Papers by Author: Ying Min Wang

Abstract: With the aid of the atomic-cluster-plus-glue-atom model (ACPGA model) proposed by Dong et al [1] for bulk metallic glasses (BMGs), the formation and characteristic of Ni-Ta binary BMGs were investigated in this work. Binary glass-forming compositions containing 56.3–62.5 at.%-Ni were obtained by a composition formula [M-Ni₆Ta₆]Ni₃ based on the ACPGA model. It was found that Ni-Ta BMGs with a diameter of 2 mm was obtained over a composition range of 59 ~ 62 at.%-Ni by copper mold casting method, which are in good agreement with our model prediction. Newly-developed Ni–Ta BMGs are a kind of extreme materials, which exhibit superior thermal stability (T_g = 993K) and a ultrahigh fracture strength of about 3.5 GPa.

Abstract: The microstructures and mechanical behavior of the as-cast and isothermally annealed Zr63Al9.7Ni9.7Cu14.6Nb3 bulk metallic glasses (BMGs) were studied by differential scanning calorimetry (DSC), X-ray diffraction (XRD), transmission electron microscopy (TEM), and room temperature uniaxial compression. The as-cast BMG alloy shows a wide undercooled liquid span of 73 K at a constant heating rate of 40 K/min. Composite microstructures containing nanometer scaled icosahedral quasicrystals (i-phase) were produced upon annealing at 705 K. Under uniaxial room-temperature compression at a strain rate of 510-4 s-1, the as-cast BMG alloy exhibits a elastic deformation εy ~ 1.95%, a yield stress σy ~ 1650 MPa, and a Young’s modulus E ~ 84.5 GPa. The alloy shows a plastic strain εp ~ 8.0 % in a serrated plastic deformation process. Annealing induced embrittlement was observed in the relaxed BMG alloys. Comparing with the as-cast alloy, the relaxed and the composite alloys show negligible changes in elastic strain and Young’s modulus. The partially crystallized alloys are macroscopically brittle. Well developed vein patterns were observed in the fracture surfaces of all these alloys. The present work revealed that the dispersion of nanometer scaled i-phase particles is not effective as a barrier against shear localization in these partially quasicrystallized alloys.

Abstract: Ternary Sm-Al-Co bulk metallic glass formation is investigated with the guidance of a cluster line approach which is defined by linking a special cluster composition to the third element in the ternary phase diagram. Two dense-packed cluster lines Sm6Al3Co2-Co and Sm8Al1Co4-Al are constructed and they intersect at a good BMG composition Sm50Al25Co25. This composition can also be interpreted with a cluster-plus-glue atom model. The characteristic parameters of this optimum BMG are respectively Tg = 579 K, Tx = 640 K, Trg= 0.648, γ = 0.435 and
E=244 kJ/mol.

Abstract: The present paper covers in a comprehensive manner the formation of the Cu-based Cu-Zr-Al bulk metallic glasses (BMGs). Composition optimization for BMG formation is realized by using an “e/a-variant criterion”. This criterion is incorporated into the ternary phase diagram by a straight composition line, which is defined by linking a specific binary composition to the third element. There e/a-variant composition lines are constructed: (Cu9Zr4)1-xAl, (Cu61.8Zr38.2)1-xAlx and (Cu56Zr44)1-xAlx, where Cu9Zr4, Cu61.8Zr38.2 and Cu56Zr44 are specific cluster compositions in the Cu-rich Cu-Zr binary system. No Cu-based BMGs are obtained in the composition line (Cu9Zr4)1-xAlx using our suction casting techniques, while BMGs are obtained within an e/a span from 1.24 to 1.3 and from 1.28 to 1.36 respectively along the other two lines (Cu61.8Zr38.2)1-xAlx and (Cu56Zr44)1-xAlx. Thermal analysis results indicate that the BMGs on every composition line manifest increased thermal stability and glass forming ability (GFA) with increasing e/a ratios. The maximum appears in Cu58.1Zr35.9Al6 with the e/a value of 1.3, which belongs to the (Cu61.8Zr38.2)1-xAlx series. The characteristic thermal parameters of this BMG are Tg = 760K, Tg/Tm = 0.659 and Tg/Tl = 0.648, which are all superior to those reported for the known Cu55Zr40Al5 BMG.