Porous NiTi Shape Memory Alloy Fabricated via Powder Metallurgy Technique Using Pore Forming Agent

Abstract:

Porous NiTi shape memory alloy is of special interest for biomedical purposes especially for human bones application due to its attractive features such as lower stiffness to minimize the effect of stress shielding and good strength to prevent deformation and fracture apart from its shape memory effect and superelastic behavior. With all these great benefits, however, the challenge is to produce porous NiTi which resembles cancellous bone. Therefore, in this research, pore forming agent such as calcium hydride, CaH₂, is added to the equiatomic of Ni and TiH₂ powder mixture to produce porous NiTi with higher porosity level using powder metallurgy technique. Here, the effect of composition of pore forming agent on porosity level, phase formation and transformation behaviour of porous NiTi were investigated. From the observation, the pores formation exhibits small closed pores instead of interconnected pores. The result also shows that by adding 3wt% composition of pore forming agent, the porosity level of sample sintered can reach up to 32%. For phase transformation behavior, there are martensitic transformation peaks observed both upon cooling and heating for all samples, however the overall enthalpy changes are significantly lower (<2 J/g). This due to undesirable phase such NiTi₂, Ni-rich phase and also Ni₃Ti that co-exist with NiTi formation, thus jeopardize the transformation enthalpy for porous NiTi.

• Periodical: Key Engineering Materials (Volume 908)
• Pages: 119-124
• DOI: https://doi.org/10.4028/p-h2coqn
• Online since: January 2022
• Authors: Nur Amanina Abd Kadir, Hafizah Hanim Mohd Zaki*, Jamaluddin Abdullah, Farah Diana Mohd Daud, Norshahida Sariffudin
• Keywords: Martensitic Transformation, Pore Forming Agent, Porous, Shape Memory Alloy

References

[1] Liu, Y. and Xiang, H, Apparent modulus of elasticity of near-equiatomic NiTi, Journal of Alloys and Compounds, vol. 270, pp.154-159, (1998).

DOI: 10.1016/s0925-8388(98)00500-3

[2] Elahinia, M., Hashemi, M., Tabesh, M. and Bhaduri, S., Manufacturing and processing of NiTi implants: A review. Progress in Materials Science, 57(5), pp.911-946, (2012).

DOI: 10.1016/j.pmatsci.2011.11.001

[3] Otsuka, K., Saxena, A., Deng, J. and Ren, X., Mechanism of the shape memory effect in martensitic alloys: an assessment. Philosophical Magazine, 91(36), pp.4514-4535, (2011).

DOI: 10.1080/14786435.2011.608735

[4] Zhou, D., Gao, Y., Lai, M., Li, H., Yuan, B. and Zhu, M., Fabrication of NiTi Shape Memory Alloys with Graded Porosity to Imitate Human Long-bone Structure. Journal of Bionic Engineering, 12(4), pp.575-582, (2015).

DOI: 10.1016/s1672-6529(14)60147-5

[5] Oh, I., Nomura, N. and Hanada, S., Microstructures and Mechanical Properties of Porous Titanium Compacts Prepared by Powder Sintering. Materials Transactions, 43(3), pp.443-446, (2002).

DOI: 10.2320/matertrans.43.443

[6] Yusop, A., Bakir, A., Shaharom, N., Abdul Kadir, M. and Hermawan, H., Porous Biodegradable Metals for Hard Tissue Scaffolds: A Review. International Journal of Biomaterials, 2012, pp.1-10, (2012).

DOI: 10.1155/2012/641430

[7] Amal, M., Annur, D., Lestari, F., Sutowo, C. and Kartika, I., Processing of porous Mg-Zn-Ca alloy via powder metallurgy. AIP conference, 1778, (2016).

DOI: 10.1063/1.4965744

[8] Chen, G., Cao, P. and Edmonds, N., Porous NiTi alloys produced by press-and-sinter from Ni/Ti and Ni/TiH2 mixtures. Materials Science and Engineering: A, 582, pp.117-125, (2013).

DOI: 10.1016/j.msea.2013.05.082

[9] Kaya, M. and Çakmak, Ö., Shape Memory Behavior of Porous NiTi Alloy. Metallurgical and Materials Transactions A, 47(4), pp.1499-1503, (2016).

DOI: 10.1007/s11661-015-3318-1