Abstract: Effects of isothermal annealing treatment at different temperatures and time on microstructure and properties of 50 μm thick Inconel 625 alloy foils were studied by means of OM, SEM and mechanical properties test. The results show that during isothermal annealing at 650 ℃ and 700 ℃, the foils recrystallize, the grain size decreases significantly, and a large number of Ti- and Nb-rich carbides are precipitated at the grain boundaries. Due to the combined effect of recrystallization-induced fine-grain strengthening and carbide-induced precipitation strengthening, the strength and plasticity of the foils are significantly improved, especially after isothermal annealing at 650 ℃ for 48 h, the tensile strength reaches 1513 MPa, which is nearly 90% higher than that of the unannealed foils, and elongation also is increased by 105%. However, after isothermal annealing at 700 ℃ for 48 h, the recrystallized grains become coarser, resulting in a significant decrease in mechanical properties. The tensile elongation of the foils is closely related to the grain size.

Key words: Inconel 625 alloy, foil, microstructure, recrystallization, tensile properties