New developments of biomedical porous titanium alloys prepared by spark plasma sintering

doi:10.1016/j.metadv.2026.02.010

Abstract

Abstract:

Characterized by exceptionally high heating rate, low sintering temperature, and remarkable process flexibility, spark plasma sintering (SPS) is an efficient near-net-shape powder metallurgy technology that is highly suitable for manufacturing porous titanium alloys intended for biomedical implants. This review comprehensively outlines the fundamental requirements of pore structure and mechanical properties for biomedical implant materials, and elaborates on the principles and advantages of SPS for preparing porous titanium biomaterials. The methods for fabricating porous titanium alloys by SPS are critically discussed. Furthermore, the key process parameters and the performance of SPS-prepared porous titanium and its alloys are summarized. Finally, this review delineates the prevailing challenges and future research orientations for SPS-fabricated biomedical porous titanium alloy implant materials.

Key words: Spark plasma sintering, Biomedical porous titanium alloys, Fabrication methods, Pore structure, Properties

Yuhua Li, Shuailong Dong, Qiming Bai, Hongming Zhang, Qian Zhang, Qingyu Li. New developments of biomedical porous titanium alloys prepared by spark plasma sintering[J]. Metals Advances, 2026, 41: 72-84.

Figures/Tables 14

Table 1. Mechanical properties of human bones [24], [25], [26].

Human bones	Compressive strength (MPa)	Tensile strength (MPa)	Flexural strength (MPa)	Elongation (%)	Elastic modulus (GPa)
Cortical bone	20-193	42-58	110-184	1-3	4-30
Cancellous bone	2-80	2-5	-	2-8.5	0.02-4

Fig. 1. (a) Comparison of elastic modulus of various titanium and its alloys (PM means powder metallurgy method); (b) Compressive strength of titanium alloys prepared by SPS. Reproduced from Ref. [34] under terms of the CC-BY license.

Fig. 2. (a) A diagram of the SPS system. Reproduced from Ref. [40] under terms of the CC-BY license. (b) Discharge occurred at the interface between the second and third punch on the die during the SPS process: t = 60 s, T = 337 °C. Reproduced with permission from Ref. [9]. Copyright 2014, Elsevier. (c) Magnified characteristic microstructure during the SPS process. Reproduced with permission from Ref. [9]. Copyright 2014, Elsevier.

Table 2. Comparison of conventional sintering and SPS of Ti-6Al-4V alloy powders [46], [47], [48], [49].

Empty Cell	Temperature (℃)	Time (min)	Heating rate (°C/min)
SPS	650-1100	5-15	100
Microwave sintering	1200-1300	30-240	30-35
HP	900-1300	30-60	10
HIP	880-980	240	10

Table 3. Preparation methods of porous titanium and titanium alloys by SPS.

Preparation methods		Advantages	Disadvantages	Refs.
Without space holder		Low-temperature and low-pressure sintering is cost-effective and requires no additional steps.	Inability to achieve high porosity.	[50], [51], [52]
With space holder	Space holder decomposes during sintering	Pre-pressing can achieve higher porosity and is relatively cost-effective.	It may affect the densification of pore walls, thereby influencing the mechanical properties of the material.	[53], [54]
With space holder	Space holder removed after sintering.	Applying higher pressure during sintering to promote densification of pore walls.	Requires additional space holder removal, increasing process complexity and cost.	[55], [56]

Fig. 3. Porous structures fabricated by different methods. (a) Porous structure fabricated using MgO as pore-forming agent. Reproduced with permission from Ref. [57]. Copyright 2023, Elsevier. (b) Porous structure fabricated using NaCl as pore-forming agent. Reproduced with permission from Ref. [58] under terms of the CC-BY license. (c) Porous structure fabricated using NH4HCO3 as pore-forming agent. Reproduced from Ref. [13] under terms of the CC-BY license. (d) Porous structure fabricated by partial densification. Reproduced with permission from Ref. [50]. Copyright 2022, Springer.

Fig. 4. Density and porosity of porous bulk metallic glass varied with the sintering temperature (a), holding time (b) and heating rate (c) during SPS. Reproduced with permission from Ref. [65] under terms of the CC BY license.

Fig. 5. (a) Process to fabricate porous Ti foams; SEM micrographs of macropore walls sintered at 500 °C (b) and corresponding vacuum sintered (c), and at 650 °C (d) and corresponding vacuum sintered (e). Reproduced with permission from Ref. [58] under terms of the CC-BY license.

