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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 (Ti 0.505 Zr 0.353 Fe 0.028 Be 0.114 ) 100− x Cu x ( 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. [ABSTRACT FROM AUTHOR]

Abstract: The wetting behavior and interfaces of CuZr-based glassy alloys/W system were investigated by the sessile drop method. It was found that Cu50Zr50/W, Cu47.5Zr47.5Al5/W and Cu40Zr44Al8Ag8/W system had the final equilibrium contact angle around 18°, 8° and 3° at corresponding experimental temperatures. Base on the scanning electron microscopy observing, no reaction product can be found at the interface of Cu47.5Zr47.5Al5/W and Cu40Zr44Al8Ag8/W, and some granular reaction products appeared along the interface of Cu50Zr50/W. The present work indicates that Cu47.5Zr47.5Al5 and Cu40Zr44Al8Ag8 bulk metallic glasses (BMGs) are appropriate for the fabrication of W reinforced BMGs matrix composite. [Copyright &y& Elsevier]

Abstract: This paper presents a class of Zr-based bulk glassy alloy with enhanced plasticity. The microstructure of this glassy alloy consists of dispersion of 2–5nm nanocrystallites embedded in the glassy matrix. Under compression, this glassy alloy displays high strength up to 2250MPa together with a large plastic strain of 5.5–14.5%. The improved plasticity is ascribed to the interaction between shear bands and nanocrystallites. [Copyright &y& Elsevier]

The wetting characteristics of Ti 32.8 Zr 30.2 Fe x Cu 14.3- x Be 22.7 (at.%, x = 0, 2.5, 5.3) bulk metallic glasses (BMGs) with W substrate are conducted using the sessile drop method at different temperatures. The effect of Fe content on wettability is systematically studied. At a given temperature, contact angle initially rises and subsequently declines as the Fe content increases from 0 at.% to 5.3 at.%. Optimal wettability is observed in BMGs devoid of the Fe element. This is attributed to the influence of Fe addition on the elemental diffusion behaviors and two-phase interfacial morphologies during wetting. The addition of 2.5 at.% Fe leads to a significant accumulation of Ti element at the wetting interface and prevents the wetting process. As the Fe content increases to 5.3 at.%, the conspicuous abundance of Fe in the glass phase together with the diffused Cu in W substrate determines the wettability of the system. These findings not only reveal the influence of Fe content on the wetting properties of the TiZr-based BMGs/W system but also provide a theoretical basis for the preparation of ex-situ BMG composites. • The contact angle first increases and then decreases with increasing Fe content. • Optimal wettability is observed in BMGs devoid of the Fe element. • Fe content has a significantly influence on the interface morphology of wetting. • Diffusion behavior of atomic clusters directly determines interfacial wettability. [ABSTRACT FROM AUTHOR]

Bulk metallic glass composites containing in-situ formed β-Ti/Zr phases (β-type BMGCs), which exhibit a good combination of strength and plasticity, were generally developed by adding β-stabilizers, such as Nb, Ta, V, etc., into Ti/Zr-based bulk metallic glasses (BMGs). In this work, an iteration method is proposed to develop β-type BMGCs from Ti/Zr-based BMGs, and the compositions of BMGCs can be designed by “the composition of in-situ formed β phase (the iterative variable) + the composition of BMG”. Due to the fast elemental diffusions between the β phase and the (supercooled) liquid phase, the iteration method can develop β-type BMGCs in which both phases can maintain a mutual (metastable) equilibrium during solidification. The procedures of the iteration method and its underlying thermodynamic and kinetic principles are discussed, and a Zr 56.9 Ti 18.8 Cu 7.4 Ni 5.7 Be 11.3 BMGC was developed from Vitreloy 1 by using the iterative method. As compared with β-type BMGCs developed by the conventional method, β-type BMGCs developed by the iteration method have two advantages: (i) the good glass-forming ability of the initial BMGs can be largely inherited by the glassy matrices in BMGCs; (ii) without adding β-stabilizers, the in-situ formed β phases are more likely to be metastable. The current iteration method is of scientific significance on improving plasticity of Ti/Zr-based BMGs and developing new β-type BMGCs. [ABSTRACT FROM AUTHOR]

Addition of a small amount of La and Co enhances the stabilization of supercooled liquid and glass-forming ability (GFA) of an Al 85 Ni 7 Er 8 metallic glass. The Al 85 Ni 5 Co 2 Er 6 La 2 alloy exhibits large supercooled liquid region of 40 K, high GFA with a critical thickness of 450 μm, and the viscosities on the order of 10 7 −10 9 Pa s in the supercooled liquid state. The Al-based glassy nano-scale patterns were formed by imprinting, indicating its good thermoplastic formability. The possible mechanism for the improvement of the supercooled liquid stability of the Al Ni Er alloy by addition of La and Co elements was discussed in terms of the crystallization behavior. [ABSTRACT FROM AUTHOR]

A new method was proposed to pinpoint the compositions with good glass forming ability (GFA) by combining atomic clusters and mixing entropy. The clusters were confirmed by analyzing competing crystalline phases. The method was applied to the Zr–Al–Ni–Cu–Ag alloy system. A series of glass formers with diameter up to 20 mm were quickly detected in this system. The good glass formers were located only after trying 5 compositions around the calculated composition. The method was also effective in other multi-component systems. This method might provide a new way to understand glass formation and to quickly pinpoint compositions with high GFA. [ABSTRACT FROM AUTHOR]

Abstract: The solidification process of the immiscible alloys exhibit a unique opportunity in designing the composites with the spherical crystalline particles dispersed in the amorphous metal matrix. The typical Al–Pb immiscible alloy and the additional elements Ni, Y and Co were selected, and the Al82.87Pb2.5Ni4.88Y7.8Co1.95 multicomponent immiscible alloy has been designed. The ribbon samples of the multicomponent alloy were prepared by using the melt spinning technique. The ribbons were characterized by the scanning electron microscopy (SEM). The phase constitution and transformation were studied by the X-ray diffraction (XRD) and the differential scanning calorimeter (DSC). It was revealed in the as-quenched ribbons the Al-based metallic glass matrix is embedded by the spherical crystalline Pb-rich particles. The microstructure evolution, the glass formation and the thermal stability of the as-prepared composite have been discussed in detail. A method has been developed based on the mechanism of the liquid–liquid phase transformation in the miscibility gap of the multicomponent immiscible alloy to produce the spherical crystalline particles in the amorphous matrix. [Copyright &y& Elsevier]