner up to 400 1C [14].…”

“…The stress field imposed on matrix by hydride is expected to depend on whether hydride is expanding (as happens during cooling) or contracting (as happens during heating) [11,20]. The stress field of hydride in conjunction with externally applied stress field is expected to govern the susceptibility of hydride forming metals and alloys to hydride embrittlement.…”

“…The stress field of hydride in conjunction with externally applied stress field is expected to govern the susceptibility of hydride forming metals and alloys to hydride embrittlement. To explain this, recently Singh et al [11] carried out FEM computation of stress field on matrix due to expanding and contracting hydride. The expanding hydride plate is encountered when the test temperature is approached during cooling from a peak temperature while a contracting hydride plate is encountered when the test temperature is attained by heating from ambient temperature.…”