Bulk Glassy Alloys Research Articles

The Influence of Boron and Carbon Addition on the Glass Formation and Mechanical Properties of High Entropy (Fe, Co, Ni, Cr, Mo)-(B, C) Glassy Alloys

Coatings made from metallic glasses are a promising solution for protecting surfaces of materials in various challenging environments. From an engineering perspective, glassy alloy coatings containing carbon are of greater importance compared to those without carbon but containing boron. Despite anticipating improved coating characteristics, there is no data on using high entropy glassy alloy as a coating material. In this paper, we investigated the influence of the simultaneous addition of boron and carbon elements on the glass-forming ability, thermal stability, crystallization behavior, yield strength, hardness, and corrosion resistance of high entropy (Fe, Co, Ni, Cr, Mo)-(B, C) glassy alloys. It was found that the content of boron and carbon had a significant effect on the improvements of glass-forming ability, mechanical properties, and corrosion resistance. The (Fe0.25Co0.25Ni0.25Cr0.125Mo0.125)75(B0.7C0.3)25 bulk glassy alloy exhibits high glass-forming ability, high yield strength of 3500 MPa, Vickers hardness of 1240, and the highest corrosion resistance among the alloys. We also discussed the reason for their good engineering properties, and the possibility of using high entropy glassy alloys as coating materials, in addition to the guidelines for designing high-performance multicomponent glassy alloys.

Formation and ultrahigh mechanical strength of multicomponent Co-based bulk glassy alloys

A glassy phase with glass transition (GT) was formed in a wide B content range of 12–31 at% for (Co0.75Cr0.125Mo0.125)100-xBx alloys. The appearance of GT at the low metalloid content of 12%B among Co-, Fe- and Ni-based alloys is the first, in contrast to the absence of GT for (Fe0.75Cr0.125Mo0.125)88B12 and (Ni0.75Cr0.125Mo0.125)88B12 alloys. The Co-based 12%B glassy alloy crystallized through unique three stages, i.e., glass (G) → [G + hcp + fcc] → [G + fcc] → [fcc + M23B6]. The appearance of GT is due to the necessity of long-range rearrangement of constituent elements for the simultaneous precipitation of hcp and fcc phases from glassy phase. The glass transition temperature, crystallization temperature, Vickers hardness (Hv) and Young's modulus for the Co-based glassy alloys increase linearly with increasing B content and reach 904 K, 946 K, 1566 and 188 GPa, respectively, at 31%B. The good bending plasticity is retained up to 29%B. The crystallization of the 27–29%B alloy occurs through G → [G + M23B6] → [M23B6 + M2B] and the ultrahigh Hv above 2000 is attained for the metastable [G + M23B6] phase state. The glassy alloy rod with a diameter of 1 mm was prepared for the 27%B alloy and exhibited ultrahigh yield strength of 4700 MPa, plastic strain of 1% and high oxidation resistance up to about 1200 K. The Co-based bulk glassy alloy with simultaneously high strength, ultrahigh hardness and high oxidation resistance, is promising for the future high hardness and heat-resistance materials.

The dry-sliding and micro-scratching behaviors of a Mg65Zn30Ca5 bulk glassy alloy

The macro-sliding and micro-scratching behaviors of a Mg65Zn30Ca5 bulk glassy alloy (BGA) were studied in the present work. The dry sliding results show that the wear mechanism of the Mg-based BGA includes the abrasion and oxidation wear. Increasing the normal load does not change the wear mechanism of macro-sliding. The cross-sectional morphology of the subsurface under the worn scar shows obvious brittle cracks across shear bands. The micro-scratching results illustrates that as the normal load increases, plastic deformation occurs and accumulates, then micro-cracks form and propagate, and cracks generate and expand in the scratch when the load excesses 5 N. The cross-sectional morphology below the scratch scar after 1 min repeating scratching shows river pattern fracture surface with nanoscale swirling periodic corrugations, which indicates the brittle fracture characteristic of the Mg-based BGA.

