Reverse Martensitic Transformation in Oil-Quenched Ni₆₄Al₃₆ Alloy

The reverse martensitic transformations of oil-quenched and furnace-cooled Ni64Al36 (at%) alloys at temperature from room temperature to 400 ℃ were studied by internal friction measurement, differential scanning calorimetry (DSC) and X-ray diffractometry (XRD). The results show that there was an internal friction peak appeared at temperature about 220 ℃ during heating for the oil-quenched Ni64Al36 alloy, and it moved to 160 ℃ in cooling process. But the furnace-cooled Ni64Al36 alloy did not have any internal friction peak. The peak-height increased with decreasing vibration frequency and increasing heating rate. The internal friction peaks of the oil-quenched Ni64Al36 alloy during heating and cooling were attributable to γ→L10 martensitic transformation and its reverse process respectively. The influence of the thermal cycle times on martensitic transformation and its reverse process was not observed in the limited thermal cycles from room temperature to 400 ℃ for oil-quenched Ni64Al36 alloy.