Porous Ti-Mo Research Articles

Open Porous α + β Titanium Alloy by Liquid Metal Dealloying for Biomedical Applications

Open porous dendrite-reinforced TiMo alloy was synthesized by liquid metal dealloying of the precursor Ti47.5Mo2.5Cu50 (at.%) alloy in liquid magnesium (Mg). The porous TiMo alloy consists of α-titanium and β-titanium phases and possesses a complex microstructure. The microstructure consists of micrometer scale β-titanium dendrites surrounded by submicrometer scale α-titanium ligaments. Due to the dendrite-reinforced microstructure, the porous TiMo alloy possesses relatively high yield strength value of up to 180 MPa combined with high deformability probed under compression loading. At the same time, the elastic modulus of the porous TiMo alloy (below 10 GPa) is in the range of that found for human bone. This mechanical behavior along with the open porous structure is attractive for biomedical applications and suggests opportunities for using the porous TiMo alloy in implant applications.

Microstructural evolution and mechanical properties of bulk and porous low-cost Ti–Mo–Fe alloys produced by powder metallurgy

A series of low-cost Ti–10Mo-xFe (x = 1, 5, 9 wt%) alloys were fabricated using conventional press and sinter powder metallurgy to investigate the effect of Fe content on their phase stability, sintering response, microstructure and mechanical properties. Phase analyses indicated that all alloys were composed of α, β and intermetallic phases. However, Fe additions increased the proportion of β and intermetallic phases and reduced the propensity of the alloy system to form α phase during slow furnace cooling. Densification of the Ti–10Mo-xFe alloys was subjected to two contradicting effects; a strong sintering response caused by the fast diffusion rate of Fe atoms which promotes densification and formation of Kirkendall pores related to the fast diffusion rate of Fe atoms in conjunction with comparatively slower diffusion of Ti and Mo. Nonetheless, the porosity level of the alloys was less than that of the sintered CP-Ti. Depending on the content of α, β and intermetallic phases, the alloys exhibited varied mechanical properties. It was found that Ti–10Mo–5Fe presented the best combination of mechanical properties including the highest compressive strength (2392 MPa) and strain (43%) and low elastic modulus (91 GPa) superior to the corresponding ones for the commonly used CP-Ti and some other Ti-based alloys. Porous Ti–10Mo–5Fe alloy was also fabricated by addition of 30 and 60 vol% ammonium hydrogen carbonate (NH4HCO3) space holder which generated sintered scaffolds with 25% and 52% porosity, respectively, with an increased effective pore size at higher porosity. This reduced the compressive strengths to 649 MPa and 168 MPa and the elastic moduli to 34 GPa and 16 GPa, respectively. This study demonstrates that Ti–Mo–Fe alloys offer significant savings on raw materials compared to current commercial and many recently developed biomedical Ti alloys. It also shows that porous Ti–10Mo–5Fe scaffolds are promising for hard tissue engineering applications offering mechanical properties which closely match with the human bone and optimal pore sizes essential for bone ingrowth.

Porous Ti-10Mo alloy fabricated by powder metallurgy for promoting bone regeneration

Porous Ti-10Mo alloys were fabricated by powder metallurgy using a space-holder method. The pore characteristics, microstructure, mechanical properties, in vitro biocompatibility, and in vivo osseointegration of the fabricated alloys were systematically investigated. The results show that with different weight ratios of the space-holder (NH 4 HCO 3 ) added, all of the porous Ti-10Mo alloys sintered at 1,300°C exhibited a typical Widmanstatten microstructure. The porosity and average pore size of the porous structures can be controlled in the range of 50.8%66.9% and 70.1381.4 μm, respectively. The Ti-10Mo alloy with 63.4% porosity exhibited the most suitable mechanical properties for implant applications with an elastic modulus of 2.9 GPa and a compressive yield strength of 127.5 MPa. In vitro, the alloyconditioned medium showed no deleterious effect on the cell proliferation. The cell viability in this medium was higher than that of the reference group, suggesting non-toxicity and good biological characteristics of the alloy specimens. In vivo, after eight weeks implantation, new bone tissue formed surrounding the alloy implants, and no noticeable inflammation was observed at the implantation site. The bone bonding strength of the porous Ti-10Mo alloy increased over time from 46.6 N at two weeks to 176.4 N at eight weeks. Suitable mechanical properties together with excellent biocompatibility in vitro and osteointegration in vivo make the porous Ti-10Mo fabricated by powder metallurgy an attractive orthopedic implant alloy.