Self-lubricating behavior of a PdCuNiP glassy alloy by in-situ nanocrystallization during dry friction

In the present work, dry-sliding behavior of a PdCuNiP bulk glassy alloy (BGA) was studied and compared with that of a ZrAlNiCu BGA. The PdCuNiP BGA exhibits a 2-fold smaller coefficient of friction (COF) and a 100-fold lower wear rate than those of the ZrAlNiCu BGA, although the PdCuNiP BGA shows the smaller hardness and fracture toughness. The unprecedented low COF and wear rate of the PdCuNiP BGA stem from in-situ formation of an amorphous/ultrafine nanocrystalline structure layer on the wear-scar surface during the dry sliding. The Von-Mises stress simulation mapping in the contact area reveals that the effect of stress and deformation is not the primary cause for the nanocrystallization. The model calculated frictional heat generated during the friction process causes the in-situ nanocrystallization, which increases the hardness and strength of surface layer. The self-lubrication effect results from the effective suppression of the sliding-induced plastic deformation and surface roughening.

The effects of normal load on the dry-sliding, micro-scratch and nanoindentation behaviors of the Zr-based bulk glassy alloys

In this work, the macro-sliding, micro-scratch and nanoindentation behaviors of the Zr55Cu30Al10Ni5 bulk glassy alloy (BGA) were investigated. It was found that the frictional coefficient and wear rate of the BGA in the dry-sliding test increase with the increasing normal load, and the wear mechanism includes abrasive and oxidative wear. The micro-scratch test results show that the plastic deformation of the alloy and the density of shear bands at the edge of scratch scar increase with the increase in normal load. The friction mechanism between the indenter and the BGA shifts from stick-slip friction to ploughing friction and to micro-cutting as the applied normal load elevates. The nanoindentation result reveals that increasing the normal load leads to the plastic deformation accumulation, and the decreasing elastic modulus and hardness, which are related to the increase in the free volume and shear bands during the deformation process.

High-strength Cu–Ti-rich bulk metallic glasses and nano-composites

Abstract Cu47Ti34Zr11Ni8, Cu47Ti33Zr11Ni8Fe1 and Cu47Ti33Zr11Ni8Si1 bulk glassy alloys were prepared by injection copper mold casting. Mechanical properties, glass-forming ability, thermal stability and microstructural characteristics of as-cast rods were investigated. Calorimetric studies indicate a beneficial role of small Si or Fe addition on the thermal stability of Cu–Ti – Zr –Ni bulk glassy alloys. Compression tests reveal fracture strengths of 2040 to 2190 MPa, Young’s moduli of 100 to 109 GPa and elastic strains up to 2.4 %. The Si-containing glassy alloy exhibits a plastic elongation of 2.2%. The significant increase in plasticity observed for the Si-containing alloy is due to a special bimodal composite structure consisting of nano-scaled Cu crystals homogeneously dispersed in the bulk metallic glass matrix. The increase of the global plasticity can be explained by the formation of multiple shear bands that make the glassy alloy resistant to crack propagation.

Shape memory effect in metallic glasses

Shape memory effect in metallic glasses

Significant plasticity and atomic-scale deformation mechanism of high glass-forming Zr-Cu-Ni-Ti-Al bulk glassy alloys

The authors report a series of monolithic Zr(65.4-x)Cu(12+x)Ni9.6Ti6Al7 (x = 0, 3, 6, 9 at.%) bulk glassy alloys with significant room-temperature plasticity and high glass-forming ability (GFA). Upon substitution of Cu for Zr, the GFA of glassy alloys is gradually increased, and the alloy possesses a critical casting size up to 10 mm when x=9. On the contrary, the plasticity is evidently increased with decreasing of Cu content in the glassy alloys, and the alloy exhibits the best plastic strain of 29.6% when x=0. Theoretical calculations indicate that the small differences in atomic sizes and atomic affinity among constituent elements should be necessary before pronounced plastic deformation can occur.

