NiAlのクリープ特性に及ぼす化学量論組成からのずれとボロン添加の影響

抄録

The effects of deviation from stoichiometry and addition of boron have been investigated on the creep behaviour of NiAl. It is found that the creep behaviour of near stoichiometric NiAl alloys is of the class II type with a stress exponent, n, being 4.5, while that of off-stoichiometric alloys of the class I type with n being 3.5. The activation energy for creep, Q_C, decreases with increasing Al concentration at the Ni-rich side of offstoichiometry but vice versa on the Al-rich side of offstoichiometry. At near stoichiometry, the values for the Q_C are off the relation being found at offstoichiometry and are almost constant within 1 at% on both sides of stoichiometry. The Q_C seems to correspond to the value of the activation energy for self diffusion of Ni at near stoichiometry and to that for interdiffusion at offstoichiometry.
The effect of boron addition is found to increase the creep resistance of NiAl alloys at Ni-rich side of offstoichiometry without an appreciable change in the stress exponent. The reason for the enhancement of creep resistance should be due to the solution hardening by boron. At Al-rich side of offstoichiometry, no effect on the creep resistance is found by the boron addition.