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We studied the glass forming ability of Ni-Nb binary alloys and found that some of the alloys can be prepared into bulk metallic glasses by a conventional Cu-mold casting. The best glass former within the compositional range studied is off-eutectic Ni 62 Nb 38 alloy, which is markedly different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism for binary Ni-Nb alloys was studied from the thermodynamic point of view and a parameter ␥ * was proposed to approach the ability of glass formation against crystallization. © 2006 American Institute of Physics. ͓DOI: 10.1063/1.2158130͔ Bulk metallic glasses ͑BMGs͒ as a prominent class of functional and structural materials with unique properties have attracted intensive interests due to their considerable significance in science and technology. [1][2][3][4][5][6][7][8][9][10][11] In order to make the best use of these noncrystalline materials, the key problem is to develop BMGs with improved properties and excellent glass forming ability ͑GFA͒. It is commonly regarded that the formation of metallic glasses is controlled by two factors, i.e., the cooling rate and the composition of the alloys. The critical cooling rate, which is the most effective gauge for GFA of the alloys, is hard to be measured experimentally. Hence, a great deal of efforts have devoted to the investigation on the composition of glass forming alloys. Inoue et al. 11 and Johnson 1 framed the empirical rules to predict the element selection and compositional range of glass forming alloys. These rules have played an important role as a guideline for synthesis of BMGs for the last decade.Binary alloys are usually considered to have a lower GFA due to their lack of complicated structure with atomic configuration according to the "confuse principal." 2,3 However, recent experimental results have shown that binary Zr-Cu alloys can also be vitrified into BMGs. [12][13][14] In contrast with the deep eutectic rule, the better glass formers in Zr-Cu binary alloy system such as Zr 35.5 Cu 64.5 and Zr 50 Cu 50 are off eutectic. Therefore, the empirical rules for glass formation, that is, multicomponent alloys with composition near deep eutectic, could be no longer the major concern for designing BMGs.In this work, we reported that some of the Ni-Nb binary alloys can be prepared into fully glassy rods up to 2 mm in diameter by a conventional Cu-mold casting method. The best glass former within the compositional range studied is off-eutectic Ni 62 Nb 38 alloy, which is different from those predicted by the multicomponent and deep eutectic rules. The glass formation mechanism of the binary alloys was studied from the thermodynamic point of view based on Miedema's calculation model.Ingots of Ni-Nb binary alloys with different compositions were prepared separately by arc-melting of 99.9% ͑at. %͒ pure Ni and Nb in titanium-gettered argon atmosphere. The rods of 2 mm in diameter were prepared by suction casting under argon atmosphere. The structure of the samples was charact...

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We studied the glass forming ability (GFA) of Cu-rich Cu–Hf binary alloys and found that some of the alloys can be prepared as bulk metallic glasses with maximum diameter up to 2 mm by a conventional Cu-mould casting. The best glass former within the compositional range studied is off-eutectic Cu65Hf35 alloy, which is markedly different from the prediction from the multicomponent and deep eutectic rules. The GFA, thermal stability, kinetics of the glass transition and crystallization for Cu65Hf35 glassy rods were studied. The glass formation mechanism for binary Cu–Hf alloys was investigated from the thermodynamic point of view. It is suggested that the better GFA of off-eutectic Cu65Hf35 alloy could be due to its higher value of the parameter γ*, which is defined as the ratio between the driving force for glass formation and the resistance of glass formation to crystallization.

The thermal stability of Nd 60 Fe 20 Co 10 Al 10 bulk metallic glass (BMG) has been studied by differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), isochronal dilatation and compression tests. The results show that the glass transition of the BMG takes place quite gradually between about 460 and 650 K at a heating rate of 0.17 K/s. Several transformation processes are observed during continuous heating with the first crystallization process beginning at about 460 K, while massive crystallization takes place near the solidus temperature of the alloy. The positive heat of mixing between the two major constituents, Nd and Fe, and, consequently, a highly inhomogeneous composition of the attained amorphous phase are responsible for the anomalous thermal stability in this system. 

The plastic flow of bulk metallic glasses (BMGs) is characterized by intermittent bursts of avalanches, and this trend results in disastrous failures of BMGs. In the present work, a double-side-notched BMG specimen is designed, which exhibits chaotic plastic flows consisting of several catastrophic avalanches under the applied loading. The disastrous shear avalanches have, then, been delayed by forming a stable plastic-flow stage in the specimens with tailored distances between the bottoms of the notches, where the distribution of a complex stress field is acquired. Differing from the conventional compressive testing results, such a delaying process is independent of loading rate. The statistical analysis shows that in the specimens with delayed catastrophic failures, the plastic flow can evolve to a critical dynamics, making the catastrophic failure more predictable than the ones with chaotic plastic flows. The findings are of significance in understanding the plastic-flow mechanisms in BMGs and controlling the avalanches in relating solids.

Controllable spin-glass behavior and large magnetocaloric effect in Gd-Ni-Al bulk metallic glasses Appl. Phys. Lett. 101, 032405 (2012); 10.1063/1.4738778 Weak exchange effect and large refrigerant capacity in a bulk metallic glass Gd 0.32 Tb 0.26 Co 0.20 Al 0.22 Appl. Phys. Lett. 94, 112507 (2009); 10.1063/1.3097237 Large magnetocaloric effect and enhanced magnetic refrigeration in ternary Gd-based bulk metallic glassesGd 55 Al 20 Co 20 Ni 5 bulk metallic glass (BMG) was synthesized by minor Ni substitution for Co in the Gd 55 Al 20 Co 25 BMG in which excellent glass forming ability (GFA) and magneto-caloric effect were reported previously. The Gd 55 Al 20 Ni 20 Co 5 amorphous rod has a similar GFA to the Gd 55 Al 20 Co 25 BMG but exhibits better magnetic properties. The peak value of magnetic entropy change (ÀDS m peak ) of the Gd 55 Al 20 Co 20 Ni 5 BMG is 9.8 Jkg À1 K À1 . The field dependence of ÀDS m peak follows a ÀDS peak m / H 0:85 relationship. The adiabatic temperature rise of the rod is 4.74 K under 5 T and is larger than of other BMGs previously reported. The improved magnetic properties were supposed to be induced by the enhanced interaction between 4f electron in the rare-earth and 3d electron in the transition metal elements by means of a minor Ni substitution for Co. V C 2014 AIP Publishing LLC. [http://dx.

Cellular bulk metallic glasses (BMGs) with macroscopic cellular structures were designed and fabricated. The cellular BMGs exhibited remarkable energy absorption capacity as compared with reported BMG foams and honeycombs. The enhanced energy absorption capability is attributed to the large plastic bending of the struts, the blunting of the cracks, and the large plastic deformation at the nodes. This work shows that, in cellular BMGs, the macroscopic cellular structures are more efficient in dissipating mechanical energy than microscopic cellular structures, opening a window for developing energy absorption devices using BMGs. V