Strong work hardening in a high niobium-containing TiNi-based bulk glassy alloy composite

In this study, a high niobium-containing bulk glassy alloy composite Ti41Ni39Nb17.5Al2.5 consisting of amorphous, B2-TiNi and β-Nb phases was fabricated through in situ precipitation strategy by utilizing copper-mold suction casting. Upon compressive loading, the composite alloy showed a pronounced average plastic strain of (17.6 ± 3.5)% and a high fracture strength of (2279 ± 33) MPa together with a strong work-hardening deformation behavior. The volume fraction of the amorphous phase in the composite was determined to be around 23 vol%. The work softening caused by the formation of shear bands can be compensated by the work hardening arising from the pile-ups of dislocation and severe lattice distortion in the precipitated crystals and thereby stabilize the plastic deformation of the composite material. The findings imply that the room-temperature mechanical properties of bulk glassy alloy composites can be well tailored by selecting suitable reinforcers.

Effects of Cu content on crystallization behavior, mechanical and soft magnetic properties of Fe80-xCuxP13C7 bulk metallic glasses

Bulk Fe80-xCuxP13C7 (x = 0, 0.1, 0.3 and 0.6 at.%) amorphous alloys were successfully fabricated utilizing the combining fluxing treatment and J-quenching technique. The influence of Cu content on the crystallization characteristic temperatures and primary crystallization phase evolution, glass formation ability, mechanical and soft magnetic properties of Fe-Cu-C-P BMGs have been systematically investigated. Additionally, the proper addition of Cu content can significantly improve the compression plasticity of present Fe-Cu-C-P bulk glassy alloys, and the Fe79.4Cu0.6P13C7 bulk glassy rod exhibits an excellent plasticity of 5% as well as a high fracture strength (over 2700 MPa). Then, the multiple effects of annealed Fe80-xCuxP13C7 BMGs on mechanical properties and soft magnetic property have been investigated. More importantly, Fe79.4Cu0.6P13C7 BMG annealed at Tg-30 K for half an hour exhibits excellent soft magnetic properties with relatively high saturation magnetization of 1.5 T, and mechanical properties with the fracture strength of 3280 MPa and plastic strain of 4%.

Mechanical, corrosion, and wear performances of a biocompatible Ti-based glassy alloy

The mechanical, electrochemical, wear, and corrosive-wear behaviors of a TiZrCuPd bulk glassy alloy were investigated. The Ti-based glassy alloy demonstrates a high yield strength of 2.3 GPa, low Young's modulus of 95 GPa, and Vickers microhardness of 7.2 GPa, which are superior to those of the Ti-6Al-4V biomedical alloy. The TiZrCuPd glassy alloy shows a good corrosion resistance in the phosphate buffer saline (PBS) solution, owing to the formation the Ti- and Zr-enriched passivation film on the alloy surface. The TiZrCuPd alloy displays the lowdry-wear rate of 6.1 × 10−8 mm3 mm N−1and wet-wear rate of 8.0 × 10−8 mm3 mm N−1. The triobocorrosionresults illustrate that the TiZrCuPd alloyshows a high pitting corrosion resistance during the wet sliding, which render its good corrosive wear performance. The good combination of mechanical, corrosion, and wear properties of the Ti-based glassy alloy make it promising for biomedical applications.

Significant room-temperature plasticity in a high Zr-containing bulk glassy alloy

Abstract

Strain perceptibility of elements on the diffusion in Zr-based amorphous alloys

With the discovery of bulk metallic glasses (BMGs), there has been considerable interest in understanding their mechanical behavior. In spite of these previous observations on the relation between plastic deformation of metallic glasses and their diffusion behavior, a detailed understanding on the diffusion of BMGs is still unexplored. We evaluated the contribution of deformation-induced structural transformations (elastic, anelastic, viscoplastic or viscoelastic responsive and plastic strain) on the diffusion of Zr-based bulk metallic glasses in as-cast, elastostatically stressed and plastically deformed states. Experimental investigations of the diffusion process and the elemental distributions in the glassy alloy were performed following plastic deformation by multiple cold rolling and elastostatic cyclic compression, respectively. We compared the vacancy model and the transition state model to verify the diffusion mechanism in the deformed bulk metallic glass. The diffusion of tracer atoms, i.e., Fe, in the bulk metallic glass is affected by viscoelastic responsive strain governing the transition-state model. In contrast, the diffusion of constituent atoms, i.e., Ti, Zr, in the bulk metallic glass is dominantly affected by plastic strain governing the vacancy model. The results reveal that the diffusion behavior of bulk glassy alloys can be changed by variation of the constituent elements and applying different strain modes upon deformation.

