Porous Bulk Metallic Glass Research Articles

The influence of porous structure on the corrosion behavior and biocompatibility of bulk Ti-based metallic glass

To mimic the biomechanical properties of natural bone, the porous Ti45Zr10Cu31Pd10Sn4 bulk metallic glass (BMG) with bone-like mechanical characteristics was developed by one step SPS method. In this work, the introduced pore contributions to the corrosion behavior in simulated body fluid and the biocompatibility of BMG were further explored. According to the findings, the porous BMG not only outperforms commercial Ti-based orthopedic implants (CP-Ti and Ti-6Al-4V) in terms of corrosion resistance, but also ranks among the porous biomedical alloys that have been reported. Simultaneously, in vitro investigations revealed that MC3T3 cells co-cultured with porous BMGs could multiply normally, indicating the porous BMG's remarkable biocompatibility.

Development of non-toxic low-cost bioactive porous Ti–Fe–Si bulk metallic glass with bone-like mechanical properties for orthopedic implants

The clinical value of large-sized Ti-based bulk metallic glass (BMG) used in orthopedic implants has greatly diminished because of the internal toxic/precious elements and the aseptic loosening caused by not only the “stress shielding” effect, but also the biological inertia of the alloy surface. Here, a toxic elements-free low-cost Ti–Fe–Si porous BMG with bone-like compressive strength (130 MPa) and Young's modulus (37 GPa) was fabricated by mechanical alloying (MA) and bonded with spark plasma sintering (SPS). By altering the loading pressure during the SPS process, the porosity and mechanical properties of the Ti–Fe–Si BMG can be effectively regulated to meet the requirements of the load-bearing cortical bone. Moreover, in vitro biological experiments revealed that the Ti–Fe–Si BMG possesses favorable bioactivity to induce the apatite and excellent biocompatibility for cell proliferation, similar to that of commercial pure Ti (cp-Ti). State-of-art Ti–Fe–Si porous BMG with global bone-like properties can be expected to be an important biomaterial for clinical orthopedic use.

Porous Ti-based bulk metallic glass orthopedic biomaterial with high strength and low Young's modulus produced by one step SPS

Abstract To alleviate the “stress shielding” of metallic biomaterials used as artificial bone, the state of art Ti45Zr10Cu31Pd10Sn4 porous bulk metallic glass (BMG) with adequate compressive strength of 180 MPa and Young's modulus of 27.2 GPa similar to nature bone was produced by a novel partial densification method using spark plasma sintering (SPS). The thermal mechanistic (sintering temperature, sintering rate and holding time) during SPS contributions to the densification behavior and the structures and mechanical properties of porous BMG were systematically explored under low loading pressure condition to obtain the optimal sintering process. With the help of this work, the potential application value of Ti–Zr–Cu–Pd–Sn BMG as substitute of human bone will be further enhanced.

Ti-based bulk metallic glass implantable biomaterial with adjustable porosity produced by a novel pressure regulation method in spark plasma sintering

Ni- and Be-free Ti-based (Ti45Zr10Cu31Pd10Sn4) bulk metallic glass (BMG) with high glass forming ability shows great potentials as implantable orthopedic biomedical materials, but the excessively high Young's modulus compared with human bones greatly affects its clinical practicability. To solve this problem, we successfully prepared porous Ti45Zr10Cu31Pd10Sn4 BMG (diameter >15 mm) with similar mechanical properties to human bones only by adjusting the sintering parameters of spark plasma sintering (SPS) without additional additives and process procedures. In this study, the influence of loading pressure during SPS on the phase composition, thermal stability, porosity, microstructure, mechanical properties and corrosion resistance of porous BMG were systematically studied. This work may open a new door for promoting novel Ti–Zr–Cu–Pd–Sn metallic glass as an implantable orthopedic biomedical material.

Open-Cell Tizr-Based Bulk Metallic Glass Scaffolds with Excellent Biocompatibility and Suitable Mechanical Properties for Biomedical Application.

A series of biocompatible high-porosity (up to 72.4%) TiZr-based porous bulk metallic glass (BMG) scaffolds were successfully fabricated by hot pressing a mixture of toxic element-free TiZr-based BMG powder and an Al particle space holder. The morphology of the fabricated scaffolds was similar to that of human bones, with pore sizes ranging from 75 to 250 μm. X-ray diffraction patterns and transmission electron microscopy images indicated that the amorphous structure of the TiZr-based BMG scaffolds remained in the amorphous state after hot pressing. Noncytotoxicity and extracellular calcium deposition of the TiZr-based BMG scaffolds at porosities of 32.8%, 48.8%, and 64.0% were examined by using the direct contact method. The results showed that the BMG scaffolds possess high cell viability and extracellular calcium deposition with average cell survival and deposition rates of approximately 170.1% and 130.9%, respectively. In addition, the resulting TiZr-based BMG scaffolds exhibited a considerable reduction in Young’s moduli from 56.4 to 2.3 GPa, compressive strength from 979 to 19 MPa, and bending strength from 157 MPa to 49 MPa when the porosity was gradually increased from 2.0% to 72.4%. Based on the aforementioned specific characteristics, TiZr-based BMG scaffolds can be considered as potential candidates for biomedical applications in the human body.

