Two-layered Zr-base amorphous alloy/metal surface composites fabricated by high-energy electron-beam irradiation
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RECENTLY, remarkable advances in amorphous alloys have been made because of the development of amorphous alloys having substantially high glass forming ability by conventional casting methods.[1–4] Among them, Zr-base amorphous alloys show superb glass forming ability[5] (critical cooling rate: about 1 °C/s, maximum sample diameter: over 30 mm), excellent hardness, stiffness, strength, and corrosion resistance,[4,6] and thus have been applied to components of sporting goods and electrical products. However, they have poor ductility and toughness because brittle fracture readily occurs due to the formation of localized shear bands under tensile or compressive stress,[7] and have difficulties of fabrication of large structures or components, thereby limiting wide applications to advanced structural materials. Thus, if the fabrication of amorphous alloy/metal surface composites, in which the surface region consists of an amorphous alloy and the interior substrate consists of a ductile metal having sufficient ductility and fracture toughness, can be newly developed, the aforementioned problems of amorphous alloys can be solved while fully taking advantage of amorphous alloys. As a promising method to fabricate these amorphous alloy/metal surface composites, direct irradiation of highenergy electron beam is suggested. Upon irradiation on the metal substrate surface with highenergy electron beam, high kinetic energy of electrons, being struck into material lattices and forming phonons, is transformed to high thermal energy, which can easily melt alloys or ceramics with high melting points. When high-energy electron beam is irradiated on a metal substrate, where amorphous powders are evenly deposited, the substrate surface and amorphous powders are completely melted and solidified to form an amorphous alloy layer, thereby fabricating amorphous alloy/metal surface composites. This high-energy electron-beam irradiation has several advantages: (1) strong interfacial bonding between surface composite layer and substrate, (2) prevention of surface oxidation and intrusion of
KYUHONG LEE and EUNSUB YUN, Research Assistants, are with the Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang, 790-784 Korea. SUNGHAK LEE and NACK J. KIM, Professors, Center for Advanced Aerospace Materials, Pohang University of Science and Technology, are jointly appointed with the Materials Science and Engineering Department, Pohang University of Science and Technology. Contact e-mail: [email protected] JAE-CHUL LEE, Associate Professor, is with the Division of Materials Science and Engineering, Korea University, Seoul 136-701, Korea. MIKHAIL G. GOLKOVSKI, Senior Researcher, is with the Budker Institute of Nuclear Physics, Novosibirsk, 630090 Russia. Manuscript submitted April 5, 2004. METALLURGICAL AND MATERIALS TRANSACTIONS A
inclusions because of short irradiation time, (3) prevention of pores or cracks because of homogeneous heating and cooling, and (4) possible continuous processing of large-scale stru
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