Zr-based Bulk Metallic Glass Matrix Research Articles

Research on explosive damage effects of tungsten fiber-reinforced Zr-based bulk metallic glass matrix composite shell

To expand the application range of explosive fragmentation projectiles, tungsten fiber-reinforced bulk metallic glass matrix composite (WF/Zr-MG) is used as the warhead shell in static explosion experiments, and is compared with 40CrMnSiB steel shells. The experimental results showed that, compared with 40CrMnSiB steel shells, the fragments produced by the WF/Zr-MG shell exhibit a larger aspect ratio, smaller average size, and a greater number of fragments at distances of 3 m and 5 m, with an equal number of fragments at a distance of 8 m. Theoretical calculations showed that the initial velocity of the fragments produced by the WF/Zr-MG shell is lower, but their velocity decay is slower, resulting in a greater determined damage range. The research results showed that WF/Zr-MG can be used as a shell material for explosive fragmentation projectiles, which can enhance their destructive power.

Penetration Fracture Mechanism of Tungsten-Fiber-Reinforced Zr-Based Bulk Metallic Glasses Matrix Composite under High-Velocity Impact

In order to adapt to the launch velocity of modern artillery, it is necessary to study the fracture mechanism of the high-velocity penetration of penetrators. Therefore, the penetration fracture mode of tungsten-fiber-reinforced Zr-based bulk metallic glass matrix composite (WF/Zr-MG) rods at a high velocity is studied. An experiment on WF/Zr-MG rods penetrating into rolled homogeneous armor steel (RHA) was carried out at 1470~1650 m/s. The experimental results show that the higher penetration ability of WF/Zr-MG rods not only results from their "self-sharpening" feature, but also due to the fact they have a longer quasi-steady penetration phase than tungsten alloy (WHA) rods. Above 1500 m/s, the penetration fracture mode of the WF/Zr-MG rod is the bending and backflow of tungsten fibers. Our theoretical calculation shows that the deformation mode of the Zr-based bulk metallic glass matrix (Zr-MG) is an important factor affecting the penetration fracture mode of the WF/Zr-MG rod. When the impact velocity increases from 1000 m/s to 1500 m/s, the deformation mode of Zr-MG changes from shear localization to non-Newtonian flow, leading to a change in the penetration fracture mode of the WF/Zr-MG rod from shear fracture to the bending and backflow of tungsten fibers.

Rejuvenation of Zr-based bulk metallic glass matrix composite upon deep cryogenic cycling

The rejuvenation behavior of Ta-rich particle reinforced Zr-based bulk metallic glass matrix composites upon deep cryogenic cycling treatment has been studied. The composite can be rejuvenated resulting in a higher enthalpy of relaxation and lower density. The internal stress generated from both the intrinsic heterogeneity in amorphous matrix and the interfaces between the matrix and Ta-rich phase should contribute to the rejuvenation behavior. The composite structure can generate a 4 times higher internal stress than that from the intrinsic heterogeneity, which causes the more rejuvenated state of the composites compared with the monolithic counterpart. With a higher volume fraction of Ta-rich phase, both the increment in enthalpy of relaxation and free volume between as-cast and thermal treated state increases almost linearly. The rejuvenated samples show better plasticity compared with as-cast counterparts because of more induced free volume.

In-situ Ta-rich particle reinforced Zr-based bulk metallic glass matrix composites with tensile plasticity

In-situ Ta-rich particle reinforced Zr-based bulk metallic glass matrix composite has been successfully fabricated by doping Ta. The dispersion of Ta-rich particles was quite homogenous. The size and inter-particle spacing of the Ta-rich particles were very close to the plastic processing zone size. By varying the doping amount of Ta, the volume fraction of Ta-rich particles can be tailored. Furthermore, the bonding between Ta-rich particle and glassy matrix seemed to be strong for the lack of oxide or compound layer at the interfaces. With more Ta-rich particles, the composites show better mechanical properties, including higher fracture strength and larger plastic strain. The Ta-rich particles can hinder the rapid propagation of main shear band, generating multiple shear bands. Smaller value of average stress drop after yielding for the composites with more Ta doping indicates lower formation energy of shear bands, which links to the better plasticity. The deformation of Ta-rich particle itself also contributes to the plasticity and hardening behavior of the composite. The composite with 10 at.% Ta doping even shows ∼2% plastic strain under tension.

