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The changes in the atomic structure and mechanical properties of Zr–Cu metallic glasses caused by low-temperature annealing were studied by X-ray diffraction synchrotron radiation and nanoindentation. Results show that the nanohardness, wear resistance, and uniformity were improved by low-temperature annealing, which indicated that annealing plays a significant contribution. Diffractions patterns showed that the content of high-strength Zr–Cu pairs was increased whereas those of Zr–Zr and Cu–Cu pairs were decreased after low-temperature annealing. Thus, the process improvement was achieved by increasing the proportion of Zr–Cu pairs. [ABSTRACT FROM AUTHOR]

Zr x Cu 100−x (x=15–70) metallic glass (MG) models were constructed by molecular dynamics simulations to explore the intrinsic correlation between elastic modulus and atomic bond stiffness in MGs. The elastic modulus and atomic mole fraction of MGs approximately behave parabolically, and their maxima location shifts to lower Zr mole fraction. This phenomenon is due to the variation of their atomic bond percentages, which suggests that elastic modulus reflects the inherent stiffness of atomic bonds. The “rule of mixture”, which uses atomic bonds as the components, is more applicable than that in which atoms are used as the components to explain the inheritance of elastic modulus. [ABSTRACT FROM AUTHOR]

Identifying the underlying mechanisms of the special physical properties of metallic glasses (MGs) is of fundamental interest. The complexity and uncertainty in the structure of MGs have been obstacles to develop an efficient structure–property relationship. In this letter, we present a simplified structural parameter, atomic bond proportion, instead of exploring the complicated atomic structure to predict the properties of MGs. Based on statistical calculations and partial coordination number methods, the proportion of different types of atomic bonds for a series of MGs (e.g., Ca 60 Mg 15 Zn 25 , Zr 67 Ni 33 , and Al 90 Y 10 ) is successfully given, and the results from both methods significantly agree with each other. The weighted averages of the physical properties corresponding to the constituent atomic bonds were used to analyze the relationship between the composition and physical properties. The predicted atomic bond proportion may better elucidate the structure and properties of these materials. [ABSTRACT FROM AUTHOR]

2D finite element analysis was conducted on the temperature field to create an amorphous ingot by vacuum water quenching. An optimized analysis document was then written by ANSYS parametric design language, and the optimal design modules of ANSYS were used to study the inside diameter and wall thickness of the quartz tube, as well as the water temperature. The microstructure and the phase structure of the amorphous ingot were evaluated by scanning electron microscopy and X-ray diffraction, respectively. Results show that during the cooling process, the thinner wall thickness, smaller diameter of the ingot, or lower temperature of the water environment can result in higher cooling rate at a given temperature. Besides, the gap between the different cooling rates induced by wall thickness or diameter of the ingot narrows down as the temperature decreases, and the gap between the different cooling rates induced by temperature of the water environment remains constant. The process parameters in creating an amorphous ingot, which is optimized by the finite element analysis on the temperature field, are reliable. [ABSTRACT FROM AUTHOR]

Abstract: Volume change of bulk metallic glasses (BMGs) during the repeated loading and unloading was investigated using in situ high-pressure synchrotron diffraction. Molecular dynamics simulations, which were used for further research of the microstructure change, were presented on an approximately 5.0×105 atom sample of an amorphous Fe80P20 model. The results show that the first compression process includes irreversible annihilation of free volume and elastic volume change. The main form of annihilation of free volume is that smaller atoms are extruded into the larger atomic clearance. Hydrostatic pressure can make the microstructure of BMGs more stable and dense. As a result of the decrease in free volume, hardness and bulk modulus of BMGs treated with hydrostatic pressure are obviously improved. [Copyright &y& Elsevier]

Abstract: The structure of Yb60Ca2.5Zn20Mg17.5 bulk metallic glasses was investigated by in situ angle-dispersive X-ray diffraction with a synchrotron radiation source. The glassy nature of the samples was stable up to ~30GPa at room temperature. The volume and bulk modulus as a function of hydrostatic pressure were extracted from the diffraction data. A sudden change was observed in the volume and bulk modulus during compression. Results indicated that pressure induced polyamorphic phase transition in Yb-based bulk metallic glasses compared with Pr- and Gd-based bulk metallic glasses. The critical pressure of the transition was about 10GPa. The delocalization of 4f electrons under high pressures was responsible for the amorphous-to-amorphous phase transition in Yb-based bulk metallic glasses. [Copyright &y& Elsevier]

