Ti-based Bulk Metallic Glass Research Articles

Development of in-situ β-Ti reinforced Be-free Ti–based bulk metallic glass matrix composites

In this paper, in-situ β-Ti phase reinforced (Al, Ni, Be)-free Ti-based bulk metallic glass matrix composites (BMGMCs) were developed by microalloying Mo. The BMGMCs showed higher fracture strength and larger plastic strain than the monolithic glassy counterpart and other Be-free Ti-based BMGMCs, under both compression and bending tests. The ductile and soft β-Ti secondary phase appeared to hinder the rapid propagation of the main shear band, improving the plasticity. Furthermore, the size and interparticle spacing of the secondary β-Ti were very close to the processing zone size, further stabilizing the shear band against developing into cracks and thus improving mechanical properties. But under tension, no obvious ductilization was observed for the BMGMCs, maybe resulting from the lower volume fraction of β-Ti phase because of higher cooling rate during the fabrication for them. Further work should be focused on optimizing the composition and increasing the volume fraction of β-Ti phase and sample size.

β-type Ti-based bulk metallic glass composites with tailored structural metastability

Abstract Bulk metallic glass composites (BMGCs) containing an in-situ formed metastable β phase (β-type BMGCs) being capable of transforming to martensites, are a promising class of alloys. Nonetheless, the influence of the structural metastability of β phases on the deformation mechanisms of BMGCs remains largely unclear. This, however, is crucial for understanding and optimizing plastic deformability. In this study, three Ti-based β-type BMGCs with nominal compositions of (Ti0.505Zr0.353Fe0.028Be0.114)100−xCux (x = 1, 5, 8) have been developed, in each of which the β-Ti phase has a different metastability. For x = 8, the β phase precipitates exclusively and does not transform martensitically during deformation. At the lowest Cu content (x = 1), however, the β phase contains a high density of fine ω phase upon quenching, which hinders the deformation-induced martensitic transformation. β phases in both BMGCs deform plastically by dislocation glide. Only when x = 5 does the β phase undergo the martensitic transformation to α″-Ti due to an appropriate degree of metastability. The reversible phase transformation between β and α″ followed by twinning in α″ on continuing deformation leads to a “double yielding” behavior and results in strong work-hardening capability as well as superelasticity during compression (cyclic loading) tests.

Enhancing the compressive and tensile properties of Ti-based glassy matrix composites with Nb addition

Combining copper mold suction-casting and copper mold pouring-casting techniques, in-situ Ti-based bulk metallic glass matrix composites (Ti0.45Zr0.31Be0.17Cu0.07)100−xNbx (x=4, 6, 8 and 10) with Φ=3mm and composites (x=6, 8 and 10) with Φ=8mm are fabricated in order to perform compressive and tensile tests, respectively. The volume and size of crystalline β-Ti(Zr, Nb) dendrites of these composites increase with the increasing Nb content, resulting in the improvement of compressive and tensile properties of the composites. Among these composites, Ti40.5Zr27.9Be15.3Cu6.3Nb10 (x=10) has the highest compressive ultimate strength of 2756MPa and plastic strain of 39.5%; meanwhile, it possesses a high tensile ultimate strength of 1428MPa and a large tensile plasticity of 7.7%. As indicated by the SEM micrographs, in compressive tests, the more branched the dendrites, the more shear bands, and the higher compressive strength and plasticity of these composites. In tensile tests of Ti40.5Zr27.9Be15.3Cu6.3Nb10 (x=10), ductile fracture features, including the macroscopic necking, fracture of ligament, vein patterns and sliding traces, are observed. The reason of the excellent mechanical properties of the measured composites is that the propagation of shear bands and cracks are impeded by β-Ti(Zr, Nb) dendrites, and then be confined in a small space.

