Reinforced Bulk Metallic Glass Matrix Research Articles

Fracture toughness of a rejuvenated β-Ti reinforced bulk metallic glass matrix composite

• Cryothermal cycling is performed on embrittled bulk metallic glass composite. • Plasticity of BMGC examined using nanoindentation, DSC and compression tests. • Mode I notch toughness of CTC treated BMGC is same as brittle BMGC. • Rejuvenation is hampered by chemical short range ordering of constituents in amorphous matrix. A β-Ti dendrite reinforced Zr-based bulk metallic glass composite (BMGC) was found to be brittle when cast in a large size. The reasons for the embrittlement and the effectiveness of the cryothermal cycling (CTC) treatment in restoring the mode I fracture toughness are examined. Plasticity in all the CTC treated BMGC is estimated from the distribution and occurrence of pop-ins in nanoindentation tests and by measuring the magnitude of enthalpy of relaxation (Δ H rel ) via differential scanning calorimetry (DSC). This is further validated by examining the strain-to-failure ( ε f ) in compression tests. Mode I fracture behaviour of the as-cast embrittled BMGC and the CTC treated BMGC, which exhibits maximum plasticity, is examined. Results show that both BMGCs are equally brittle and exhibit 5 times lower notch toughness ( K QJ ) than their tougher counterpart. Post-facto imaging of the side surfaces reveals the absence of notch-tip plasticity in both BMGCs. The lack of notch tip plasticity of CTC treated BMGC, despite exhibiting signatures of plasticity in nanoindentation and higher Δ H rel is rationalized by reassessing the origin of pop-ins in nanoindentation tests and describing the variations in chemical and topological short range ordering during CTC, respectively. Implications of these results in terms of improving the fracture toughness of structurally relaxed BMGCs via CTC are discussed.

Fabrication and mechanical property of three-dimensional carbon fiber reinforced Mg-based bulk metallic glass matrix composite

Carbon fiber (CF) reinforced bulk metallic glass matrix composites (BMGMCs) have received widespread attention due to their light weight, but subsequent development is facing urgent challenges of uncontrollable interface reaction and poor plasticity. Here, we report a three-dimensional CF-reinforced Mg-based BMGMC, which significantly improves the microstructure and compressive plasticity by adjusting the pressure infiltration parameters. It has been found that the electroless copper plating improves the wettability of the CF and the melt without inducing the crystallization of the matrix, in spite of the partially dissolving and diffusing of the coating to the matrix. Under a similar infiltration pressure difference, high vacuum conditions are beneficial to reduce the capillary resistance of the porous CF preform, thereby improving the formability of BMGMC. Compression test results prove that the introduction of three-dimensional CF effectively improves the plasticity of the composite material and reduces its brittleness tendency. It can be attributed to the fact that the carbon fibers distributed in different directions effectively bridge the multi-directional cracks and prevent the early rapid shear band propagation. The present work provides meaningful enlightenment for the development of CF-reinforced BMGMC materials.

2D Micromechanical Modeling and Simulation of Ta-Particles Reinforced Bulk Metallic Glass Matrix Composite

The influence of particle shape, orientation, and volume fractions, as well as loading conditions, on the mechanical behavior of Ta particles reinforced with bulk metallic glass matrix composite is investigated in this work. A Matlab program is developed to output the MSC.Patran Command Language (PCL) in order to generate automatically two-dimensional (2D) micromechanical finite element (FE) models, in which particle shapes, locations, orientations, and dimensions are determined through a few random number generators. With the help of the user-defined material subroutine (UMAT) in ABAQUS, an implicit numerical method based on the free volume model has been implemented to describe the mechanical response of bulk metallic glass. A series of computational experiments are performed to study the influence of particle shapes, orientations, volume fractions, and loading conditions of the representative volume cell (RVC) on its composite mechanical properties.

Prediction of effective mechanical properties of composite materials using homogenization approach: Application to tungsten fiber reinforced bulk metallic glass matrix composite

In this paper, the homogenization approach was presented to predict the effective mechanical properties of heterogeneous materials such as composite materials. Indeed, the main idea of this approach is to characterize the effective mechanical properties from a microstructural description of the heterogeneous materials and the knowledge of the local behavior of constituents using the homogenization process. It is a very efficient tool which is intensively developed in the field of numerical simulation of heterogeneous materials. Different scheme established from the solution of Eshelby’s inclusion problem are recalled such as Mori-Tanaka scheme, dilute scheme and Voigt and Reuss bounds. Homogenization approach was applied to estimate the effective mechanical properties of tungsten fiber reinforced bulk metallic glass matrix composite. Predicted values were confronted with those obtained by experimental approach from literature. These comparisons show good agreement between the predicted and experimental values. The maximum deviations remain lower than 10.5% using Voigt bound. A parametric study shows that the mechanical properties depend strongly on the shape of inclusions.

