Formation Range, Mechanical Properties and Thermal Stability of Superconducting Zr-Si Amorphous Alloys

概要

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New type of refractory metal-metalloid amorphous alloys containing less than 20 at% Si have been found in binary Zr-Si system by a modified melt-spinning technique for high melting point alloys. Specimens are in the form of continuous ribbons of 1-2 mm width and 0.02-0.03 mm thickness. The silicon content in the amorphous range is limited to the range 12 to 24 at%. The Vickers hardness increases from 395 to 495 DPN with increasing silicon content and the tensile strength is of the order of 1400 MPa. Crystallization temperature is the lowest (720 K) at Zr_<83>Si_<17>, increases with decreasing and increasing silicon content and reaches 804 K at Zr_<88>Si_<12> and 768 K at Zr_<76>Si_<24>. The activation energy for crystallization is in the range 175 to 202 kJ/mol. These amorphous alloys are so ductile that no cracks are observed even after closely contacted bending test. The good ductility remains unchanged for 3.6 ks at temperatures below 650 K. Further, these amorphous alloys exhibit a superconducting transition which occurs very sharply. The superconducting transition temperature (T_c) increases with decreasing silicon content and reaches a maximum value of 3.2 K for Zr_<88>Si_<12>. Thus, the Zr-Si amorphous alloys are a superconductor which possesses the T_c values higher than zirconium metal in addition to high strength combined with good ductility.
東北大学の論文