Effect of high temperature aging on microstructure and mechanical properties of a directionally solidified Ni₃Al based alloy IC6A

The effect of aging at 950°C for up to 2000 h on the microstructure and mechanical properties of a directionally solidified Ni₃Al based alloy IC6A was investigated by scanning electron microscopy, transmission electron microscopy and energy dispersive spectroscopy of electron probe micro-analyzer. The results show that Ni₃Y and Mo_1.24Ni_0.76 precipitated in the interdendritic area due to the addition of yttrium have no obvious change during high temperature aging. A needle like or rod like phase named Y-NiMo precipitates after aging for about 200 h. The amount and size of the Y-NiMo phase increase with the increase of aging time, which is similar with that in the alloy IC6. The ultimate tensile strength at room temperature and stress rupture life under 1100°C, 90MPa of the alloy IC6A have no obvious change before aging for 1000 h and decrease obviously with the increase of aging time after aging for 1000 h. The yield strength of the alloy IC6A at room temperature decreases obviously after aging for 500 h and has no obvious change during further aging.