Influence of Mo addition on the solvus temperature of Ni2(Cr,Mo) phase in Ni2(Cr,Mo) alloys

The present paper reports the results of a detailed investigation carried out to determine the solvus temperature of Ni2(Cr,Mo) phase in Ni0.66Cr1−x,Mox alloys, with x varying from 0 to 0.5, using differential scanning calorimetry and transmission electron microscopy. It was noticed that the precipitation of this phase is very sluggish. The solvus temperature was determined from specimens aged for long periods of time to precipitate Ni2(Cr,Mo) phase. The solvus temperature was found to vary from 627 °C (for a Mo/Cr ratio = 0) to 773 °C (for a Mo/Cr ratio = 1) for a heating rate of 2 °C/min and the data could be fitted with second-order polynomial relation. The isothermal solvus temperature for two alloy compositions was determined from the results of influence of heating rate on solvus temperature. The experimentally observed results on solvus temperature were confirmed by the microstructural examination of aged specimens in electron microscope.