The effect of thermal history on the atomic structure and mechanical properties of amorphous alloys

The influence of thermal processing on the potential energy, atomic structure, and mechanical properties of metallic glasses is examined using molecular dynamics simulations. We study the three-dimensional binary mixture, which was first relaxed near the glass transition temperature and zero pressure, and then rapidly cooled deep into the glass phase. It was found that glasses annealed at higher temperatures are relocated to higher energy states and their average glass structure remains more disordered, as reflected in the height of the first two peaks in the pair distribution function. The results of mechanical testing demonstrate that both the shear modulus and yielding peak increase significantly when the annealing temperature approaches Tg from above. Moreover, the shear modulus becomes a strong function of strain rate only for glasses relaxed at temperatures sufficiently higher than the glass transition temperature. Based on the spatial distribution of nonaffine displacements, we show that the deformation mode changes from brittle to ductile upon increasing annealing temperature. These results can be useful for the design and optimization of the fabrication processes of bulk glassy alloys with improved plasticity.

Structural and electrochemical study of resorbable Ca32Mg12Zn38Yb18-xBx (x=1, 2, 3) metallic glasses in Ringer's solution

A new class of CaZn-based bulk glassy alloys with minor addition of boron and enhanced corrosion resistance for use in bioresorbable materials is introduced. The CaMgZnYbB alloys represent a new family of biomaterials with potential applications in orthopedic implants with controlled degradation rates and corrosion in the human body. The effect of substituting Yb for B in the structure on the corrosion and mechanical properties of quinternary Ca32Mg12Zn38Yb18-xBx (x = 1,2,3 at.%) alloys was investigated using X-ray diffraction, high-resolution transmission electron microscopy, differential scanning calorimetry, immersion and electrochemical polarization, compressive tests, and hardness measurements. The corrosion behavior was also evaluated using electrochemical impedance spectroscopy and X-ray photoelectron spectroscopy. Microstructural investigations showed that the Ca32Mg12Zn38Yb16B2 alloy was mainly amorphous, while small reflections from nanocrystals were observed in Ca32Mg12Zn38Yb17B1 and Ca32Mg12Zn38Yb15B3. Electrochemical polarization and immersion tests in Ringer's solution at 37 °C revealed that the CaMgZnYbB alloys had significantly higher corrosion resistance than CaMgZn alloys. Electrochemical impedance spectroscopy of alloys showed only single capacitive loops. The corrosion products were identified as CaO, MgO, Mg(OH)2, and CaCO3. The compressive strengths of the alloys from 220 MPa to 283 MPa were suitable for implant applications.

Enhanced plasticity of FeCoBSiNb bulk glassy alloys by controlling the structure heterogeneity with Cu addition

In this work, an FeCoBSiNbCu bulk glassy alloy (BGA) with a diameter up to 4 mm was successfully prepared by copper mold casting method. The (Fe0.5Co0.5)71.6B20Si4Nb4Cu0.4 BGA exhibits a high strength over 4 GPa and an enhanced plasticity of 3.7%, combined with good soft magnetic properties. A well-developed vein pattern on the fracture surface and highly dense multiple shear bands throughout the overall rod were observed on the deformed specimen. The improved plasticity is strongly related to the nano-scale heterogeneous structure introduced to the glassy alloy by phase separation with minor Cu addition, which can hinder the propagation of shear bands, promote multiple shearing and enhance the plasticity. This work might have a guiding significance for a deep-understanding of the plastic deformation mechanism of Fe-based BGA in a high strength level.

