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Metallic Glasses in Cell Phones

Metallic Glasses in Cell Phones

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Metallic Glasses in Cell Phones

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  1. Metallic Glasses in Cell Phones Angelika Franz

  2. what is a metallic glass structure properties processing cell phone cases cell phone hinges Outline

  3. Metallic Glass I • amorphous material: atoms “frozen” in non-crystalline form • lack long-range atomic order • first formed in 1957 by Duwez by rapid quenching • gold-silicon alloy • only very thin, small samples could be produced (order or micrometers)

  4. Metallic Glass II • 1990: found new alloys to form bulk metallic glasses • typically used three or more metallic elements • cooling rates needed decreased • could produce samples on order of centimeters Zr-Ti-Cu-Ni-Al alloy

  5. Structure I • first believed atoms were randomly packed together densly like hard spheres in a liquid • solvent atoms randomly arranged with solute atoms fitting into open cavities • now believe short-range, even medium-range order exists in materials

  6. Structure II • form nanoscale “superclusters” • difference in size between alloyed elements make solvent atoms cluster around solute atoms • Kasper polyhedra: 7 to 15 atoms arranged around central atom • polyhedra shape depends on size of constituent atoms • range of coordination numbers: different polyhedra exist within same material

  7. Structure III • was proposed that clusters conform to fcc lattice for closest-packing with strain factor to limit order to 1-1.5 nm • actually found clusters pack into icosahedral structures usually 1.5 nm wide • creates cavities into which extra solute atoms can pack

  8. Properties I • lack of crystallinity means lack of defects • gives rise to interesting properties • stronger and lighter than metals • tough: resistant to fracture • unlike ceramic glass is not brittle • easily heated, softened and molded into shapes

  9. Properties II • uncorrosive • not transparent • very high elastic strain limit • makes material bouncy

  10. Processing I • formed by quenching at rates of 1-100 degrees Celsius per second • used to be 1 million degrees Celsius per second • prevent atoms from forming into crystalline structure, instead freeze into liquid-like structure • limits size and shape of material produced

  11. Processing II • near net-shape casting • alloy is cast near to final shape • injection molding • metallic glass is heated until it softens and can flow into the mold • physical vapor deposition • ion irradiation • mechanical alloying

  12. Cell Phone Cases I • alloy of zirconium, titanium, copper, nickel and beryllium • produced using near net-shape casting • smaller, thinner designs with greater protection of internal components

  13. Cell Phone Cases II • sleek metallic surface • scratch and corrosion resistant • ~2.5 times strength of titanium alloy • ~1.5 times hardness of stainless steel • non-reactive • thinner walls with greater strength

  14. Cell Phone Hinges • deformation resistant • high yield strength and elasticity • more durable than conventional materials • very resilient to impact and daily wear-and-tear • reliable in repeated load-bearing conditions

  15. References • http://www.liquidmetal.com/ • http://www.jhu.edu/news/home06/jan06/glass.html • http://engr.oregonstate.edu/momentum/stories/liquid_metal.html • http://www.jhu.edu/matsci/people/faculty/hufnagel/background.html • http://www.nature.com/nature/journal/v439/n7075/full/439405a.html;jsessionid=396A417548AD57212FA5DAF138B540CA • http://www.sciencedaily.com/releases/1998/03/980331074950.htm • B. Van Aken, P. de Hey, and J. Sietsma: Structural relaxation and plastic flow in amorphous La50Al25Ni25. Mater. Sci. Eng. A278, 247 (2000). • http://www.sciwrite.caltech.edu/journal03/owensmichael.html