Environmental and internal hydrogen embrittlement of a directionally solidified Ni-rich Ni3AI intermetallics

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The influence of tensile orientation, test environments and internal hydrogen contents on the room temperature tensile properties of a directionally solidified Ni3Al alloy was investigated. The specimens parallel to the growth direction exhibited a good ductility and little susceptibility to test environment. The values of elongation in vacuum, air and H2 are 39.7%, 39.2% and 29.7%, respectively. Also, a transgranular fracture mode was observed in the specimens. However, the specimens perpendicular to the growth direction exhibited lower ductility, much more sensitivity to test environment and intergranular fracture mode. The elongation values in vacuum, air and H2 are 13.7%, 10.3% and 3.3%, respectively. The results indicate that the cohesive strength of grain boundaries in the alloy is low and they are more susceptible to test environment than are grain interiors. In addition, only a slight embrittlement of the internal hydrogen was found in the specimens parallel to the growth direction.

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