EFFECT OF Ir ADDITION ON HIGH-TEMPERATURE STRENGTH OF NiAl SINGLE CRYSTALS

초록

In order to examine the strengthening effect of the Ir additions on the high-temperature strength of the NiAl intermetallic compound, compressive and creep tests of the soft oriented single crystalline NiAl and Ir-doped NiAl ( Ni0.9Ir0.1Al ) have been conducted in the temperature range from room temperature to 1473K. CRSSs of the NiAl-Ir single crystal are significantly higher than those of the binary NiAl single crystal in the whole temperature range tested. While the binary NiAl single crystal exhibits uniform deformation at entire temperatures tested, the localized deformation takes place in the NiAl-Ir single crystal in the temperature region between 673K and 1273K. It is likely that the localized deformation behavior observed in the NiAl-Ir single crystal results from the suppression of the easy slip system which normally glide in the binary NiAl single crystal with soft crystal axis. Secondary creep rate of the NiAl-Ir single crystal is about a magnitude of 5 lower than that of binary NiAl single crystal at 1273K, indicating that Ir additions are significantly effective in improving the creep strength of NiAl.