Papers by Keyword: Supercooled Liquid Region

Abstract: in the present study, amorphous ti50cu35-xni15snx (x=0~7) alloy powders were synthesized by mechanical alloying technique. the amorphization behavior of ti50cu28ni15sn7 alloy powders was examined in details by scanning electron microscopy, differential scanning calorimeter, x-ray diffraction, and synchrotron x-ray absorption spectroscopy. the results show that fully amorphous powders formed after 7 hours of milling. The thermal stability of the Ti50Cu35-xNi15Snx amorphous powders was investigated by differential scanning calorimeter. The amorphous Ti50Cu35Ni15 powders (i.e., x=0) exhibit no glass transition behavior. However, the amorphous Ti50Cu35-xNi15Snx (x=3~7) powders were found to exhibit a supercooled liquid region before crystallization. Amorphous Ti50Cu28Ni15Sn7 alloy powders exhibits a wide supercooled liquid region of 61 K.

Abstract: In the present study, WC/Cu60Zr30Ti10 metallic glass composite powders were prepared by mechanical alloying of pure Cu, Zr, Ti, and WC powder mixtures. Cu60Zr30Ti10 metallic glass composite powders were obtained after 5 h of milling as confirmed by X-ray diffraction and differential scanning calorimetry. The metallic glass composites powders were found to exhibit a supercooled liquid region before crystallization. Bulk metallic glass (BMG) composites were synthesized by vacuum hot pressing the as-milled Cu60Zr30Ti10 metallic glass composite powders at 723 K in the pressure range of 0.72-1.20 GPa. BMG composite with submicron WC particles homogeneously embedded in a highly dense anocrystalline/amorphous matrix was successfully prepared under applied pressure of 1.20 GPa. It was found that the pressure could enhance the thermal stability and promotes nocrystallization of WC/Cu60Zr30Ti10 BMG composites.

Abstract: New Cu-based bulk amorphous alloys exhibiting a large supercooled liquid region and good mechanical properties were formed in a quaternary Cu-Ni-Zr-Ti systems consisting of only metallic elements. The compositional range for the formation of the amorphous alloys that have high glass forming ability (GFA) (> 3 mm diameter) and large supercooled liquid region (> 50 K) is defined in the pseudo-ternary phase diagram Cu-Ni-(Zr, Ti). A bulk amorphous Cu₅₄Ni₆Zr₂₂Ti₁₈ alloy with the diameter of 6 mm can be prepared by copper mold casting. The Cu₅₄Ni₆Zr₂₂Ti₁₈ alloy shows glass transition temperature (T_g) of 712 K, crystallization temperature (T_x) of 769 K and supercooled liquid region (ΔTx) of 57 K. The Cu₅₄Ni₆Zr₂₂Ti₁₈ alloy exhibits high compressive fracture strength of about 2130 MPa with a plastic strain of about 1.5 %. The new Cu-based bulk amorphous alloy with high GFA and good mechanical properties allows us to expect the extension of application fields as a new engineering material.

Abstract: The effects of partial replacements of Zr by Y in the alloy Ni₆₀Zr_25-xAl₈Y_x(x=0 and 7 at %) on the crystallization behaviors of amorphous alloys were studied using isothermally heattreated ribbons. With the partial replacement, the supercooled liquid region upon continuous heating was significantly extended indicating that crystallization can be effectively suppressed by the optimum amount of Zr replacement by Y. The first phase appeared during crystallization was identified as the ternary compound AlNi₂Zr while the single exothermic event could be observed upon heating the amorphous ribbons. The AlNi₂Zr phase was decomposed into binary compounds upon further heating. Therefore, the extended supercooled liquid region of the alloy Ni₆₀Zr₂₅Al₈Y₇ was attributed to the suppression of AlNi₂Zr phase formation by the partial replacement of Zr by Y. The effects of Y on the crystallization behaviors were discussed on the basis of atomic configuration of the supercooled liquid.