Physical and Mechanical Behavior of NiTi Composite Fabricated by Newly Developed Uni-Axial Compaction Die

Rajeev Singh,Ajay K Sharma,Avadesh K Sharma

doi:10.1590/1980-5373-mr-2020-0549

Rajeev Singh, Ajay K Sharma + Show 1 more

Open Access

https://doi.org/10.1590/1980-5373-mr-2020-0549

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Abstract

Owing to better mechanical properties and shape memory effect, the NiTi composites fabricated by powder metallurgy are suitable for biomedical implants. However, the excessive porosity and formation of micro-cracks are the major issues related to the NiTi composite. This work focused on developing crack-free dense NiTi composites by newly developed uni-axial compaction die. The work includes the design and manufacturing of uni-axial compaction die. The die was tested by SOLIDWORKS software in a simulated environment. Further, composite samples were successfully fabricated without circumferential micro-cracks at 1910.82 MPa compaction pressure. The effects of compaction pressure on microstructural, densification, and mechanical behavior of NiTi composites were also analyzed. Microstructural characterization shows that the Ni-rich phase increased and the Ti-rich phase decreased with the increase of compaction pressure. The porosity reduces from 17.04 to 8.75% by increasing the compaction pressure from 1273.88 to 1910.82 MPa, and a maximum density of 5.50 g.cm–3 was obtained. The NiTi150 composite has similar Young’s modulus, and compressive strength (6.93 GPa and 94.36 MPa) compared to cortical and cancellous bone. The high compaction pressure also increases the micro-hardness of NiTi composite up to 453.8 HV0.5.

Highlights

Nickel-titanium (NiTi) composite with 48–55 Wt.% Ni content is a suitable material for biomedical applications because of their high ductility[1], good fatigue life[2], low young’s modulus[3,4] and shape memory effect (SME)[5,6]
The results show that the compaction pressure has a significant effect on the physical and mechanical properties of NiTi composite
The quantification of phases shows that NiTi and Ni3Ti phases increased, and NiTi2 phase decreased with the increase of compaction pressure

Summary

Introduction

Nickel-titanium (NiTi) composite with 48–55 Wt.% Ni content is a suitable material for biomedical applications because of their high ductility[1], good fatigue life[2], low young’s modulus[3,4] and shape memory effect (SME)[5,6]. The mechanical characteristics of the composites depend on their porosity and pores distribution. The porous structure of NiTi composite promotes the development of bone tissues. It helps to maintain bone-level stiffness to avoid stress shielding and withstand physiological loads for a more extended service life. The excessive porosity decreases the mechanical strength of implants[7,8]. Optimizing the porosity of the composites is essential to achieve suitable mechanical strength and stiffness[9]

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Conclusion