The Microstructure of Zr-Based Bulk Metallic Glass and Glass Matrix Composite

The Microstructure of Zr-Based Bulk Metallic Glass and Glass Matrix Composite

In-situ synthesis and mechanical properties of Zr-based bulk metallic glass matrix composites manipulated by nitrogen additions

Our study investigates in-situ synthesis and mechanical properties of Zr-based bulk metallic glass (BMG) matrix composites via arc plasma-induced accelerated displacement reaction (APADR) process. The aluminum nitride precursor under arc plasma-induced ultra-high temperature results in higher contents of dissolved nitrogen as well as precipitation of zirconium nitride (ZrN) particles in a Zr-based amorphous matrix. The nitrogen in the matrix results in a decrease of crystallization resistance (lower Tx and reduced glass-forming ability), but an increase of mechanical stability (a decrease of strain burst sizes). In particular, in-situ formed ZrN, which exhibits a homogeneous distribution and strong interfacial bonding with the matrix, causes an increase in compressive fracture strength and significant plastic deformation in the composite compared with the monolithic BMG. The formation of multiple shear bands and the enhancement of shear band interactions by the dissolved nitrogen as well as the in-situ formed ZrN particles were carefully confirmed by a statistical analysis on serrated flows. These results give us a guideline on how to manipulate nitrogen contents and fabricate in-situ BMG matrix composites with improved mechanical properties via APADR process.

Effects of Changes in Test Temperature on Tensile Properties and Notched Vs Fatigue Precracked Toughness of a Zr-Based BMG Composite

Tensile and fracture toughness behavior of a Zr-based bulk metallic glass matrix composite (BMGMC) containing a body-centered cubic crystalline phase was examined over temperatures from 77 K to 653 K (−196 °C to 380 °C). The BMGMC exhibited tensile plasticity at all test temperatures. The sample tested in tension at 173 K (−100 °C) exhibited work hardening but the remaining samples tested at higher temperatures exhibited work softening. EBSD analysis of the crystalline phase after tensile testing provides insight into active deformation mechanisms in the crystalline phase. At 603 K (330 °C), the dendrites exhibit significant plastic strain, with the dendrites oriented {101} parallel to the loading direction exhibiting the least amount of strain. Schmid factor analysis leads to the hypothesis that {110}〈111〉 dislocation mechanisms are active at this temperature. Additionally, measurements of dendrite shape as a function of macroscopic strain state in the tension experiments provide insight into cooperative deformation mechanisms in the composite. At low temperatures, the fracture toughness of the notch toughness samples exceeded that of fatigue precracked samples; but at and above room temperature, the toughness values of notched and fatigue precracked samples converge. These observations are rationalized based on the changes to the flow and fracture behavior of the glass and the crystalline phases over this temperature range. At low temperatures, the crystalline phase is sensitive to defects and changes in stress state that reduce its energy absorbing ability. At higher temperatures, both constituents possess lower strength and are less sensitive to defects, enabling more significant crack tip blunting in the fatigue precracked samples. This produces toughness values that are similar to those obtained for the notched samples.

Fabrication and mechanical properties of bulk metallic glass matrix composites by in-situ dealloying method

