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(Zr53Al11.6Ni11.7Cu23.7)1–x(Fe77.1C22.9)x (x=0−2.2, at.%) bulk metallic glasses (BMGs) were prepared by copper mold suction casting method. Their glass forming ability and physical and chemical properties were systematically investigated. The glass forming ability is firstly improved with increasing x, and then decreased when x exceeds 0.44 at.%. Both glass transition temperature and crystallization temperature are increased, while the supercooled liquid region is narrowed, with Fe–C micro-alloying. The hardness, yielding and fracture strength, and plasticity firstly increase and then decrease when x reaches up to 1.32 at.%. The plasticity of the BMG (x=1.32 at.%) is six times that of the Fe-free and C-free BMG. In addition, by the Fe–C micro-alloying, the corrosion potential is slightly decreased, while the corrosion current density increases. The pitting corrosion becomes increasingly serious with the increase of Fe and C content.

The effect of Fe-C alloy additions on thermal, mechanical and corrosive properties of (Cu50Zr40Ti10)1-x(Fe-C)x (x = 0–2.20 at%) alloys were systematically investigated. The results show that the Fe and C additions can enhance glass transition temperature Tg and onset crystallization temperature Tx, but narrow supercooled liquid region ΔTx. Work-hardening can be clearly observed for the Cu-based bulk metallic glasses (BMGs) containing Fe and C elements. The yield strength (σy), fracture strength (σf) and plastic strain (ep) are drastically increased by Fe-C alloy additions. The corrosion potential Ec increases and the corrosion current density ic decreases with increasing Fe and C contents. The studied Cu-based BMGs exhibit unique and novel anodic polarization behavior characterized by current platforms plus current serrations. The current serrations are much larger for the Cu-based BMGs with 0 ≤ x ≤ 1.32 at% than for those with 1.76 ≤ x ≤ 2.20 at%. The corrosion surface images are changed from the pits to the passive films by Fe-C alloy additions. The corrosion behavior gradually transforms from the pitting corrosion to the self-passivization with increasing Fe and C contents. The corresponding mechanisms are also discussed.

(Cu50Zr50)x(Cu73Ti27)100-x (x = 0.63–0.75 at.%) alloys are designed using the proportional mixing of Cu50Zr50 and Cu73Ti27 binary alloys. Their thermal, mechanical and corrosive properties as well as the glass forming ability (GFA) are systematically investigated. The results show that the studied Cu-based glass forming alloys are bulk metallic glass composites (BMGCs) with off-eutectic compositions and display work-hardening behavior. The glass transition temperature and the reduced glass transition temperature increase and then decrease with increasing x when x ≥ 0.74 at%, while on the contrary for the critical cooling rate and supercooled liquid region. Both yield strength and fracture strength firstly increase and then decrease with decreasing x when x ≤ 0.71 at%. The plastic strain of (Cu50Zr50)0.75(Cu73Ti27)0.25 BMGC is the largest among the studied Cu-based BMGCs. Potentiodynamic polarization measurements show that all studied BMGCs exhibit a step-like anodic polarization behavior, indicating two competitive procedures of pitting corrosion and self-passivization. The corrosion behavior gradually transforms from predominant self-passivization to the pitting corrosion with decreasing x. Both corrosion current density and onset passive current density of (Cu50Zr50)0.75(Cu73Ti27)0.25 BMGCs are two orders of magnitude lower than those of the other Cu-based BMGCs. The mechanisms for the GFA and the corrosion are also discussed. The present work would shed light on how to design and develop BMGCs with superior comprehensive performances.

The intrinsic correlation between the fracture morphology evolution and the structural heterogeneity of flow units in a typical Zr 52.5 Ti 5 Cu 17.9 Ni 14.6 Al 10 (vit105) metallic glass (MG) upon annealing was investigated. By systematically tuning the annealing time at temperature below the glass transition temperature, a series of dimple-like fracture morphology were obtained, which is the unique fingerprint-like pattern for every annealing state. Based on the structural relaxation model of flow units, the evolution of the typical dimple sizes, the largest and smallest dimple size, with annealing were well fitted. Then the evolution of flow unit density was estimated from the fracture morphology evolution, which displays the same evolution trend with that measured from thermal relaxation. A stochastic dynamic model considering the interaction of activated flow units was proposed to analyze the effect of the initial flow unit density and the flow unit interaction intensity on the dynamic evolution of dimple distribution. Our work may provide a novel scheme to investigate the structural fingerprint information on flow units from fracture morphology, and enlighten the microscopic structural origin of the ductile-to-brittle transition during structural relaxation in MGs.

