Fabricated High-Strength, Low-Elastic Modulus Biomedical Ti-24Nb-4Zr-8Sn Alloy via Powder Metallurgy

Abstract

With the huge demands of an aging society, it is urgent to develop a new generation of non-toxic titanium alloy to match the modulus of human bone. Here, we prepared bulk Ti2448 alloys by powder metallurgy technology, and focused on the influence of the sintering process on the porosity, phase composition, and mechanical properties of the initial sintered samples. Furthermore, we performed solution treatment on the samples under different sintering parameters to further adjust the microstructure and phase composition, so as to achieve strength enhancement and reduction of Young's modulus. Solution treatment can effectively inhibit the continuous α phase precipitated along the grain boundaries of the β matrix, which is beneficial to the fracture resistance. Therefore, the water-quenched sample exhibits good mechanical properties due to the absence of acicular α-phase. Samples sintered at 1400 °C and subsequently water quenched have excellent comprehensive mechanical properties, which benefit from high porosity and the smaller feature size of microstructure. To be specific, the compressive yield stress is 1100 MPa, the strain at fracture is 17.5%, and the Young's modulus is 44 GPa, which are more applicable to orthopedic implants. Finally, the relatively mature sintering and solution treatment process parameters were screened out for reference in actual production.

Keywords: Ti2448 alloy; mechanical properties; microstructure analysis; porosity.

Figure 6

SEM images and XRD spectrums of the solution-treated samples: (A1,B1) S1400 + Q sample; (A2,B2) S1450 + Q sample; (A3,B3) S1500 + Q sample.

Figure 7

SEM images of the solution-treated samples and corresponding elemental maps: (A) and (A1–A4) S1400 + Q sample; (B) and (B1–B4) S1450 + Q sample; (C) and (C1–C4) S1500 + Q sample.

Figure 8

The relative density and phase composition of the as-sintered and water-quenched Ti2448 samples: (A) the relative density; (B) the α phase composition.

Figure 10

Mechanical properties of the as-sintered and water-quenched Ti2448 samples: (A) the compressive yield strength; (B) the Young’s modulus; (C) strain at fracture.

Figure 1

A schematic representation of the main stages of experimental work performed in the present study: (A) mechanical alloying procedure; (B) powder metallurgy procedure; (C) equipment used for microstructure and mechanical properties characterization.

Figure 2

SEM images and XRD spectrums of raw powder: (A1,B1) titanium powder; (A2,B2) niobium powder; (A3,B3) zirconium powder; (A4,B4) tin powder.

Figure 3

(A) SEM images and (B) XRD spectrums of pre-alloyed powder.

Figure 4

SEM images and XRD spectrums of as-sintered samples: (A1,B1) S1400 sample; (A2,B2) S1450 sample; (A3,B3) S1500 sample.

Figure 5

SEM images of the as-sintered samples and corresponding elemental maps: (A) and (A1–A4) S1400 sample; (B) and (B1–B4) S1450 sample; (C) and (C1–C4) S1500 sample.

Figure 9

The compressive stress-strain curves and fracture topography of the as-sintered and water-quenched Ti2448 samples: (A1) the compressive stress-strain curves of S1400 and S1400 + Q sample; (A2) fracture topography of S1400 sample; (A3) fracture topography of S1400 + Q sample; (B1) the compressive stress-strain curves of S1450 and S1450 + Q sample; (B2) fracture topography of S1450 sample; (B3) fracture topography of S1450 + Q sample; (C1) the compressive stress-strain curves of S1500 and S1500 + Q sample; (C2) fracture topography of S1500 sample; (C3) fracture topography of S1500 + Q sample.