Alloy Design and Fabrication of Duplex Titanium-Based Alloys by Spark Plasma Sintering for Biomedical Implant Applications

Abstract

Very often, pure Ti and (α + β) Ti-6Al-4V alloys have been used commercially for implant applications, but ensuring their chemical, mechanical, and biological biocompatibility is always a serious concern for sustaining the long-term efficacy of implants. Therefore, there has always been a great quest to explore new biomedical alloying systems that can offer substantial beneficial effects in tailoring a balance between the mechanical properties and biocompatibility of implantable medical devices. With a view to the mechanical performance, this study focused on designing a Ti-15Zr-2Ta-xSn (where x = 4, 6, 8) alloying system with high strength and low Young's modulus prepared by a powder metallurgy method. The experimental results showed that mechanical alloying, followed by spark plasma sintering, produced a fully consolidated (α + β) Ti-Zr-Ta-Sn-based alloy with a fine grain size and a relative density greater than 99%. Nevertheless, the shape, size, and distribution of α-phase precipitations were found to be sensitive to Sn contents. The addition of Sn also increased the α/β transus temperature of the alloy. For example, as the Sn content was increased from 4 wt.% to 8 wt.%, the β grains transformed into diverse morphological characteristics, namely, a thin-grain-boundary α phase (α_GB), lamellar α colonies, and acicular α_s precipitates and very low residual porosity during subsequent cooling after the spark plasma sintering procedure, which is consistent with the relative density results. Among the prepared alloys, Ti-15Zr-2Ta-8Sn exhibited the highest hardness (s340 HV), compressive yield strength (~1056 MPa), and maximum compressive strength (~1470). The formation of intriguing precipitate-matrix interfaces (α/β) acting as dislocation barriers is proposed to be the main reason for the high strength of the Ti-15Zr-2Ta-8Sn alloy. Finally, based on mechanical and structural properties, it is envisaged that our developed alloys will be promising for indwelling implant applications.

Keywords: mechanical properties; metallic implants; microstructure; powder metallurgy; spark plasma sintering.

Figure 1

Optical micrographs of the experimental alloys fabricated by high-pressure spark plasma sintering (HFIHS) procedure.

Figure 2

XRD patterns of the experimental alloys fabricated by high-pressure spark plasma sintering (HFIHS) procedure.

Figure 3

Vickers hardness values of the experimental alloys fabricated by high-pressure spark plasma sintering (HFIHS) procedure.

Figure 4

Compressive stress–strain curves of the experimental alloys fabricated by high-pressure spark plasma sintering (HFIHS) procedure.

Figure 5

A schematic explanation showing the effect of microstructure and resulting mechanical evolution of the experimental alloys fabricated by high-pressure spark plasma sintering (HFIHS) procedure.