Quaternary and Quinary Ni-based Amorphous Alloys in the Ni-Zr-Ti-X (X=Al, Si, P) and Ni-Zr-Ti-Si-Y (Y=Sn, Mo, Y) Systems
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Quaternary and quinary Ni-based amorphous alloys in the Ni-Zr-Ti-X (X=Al, Si, P) and Ni-Zr-Ti-Si-Y (Y=Sn, Mo, Y) systems M.H. Lee1, S. Yi2, T.G. Park1, W.T. Kim1 and D.H. Kim1 1 Center for Noncrystalline Materials, Dept. of Metallurgical Eng., Yonsei University, 134 Shinchon-dong, Seodaemun-gu, Seoul, 12-749 Korea 2 Reliability Assessment Center for Metallic Materials, Korea Institute of Industrial Science and Technology, Chonan, Korea
ABSTRACT New Ni-based bulk amorphous alloys in the alloy system Ni-Zr-Ti-X (X=Al, Si, P) and Ni-ZrTi-Si-Y (Y=Sn, Mo, Y) were developed through systematic alloy design based upon the empirical rules for high glass forming ability (GFA). Additions of a small amount of Si and/or Sn to a ternary Ni-Ti-Zr alloy are very effective to increase GFA as well as the undercooled liquid region (∆TX). Changes in crystallization mode during continuous heating of amorphous phase and lowered liquidus temperature by quaternary and quinary additions are associated with the enhanced GFA and the enlarged ∆Tx. Development of new Ni-based amorphous alloys with high GFA and large ∆Tx expands structural application of amorphous alloys. INTRODUCTION A number of bulk amorphous alloys has been developed as a potential engineering material that has unique properties attributed to the atomic structure of amorphous phase [1-3]. Development of Ni-based bulk amorphous alloys is expected to expand structural application fields of the amorphous alloys. Recently, fully amorphous rods with the maximum diameter of 1mm have been prepared in the Ni-Nb-Cr-Mo-P-B system [4]. Since the GFA of the Ni-based amorphous alloys can be effectively improved by the addition of P or B, large amount additions of P and B (~20 at% in total) are necessary for the enhanced GFA of the Ni-Nb-Cr-Mo-P-B alloys. However, the addition of a large amount of P and B brings about economical and technological demerits. For example, due to high vapor pressure of P, specific facilities are required during the P addition into melts. In the present study, we report new Ni-based amorphous alloys in the NiTi-Zr-X (X=Al, Si, or P) and Ni-Zr-Ti-Si-Y (Y=Sn, Mo, or Y) systems. The new Ni-based bulk amorphous alloys exhibit high Tg, Tx, and ∆Tx(=Tx-Tg) that reflect high GFA. EXPERIMENTAL DETAILS Ingots (30g) were prepared by arc-melting under Ar atmosphere. Raw materials of purity ranging from 99.8% to 99.99% were used in the arc-melting process. Each alloy was re-melted at least four times to ensure the compositional homogeneity. For melt-spinning experiments, pieces of a sliced ingot were inductively re-melted in a fused silica tube and quenched onto a rotating copper wheel (wheel surface velocity ~30 m/s), to give an amorphous ribbon of approximately 30µm in thickness and 3-4mm in width. Using the amorphous ribbons, crystallization behaviors L4.8.1
were studied in a differential scanning calorimetry (DSC, Perkin Elmer DSC 7) and a differential thermal analysis (DTA, Perkin Elmer DTA 7). The phases present were identified by X-ray diffraction (XRD, Rigaku CN
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