William L. Johnson Named 1998 MRS Medalist for Metallic Glass
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William L. Johnson Named 1998 MRS Medalist for Metallic Glass The development and characterization of bulk metallic glass forming alloys, by William L. Johnson, Ruben and Donna Mettler Professor of Materials Science at the California Institute of Technology, have led to a new class of structural materials for advanced engineering applications. For his pioneering work, Johnson has been selected to receive the 1998 MRS Medal, which will be presented at the Materials Research Society Fall Meeting in Boston. He is cited for "the development and fundamental understanding of bulk metallic glass forming alloys." Johnson's work, based on two decades of fundamental research on amorphous alloys, premiered in 1993 with a report published in Applied Physics Letters on the
fabrication of Zr4i 2Ti13 8Cui2 5Niio.oBe22.s alloyed by induction melting. He and A. Peker, also at Caltech, found that their 5-6 g samples froze without any crystallization during preparation, resulting in a glassy ingot. According to their report, the alloy forms glass at cooling rates of less than 10 K/s. Johnson prepared the alloys by melting the material in a silica mold then quenching it in water. Previous techniques, such as rapid quenching methods, have been used to form metallic glasses by cooling the melt at rates of 105-106 K/s. According to Johnson, "the new materials can be cast from the molten state into glassy objects with dimensions up to several centimeters as compared with maximum thicknesses of 10-100 micrometers for rapidly quenched ribbons and powders." The uniqueness of these alloys resides in their high resistance to crytallization. Johnson attributes this resistance to two factors: the low melting point of the corresponding crystalline alloys, and the fact that the alloys "generally have several
new engineering applications. Johnson said, "The undercooled liquid state...presents opportunities for the manufacture of inexpensive, high-quality, net-shape metal components with high strength and strength-to-weight ratio, high fracture toughness, fatigue resistance, and resistance to wear and corrosion." Johnson is currently involved in the development of technical applications of these bulk metallic glasses and metallic glass matrix composites through collaborative research with several other laboratories, including national laboratories in Oak' Ridge and Argonne, the University of California in Berkeley, and with several companies, including Amorphous Technologies, MMM Corporation, Alcoa Research William L. Johnson Laboratories, and General Motors. Johnson received his PhD degree in applied physics from Caltech in 1974, and (four or more) constituents with atoms of substantially different sizes." The alloys' has been on the faculty there for 20 years. He has authored or co-authored over 275 resistance to crystallization has opened articles, contributed eight chapters to further opportunities for experimental study of the liquid state and glass transi- books, and is an inventor or coinventor on 17 issued and pending U.S. patents. He is t
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