The effect of phosphorous addition on microstructure and mechanical properties of NiAl alloy has been investigated. The results indicate that a certain level of P additions can induce softening of polycrystalline NiAl, i.e., decreases yield stress and hardness and increases room temperature compressive ductility. Trapping of interstitial atoms and reducing of Peierls stress are proposed to be responsible for the softening. In addition, the macro-deforming behavior (compressive properties) of the alloy results from a competitive process of softening of grain interiors and hardening of grain boundaries.
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