Bulk Metallic Glass Matrix Composites Research Articles

Development and microstructure optimization of Mg-based metallic glass matrix composites with in situ B2-NiTi dispersoids

Abstract In this paper, we designed a novel processing method and successfully developed in situ precipitated B2-NiTi shape-memory-alloy reinforced Mg-based bulk metallic glass matrix composites (BMGMCs). The composites exhibited improved fracture strength in both compressive and flexural modes and large plastic deformation in compressive mode compared with those of its monolithic glassy counterpart. The stress-induced martensitic transformation of B2-NiTi in this system caused the composite to exhibit work-hardening behavior, especially during compression. The microstructure of the composite was optimized by decreasing the size and increasing the volume fraction of the B2-NiTi phase, to obtain better mechanical properties. This novel in situ method is applicable to fabricating various BMGMCs, making it a breakthrough for designing ductile work-hardenable BMGMCs.

Infrared thermal processing history of a Ti-based bulk metallic glass matrix composite manufactured via semi-solid forging

A method for using non-contact infrared thermal imaging for determining the processing history of bulk metallic glass matrix composites (BMGMCs) during semi-solid forging is presented. The technique allows for the first estimations of the relevant parameters associated with semi-solid forging, including the heating profile, forging temperatures, cooling rates, and formability parameters. The processing parameters are correlated with microstructure and a new forging viscosity estimation is developed and compared with other techniques. The research offers a new strategy for thermal measurements that is widely applicable to other manufacturing processes.

A micromechanics-based incremental damage theory of bulk metallic glass matrix composites

Based on the Mori–Tanaka’s mean field concept, a micromechanics-based incremental damage theory was developed to investigate the mechanical performance of bulk metallic glass matrix composites under tension. Firstly, the shear band was considered to be a microcrack, and therefore a spherical fictitious inclusion-containing microcracks and the surrounding bulk metallic glass matrix were constructed. Based on the equivalence between the effective elasticity of microcrack-containing media and porous material, the volume fraction of the fictitious inclusion could be determined by the density of microcracks generated during a strain increment. The stress-based Weibull probability distribution function and percolation theory were applied to describe the microcrack evolution that results in the progressive damaging of bulk metallic glass composites. Based on the present model, the impact of shear bands on the tensile ductility was discussed for the composites with various microstructures. The predictions are in fairly good agreement with the experimental data, demonstrating that the developed analytical model is capable of successfully capturing the main features, such as yield strength, strain hardening, and stress softening elongation, of particle-toughened bulk metallic glass. The main conclusions will shed some light on optimizing the microstructures in effectively improving the tensile ductility of bulk metallic glass composites.

Strong work-hardening behavior induced by the solid solution strengthening of dendrites in TiZr-based bulk metallic glass matrix composites

A series of TiZr-based bulk metallic glass matrix composites (BMGMCs) with distinguished mechanical properties are successfully fabricated by adding different volume fractions of Ta (Ti38.8Zr28.8Cu6.2Be16.2Nb10 as the basic composition, denoted as Ta0.0–Ta8.0). Along with the growth of precipitated phase, typical dendritic morphology is fully developed in the TiZr-based BMGMCs of Ta8.0. Energy-dispersive spectrometry analysis of the dendrites and glass matrix indicates that the metallic elements of Nb and Ta should preferentially form solid solution into dendrites. The chaotic structure of high-temperature precipitate phase is trapped down by the rapid cooling of the copper-mould. The detected lattice distortions in the dendrites are attributed to the strong solid solution strengthening of the metallicelements of Ti, Zr, Nb, and Ta. These lattice distortions increase the resistance of the dislocation motion and pin the dislocations, thus the strength and hardness of dendrite increase. Dendrites create a strong barrier for the shear band propagation and generate multiple shear bands after solid solution strengthening, thereby providing the TiZr-based BMGMCs with greatly improved capacity to sustain plastic deformation and resistance to brittle fracture. Thus, the TiZr-based BMGMCs possess distinguished work-hardening capability. Among these TiZr-based BMGMCs, the sample Ta0.5 possesses the largest plastic strain (εp) at 20.3% and ultimate strength (σmax) of 2613MPa during compressive loading. In addition, the sample of Ta0.5 exhibits work-hardening up to an ultrahigh tensile strength of 1680MPa during the tensile process, and then progressively softens until it fractures at a strain of 10.2%.

