Influence of precipitation on phase transformation and mechanical properties of Ni-rich NiTiNb alloys

Abstract Ni-rich Ni x Ti y Nb z (x/y = 1.0645/x-y ≈ 3, z = 0, 2, 4, 6, 9 at.%) alloys were designed and prepared in this work. Based on these alloys, the precipitation evolution of Ni-rich NiTiNb alloys and its influence on phase transformation and mechanical properties were investigated. Ni 4 Ti 3 precipitates are observed in Nb0 and Nb2 alloys after aging and furnace cooling. Ni 4 Ti 3 precipitation sharply increases Ms in Nb0 alloy, however, causes no obvious change of Ms in Nb2 alloy. With increasing Nb addition, large numbers of β-Nb precipitates densely distribute among eutectic regions of Nb6 and Nb9 alloys. β-Nb precipitates and eutectic β-Nb particles decrease Ms. The critical yield stresses of all Ni-rich NiTiNb alloys are determined by Ms , and present same minus linear relationship with Ms . Precipitation and element variation change Ms and then influence mechanical properties. Meanwhile, this result is demonstrated by thermodynamic analysis.