The Combined effect of Nb and Fe additions on the microstructure, mechanical characteristics and corrosion resistance of Ni-Ti shape memory alloy

Document Type : Original Article

Authors

1 Department of Casting Technology, Manufacturing Technology Division, Central Metallurgical Research and Development Institute (CMRDI), P.O. 87, Helwan, Egypt)

2 (Department of Casting Technology, Manufacturing Technology Division, Central Metallurgical Research and Development Institute (CMRDI), P.O. 87, Helwan, Egypt)

3 Department of Mechanical Engineering, Higher Technological Institute 10th of Ramadan city (HTI),10 th of Ramadan city, Egypt).

Abstract

The combined effect of Nb and Fe additions on the microstructure, hardness, compressive strength, and corrosion properties of Ni-Ti shape memory alloy “SMA” in Hank's solution “simulated bodily fluid” was studied. To avoid oxidation, the investigated alloys were prepared using a vacuum arc melting furnace. The results showed that the combined additions of Nb and Fe cause grain refinement in the investigated alloy. The optimum combined addition of 10 wt.%Nb and 5 wt.%Fe has a significant improvement in grain refinement of the investigated NiTi SMA which leads to 71% decreasing in the average grain size. Furthermore, the mechanical properties including compressive strength and hardness as well as the corrosion performance of NiTi SMA were found to be sensitive to the combined additions of Nb and Fe. The optimum combined addition of 10 wt.%Nb and 5 wt.%Fe increases the hardness (27.3%) and compressive strength (16.2%) of the investigated Ni-Ti SMA. Furthermore, electrochemical studies revealed that the corrosion resistance of the investigated Ni-Ti SMA was also improved with the combined additions of Nb and Fe. Corrosion rate (CR) decreased from 0.0019255 mm/y to 0.000624 mm/y (67.6% reduction in CR) with the optimum combined addition of 10 wt.%Nb and 5 wt.%Fe. Therefore, Ni-Ti SMA containing 10 wt.%Nb and 5 wt.%Fe is a promising alloy for the advanced biomedical applications such as orthopedic and dental implants.

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