# 材料期刊网

The low temperature superelastic alloys are of wide range of applications, such as to make the energy storage devices, the earthquake protective devices and the abrasion parts, etc. The shape memory alloy (SMA) Ti-50.8Ni-0.3Cr (atomic fraction, \%) is a good low temperature superelastic alloy with low martensitic transformation temperature and high critical stress for inducing martensitic transformation. So far, the effects of the annealing and aging processes on the transformation behaviors of Ti-50.8Ni-0.3Cr SMA, and the characteristics of the shape memory effect, the superelasticity and the stress-strain cycle for annealed Ti-50.8Ni-0.3Cr SMA have been studied, systematically, while the microstructure and deformation characteristics of aged Ti-50.8Ni-0.3Cr SMA were not studied yet. In this paper, the influences of aging processes on the microstructure and superelasticity in Ti-50.8Ni-0.3Cr SMA were investigated using TEM and tensile test. With increasing aging time (tag), the morphology of Ti3Ni4 precipitate shows fine particle-shape in 300 ℃ aged Ti-50.8Ni-0.3Cr SMA, the morphology of Ti3Ni4 precipitate changes from the fine particle-shape to the needle-shape in 400 ℃ aged alloy, and the morphology of Ti3Ni4 precipitate  changes from the needle-shape to the plate-shape in 500 ℃ aged alloy. The effect of aging temperature on the precipitate morphology is more outstanding than that of aging time. With increasing tag, the tensile strengths (σb) in 300 and 400 ℃ aged alloys are increase first and then tend to stable, while σb (500 ℃) is decrease first and then tend to stable, and σb(400 ℃)>σb(300 ℃)>σb(500 ℃). The superelasticities of 300 and 400 ℃ aged alloys are better than that of 500 ℃ aged alloy. With increasing tag, the critical stress for inducing martensitic transformation of Ti-50.8Ni-0.3Cr SMA is decrease, the superelasticity energy dissipation (ΔW) of 300 ℃ aged alloy is decrease, the $\Delta W$ of 400 ℃ aged alloy is increase, and the ΔW of 500 ℃ aged alloy is increase first and then decrease.

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