Biocompatibility study on Ni-free Ti-based and Zr-based bulk metallic glasses

Safety and reliability are crucial issues for medical instruments and implants. In the past few decays, bulk metallic glasses (BMGs) have drawn attentions due to their superior mechanical properties, good corrosion resistance, antibacterial and good biocompatibility. However, most Zr-based and Ti-based BMGs contain Ni as an important element which is prone to human allergy problem. In this study, the Ni-free Ti-based and Zr-based BMGs, Ti40Zr10Cu36Pd14, and Zr48Cu36Al8Ag8, were selected for systematical evaluation of their biocompatibility. Several biocompatibility tests, co-cultural with L929 murine fibroblast cell line, were carried out on these two BMGs, as well as the comparison samples of Ti6Al4V and pure Cu. The results in terms of cellular adhesion, cytotoxicity, and metallic ion release affection reveal that the Ti40Zr10Cu36Pd14 BMG and Ti6Al4V exhibit the optimum biocompatibility; cells still being attached on the petri dish with good adhesion and exhibiting the spindle shape after direct contact test. Furthermore, the Ti40Zr10Cu36Pd14 BMG showed very low Cu ion release level, in agreement with the MTT results. Based on the current findings, it is believed that Ni-free Ti-based BMG can act as an ideal candidate for medical implant.

Micro-patterning by thermoplastic forming of Ni-free Ti-based bulk metallic glasses

The development of bulk metallic glasses for biomedical applications has become the focus of intense research interest. In this work, we report on the unique thermoplastic behavior of two Ni-free Ti-based bulk metallic glasses by utilizing the dramatic softening of the amorphous structure in the super cooled liquid region. Ti40Zr10Cu34Pd14Ga2 and Ti40Zr10Cu34Pd14Sn2 bulk glassy alloys were produced by copper mold casting. Ga and Sn micro-alloying (2at%) improve the glass-forming ability and mechanical properties of Ti40Zr10Cu36Pd14 alloy effectively. The cast rods were thermo-mechanically characterized to determine the most suitable processing temperature and time, and the load that has to be applied for thermoplastic net-shaping of the BMGs into anisotropically etched cavities of silicon chips. Periodic features with high surface smoothness and uniform height (24μm high circular bumps with sub-μm roughness) were created on the surface of the BMGs. The surface patterning with controllable roughness of Ti-based BMGs can be useful in biomedical studies by mediating material - cell interactions.

Wear Behavior of Mechanically Alloyed Ti-Based Bulk Metallic Glass Composites Containing Carbon Nanotubes

The present paper reports the preparation and wear behavior of mechanically alloyed Ti-based bulk metallic glass composites containing carbon nanotube (CNT) particles. The differential scanning calorimeter results show that the thermal stability of the amorphous matrix is affected by the presence of CNT particles. Changes in glass transition temperature (Tg) and crystallization temperature (Tx) suggest that deviations in the chemical composition of the amorphous matrix occurred because of a partial dissolution of the CNT species into the amorphous phase. Although the hardness of CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composites is increased with the addition of CNT particles, the wear resistance of such composites is not directly proportional to their hardness, and does not follow the standard wear law. A worn surface under a high applied load shows that the 12 vol. % CNT/Ti50Cu28Ni15Sn7 bulk metallic glass composite suffers severe wear compared with monolithic Ti50Cu28Ni15Sn7 bulk metallic glass.

The Effect of Thermal Cycling Treatments on the Thermal Stability and Mechanical Properties of a Ti-Based Bulk Metallic Glass Composite

The effect of thermal cycling treatments on the thermal stability and mechanical properties of a Ti48Zr20Nb12Cu5Be15 bulk metallic glass composite (BMGC) has been investigated. Results show that moderate thermal cycles in a temperature range of −196 °C (cryogenic temperature, CT) to 25 °C (room temperature, RT) or annealing time at CT has not induced obvious changes of thermal stability and then it decreases slightly over critical thermal parameters. In addition, the dendritic second phases with a bcc structure are homogeneously embedded in the amorphous matrix; no visible changes are detected, which shows structural stability. Excellent mechanical properties as high as 1599 MPa yield strength and 34% plastic strain are obtained, and the yield strength and elastic modulus also increase gradually. The effect on the stability is analyzed quantitatively by crystallization kinetics and plastic-flow models, and indicates that the reduction of structural relaxation enthalpy, which is related to the degradation of spatial heterogeneity, reduces thermal stability but does not imperatively deteriorate the plasticity.

Review on the Research and Development of Ti-Based Bulk Metallic Glasses

Ti-based bulk metallic glasses (BMGs) are very attractive for applications because of their excellent properties such as high specific strength and high corrosion resistance. In this paper, we briefly review the current status of the research and development of Ti-based bulk metallic glasses. Emphasis is laid on glass-forming ability, mechanical properties, corrosion resistance, and biocompatibility.