Fig. 6. (a) Schematic experimental procedures of FGPT and uniform samples produced by SPS; Elongated pores on the lateral sides of (b) uniform porous, and (c) FGPT samples. Reproduced with permission from Ref. [67]. Copyright 2022, Elsevier.

Fig. 7. Experimental setup of direct ink writing of titanium (a), and pressure-less spark plasma sintering (PL-SPS) of the debound porous structure (b). The images include an example of the as printed (green) and sintered titanium structures, respectively. Representative images of titanium strands after PL-SPS at different temperatures with heating rate of 100 ℃/min: (c, f, i) 1400 °C, (d, g, j) 1500 °C, and (e, h, k) 1600 °C. Reproduced with permission from Ref. [68] under terms of the CC-BY license.

Table 4. Mechanical properties of porous titanium alloys fabricated by SPS.

Composition	Sintering temperature (°C)	Sintering pressure (MPa)	Sintering time (min)	Porosity (%)	Compressive strength (MPa)	Elastic modulus (GPa)	Ref.
Without space holder
Ti	600-800	9.5	5	4-28	143-374 (yield strength)	14-24	[50]
Ti-6Al-4V	700	20-30	3-10	32	113-125	16-18	[52]
Ti-5Al-2.5Fe	750-850	5	5	28-29	250-300	-	[64]
Ti₄₅Zr₁₀Cu₃₁Pd₁₀Sn₄	653 K	50	10	21	180	27	[65]
With space holder
Ti Spacer: NH₄HCO₃	1000-1200	Pressureless	5	38-56	61-287	6-11	[69]
Ti-6Al-4V Spacer: NaCl	700-725	30-60	-	33-44	79-124	20-45	[70]
Ti-13Nb-13Zr Spacer: NH₄HCO₃	1123 K	30	-	19-22	900-1166	45-53	[71]
Ti-2Cu-4Ca Spacer: NH₄HCO₃	1173-1373 K	Pressureless	5	43	206-325	6-12	[72]
Porous gradient alloys Outer: Porous Ti-5Ag; Inner: dense NiTi Spacer: NH₄HCO₃	950	Pressureless	5	37-62 (Ti-5Ag)	380-540	17-25	[73]
NiTi Spacer: NH₄HCO₃	800-1050	Pressureless	5	18-61	153-1183	8-18	[62]
TiZrNbTa/Ti Spacer: MgO (30-50 vol.%)	1000	30	-	-	142-698	9-57	[57]

Fig. 8. Relationship curve (a) of elastic modulus and the volume fraction MgO added; Compressive strength and elastic modulus of porous TiZrNbTa/Ti TMC compared with human bone (b) and previous reports about porous implant materials (c); (d) Compared elastic modulus of porous TiZrNbTa/Ti TMC with dense implant materials. Reproduced with permission from Ref. [57]. Copyright 2023, Elsevier.

Fig. 9. Cell morphologies on Ti-40Nb alloy after cell culture for 3 days imaged by SEM (a) cells on the flat surface, (b) cells near the porous structure, and (c) cells in porous structure. Fluorescence images of cells on porous Ti-40Nb alloys with different volume ratios of space holder after cell culture for 7 days: (d) 10 vol.%; (e) 30 vol.%; (f) 50 vol.%. Reproduced with permission from Ref. [54]. Copyright 2019, IOP Publishing.

Table 5. Corrosion parameters of the porous titanium with different pore size distributions in 0.9 wt% NaCl solution at 37 °C. Reproduced from Ref. [55] under terms of the CC-BY license.

Pore size (μm)	E_corr (V)	j_corr (A/cm²)	CR (mm/y)
100-212	0.061 ± 0.0001	(7.69 ± 0.33)× 10⁻⁶	0.036810 ± 0.006
212-425	−0.0020 ± 0.0001	(1.85 ± 0.28)× 10⁻⁵	0.16074 ± 0.03
425-600	0.022 ± 0.0003	(1.25 ± 0.44)× 10⁻⁵	0.10816 ± 0.02
100-425	0.010 ± 0.0001	(2.44 ± 0.65)× 10⁻⁶	0.063040 ± 0.001
100-600	−0.0050 ± 0.0002	(2.61 ± 0.71)× 10⁻⁵	0.20016 ± 0.0005

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