The effects of cooling rate and aging process on the characteristic phase transformations of NiTiNb shape memory alloy

When nickel-rich NiTi shape-memory alloys are compared with NiTi alloys with close equiatomic composition; these alloys have managed to be in the center of attention due to their functional properties such as pronounced superelasticity and shape memory effect, high hardness and wear resistance, low density and excellent corrosion resistance. The NiTiNb ternary alloys modified by adding niobium to these alloys attract attention due to their wide hysteresis. On the other hand, the high material value and high specific gravity of the niobium element make NiTiNb alloys with lower Nb concentration are more attractive. The influence of aging conditions on the phase transformation behavior and hardness phenomenon of Ni55Ti44Nb1 alloy with high nickel content was examined in this work. As a result of the examinations, heat treatment temperature, duration, and preferred method for cooling after aging modified the alloy microstructure and in connection with these changes, the transformation type, characteristic transformation temperatures and alloy hardness were shaped.Variations in the aging parameters were found to have a significant impact on the precipitation process and the determination of precipitate morphology, and it was discovered that the physical and thermodynamic properties were defined by various outcomes in connection to this effect.