The wear properties of Ti-based bulk metallic glass composites containing carbon particles

Abstract This paper reports the preparation and wear behavior of mechanically alloyed Ti-based bulk metallic glass composites containing carbon particles. The carbon/Ti 50 Cu 28 Ni 15 Sn 7 metallic glass composite powders are formed by two-stage mechanical alloying (MA) process. The bulk metallic glass composite was successfully prepared by vacuum hot pressing of as-milled carbon/Ti 50 Cu 28 Ni 15 Sn 7 metallic glass composite powders. The differential scanning calorimeter (DSC) results show that the thermal stability of the amorphous matrix is affected by the presence of the carbon particles. Changes in T g and T x suggest deviations in the chemical composition of the amorphous matrix that were developed due to a partial dissolution of the carbon species into the amorphous phase. Although the hardness of carbon/Ti 50 Cu 28 Ni 15 Sn 7 bulk metallic glass composite is increased with carbon addition, but their wear resistances is not directly proportional to hardness and does not follow the standard wear law. The increase in the wear rate of a carbon/Ti 50 Cu 28 Ni 15 Sn 7 bulk metallic glass composite with high carbon content may be attributed to the residual porosity and in-situ formed hard TiC particles formed in situ in the matrix of the composite.

Effect of transition metal elements (Cu, Ni, Co and Fe) on the mechanical properties of Ti-based bulk metallic glass composites

A series of Ti-based Ti45Zr25Nb6Sn2TM5Be17 (at.%, TM = Cu, Ni, Co and Fe) BMG composites were studied to show the effect of transition metal elements on the microstructure, intrinsic properties and mechanical properties of Ti-based BMG composites. The research shows that the transition metal elements are distributed mainly in the glass-matrix, substitution of which influences significantly the Young's modulus and hardness of glass-matrix. Different from the load-bearing model, the yielding strength of the BMG composites relates highly to not only the yielding strength of the dendrite-phase but also that of the glass-matrix. The plasticity of the BMG composites is highly dependent on the average stress concentration factor of the dendrite-phase. A useful rule for preparing of BMG composite with high strength and excellent plasticity is herein proposed, where tailoring simultaneously the properties of dendrite-phase and glass-matrix is suggested to be a better choice to obtain a good compromise between strength and plasticity.

Distribution of Be in a Ti-Based Bulk Metallic Glass Composite Containing B-Ti

In order to obtain a glassy matrix during quenching, Be is often selected as a constituent of the compositions of Ti/Zr-based bulk metallic glass composites (BMGCs). The in situ formed β phase in Be-bearing BMGCs was reported to be Be-free. However, a thorough investigation of the distribution of Be in BMGCs is still missing to date. In this work, the distribution of Be in a Ti 47.5 Zr 33 Cu 5.8 Co 3 Be 12.5 (at.%) BMGC was studied by the secondary ion mass spectrometry (SIMS) and the electron energy loss spectroscopy (EELS). It is found that Be almost totally dissolves in the glassy matrix, but a very weak intensity of Be in β phase is still detectable by SIMS, and the content of Be in β-Ti is estimated to be about 0.3 at.%. Based on the recently established two-phase quasi-equilibrium of BMGCs, the distinct solubility of Be in the glassy matrix and in β-Ti has been explained.

Evolution of residual stress, free volume, and hardness in the laser shock peened Ti-based metallic glass

Laser shock peening (LSP) with different cycles was performed on the Ti-based bulk metallic glasses (BMGs). The sub-surface residual stress of the LSPed specimens was measured by high-energy X-ray diffraction (HEXRD) and the near-surface residual stress was measured by scanning electron microscope/focused ion beam (SEM/FIB) instrument. The sub-surface residual stress in the LSP impact direction (about −170MPa) is much lower than that perpendicular to the impact direction (about −350MPa), exhibiting anisotropy. The depth of the compressive stress zone increases from 400μm to 500μm with increasing LSP cycles. The highest near-surface residual stress is about −750MPa. LSP caused the free volume to increase and the maximum increase appeared after the first LSP process. Compared with the hardness (567±7HV) of the as-cast BMG, the hardness (590±9HV) on the shocked surface shows a hardening effect due to the hardening mechanism of compressive residual stress; and the hardness (420±9HV) on the longitudinal section shows a softening effect due to the softening mechanism of free volume.

