Effect of aging on microstructures and properties of Mo-alloyed Fe-36Ni invar alloy

The Mo-alloyed invar alloy was prepared and its microstructures, mechanical properties, and thermal expansion behavior were investigated. It was found that precipitation of the Mo2C secondary phase could be tailored by adjusting the aging processes, accordingly, the highest strength of 820 MPa and good elongation of 35%, together with a low coefficient of thermal expansion (CTE) value of 3.37×10−6/°C were obtained upon solution-treated at 1050 °C for 1 h and then aged at 525 °C for 3 h. The aggregation and growth of the Mo2C secondary phase at the grain or sub-grain boundaries of the austenite could be observed with the increase of the aging time, resulting in deterioration in strength and thermal expansion of the materials.