In this paper, we prepare the alloys of Zr41.2Ti13.8Cu12.5Ni10Be22.5, Zr44.4Ti14.8Cu14.3Ni11.5Be15, and Zr38Ti12.7Cu9.6Ni7.7Be32 to show the effects of alloy composition on the inhomogeneity structures and mechanical properties of Zr-based bulk metallic glasses (BMGs). Compared with the best glass former Zr41.2Ti13.8Cu12.5Ni10Be22.5, some nanoscale inhomogeneity structures can be induced by shifting the compositions towards a primary phase in the alloys of Zr44.4Ti14.8Cu14.3Ni11.5Be15 and Zr38Ti12.7Cu9.6Ni7.7Be32. The room temperature compression tests reveal that theBMGs contained nanoscale inhomogeneity structures exhibit superior mechanical properties with the high strength of 1780 MPa and especially a remarkable plastic strain of over 9%. These findings provide a new perspective to enhance the ductility of BMGs by introducing nanoscale inhomogeneity structures based on the phase competition strategy. [ABSTRACT FROM AUTHOR]

The glass formation and microstructure evolution of Mg61Cu28Gd11 and alloys laying on the line linking this composition to pure magnesium, i.e. alloys with fixed Cu:Gd ratio but increasing Mg content were systematically studied. A schematic phase diagram with three ternary phase regions was built based on the related competitive crystalline phases. Moreover, the results indicate that the alloys located in the Mg 2 Cu-Mg 2 CuGd-Mg 6 CuGd ternary phase region have higher glass forming ability than alloys with increased magnesium content. [ABSTRACT FROM AUTHOR]

The effects of nitrogen on both the glass forming ability (GFA) and mechanical properties of Zr-based bulk metallic glasses were studied experimentally. The results show that the doping of nitrogen could induce the precipitation of N-rich Zr 3 Ni-type crystals, and the precipitated crystals don’t trigger heterogeneous nucleation. Therefore, the remainder molten metal contains very lower nitrogen content and keeps good glass formation ability. Based on this, using the precipitated β -Zr(Ti, Nb) acted as a solid solvent for absorbed nitrogen, the optimum mechanical properties of bulk metallic glass composites can be obtained by doping an appreciate amount of nitrogen. This finding not only gives us a clue to avoid the detriment of light interstitial impurity to glass formation, but also opens a window to adjust the mechanical properties of the composites. [ABSTRACT FROM AUTHOR]

The alloying addition was widely and effectively used to develop the new BMGs and improve the glass formation ability (GFA) of the BMG materials. In this study, using the Zr-Cu-Ni-Al system as a mold, the effects of Al addition on both the microstructural evolution and glass forming ability were studied experimentally. The results indicate that when the amount of added Al is less than 10 at. % in the present alloys, Al is dissolved into the phases of ZrCu and Zr 2 Cu, and does not change the phase competition. However, both the kinetic and thermodynamic conditions for the amorphous formation are enhanced with increasing Al content. The rods of at least 10 mm diameter can be cast fully amorphous for the alloy (Zr 57.4 Cu 33.3 Ni 9.3) 90 Al 10. When Al content is further increased to 12% or more, some Al-rich Zr 51 Cu 28 Al 21 (τ 3) and Zr 38 Cu 36 Al 26 (τ 5) phases precipitate firstly during solidification, thereby deteriorating the GFA of alloys. These findings give a new perspective to apply alloying addition in a way that enhances the GFA. • The effects of Al content on the microstructure and GFA of Zr-Cu-Ni-Al were studied. • The GFA of Zr-Cu-Ni-Al depends on the competitive growth of ZrCu, Zr 2 Cu and amorphous. • The rods of at least 10 mm diameter can be cast fully amorphous in the Zr-Cu-Ni-Al. • The T g and T x increase with increasing Al content, while the T m and T L decrease. [ABSTRACT FROM AUTHOR]

Abstract: Molecular-dynamics simulations of the deformation behavior of ZrCu metallic glass reveal that plasticity and strength can be effectively improved by pre-introducing shear bands. A local strain region 1–2nm in size can be clearly observed. We name these regions shear origin zones. Strong interactions produced in these shear origin zones lead to uniform strain distribution and to the avoidance of stress localization. The simulation data well agree with the experimental results. [Copyright &y& Elsevier]