Effects of Mo contents on the microstructure, properties and cytocompatibility of the microwave sintered porous Ti-Mo alloys

The porous Ti-Mo alloys were prepared by microwave sintering, and the effects of Mo contents on the pore structure, phase composition, compressive strength, elastic modulus, bending strength, corrosion resistance and cytocompatibility of porous Ti-Mo alloys were investigated. The results show that the porous Ti-Mo alloys are composed of α phase and β phase, and the volume fraction of β phase increases with increasing the Mo contents. The amount of Kirkendall pores distributed over the porous Ti-Mo alloys skeleton increases with increasing the Mo contents, which greatly increases the porosities and pore sizes of the porous Ti-Mo alloys. Correspondingly, all of the compressive strength, elastic modulus and bending strength of the porous Ti-Mo alloys decrease with increasing the Mo contents. The porous Ti-Mo alloys present excellent corrosion resistance in the Hank's solution due to the oxidation film of TiO2, MoO2 and MoO3 naturally formed on the surface, and the Mo contents have no obvious effect on the corrosion resistance. The cell viabilities of the porous Ti-Mo alloys are higher than 94%, indicating the porous Ti-Mo alloys possess favorable cytocompatibility. Moreover, the porous Ti-Mo alloys are beneficial to the spread, proliferation and differentiation of osteoblast-like cells, and the Mo contents have no significant effect on the cytocompatibility of the porous Ti-Mo alloys.

Effects of Porosity on Mechanical Properties and Corrosion Resistances of PM-Fabricated Porous Ti-10Mo Alloy

Porous binary Ti-10Mo alloys were prepared using non-spherical titanium, molybdenum powders by the powder metallurgy (PM) space holder technique. Based on the three-dimensional analysis of porosity characteristics, a detailed assessment of the effects of porosity on mechanical properties and corrosion resistances in phosphate-buffered saline (PBS) was carried out. For comparison, PM-fabricated CP-Ti with 50.5% porosity sintered at 1200 °C for 2 h and dense Ti-10Mo alloy sintered at 1450 °C for 2 h (relative density is 97.2% and porosity is 2.8%) were studied simultaneously. The results show that with the space-holder volume contents rising from 63 to 79%, the open porosity and average pore size (d50) increase remarkably, while the pore size distribution (d10–d90) tends to be stable at about 100 μm. The average pore sizes (d50) of porous Ti-10Mo alloy can be controlled in the range of 70–380 μm. The PM-fabricated porous Ti-10Mo alloy can achieve a wide range of mechanical properties, with yield compression strength of 248.2–76.9 MPa, and elastic modulus of 6.4–1.7 GPa. In addition, the yield compression strength and the elastic modulus meet the linear regression and exponential formula, respectively. With the porosity of Ti-10Mo alloy increasing from 2.8 to 66.9%, the corrosion rate rises exponentially from 1.6 g/m2·day to 17.1 g/m2·day. In comparison to CP Ti with nearly the same porosity, Ti-10Mo alloy shows significantly higher corrosion resistance. As a result, the relationships between porosity and mechanical properties, corrosion resistances of Ti-10Mo alloys were established, which can be used as a design reference in material selection for orthopedic applications.

High strength, low modulus and biocompatible porous Ti–Mo–Fe alloys

Porous Ti–10Mo–xFe (x = 2–5) alloys were prepared by powder metallurgy using ammonium hydrocarbonate (NH4HCO3) as the space-holder. When 7 wt% NH4HCO3 is added, the porosity of the Ti–Fe and Ti–Mo–Fe alloys is about 20 %. It was found that Fe has a significant strengthening effect on the Ti-based alloys, while Mo is effective in stabilizing the Ti–10Mo–xFe alloys into β-phase. The inherent better ductility of β-phase than that of the α-phase and the efficient strengthening effect Fe provide a good combination of strength and ductility to the Ti–10Mo–xFe alloys. The compressive yield strength of the porous Ti–10Mo–xFe alloys is from 500 to 800 MPa, much higher than that of the Fe–10Mo alloy (about 260 MPa) and human bone (about 130–180 MPa). Elastic modulus of the alloys is <10 GPa. The alloys also have corrosion resistance similar to that of pure Ti. Cytotoxic tests show that the L929 cell RGR values of the Ti–10Mo–xFe alloys are over 80 % at day 1, day 4 and day 7. The cells grew in good condition on the seventh day. The results indicate that the porous Ti–10Mo–xFe alloys have superior mechanical properties, good corrosion resistance, and excellent biocompatibility, and are promising candidates for bone substitute materials.

Preparation and properties of porous Ti–10Mo alloy by selective laser sintering

In this study, porous Ti–10Mo alloy was prepared from a mixture of titanium, molybdenum and epoxy resin powders by selective laser sintering preforming, debinding and sintering at 1200°C under a pure argon atmosphere. The influence of sintering process on the porous, microstructural and mechanical properties of the porous alloy was discussed. The results indicate that the pore characteristic parameters and mechanical properties mainly depend on the holding time at 1200°C, except that the maximum strain keeps at about 45%. The matrix microstructure is dominated by α phase with a small quantity of β phase at room temperature. As the holding time lengthens from 2 to 6h, the average pore size and the porosity decrease from 180 to 50μm and from 70 to 40%, respectively. Meanwhile, the Young's modulus and the compressive yield strength increase in the ranges of 10–20GPa and 180–260MPa, respectively. Both the porous structure and the mechanical properties of the porous Ti–10Mo alloy can be adjusted to match with those of natural bone.