Viscous surface flow induced on Ti-based bulk metallic glass by heavy ion irradiation

Ti-based bulk metallic glass was irradiated by a 20MeV Cl4+ ion beam under liquid-nitrogen cooling, which produced remarkable surface smoothing and roughening that respectively correspond to normal and off-normal incidence angles of irradiation. Atomic force microscopy confirms two types of periodic ripples distributed evenly over the rough glass surface. In terms of mechanism, irradiation-induced viscosity agrees with the theoretical prediction for metallic glasses near glass transition temperature. Here, a model is introduced, based on relaxation of confined viscous flow with a thin liquid-like layer, that explains both surface smoothing and ripple formation. This study demonstrates that bulk metallic glass has high morphological instability and low viscosity under ion irradiation, which assets can pave new paths for metallic glass applications.

Effects of Sn addition on mechanical properties of Ti-based bulk metallic glass composites

Ti-based bulk metallic glass (BMG) composites were prepared by a minor addition of Sn to match the Young's modulus of dendrite-phase and glass-matrix, and prepared by suction casting into a water-cooled copper mold. The largest compressive fracture strain of 28.07% and the highest fracture strength of 1820MPa are obtained simultaneously in the Ti45Zr25Nb6Cu5Be17Sn2 BMG composite. The average stress concentration factor of dendrite-phase, which characterizes the concentrated stress in the dendrite-phase that is transferred to the glass-matrix through the interface, is found to be highly related to the mechanical properties and thus would be a guide for matching the Young's modulus. The microscopic deformation mechanism shows that the high average stress concentration factor of dendrite-phase promotes the transfer of concentrated stress from the dendrite-phase to the glass-matrix, thus leading to the formation of multiple shear bands. Matching the Young's modulus of dendrite-phase and glass-matrix is concluded to be a useful recipe to prepare the BMG composites with excellent mechanical properties.

Enhanced Mechanical Properties, Corrosion Behavior and Bioactivity of Ti-based Bulk Metallic Glasses with Minor Addition Elements

In this research, corrosion behavior, mechanical properties and bioactivity of Ti–Zr–Cu–Pd–Sn bulk metallic glasses with minor addition of Au, Pt, Nb or Ta elements were investigated. The results revealed that minor additions of the elements were beneficial to enhancing mechanical properties and corrosion resistance of Ti-based bulk metallic glasses. Minor addition of the element (especially with Nb and Ta addition) results in the improvement in plastic deformation ability due to the existing of nanoparticles with a size smaller than 10 nm in glassy matrix, inhibiting the deformation of the shear bonds. Enrichments of Ti and Zr elements in oxide layer were responsible for high corrosion resistance. The bioactivity of Ti-based bulk metallic glasses was also investigated. The best combination of large plastic deformation ability, good corrosion resistance and bioactivity in Ti40Zr10Cu33Pd14Sn2Ta1 BMG was obtained.

Mechanical behavior and wear performance of a Ti-based bulk metallic glass composite containing dendritic and intermetallic phases

A biocompatible bulk metallic glass composite (BMGC) alloy with a nominal composition of Ti56Zr6Cu19.8Pd8.4Sn1.8Nb8 was designed to obtain microstructure consisting of β-Ti dendrites and glassy matrix. It was found that Nb-rich β-Ti dendrites were the primary phase in the alloy, and extra discontinuous island-like Ti2Cu phase was also produced in the glassy matrix. The BMGC alloy presented higher yield strength, remarkably increased plasticity and pronounced work-hardening characteristic. Furthermore, excellent sliding wear resistance was exhibited by the alloy due to the work-hardening capability and the contribution of the Ti2Cu intermetallic phase.

