Wear Properties of a Shock Consolidated Metallic Glass and Glass-Crystalline Mixtures
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WEAR PROPERTIES OF A SHOCK CONSOLIDATED METALLIC GLASS AND GLASS-CRYSTALLINE MIXTURES THAD VREELAND, JR., NARESH N. THADHANI, AND ANDREW H. MUTZ, Division of Engineering and Applied Science, California Institute of Technology, Pasadena, CA 91125 SUSAN P. THOMAS AND ROGER K. NIBERT, Roy C. Ingersoll Research Center, BorgWarner Corp., Des Plaines, IL 60018 ABSTRACT Powder flakes prepared from 50 pm thick melt spun ribbons of Markomet wt%) were shock consolidated in the unanneal~d Mo) Cr B1 1064 (Ni and anneFA co~itign. 'he unannealed flakes (microhardness 933 kg/mm ) are amorphous while flakes annealed at 900%C for 2 hours have an2 fcc structure with a grain size of 0.3 pm and microhardness of 800 kg/mm . The shock consolidated amorphous powder compact (250 kJ/kg shock energy) shows no crystal peaks in an X-ray diffractometer scan. Compacts of annealed powder (400 to 600 kJ/kg shock energies) contain amorphous material (18-21%) which was rapidly quenched from the melt formed at interparticle regions during the consolidation process. The microhardness of the amorphous interparticle 2 material is 1100 kg/mm . Wear properties of the compacts measured in low velocity pin on disk tests show low average dynamic friction values (nuo.03). The 60 hour cumulative wear appears to correlate with the energy of shock compaction and surface porosity of the compacts rather than the metallic glass content. INTRODUCTION Metallic glasses, with high metalloid concentration and associated hardness, have been observed to show superior wear resistance when used as coatings on steel substrates [1]. Shock wave consolidation has been employed
to produce bulk solids with metastable structures [2-5]. During consolidation, the shock energy is preferentially utilized in heating and melting interparticle surfaces [6,7]. The melted regions rapidly solidify and may form new metastable structures or retain the metastable structure of the starting powder. Shock consolidation is a unique form of thermal and mechanical processing and can be used to process metallic glass powders to form bulk amorphous solids [8,9], and crystalline powders of glass forming alloys to produce a solid mixture of metallic glass and microcrystalline material [6,10]. In this paper, we report some wear properties of a shock consolidated glass forming alloy powder containing varying amounts of glass and microcrystalline phases. SHOCK CONSOLIDATION Powder Characterization r B6 5 wt%) powder was prepared 5o M° The Markomet 1064 alloy (Ni 0"1m thick). Annealing of spun amorphHtJ rib99ns t-5 by ball milling melt 0 the powder at 900 C for 2 h produces a fully microcrystalline powder (confirmed by x-ray and electron diffraction). Optical microscope observations on polished and etched powder particles show that the amorphous phase resists attack by the Marbles reagent, while microcrystalline grains in the annealed powder are attacked and show a dark etching contrast [10].
Mat. Res. Soc. Symp. Proc. Vol. 58. 1986 Materials Research Society
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