Effects of boron content on environmental embrittlement of ordered Ni₃Fe alloys

Abstract

The effects of boron content (C _B = 0–0.14% (mass fraction)) on the tensile properties and environmental embrittlement of ordered Ni-24%Fe (atom fraction)-B (Ni₃Fe-B) alloys have been investigated using tensile tests in vacuum and under gaseous hydrogen. The results indicate that, when C _B < 0.06% (mass fraction), the tensile strength and elongation of the alloys in vacuum and gaseous hydrogen increase as C _B in the ordered Ni₃Fe-B alloy increases. The tensile strength and elongation are maximum, and the hydrogen embrittlement factor (I _H) is minimum for the ordered Ni₃Fe-0.06%B (mass fraction) alloy. Compared with the ordered B-free Ni₃Fe alloy, I _H of the ordered Ni₃Fe-0.06%B (mass fraction) alloy decreases by 98.1%, and the fracture morphology of the alloy changes from fully intergranular to fully transgranular, when tested in gaseous hydrogen. A critical level of boron segregation at the grain boundaries of ordered Ni₃Fe-B alloys is observed. The hydrogen embrittlement of ordered Ni₃Fe-B alloys in gaseous hydrogen can be completely suppressed by boron atoms when C _B $\geqslant$ 0.06% (mass fraction).

Keywords

Ordered Ni₃Fe alloy / Boron content / Environmental embrittlement

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