Composition design procedures of Ti-based bulk metallic glasses using the cluster-plus-glue-atom model

It is known that bulk metallic glasses are interpreted by simple composition formulas [cluster](glue atom)1 or 3, with the valence electron number per unit formula (e/u) being universally 24. In the present work, this cluster-plus-glue-atom approach was explored in great details for the objective of establishing the standard procedures towards designing bulk metallic glasses, via example of Ti-Cu-based alloys. The cluster selection from devitrification phases and the e/u calculation methods were first clarified. Then, step-by-step procedures toward developing alloys with high glass forming abilities were proposed. The cluster formula [Ti-Cu6Ti8]Cu3, with e/u ≈ 23.6, was taken as the basic composition formula. Upon properly alloying with Zr and Sn, large glass forming abilities up to 5 mm in diameter were experimentally reached at Ti40Zr10Cu56.94Sn3.06 via copper mold suction casting. Another alloy Ti45.71Zr11.43Cu39.29Sn3.57 showed a slightly inferior glass forming ability of 4 mm but contained the highest Ti(Zr) content of all the Ti-based BMGs, Ni-, Pd- and Be-free. The thus-obtained bulk metallic glasses generally exhibited high compressive strengths of about 1.8 GPa and nearly zero ductilities, except a Co-alloyed one, [Ti-Cu5.3Sn0.5Co0.2Ti6.2Zr1.8]Cu3, whose compressive ductility exceeded 6%.

Quasi-static and dynamic deformation of an in-situ Ti-based metallic glass composite in supercooled liquid region

The quasi-static and dynamic deformation behaviors of the Ti-based bulk metallic glass (BMG) composite (Ti48Zr20Nb12Cu5Be15) were investigated in the supercooled liquid region. The present BMG composite exhibits homogenous viscous flow under quasi-static deformation, but shear-band dominated inhomogeneous plastic deformation upon dynamic loading. With the increase of the temperature, the flow stress decreases in both quasi-static and dynamic conditions. Due to the effective plastic accommodation of dendrites to the glass matrix, characteristic of the formation of shear steps and multiple dislocations, the remarkable plasticity under dynamic deformation has been obtained in the present BMG composite in SLR. The constitutive equation for the present BMG composite upon quasi-static loading is obtained. Upon dynamic loading, the flow stress approximately follows a linear relationship with the temperature: σ (MPa) ≈ 2,791–2.11T(K).

Ti[sbnd]Cu[sbnd]Zr[sbnd]Fe[sbnd]Sn[sbnd]Si[sbnd]Sc bulk metallic glasses with good mechanical properties for biomedical applications

Ti-based bulk metallic glasses (BMGs) free from highly toxic elements Ni and Be and noble elements were designed and synthesized in Ti47−xCu40Zr7.5Fe2.5Sn2Si1Scx (x = 1, 2, 3 and 4 at.%) system as potential biomaterials, and the effects of Sc alloying on glass-formation and properties of the Ti-based BMGs were investigated. The Ti-based BMGs containing 2 and 3 at.% Sc exhibited high glass-forming ability (GFA) and wide supercooled liquid region, and glassy rods with a diameter of 6 mm could be prepared by tilt-pour copper-mold casting. The Ti-based BMGs possess low Young's modulus of 93–99 GPa, high yield strength of 1948–2021 MPa and specific strength of about 3.2 × 105 N m/kg and plastic strain up to 5.9% under compression, and high Vickers microhardness of 577–590 Hv. The TiCuZrFeSnSiSc glassy alloys also exhibited good bio-corrosion resistance and biocompatibility. The mechanisms for the effects of Sc addition on glass formation, mechanical properties, corrosion behaviors and biocompatibility of the Ti-based BMGs are discussed. The combination of superior GFA, good mechano- and bio-compatibility demonstrates the potential of the TiCuZrFeSnSiSc BMGs for biomedical applications.

Microstructure characterization and mechanical properties of Ti-based bulk metallic glass joints prepared with friction stir spot welding process

In this study, TiZrFeBeCu bulk metallic glass plates have been welded together by using the friction stir spot welding method. The effects of processing parameters on the microstructure and mechanical properties of the joints have been studied. It has been found that the plunge depth has a crucial effect on the fracture mode and fracture strength of the joint. Both tool rotation speed and holding time significantly influence the tensile/shear fracture load and the fracture toughness. The correlation between fracture surface and the fracture toughness have been analyzed. The results revealed that there exist three regions in the spot welding of bulk metallic glass plates: stirring zone, thermo mechanically affected zone and base metal. It shows that stirring zone under the tool shoulder and around the tool tip possesses different structures and micro-hardness from that beneath the tool tip. The thermo mechanically affected zone and the stirring zone under the tool tip have similar hardness and structure. Stress relief annealing was used to clarify the reason for the hardness difference at different regions. Changes in the hardness in different areas of the welding spot can be correlated with the shear bands pattern and plastic zone size around the Vickers indents.