Mechanical behaviour of Zr doped Ni3Al alloy:: effects of heat treatment, environment, and temperature

The mechanical behaviour of polycrystalline Ni76Al23Zr alloy was studied as a function of heat treatment, environment, and temperature. It was found that the tensile ductility was very sensitive to temperature, the alloy showing low ductility at temperatures' from 700 to 1000 degrees C both in air and vacuum. Environmental embrittlement could be alleviated for those specimens with elongated grains. The ductile transgranular fracture was explained by stress concentration at the intersection of slip bands and grain boundaries. It was also found that an oxide layer, formed during tensile testing at elevated temperature, affected the environmental embrittlement of Ni3Al(Zr) alloy. An adherent Al rich oxide film was effective in protecting the underlying alloy from oxygen penetration.