Size-dependent failure of the strongest bulk metallic glass

Upon reducing the sample size into micrometer scale, an obvious brittle-to-ductile transition accompanied by a drastic change of failure mode from shattering to shear-banding was observed when compressing the brittle but strong Co55Ta10B35 bulk metallic glass (BMG). The shattering failure under macroscopic compression is dominated by splitting cracking, which completely differs from shear-banding and originates from extrinsic defects like inclusions. To reveal the critical conditions for shear-banding and splitting cracking, various micropillar specimens with intentionally introduced holes as extrinsic defects were tested, and the stress distributions at the failure moment were analyzed with finite element simulation. The shear plane criterion was found to be quite effective to estimate the nominal stress required for the failure dominated by shear-banding. However, brittle splitting cracking does not occur although the maximum tensile stress reaches the critical value, which is different from traditional brittle solids. To initiate splitting cracking, a high-tensile-stress region over a critical distance, which depends on defect size and fracture toughness of the BMG, is required. The critical conditions for shear failure and splitting cracking demonstrated in this approach can be used to estimate the failure conditions of various BMG components with complex geometries in a wide range of length scales, and to design tough composites based on brittle BMGs. As an example, a design criterion to avoid brittle splitting fracture of porous BMG materials is proposed.

Size-Dependent Failure of the Strongest Bulk Metallic Glass

Upon reducing the sample size into micrometer scale, an obvious brittle-to-ductile transition accompanied by a drastic change of failure mode from shattering to shear-banding was observed when compressing the brittle but strong Co55Ta10B35 bulk metallic glass (BMG). The shattering failure under macroscopic compression is dominated by splitting cracking, which completely differs from shear-banding and originates from extrinsic defects like inclusions. To reveal the critical conditions for shear-banding and splitting cracking, various micropillar specimens with intentionally introduced holes as extrinsic defects were tested, and the stress distributions at the failure moment were analyzed with finite element simulation. The shear plane criterion was found to be quite effective to estimate the nominal stress required for the failure dominated by shear-banding. However, brittle splitting cracking does not occur although the maximum tensile stress reaches the critical value, which is different from traditional brittle solids. To initiate splitting cracking, a high-tensile-stress region over a critical distance, which depends on defect size and fracture toughness of the BMG, is required. The critical conditions for shear failure and splitting cracking demonstrated in this approach can be used to estimate the failure conditions of various BMG components with complex geometries in a wide range of length scales, and to design tough composites based on brittle BMGs. As an example, a design criterion to avoid brittle splitting fracture of porous BMG materials is proposed.

Three-Dimensional Unit Cell Study of a Porous Bulk Metallic Glass Under Various Stress States

Porous bulk metallic glasses (BMGs) exhibit an excellent combination of superior mechanical properties such as high strength, high resilience, large malleability, and energy absorption capacity. However, a mechanistic understanding of their response under diverse states of stress encountered in practical load-bearing applications is lacking in the literature. In this work, this gap is addressed by performing three-dimensional finite element simulations of porous BMGs subjected to a wide range of tensile and compressive states of stress. A unit cell approach is adopted to investigate the mechanical behavior of a porous BMG having 3% porosity. A parametric study of the effect of stress triaxialities T = 0, ±1/3, ±1, ±2, ±3, and ±∞, which correspond to stress states ranging from pure deviatoric stress to pure hydrostatic stress under tension and compression, is conducted. Apart from the influence of T, the effects of friction parameter, strain-softening parameter and Poisson’s ratio on the mechanics of deformation of porous BMGs are also elucidated. The results are discussed in terms of the simulated stress-strain curves, pore volume fraction evolution, strain to failure, and development of plastic deformation near the pore. The present results have important implications for the design of porous BMG structures.

3D printing of Zr-based bulk metallic glasses and components for potential biomedical applications