Abstract In-situ Ti-reinforced Mg-based (MT-D) and in-situ Ta-reinforced Zr-based (ZT-D) bulk metallic glass matrix composites (BMGMCs) were prepared by a novel dealloying method, which contains an element-selective leaching process in a metallic melt. The BMGMCs exhibit better mechanical properties, including higher fracture strength and larger plastic strain, than their monolithic glassy counterparts or similar BMGMCs by ex-situ dispersing or conventional arc-melting methods. The differences of Young's modulus between the dispersoids and the glassy matrix for these BMGMCs generate stress concentration at the interface, which is considered to suppress the propagation of the single main shear band and initiate multiple shear bands to accommodate the plastic deformation. Furthermore, the fine size of dispersoids for these BMGMCs, caused by low reaction temperature during dealloying in the metallic melt, results in more interfaces with the matrix for further improvement of mechanical properties. In addition, the low reaction temperature can also contribute to less composition fluctuation of the matrix to maintain the glass-forming ability of itself, which can introduce no undesired phases to degrade the mechanical properties. This novel in-situ dealloying method is believed to make a breakthrough in designing ductile BMGMCs with fine-sized secondary particles.

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.

Dry Sliding Tribological Properties of a Dendrite-reinforced Zr-based Bulk Metallic Glass Matrix Composite

In-situ dendrite-reinforced metallic glass matrix (MGM) composites with the composition of Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 were prepared with a vacuum arc melter by the copper mold suction casting. Effect of different normal loads and sliding velocities on the tribological properties of MGM composites was studied. The results showed that the friction coefficient and wear rate of composites initially descended with increasing the normal load and reached a minimum of 0.339 and 1.826 × 10−4 mm3/(N m) at 10 N, respectively, then ascended. Similarly, the friction coefficient and wear rate of composites initially decreased with the increase in the sliding velocity and reached a minimum of 0.330 and 2.389 × 10−4 mm3/(N m) at 0.4 m/s and 0.3 m/s, respectively, then raised. The wear mechanism of composites was mainly adhesive wear accompanied by abrasive wear at lower normal load and sliding velocity. However, the wear mechanism of composites was abrasive wear and adhesive wear as well as delamination at higher normal load and sliding velocity due to the nucleation and propagation of surface and subsurface cracks during the wear process. The flake-like and particle-like wear debris was the dominant shapes of debris observed.

Low beryllium content Zr-based bulk metallic glass composite with plasticity and work hardenability

A modified Zr-based bulk metallic glass matrix composite Zr47.67Cu40Ti3.66Ni2.66Be6 has been produced by increasing the contents of elements of Zr and Cu with higher Poisson ratio and reducing the contents of Ti, Ni, and Be elements with lower Poisson ratio based on famous metallic glass former Vitreloy 1. A compressive yielding strength of 1804 MPa, fracture strength of 1938 MPa and 3.5% plastic strain was obtained for obtained metallic glass composite. Also, work-hardening behavior was observed during compressive experiment which was ascribed to the interaction of the in situ precipitated CuZr phase and shear bands.

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.

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.

High strength tungsten wire reinforced Zr-based bulk metallic glass matrix composites prepared by continuous infiltration process

Tungsten fiber reinforced Zr41.25Ti13.75Cu12.5Ni10Be22.5 bulk metallic glass matrix composites (BMGMC) were prepared by continuously drawing a bunch of preform from molten alloys. The novel processing makes the interface of composites well combined and the mechanical properties enhanced, e.g., the tensile strength of BMGMC rod with 61.4vol% tungsten fibers reaches 2867MPa, which is the highest among this kind of composites. It is found that the strengthening of tungsten is attributed to confinement of the propagation of shear bands.

Characteristic of improved fatigue performance for Zr-based bulk metallic glass matrix composites

Zr58.5Ti14.3Nb5.2Cu6.1Ni4.9Be11.0 bulk metallic glass matrix composites exhibit improved four-point-bending fatigue endurance with a fatigue limit of 567MPa, compared to that under the tension–tension fatigue, due to the high-volume-fractioned dendrites, which can effectively blunt the fatigue-induced cracks. Illuminated by high-energy synchrotron X-ray at 200 and 100K, the corresponding diffraction peaks, such as (110), (200), and (211) shift rightward to small lattice spacings, compared to those at 298K. However, the peak widths at 100K and 200K are almost identical to that of room temperature. Since an identical fatigue specimen was measured under room temperature, 200K, and 100K, the invariant of the peak widths reveal the fact of the irreversible microstructure developments induced by fatigue. Even if the fatigue fracture stress is distinguishingly lower than the yielding strength, the deformation of dendrites locally prevails, evidenced by the occurrence of dislocations.