Effect of Cr Addition on Glass-Forming Ability and Corrosion Properties of FeCoSiBPC Bulk Glassy Alloys

Effect of Cr Addition on Glass-Forming Ability and Corrosion Properties of FeCoSiBPC Bulk Glassy Alloys

Comparison of the corrosion resistance behaviour for two metal-metal glassy alloys in neutral solution with chloride impact

The electrochemical behaviour of bulk glassy Fe78Co9Cr10Mo2Al1 and Fe49Co49V2 alloys was investigated using electrochemical techniques with different concentrations of Na2SO4 solution (0.25, 0.5 and 1.0 M). The alloys surfaces were characterized by various morphology and composition techniques. The corrosion rate of the two alloys is inversely proportional to the concentration of Na2SO4 solution. The VX9 alloy exhibited spontaneous production of a good passive layer in Na2SO4 solutions as a response to the presence of protective elements, such as Cr (10%), Mo (2%) and Al (1%). No passivation occurred on the surface of the VX50 alloy, with only salt precipitating on it. Adding chloride reduces the resistivity of both alloys as it is a localized attack.

Super-high hardness of (Fe,Co)-B-Si-Zr/Hf bulk glassy alloys

In this work, the alloying effect of similar atom substitution of Co for Fe on the glass-forming ability as well as mechanical and magnetic properties of Fe71.7-xCoxB16.7Si8.3Zr3.3 and Fe72.5-yCoyB16.7Si8.3Hf2.5 (x, y = 0, 5, 10, 15, 20 and 25) glassy alloys has been studied. Our experiments show that the substitution of Co for Fe causes a decrease in the glass-forming ability. By increasing the content of Co, the critical glass formation size gradually decreases from 2.5 mm to 1 mm. Nano-indentation results indicate that both the Young's modulus and hardness increase with increasing Co content in the bulk glassy alloys. The Fe51.7Co20B16.7Si8.3Zr3.3 bulk glassy alloy exhibits a microhardness, Hv = 13.5 GPa, and a Young's modulus, E = 230 GPa, the microhardness being the highest among all the Fe-based metallic bulk materials reported to date. All of the glassy alloys exhibit good soft magnetic properties with high saturation magnetization (1.12–1.33 T) and low coercive force (0.6–5.2 A/m).

Influence of Ag replacement on supercooled liquid region and icosahedral phase precipitation of Zr65Al7.5Ni10Cu17.5-xAgx (x = 0–17.5 at%) glassy alloys

The glass transition phenomenon for Zr65Al7.5Ni10Cu17.5-xAgx (x = 5–17.5 at%) glassy alloys was observed in the Ag content range below about 15% and the icosahedral phase precipitated as the heating-induced primary phase in the limited Ag content range. In the higher Ag content range where glass transition is not clearly observed, the primary precipitation phase changed to mixed phases of tetragonal Zr3Ag + tetragonal Zr2Ni + hexagonal Zr4Al3. The good correspondence between the appearance of glass transition and the icosahedral phase precipitation was recognized in the multicomponent glassy alloys containing the immiscible type atomic pairs of Ni-Ag and Cu-Ag. Although neither glass transition nor supercooled liquid region is observed for Zr65Al7.5Ni10Ag17.5 and no icosahedral phase is formed, a modified Zr65Al7.5Ni17.5Ag10 alloy with higher Ni/Ag content ratio exhibits glass transition and supercooled liquid region and the primary precipitates also changes to an icosahedral phase. The good correspondence can be interpreted on the basis of the previous knowledge that the appearance of glass transition and supercooled liquid state originates from icosahedral-like medium range ordered atomic configurations. Besides, the 6%Ag-containing alloy keeps high glass-forming ability which is high enough to form a bulk glassy alloy rod of 6 mm by suction casting. The close correlation between the appearance of glass transition phenomenon and the primary precipitation of icosahedral phase is expected to provide a useful knowledge on the role of icosahedral-like atomic configuration in the achievement of bulk glass-forming ability through the stabilization of supercooled liquid.