(Zr54Al10.2Ni9.4Cu26.4)100−xTix (x = 0–0.5, at%) bulk metallic glasses were prepared by water-cooled copper suction casting method. The Ti microalloying effect on glass forming ability and physical and chemical properties of Zr54Al10.2Ni9.4Cu26.4 glass forming alloy were systematically investigated. The glass forming ability is the largest for the Zr-based alloy with 0.3 at% Ti. The glass transition temperature is decreased by the Ti addition, while the supercooled liquid region is broadened. Both strength and plasticity are significantly enhanced by the Ti addition. The yield strength and the fracture strength firstly increase and then decrease when the Ti content reaches up to 0.3 at%. The plastic strain and the fracture strain increase with increasing Ti content. In addition, the corrosion potential is slightly decreased by the Ti addition. The corrosion current density increases with increasing Ti content. The pitting corrosion becomes increasingly serious with increasing Ti content. The honeycomb corrossion structure can be clearly observed when the Ti content reaches up to 0.5 at%. The corresponding mechanisms are also discussed in detail.

(Zr53Al11.6Ni11.7Cu23.7)1-x(Fe77.1C22.9)x (x = 0–2.2 at.%) bulk metallic glasses (BMGs) were prepared by water cooling copper mold suction casting and their isochronous crystallization characteristics are investigated. The glass transition temperature, crystallization temperature, and crystallization peak temperature for all studied Zr-based BMGs firstly increase with increasing heating rate, and then decrease when the heating rate increases up to 60 K/min for the BMGs (0 ≤ x ≤ 0.88 at.%) and 80 K/min for the BMGs (1.32 ≤ x ≤ 2.20 at.%). The glass transition temperature, crystallization temperature, glass transition activiation energy, crystallization activiation energy, and activiation energy for crystallization peak temperature of the Fe- and C-free Zr-based BMG are the smallest among the studied BMGs, indicating that Fe and C additions are benificial to delaying the glass transition and the crystallization. Fe and C additions influence more significantly on the glass transition than on the crystallization. The local crystallization activiation energy for the Fe- and C-free BMG are the smallest among the studied BMGs, indicating that the crystallization is easy for the Fe- and C-free BMG. The peak height of local Avrami exponent and its corresponding crystallization fraction decrease with increasing heating rate except for the BMG (x = 1.32 at.%). The fragility indexes are 32–48 for the studied Zr-based BMGs. The present results are of guiding significance for preparing the excellent BMG composites by heat treatment and selecting suitable conditions for forming the BMGs.

The thermal, mechanical and corrosive properties of (Cu45Zr45.5Ti9.5)100-xAlx (x = 0–0.25 at%) glass forming alloys were systematically studied. The thermal measurements show that Al microalloying leads to increase of glass transition temperature but decrease of supercooled liquid region. The glass transition activation energy slightly increases and then decreases with increasing Al content. The room-temperature compression tests demonstrate that all studied Cu-based bulk metallic glasses (BMGs) exhibit work-hardening behavior, but the work-hardening capacity depends on Al content. In addition, yield strength, fracture strength and fracture strain are drastically increased by Al addition. The largest plasticity of (Cu45Zr45.5Ti9.5)99.8Al0.2 BMG is 6 times larger than that of the Al-free Cu-based BMG. Moreover, the electrochemical measurements indicate that the Al minor addition cause the decrease of both corrosion potential and corrosion current density. The corrosion behavior gradually transforms from the pitting corrosion to the self-passivization with increasing Al content. The local heterogeneity of Al element is thought to be the reason for the performance change of the studied Cu-based BMGs. The present results would provide a new insight into the mechanism for the microalloying effect on the properties of the metallic glasses.

Phase formation, glass forming ability, mechanical and thermal properties of Cu50Zr50−x Al x (0⩽x⩽11.0) glass forming alloys were systematically investigated. The results show that Cu50Zr47Al3 alloy has the best glass forming ability (GFA), lowest fragility index (m) and highest fracture strength. There are B2 CuZr and B19′ CuZr phases for Cu50Zr50−x Al x (0⩽x⩽5.0) alloys. B2 CuZr phase disappears and two new phases (Cu10Zr7 and CuZr2) appear when 5.05.0). Cu50Zr50−x Al x (0⩽x⩽4.0) alloys are off-eutectic compositions while near-eutectic compositions for Cu50Zr50−x Al x (5.0⩽x⩽11.0) alloys. The E g, E x, and E p decrease with increasing sensitive factor (β) for the studied Cu-based alloys characterized in the room-temperature brittleness. The dependence of the phase formation and GFA on the Al content is discussed.

Glass forming ability, thermal, electrical and mechanical properties of Cu50Zr40Ti10 − xNix (0 ≤ x ≤ 4.0 at%) glass forming alloys were systemically investigated. It is found that the critical dimension of the present Cu-based glass forming alloys firstly increases with increasing Ni content, then decreases when Ni >2.0 at%. Ni addition results in the increase of the electrical resistivity and the thermal conductivity. The glass transition temperature increases with increasing Ni content for the present Cu-based BMGs at all studied heating rates. However, there are complex correlations for the other characteristic temperatures, crystallization enthalpy and activation energy with the Ni content and heating rate, respectively. The plastic strain firstly increases with increasing Ni content, then decreases when Ni >2.0 at%. Both yield strength and compression strength nearly increase with increasing Ni content. The plastic strain increases with decreasing m in the range of 0 ≤ Ni ≤ 2.0 at% and 2.0 ≤ Ni ≤ 4.0 at% for present Cu-based BMGs. The m linearly decreases with increasing dc for the present cu-based BMGs. The corresponding mechanisms are also investigated.