Dynamic shear punch behavior of tungsten fiber reinforced Zr-based bulk metallic glass matrix composites

Dynamic shear punch tests were carried out on the tungsten fiber reinforced Zr-based bulk metallic glass composites. The experimental results show that with the increasing fiber volume fraction, the failure mode of the composites switches from shear to tensile fracture. A new failure criterion, based on the Tsai-Hill criterion and the unified failure criterion for bulk metallic glasses, is proposed to characterize fracture behavior of this bulk metallic glass composite. It is found that the shear-to-normal strength ratio α controls the transition of failure mode of this metallic glass composite. The underlying mechanism of the transition of failure mode is discussed as well.

Effect of compositional tailoring on the glass-forming ability and mechanical properties of TiZr-based bulk metallic glass matrix composites

A large amount of free volume (FV) or the precipitation of ductile dendrites from the glass matrix generally leads to the enhanced plasticity of bulk metallic glasses (BMGs). In this study, the structural relaxation enthalpy ΔHrel (the measure of FV amount) is found to increase after adding Nb or Fe to the glass matrix. As a result, a series of centimeter-scale plastic BMGs is fabricated. Among these TiZr-based BMGs, the sample (Ti32.8Zr30.2Cu9Ni5.3Be22.7)0.9Nb10 (at%) possesses the largest plastic strain (εp) of 8.3% and ultimate strength (σmax) of 2080MPa. By further precisely tailoring the composition, a TiZr-based BMG matrix composite (BMGMC) (Ti38.8Zr28.8Cu6.2Be16.2Nb10, at%) possessing both the precipitation of β-Ti and β-Zr dendrites simultaneously has been fabricated. The TiZr-based BMGMC has both the distinguished plastic strain (εp) of 12% and ultimate strength (σmax) of 2150MPa. The values of yielding strength (σy) significantly decreased with the increase of suction casting diameter, whereas the work-hardening phenomenon is more obvious. Therefore, a critical size and volume fractions corresponding to the best mechanical properties of TiZr-based BMGMC should exist. The ductile dendrites are crucial to impeding shear band propagation and generating multiple shear bands in the glass matrix. Results indicate that a large amount of lattice distortions, pile-ups of dislocations and shear steps can be attributed to distinguished plasticity, and these constitute the deformation mechanism of TiZr-based BMGMC.

Designing Bulk Metallic Glass Composites with Enhanced Formability and Plasticity

To address the main stumbling-block of bulk metallic glasses (BMGs), i.e., room temperature brittleness, designing BMG matrix composites has been attracted extensive attention. Up to date, BMG composites in various alloy systems have been successfully developed by forming crystalline phases embedded in the amorphous matrix through either ex-situ or in-situ methods. In this paper, a brief review of our recent work in this topic will be presented and the novel approaches to improving composite formability and mechanical properties will also be highlighted. The main purpose of this manuscript is not to offer a comprehensive review of all the BMG composites, but instead focuses will be placed on illustrating recently developed advanced BMG composites including Fe-based BMG composite with no metalloids, Al-based BMG composite and BMG composites reinforced by the TRIP (transformation-induced plasticity) effects. The basic ideas and related mechanisms underlying the development of these novel BMG composites will be discussed.

Investigation of the microcrack evolution in a Ti-based bulk metallic glass matrix composite

The initiation and evolution behavior of the shear-bands and microcracks in a Ti-based metallic-glass–matrix composite (MGMC) were investigated by using an in-situ tensile test under transmission electron microscopy (TEM). It was found that the plastic deformation of the Ti-based MGMC related with the generation of the plastic deformation zone in crystalline and shear deformation zone in glass phase near the crack tip. The dendrites can suppress the propagation of the shear band effectively. Before the rapid propagation of cracks, the extending of plastic deformation zone and shear deformation zone ahead of crack tip is the main pattern in the composite.

Understanding the deformation mechanism of individual phases of a ZrTi-based bulk metallic glass matrix composite using in situ diffraction and imaging methods

The plasticity of a ZrTi-based bulk metallic glass composite consisting of glassy matrix and crystalline dendritic phase was studied in-situ under identical tensile loading conditions using scanning electron microscopy and synchrotron X-ray diffraction. A generic procedure was developed to separate the diffraction information of the crystalline phases away from that of the matrix and to precisely calculate the microscopic strains of the two phases at different macroscopic load steps. In this way, the time-evolved quantitative links between shear bands nucleation/propagation and the corresponding microscopic stress fields around them are established, providing more quantitative understanding on (1) how the shear bands are driven by the local stress field, and (2) the critical stresses required for the shear bands to nucleate in the crystalline phase, propagate through the crystalline/matrix interface, and finally into the matrix.

