Published online by Cambridge University Press: 22 February 2011
Ductility of binary and ternary Ni3Al alloys with conventional purity, fabricated by isothermal hot-forging, was examined by tensile tests in dry oxygen to eliminate environmental embrittlement. Re crystallized Ni-23A1 doped with approximately 0.4 mol% X(X=Hf, Nb, and Zr) alloys exhibits pronounced ductility, whereas recrystallized Ni-23A1–2X alloys exhibits elongation of less than 3%. Ductility of a highly purified binary Ni-23A1 alloy was also examined and showed remarkable ductility, resulting in trans granular fracture. This indicates that a Ni-rich Ni3Al alloy inherently exhibits marked ductility without intergranular fracture if impurity atoms and other extrinsic factors(e.g., environmental effect and internal microcracks) are eliminated in the alloy. Thus it is found that Hf, Nb and Zr in the significant ductilization of Ni-23A1 can act as a scavenger of harmful impurities when added in a small amount. With further increasing amount of additions of Hf, Nb and Zr, elongation decreases rapidly and reaches almost no ductility at 2 mol% additions, indicating that Hf, Nb and Zr lower the intrinsic ductility of Ni3Al alloy.
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