Structural characterization and electrochemical behavior of a laser-sintered porous Ti–10Mo alloy

The structural and electrochemical properties of a selective laser sintered porous Ti–10Mo alloy were investigated. As the sintering temperature increases from 1100 to 1400°C, the porosity and pore size decrease from 63% to 28% and from 178 to 56μm, respectively. The alloy comprises major α and minor β phases at room temperature. With the decrease of porosity, the corrosion potential shifts towards positive direction and corrosion current density reduces, while the passive current density decreases and passivation range widens. The lower porosity, smaller pore size and slightly increased β phase fraction cause a superior corrosion resistance.

Structural Characteristics and Mechanical Properties of Biomedical Porous Ti-10Mo Alloy Fabricated by Selective Laser Sintering

Ti-Mo alloy is one of the most prospective metallic biomaterials for implant application because of its low elastic modulus, high corrosion resistance and tissue compatibility. A complex-shaped porous Ti-10Mo alloy from a mixture of elemental metal powders and polymer binders was processed by selective laser sintering forming, followed by thermal debinding and sintering in vacuum. The effects of processing parameters on structural characteristics and mechanical properties were studied. The results indicate that the pore characteristic parameters, matrix microstructure and mechanical properties strongly depend on the sintering temperature. Specimens sintered at 1100 °C exhibit a higher porosity of 52.41%, and possess many three-dimensionally interconnected pores with an average size of 200 μm, and the matrix is dominated by α and β phases, and meanwhile the alloy exhibits a compressive yield strength of 95.59 MPa and an elastic modulus of 4.89 GPa at room temperature. With the rise in sintering temperature, both the porosity and the average pore size of specimens gradually decrease, and the interconnected pores tend to be closed. Specimens sintered at 1400 °C are characterized by a porosity of 26.32% and an average pore size of 60 μm with a compressive yield strength of 440 MPa and an elastic modulus of 35.26 GPa.

Mechanical modulation and bioactive surface modification of porous Ti–10Mo alloy for bone implants

The objective of this work was to fabricate a suitable porous Ti–10Mo alloy as the human bone replacement implants. The porous Ti–10Mo alloy was fabricated by mechanical alloying and then consolidated by powder metallurgy technique. NH4HCO3 powder was used as space-holder. It was indicated that the mean pore size, porosity, compressive strength, and elastic modulus of porous Ti–10Mo alloy could be tailored by the amount of NH4HCO3, and then could be matched with those of human bones. Furthermore, porous Ti–10Mo alloy was treated by alkali heat treatment and soaked in the 1.5 times simulated body fluid (1.5SBF). It was observed that the surface and the inside pore wall of porous Ti–10Mo alloy with 25wt.% NH4HCO3 covered with the apatite layer after soaked in 1.5SBF for 28days. These phenomena indicated that the surface modified porous Ti–10Mo alloy exhibited a high potential for bone-bonding, which was expected to be used as bone tissue implant.

Mechanical Properties of Porous Ti-Mo and Ti-Nb Alloys for Biomedical Application by Gelcasting

In this study, we have introduced gelcasting for prepared near-shape porous Ti-Mo and Ti-Nb alloys implants. The microstructure and the total porosity of the vacuum sintered porous Ti alloys were analyzed by using electronic microscopy (SEM) and X-ray diffraction (XRD). Moreover, compression and bending tests were conducted to investigate their mechanical properties. The results shows that three-dimensional pore morphologies and total porosity range from 39% to 50% can be achieved. The microstructure of Ti-Mo and Ti-Nab alloys contained a mixture of α and β phase. The compressive strength was significantly increased with adding Mo and Nb element. The Young's modulus ranging from 5-18GPa. In conclusion, from a mechanical strength viewpoint, we have found that the porous Ti-12.5Mo and Ti-25Nb alloys prepared by gelcasting present a promising efficient process for the direct fabrication of customized implants for personalized medicine.

Preparation of Bioactive Porous Titanium-Molybdenum Alloy through Powder Metallurgy

Porous Ti-Mo alloy samples with different porosities from 52% to 72% were successfully fabricated by the space-holder sintering method. The pore size of the porous Ti-Mo alloy samples were ranged from 200 to 500 μm. The plateau stress and elastic modulus of the porous Ti-Mo alloy samples increases with the decreasing of the porosity. Moreover, an apatite coating on the Ti-Mo alloy after an alkali and heat treatment was obtained through soaking into a simulated body fluid (SBF). The porous Ti-Mo alloy provides promising potential for new implant materials with new bone tissue ingrowth ability, bioactivity and mechanical properties mimicking those of natural bone.

Preparation of Ti-Mo getters by injection molding

Ti-Mo getters have been fabricated via metal injection molding (MIM) using three kinds of Ti powders with different mean particle sizes of 46 μm, 35 μm and 26 μm, respectively. The surface morphology, porosity, and hydrogen sorption properties of Ti-Mo getters formed by MIM using paraffin wax as a principal binder constituent were examined. It has been proven that the powder injection molding is a viable forming technique for porous Ti-Mo getters. The particle size of Ti powders and the powder loading influence the porosity of getters, and this affects the sorption capacity of Ti-Mo getters. Ti-Mo getters produced with the Ti powders possessing a mean particle size of 35 μm using a powder loading of 40 vol.% have a high porosity, resulting in a good sorption capacity.