In this work, the 3D printing technique based on selective laser melting (SLM) was applied to fabricate a Ni-free and Ag-bearing Zr-based bulk metallic glass (BMG) and porous architectures with complex geometries and various functions. The 3D-printed Zr-based BMG was systematically examined by a set of experiments, including microstructure characterizations, mechanical testing, wear and corrosion resistance measurements, in vitro biocompatibility and antibacterial capability assessments. We revealed that the 3D-printed BMG presents almost fully amorphous structure with a high strength (>1700 MPa) and relatively low Young's modulus (∼80 GPa). The wear resistance was comparable to the commercial Ti6Al4V medical alloy in simulated body fluid (SBF), and the corrosion resistance surpassed Ti6Al4V due to lower corrosion rate as well as smaller passive current density. In addition, the 3D-printed BMG showed excellent biocompatibility, as indicated by superior cell proliferation support and ppb level of ion release. More importantly, the 3D printed BMG also exhibited excellent antibacterial ability against E. coli due to the inclusion of a trace amount of Ag. Furthermore, for application purposes, porous BMG components with pore size of 500 μm were printed by SLM technique, which displayed an interconnected porosity of 70% and extremely low Young's modulus of 13 GPa (being comparable to the human bone tissue), while maintaining a high yield strength of 350 MPa. The findings in this work suggested that the SLM-based 3D printing technique could be promising for manufacturing Zr-based BMGs with complex geometries in a wide range of biomedical applications.

Corrosion behaviour of porous Ni-free Ti-based bulk metallic glass produced by spark plasma sintering in Hanks' solution

Porous bulk metallic glasses (BMGs) are promising biomedical materials to be used for surgical implants. Here we report on successful formation of porous Ni-free Ti-based BMGs with a diameter exceeding 15 mm by spark plasma sintering the mixture of the gas-atomized Ti-based (Ti45Zr10Cu31Pd10Sn4) glassy alloy powder and solid salt powder, followed by leaching treatment into water to eliminate the salt phase. Corrosion behaviour of the produced porous Ti-based BMGs was investigated in Hanks' solution. The potentiodynamic polarization curves showed that the anodic current density in the porous Ti-based BMGs slowly increased during anodic polarization, suggesting the crevice corrosion.

Processing Porous Bulk Metallic Glass Using Prealloyed Powders

AbstractZr50Cu40Al10 metallic‐glass powders are prepared via the gas‐atomization method. The powders are spherical in shape, and contain different crystalline phases depending on the particle size. Through mechanical milling, the shape and the structure of the as‐atomized metallic‐glass powders can be modified, and very‐fine and fully amorphous powders are obtained after milling for 120 h. The as‐milled powders show excellent compressibility and densification behavior. By the addition of the Cu powders and using the as‐milled metallic‐glass powders, a porous metallic‐glass compact is fabricated, which has a porosity of about 48% and a pronounced ductility.

Preparation of a Zr-based bulk glassy alloy foam

A Zr 48 Cu 36 Al 8 Ag 8 bulk metallic glass (BMG) containing spherical pores with 3.9% porosity was prepared by melting a Zr 48 Cu 36 Al 8 Ag 8 powder under 1.0 MPa pressurized helium. Annealing treatment of the porous alloy in a supercooled liquid region causes expansion of the pores. Highly porous BMG with a cellular structure was prepared by sudden reduction of the helium pressure in the crucible before quenching. The porous alloys exhibited significant plasticity due to a high density of shear bands initiated from pores.

Porous Bulk Metallic Glass Fabricated by Powder Consolidation

A synthesis method for the production of porous bulk metallic glass (BMG) is introduced. This method utilizes the superplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), x-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and percentage of amorphous phase of the as-produced porous BMG. The results suggest that the formation of porous structure by superplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. None of crystalline phases was formed during hot pressing, and less than 3.5% percent of residual salt was enclosed in the foam. In order to remove any residual salt particles, salt preform with three-dimensional network and good connectivity is necessary.

Porous bulk metallic glass fabricated by powder hot pressing

A synthesis method for the production of porous bulk metallic glass (BMG) was introduced. This method utilizes the superplastic forming ability of amorphous powder in the supercooled liquid (SCL) state and intenerating salt mixture as a placeholder to produce BMG foam by using a hot die pressing method. Scanning electron microscope (SEM), X-ray diffraction (XRD) and differential scanning calorimetry (DSC) were employed to characterize the morphologies of foaming structure, the crystallization and the percentage of crystallization of the as-produced porous BMG. The results suggested that the formation of porous structure by su-perplastic forming process is feasible. Good bonding effect was observed between amorphous powder particles. Less than 6.5% of crystalline phases were formed during hot pressing, and less than 5.5% of residual salt was enclosed in the foam. To remove any residual salt particles, salt preforms with three-dimensional network and good connectivity is necessary.

A Porous Bulk Metallic Glass with Unidirectional Opening Pores

Porous Zr-based bulk metallic glass (PMG) with unidirectional opening pores is prepared by electrochemical etching of tungsten wires of the W/bulk metallic glass (BMG) composites. The porosity and pore size can be controlled by adjusting the tungsten wires. The PMG showed no measurable loss in thermal stability as compared to the monolithic Zr-based BMG by water quenching and is more ductile and softer than the pore-free counterpart. The specific surface area of the PMGs is calculated to be 0.65, 3.96, and 10.54 m(2)/kg for 20, 60, and 80 vol % porosity, respectively. (c) 2007 The Electrochemical Society.