Effects of casting temperature on the microstructure and mechanical properties of the TiZr-based bulk metallic glass matrix composite

The effects of casting temperature on the microstructure and mechanical properties of an in-situ bulk metallic glass matrix composite (BMGMC) with a nominal composition of Ti45.7Zr33Ni3Cu5.8Be12.5 (at.%) are investigated through X-ray diffraction (XRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), transmission electron microscopy (TEM), the uniaxial compression tests and a finite-volume-method (FVM) analysis. With different casting temperatures, the cooling rate and oxygen content are found to be responsible for the partial crystallization of the amorphous matrix and the variation of the morphology of the crystalline dendrites. Furthermore, the partial crystallization in the amorphous matrix of the BMGMC together with the variation of the morphology of dendrites are the possible reasons for the different tendency observed in strength and plastic deformation of the composite.

Tensile necking and enhanced plasticity of cold rolled β-Ti dendrite reinforced Ti-based bulk metallic glass matrix composite

Abstract Tensile mechanical properties and deformation behavior of as-cast and cold-rolled β-Ti dendrite reinforced Ti-based bulk metallic glass matrix composite (BMGMC: Ti40.2Zr18Ni2.85Cu7.65Be12.3Nb19) have been investigated. The tensile test of the pre-strained BMGMC via cold rolling manifests a distinct necking and large plasticity of ∼4%. Such an improvement in tensile mechanical properties of the cold-rolled BMGMC is attributed to the strain-induced change of elastic properties of the glassy matrix, resulting in malleable interaction between the reinforced dendrites and the microstructural evolution derived from pre-introduced multiple shear bands, leading to uniform distribution of shear strain.

Study of Mushy-Zone Development in Dendritic Microstructures with Glass-Forming Eutectic Matrices Using Electrostatic Levitation

The coarsening of dendrites in two bulk metallic glass matrix composites was investigated using noncontact techniques in a high vacuum electrostatic levitator. Progressive degrees of coarsening were observed after isothermal holds of varying duration. Specific volume and surface tension during heating and cooling were measured. Hysteresis in specific volume was observed.

Effects of infiltration parameters on mechanical and microstructural properties of tungsten wire reinforced Cu47Ti33Zr11Ni6Sn2Si1 metallic glass matrix composites

Cu47Ti33Zr11Ni6Sn2Si1-based bulk metallic glass matrix composites reinforced with tungsten wires were fabricated by infiltration process at different temperatures (850, 900, 950 and 1000 °C) and time (10, 20 and 30 min) in a quartz or a steel tube. The mechanical tests were carried out by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results show that the maximum strength and total strain of the composite are 1778 MPa and 2.8% fabricated in steel tube at 900 °C for 10 min, and 1582 MPa and 3.6% fabricated in quartz tube at 850 °C for 10 min, respectively.

Effect of cooling rate on the volume fraction of B2 phases in a CuZrAlCo metallic glass matrix composite

The material properties of bulk metallic glass matrix composites (BMGMCs) depend strongly on the morphology and elastic constants of the included crystalline phase. Transformation induced plasticity (TRIP) BMGMCs based on the Cu–Zr system are alternatives to traditional dendrite-reinforced BMGMCs. Samples of a representative alloy, Zr48Cu47.5Al4Co0.5, are fabricated in various dimensions and characterized using DSC, SEM, and ultrasonic measurement of elastic constants. It is shown that the Cu–Zr system uniquely softens during crystallization, and the microstructure of the alloy depends strongly on the rate of cooling. We conclude by discussing how combinations of part design and alloy development could be used to utilize these alloys in applications.

Dendritic and spherical crystal reinforced metallic glass matrix composites

Zr-based bulk metallic glass matrix composites (BMGMCs) with a composition of Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4-Be10.0 (at%) were fabricated by an innovative process, i.e., semisolid processing plus Bridgman solidification. Different morphologies, distributions, and volume fractions of the crystalline phases can be achieved by tailoring the withdrawal velocity. The largest fracture strain of Zr60.0Ti14.7Nb5.3Cu5.6Ni4.4Be10.0(at%) composites with the withdrawal velocity of 1.0 mm/s was found to be 16.7%. The mechanism of plasticity improvement is mainly attributed to the interpenetrated structure of the crystalline phase, which greatly confines the rapid propagation of shear bands.

