Study On Structure,transformation And Mechanical Properties Of Ti-Ni-Cu-based Alloys

In this paper, alloys were fabricated by rapid solidification technology. The effects of different components, different annealing temperatures and adding of a fourth component on marentsitic transformation were studied by electrical resistance measurement method. The effects of components and annealing temperatures on structures of alloys were also studied by using X-ray diffraction analysis, while the effect of components on mechanical behavior was studied through stretching experiments.The results showed that adding a third component into Ti-Ni-based alloys can change the structure and martensitic transformation behavior. At room temperature, the structure of Ti50Ni45Cu5 alloy is composed of B2 phase and B19’ phase, and B2â†'B19’ martensitic transformation occurs while cooling. The structure of Ti50Ni45Nb5 alloy is composed of B19’ phase and NbNi phase, the structure of Ti50Ni45Sn5 alloy is composed of B2 phase and Sn3Ti5 phase, and both of the two alloys have B2â†'Râ†'B19’ martensitic transformation while cooling. Cu content can significantly change the structure and martensitic transformation of Ti-Ni-Cu alloy. When Cu content is 5at%, the structure of Ti-Ni-Cu alloy is composed of B2 phase and B19’ phase, and B2â†'B19’ martensitic transformation occurs while cooling. When Cu content is 12.5at%, the structure of Ti-Ni-Cu alloy is composed of B2 phase, B19 phase and B19’ phase, and B2â†'B19â†'B19’ martensitic transformation occurs while cooling. When Cu content is 20at%, the structure of Ti-Ni-Cu alloy is composed of only B19 phase, and B2â†'B19 martensitic transformation occurs while cooling. The effect of rapid solidification and annealing temperature on Ti-Ni-Cu-Sn alloy is different with different Sn content.Alloy composition has a great influence on the mechanical properties of Ti-Ni-Cu based alloys. At room temperature, Ti50Ni45Cu5 alloy is in B2 phase state, does not exist in martensitic phase, and the alloy has good ductility and high tensile strength. Compared with Ti50Ni45Cu5 alloy, Ti50Ni15Cu32Sn3 alloy has a higher tensile strength, and Ti50Ni15Cu32Sn3 alloy has achieved a high strength and toughness targets. Compared with Ti50Ni15Cu32Sn3 alloy, Ti50Ni15Cu32Nb3 alloy has a weaker tensile strength and ductility. Three alloys which were mentioned above have had a stress-induced martensitic transformation during stretching.