Triple-yieldable multiphase reinforced bulk metallic glass matrix composites under tension

Multiphase (Ta-rich phase, B2 and B19′-CuZr) reinforced bulk metallic glass matrix composites (BMGMCs) were successfully developed. The Ta-rich phase appeared not only to hinder the propagation of shear bands, but also to act as a nucleant for the B2 and B19′ phases to homogenize their distribution. The composites showed superior tensile plasticity, work-hardening, and a unique triple yielding behavior. The martensitic transformation of B2-CuZr, the deformation of the Ta-rich phase, and the twinning and detwinning of B19′-CuZr all contributed to these mechanical properties. The present novel BMGMC is expected to lead to a breakthrough in designing work-hardenable and ductile BMGMCs.

Internal structural evolution and enhanced tensile plasticity of Ti-based bulk metallic glass and composite via cold rolling

The influence of cold rolling on the tensile mechanical properties and deformation behavior of Ti-based bulk metallic glass (BMG: Ti40Zr25Ni8Cu9Be18) and β-Ti dendrite reinforced bulk metallic glass matrix composite (BMGMC: Ti40.2Zr18Ni2.85Cu7.65Be12.3Nb19) has been investigated. The cold-rolled BMG and BMGMC samples with 20% thickness reduction ratio exhibit a pronounced tensile plasticity of 0.8% and 4%, respectively. The malleable behavior of the cold-rolled samples originates from the internal structural evolution and modulation of elastic properties.

Investigation on Dynamic Mechanical Properties of Tungsten Fiber Reinforced Metallic Glass Composite

Recently developed bulk metallic glass (BMG) alloys have attractive mechanical properties for structural applications, and tungsten fiber reinforced bulk metallic glass matrix composite(BMGC) would further improve the properties compared to un-reinforced BMG. With INSTRON1196 test machine system and SHPB experimental system, quasi-static and dynamic compression experiments on tungsten fiber reinforced bulk metallic glass matrix composite were carried out. The material flow stress is about 2200MPa in quasi-static, and the dynamic flow stress of the material is around 2800MPa with strain rate of 740 s-1. The specimen fails with the form of axial cracks

Compressive behavior of wire reinforced bulk metallic glass matrix composites

Bulk metallic glasses (BMGs) possess a unique set of mechanical properties that make them attractive structural materials. However, when loaded without constraint, BMGs fracture catastrophically due to formation of macroscopic shear bands and this behavior reduces their reliability. To address this issue, BMG matrix composites have been developed. In this investigation, neutron diffraction was used during uniaxial compressive loading to measure the internal strains in the second phases of various BMG composites reinforced with Ta, Mo, or stainless steel wires. The diffraction data were then employed to develop a finite element model that deduced the in situ constitutive behavior of each phase. It was found that the reinforcements yielded first and started transferring load to the matrix, which remained elastic during the whole experiment. While the present composites exhibited enhanced ductility, largely due to their ductile reinforcements, they yielded at applied stresses lower than those found in W reinforced composites.

Fracture and fatigue behavior of a Zr–Ti–Nb ductile phase reinforced bulk metallic glass matrix composite

The fracture and fatigue behavior of a Zr-based metallic glass composite are presented. The fracture resistance and fatigue endurance limit was significantly higher than that of the matrix material. Results are rationalized in terms of the effects of the second phase on shear band formation and distribution.

Compressive yielding of tungsten fiber reinforced bulk metallic glass composites

In-situ uniaxial compression tests were conducted on four tungsten fiber reinforced bulk metallic glass matrix composites using neutron diffraction. The results were interpreted with a finite element model. Both phases were seen to approximately obey the von Mises yield criterion. The fibers were observed to yield first and then transfer load to the matrix.

Synthesis of La-based in-situ bulk metallic glass matrix composite

An in-situ dendritic crystalline α-La reinforced bulk metallic glass matrix composite was successfully synthesized by chill casting a La66Al14Cu10Ni10 alloy into copper mould with a rod diameter as large as 12 mm in diameter. The critical cooling rates for the formation of the in-situ composite determined by Bridgman solidification and for complete glass formation are 15 K/s and 450 K/s respectively. The thermal stability of the residual amorphous in the composite is higher than that of the fully amorphous sample of the same alloy.

Synthesis of crystaline phase rinforced bulk metallic glass matrix composite in La and Pd based alloys

In-situ dendritic crystalline phase reinforced bulk metallic glass matrix composites were successfully synthesized in La and Pd based alloys. The reinforcing phases are hcp αLa and fcc Pd solid solution in the La 66(Cu,Ni) 20Al 14 and Pd 42Cu 30Ni 10P 18 alloys, respectively. The thermal stability of the residual amorphous in the composite is higher than that of the fully amorphous sample of the same alloy.

Microstructure controlled shear band pattern formation and enhanced plasticity of bulk metallic glasses containing in situ formed ductile phase dendrite dispersions

Results are presented for a ductile metal reinforced bulk metallic glass matrix composite based on glass forming compositions in the Zr-Ti-Cu-Ni-Be system. Primary dendrite growth and solute partitioning in the molten state yields a microstructure consisting of a ductile crystalline Ti-Zr-Nb beta phase, with bcc structure, in a Zr-Ti-Nb-Cu-Ni-Be bulk metallic glass matrix. Under unconstrained mechanical loading organized shear band patterns develop throughout the sample. This results in a dramatic increase in the plastic strain to failure, impact resistance, and toughness of the metallic glass.