Fe-based bulk metallic glass composites without any metalloid elements

Glass-formation of Fe-based bulk metallic glasses (BMGs) and their composites is strongly dependent on their metalloid content. A good Fe-based glass former usually needs a metalloid content of ∼20at.% or above; however, the high content of the metalloids usually has side-effects on the performance of the alloys. In this paper, we developed a series of metalloid-free Fe-based BMG matrix composites with a diameter of more than 10mm in the Fe–Co–La–Ce–Al–Cu system. During cooling, phase separation took place, i.e. Fe-rich and Fe-depleted liquids formed. Upon subsequent cooling, the body-centered cubic (bcc)-Fe(Co, Al) solid solution and Ce(Fe, Co)2 intermetallic phase precipitated out of the Fe-rich liquid and the remaining Co–La–Ce–Al–Cu liquid was eventually vitrified to form the amorphous matrix. Due to elemental partitioning, it was found that, for a given Fe content, there exists an optimum compositional range for Co and Ce so that a large fraction of the glassy matrix can form. In addition, the final microstructure of the current composites was strongly dependent on the cooling rates applied: excessively fast cooling rates restricted the diffusion and precipitation of the Fe atoms, which reduced formation of the glassy matrix.

Wetting of WC by a Zr-base metallic glass-forming alloy

Wetting of hot-pressed polycrystalline WC substrates by a Zr55Cu30Al10Ni5 bulk metallic glass (BMG)-forming alloy was investigated at 1133–1253 K in a high vacuum using a modified sessile drop method. The alloy melt spread rapidly on the WC surface, reaching no more than 30° within 3 s, and then slowly (at T < 1213 K) or even remained steady (at T ≥ 1213 K) in the subsequent isothermal dwelling stage. The final equilibrium contact angles were between 11° and 20°, slightly increasing with rising temperature and thus presenting an appreciably anomalous temperature-dependent behavior. The reaction between WC and the Zr-base melt was moderate, slightly enhancing with increasing temperature, and yielded W, ZrC and W5Zr3 at the interface. The wetting, in principle, was driven by the formation of a precursor film in front of the triple line as a result of the adsorption of active atoms (primarily Zr) rather than by the interfacial reaction. From the viewpoint of the wettability and reactivity, WC is a good reinforcement for the preparation of the Zr-base BMG matrix composites.

Study on microstructure and fracture behavior of tungsten wire reinforced Cu-based and Zr-based bulk metallic glass matrix composites

Cu-based and Zr-based bulk metallic glasses matrix/tungsten fiber composites were produced by infiltration process at different temperatures and times. A characterization based on X-ray diffraction (XRD) and scanning electron microscopy (SEM) is presented. The composites were tested in compression and hardness. The quality of bulk metallic matrix composites is not only experienced by the properties of the matrix and reinforcement but also by the controlling of the infiltration conditions, such as infiltration temperature and time. These parameters are important for wet-ability and interface reaction of the liquid with the reinforcement. It has been found that the reaction layer cannot be detected between the wires and matrix for Cu-base BMGCs; this may be an important difference between Zr-base and Cu-base BMG matrices and their deformation mechanism.

Bio-Properties of Zr-Based BMGMC as Potential Hard Tissue Implants

In this study, an in situ formed bulk metallic glass matrix composite (BMGMC) (Zr58.5Ti14.3Ni4.9Cu6.1Nb5.2Be11.0) was synthesized. Bulk metallic glass (BMG) (Zr52.5Cu17.9Ni14.6Al10.0Ti5.0) was also included in this work and a Ti-6Al-4V alloy was used as a reference material. Due to the glassy matrix that postpones the growth of corrosion pits, the BMGMC displays high positive corrosion potentials and low corrosion current densities. The BMGMC exhibited a higher improved corrosion resistance than the Ti alloys. Furthermore, the biocompatibility of this BMGMC was assessed by studying the cellular behavior of bone-forming mouse M3T3-E1 pre-osteoblast cells. The matrix did not significantly affect cell adhesion, proliferation and ALP activity. The general biosafety of Zr-based BMGMC for M3T3-E1 cells was revealed as normal cell responses. Zr-based BMGMC shows great potential for applications in the hard tissue implants.

Varied linear phason strain and its induced domain structure in quasicrystalline precipitates of Zr-Al-Ni-Cu-Nb bulk metallic glass matrix composites – CORRIGENDUM

Quasicrystalline precipitates in ZrAlNiCuNb alloy were systematically studied by transmission electron microscopy. It was found that precipitates always contain various linear phason strains. By electron diffraction analysis, two types of linear phason strain with two different directions perpendicular to the incident beam described by strain matrices with only one nonzero element were identified. After measuring the deviations of diffraction spots and quantitatively fitting against their perpendicular components of the reciprocal lattice vectors, the phason strain matrices were obtained. Domain structures formed as a result of linear phason strain variants along directions with equal probability. Electron diffraction and high-resolution electron imaging provide supportive evidence of this result.