Cooling Slope Casting Process for Synthesis of Bulk Metallic Glass Based Composites with Semisolid Structure

A process combining cooling slope casting and suction casting was developed to generate a semisolid structure in a Zr-based bulk metallic glass matrix composite. The melt was injected onto a cooling slope and subsequently vacuum sucked into a cylindrical copper mold placed at the end of the slope. The structure obtained for 4-mm-diameter specimens of composition Zr66.4Nb6.4Cu10.5Ni8.7Al8 consists of a dispersion of spheroidal and rosettelike bcc crystals in a glassy matrix. Various slope angles, slope lengths, and injection pressures were tested. The coarsest and most spheroidal crystal structure was obtained at short slope lengths and high injection pressures. Microstructure analysis suggests that the slope is the location of extensive crystal nucleation and possible fragmentation, while the microstructure’s morphological evolution seems to occur mainly in the mold. The semisolid structure is expected to confer improved mechanical properties and ductility to the composite material.

Ta-particulate reinforced Zr-based bulk metallic glass matrix composite with tensile plasticity

[Zhu, Z.; Zhang, H.; Hu, Z.] Chinese Acad Sci, Inst Met Res, Shenyang 110016, Peoples R China. [Zhu, Z.; Zhang, W.] Tohoku Univ, Inst Mat Sci, Sendai, Miyagi 9808577, Japan. [Inoue, A.] Tohoku Univ, Adv Inst Mat Res, WPI, Sendai, Miyagi 9808577, Japan.;Zhang, H (reprint author), Chinese Acad Sci, Inst Met Res, Shenyang 110016, Peoples R China;hfzhang@imr.ac.cn

Fe-Based Nano-Structured Powder Reinforced Zr-Based Bulk Metallic Glass Composites by Powder Consolidation

The Zr-based bulk metallic glass matrix composites of a mixture of gas-atomized metallic glass powders and Fe-based nanostructured powders were fabricated by spark plasma sintering. The Fe-based nanostructured powders adopted for the enhancement of plasticity were well distributed in the matrix after consolidation, and the matrix remains as a fully amorphous phase. The successful consolidation of metallic glass matrix composite with high density was attributed to viscous flow in the supercooled liquid state during spark plasma sintering. Unlike other amorphous matrix composites, in which improved ductility could be obtained at the expense of their strength, the developed composite exhibited improvement both in strength and ductility. The ductility improvement in the composite was considered to be due to the formation of multiple shear bands under the presence of the Fe-based nanostructured particles.

Fabrication and mechanical characterization of a series of plastic Zr-based bulk metallic glass matrix composites

Coupling the high yielding strength with enhanced plasticity under compression at ambient temperature, a series of Zr-based bulk metallic glass matrix composites are designed based on a pseudo ternary phase diagram. The largest compressive fracture plastic strain of 17.0% with the yielding strength of 1070 MPa is available for Zr 60.0Ti 14.7Nb 5.3Cu 5.6Ni 4.4Be 10.0 bulk metallic glass matrix composite. The relationship between the cooling rate and the microstructure, the microstructure and the mechanical properties, and the fractographs of the composites is carefully identified.

Strain rate response of mechanical behaviors for a Zr-based bulk metallic glass matrix composite

The strain rate response of compressive mechanical behaviors for a Zr 60.0Ti 14.7Nb 5.3Cu 5.6Ni 4.4Be 10.0 bulk metallic glass matrix composite with the tensile fracture strain of 2.9%, was investigated. The dislocation-related deformation mode was employed to interpret the failure of the composite containing continuous network dendrites with high-volume fraction. Under the quasi-static compression, a positive dependence of the plasticity on the increasing strain rate was obtained. However, upon the dynamic loading, the composite exhibited premature fracture and the very limited plasticity accompanied, which suggested the strain was not kinetically accommodated during the prompt deformation.