We report that the glass transition temperature (Tg) of a variety of metallic glasses (MGs) correlates with the eutectic or peritectic temperature of two main components corresponding stoichiometric proportion in their binary phase diagram. The correlation suggests that the Tg of MGs is mainly determined by their solvent of two base components, which have composition close to the eutectic and peritectic points in the binary phase diagram and the weakest link in amorphous structure. The results have implications for understanding the structure and glass transition in MGs and for predicting and designing metallic glasses with a desirable Tg.

Cu50Zr40Ti10 (at%) glassy ribbon was prepared by melt spinning. The effect of mechanical tension on its thermal and corrosive properties was investigated by differential scanning calorimetry and electrochemical polarization experiments, respectively. After mechanical tension, the crystallization temperature and the crystallization enthalpy almost maintain the same, while the relaxation temperature and the glass transition temperature decrease. In addition, the activation energy of the glass transition decreases from 74.8 +/- 1.7 KJ mol(-1) to 71.0 +/- 1.9 KJ mol(-1). The activation energy of the relaxation decreases from 70.0 +/- 4.4 KJ mol(-1) to 50.5 +/- 3.8 KJ mol(-1) at low heating rate, while increases from 186.1 +/- 9.4 KJ mol(-1) to 289.4 +/- 9.4 KJ mol(-1) at rapid heating rate. On the other hand, corrosion potentials polarized in all studied solutions sharply decrease, while the corrosion current densities increase. The pitting corrosion vanishes in 1 M chloride-containing solutions. The passive potential and the passive current density both decrease in 0.5 M H2SO4. The corroded surface micrographs in all studied solutions remarkably change. In addition, the difference of corrosive behavior in 0.5 M H2SO4, 1 M HCl, and 1 M NaCl is also discussed. (C) 2013 Elsevier B.V. All rights reserved.

A group of plastic Zr-Al-Ni-Cu bulk metallic glasses (BMGs) with low Zr content was developed and their thermal and mechanical properties were investigated. The results show that these Zr-based BMGs have a single crystallization event for all heating rates in the studied temperature region. The glass transition temperature Tg decreases with increasing Zr content for all heating rates. There are two melting procedures for the BMGs whose Zr content is less than 52 at %, while three melting procedures for the other Zr-based BMGs. The second melting procedure is split into two melting procedures for Zr52.5Al12.2Ni12.6Cu22.7 and Zr53Al11.6Ni11.7Cu23.7 BMGs, while the first melting procedure is split into two melting procedures for the other BMGs. The activation energy decreases with increasing sensitivity index β for the studied Zr-based BMGs. The plastic strain ep is in the region of 0.2%-19.1% for these Zr-based BMGs. Both yield strength σy and fracture strength σf are smallest for Zr55Al8.9Ni7.3Cu28.8 BMG whose ep is largest among all studied Zr-based BMGs and reaches up to 19.1%. In addition, the mechanism for the large difference of the plasticity among the studied Zr-based BMGs is also discussed.

The tensile behaviors of a series of (Zr47.5Cu47.5Al5)1 − x(Zr80Nb20)x (x = 0, 0.05, 0.10, 0.15) bulk metallic glasses were studied at ambient and cryogenic (77 K) temperatures. It is found that the tensile strength of the alloys increases as the temperature decreases from 298 K to 77 K. The maximum enhancement is 15.7%, and the toughness of these alloys does not deteriorate at low temperatures. We demonstrate that the higher energy required to raise the temperature in the shear bands from the cryogenic temperature to glass transition temperature is the origin of the tensile strength enhancement at low temperatures.

Ta-based bulk metallic glasses with high strength (2.7 GPa) and hardness (9.7 GPa), high elastic modulus (170 GPa) and high density (12.98 g/mm(3)) were developed. The best glass forming ability so far for a Ta-Ni-Co system reaches a critical diameter of 2 mm by the copper mold casting method. It shows an exceptionally high glass transition temperature of 983 K and a high crystallization temperature up to 1023 K. The unique mechanical and physical properties make them a promising high strength material. (C) 2011 Elsevier B.V. All rights reserved.

The evolution of flow units associated with the flow “defects” in metallic glass is characterized by monitoring the metallic glassy density change upon isothermal annealing far below their glass transition temperature. A meaningful function for the density variation with the concentration of flow units is obtained for the metallic glasses. We show that the correlation between the density variation and the flow unit have implications for understanding the fragility, structural heterogeneous, and structural relaxation behaviors in metallic glasses.

It has been postulated that metallic glasses, in contrast to their crystalline counterparts, exhibit nano-scale structural heterogeneity which is crucial for understanding the long-standing issues of relaxations and deformation of glasses. We fabricate micrometer scale metallic glassy fibers (MGFs) with different diameters and structural configurations, and find that the thinner MGFs cooled down with faster cooling rates have smaller superconducting transition temperatures and wider transition widths. We show that the superconducting properties correlate with the heterogeneous microstructure of metallic glasses and can be used as a novel way to experimentally characterize the structural heterogeneity of metallic glasses.