Porous Ti-10Mo Alloy Research Articles

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.

Current developments of biomedical porous Ti–Mo alloys

Abstract As a biomedical hard tissue implant candidate, porous Ti–Mo alloy has received considerable attention because of its special porous structure, appropriate Young's modulus and compressive strength as well as good corrosion resistance. As a bioactive coating, hydroxyapatite is commonly used to cover the surface of bioinert metallic prostheses due to its excellent biocompatibility, bone-like structure and composition. This article reviews the current developments and the relationships between the fabrication methods, porous structure, mechanical properties, bioactive surface modification and corrosion behavior of porous Ti–Mo alloy used for hard tissue implant application. Furthermore, the future research directions are discussed to optimize the porous structure and improve the properties of porous Ti–Mo alloys.

Selective laser sintered porous Ti–(4–10)Mo alloys for biomedical applications: Structural characteristics, mechanical properties and corrosion behaviour

Porous Ti–(4–10)Mo alloys (4, 6, 8 and 10wt.% Mo) were prepared from elemental metallic powders by indirect selective laser sintering. This investigation focuses on porous, microstructural, mechanical and electrochemical properties to clarify their interrelation. The results demonstrated that lower porosity level and higher β content are beneficial to improved mechanical behaviour, while smaller pore size and lower porosity to better corrosion resistance. Namely, structural characteristics influence mechanical properties, whereas electrochemical behaviour is dominated mainly by porous features. The unique porous structure combined with suitable mechanical properties and high corrosion resistance make porous Ti–Mo alloys prospective biomaterials for orthopedic implants.

Influence of pore characteristics on microstructure, mechanical properties and corrosion resistance of selective laser sintered porous Ti–Mo alloys for biomedical applications

After preforming by selective laser sintering and subsequently post-heating at 1000°C and 1200°C, porous Ti–Mo alloys with 4, 6 and 8wt.% Mo contents display two characteristic porous structures that include three-dimensionally interconnected pores and mutually isolated pores, respectively. The cell walls exhibit a lamellar microstructure that comprises dominant α and minimal β phases at room temperature. The porous alloys experience a linear elastic deformation followed by a long plastic yield up to a peak stress and then fracture eventually under compressive loading. The mechanical properties are improved with the decrease of porosity. During potentiodynamic polarization, the high porous samples undergo several active–passive transitions prior to passivation, while the low porous samples convert directly from Tafel to passive region. The impedance data show that the passive film formed on surface of porous alloys possesses a duplex structure that consists of a barrier inner layer and a porous out layer, and the corrosion protective performance is mainly provided by the barrier layer. The electrochemical results indicate that a more porous sample is more liable to corrosion attack than a less porous one. Both mechanical properties and corrosion resistance show strong dependence on porous characteristics.

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.