Polyamorphism in a metallic glass

@article{citeulike:2678867, abstract = {A metal, or an alloy, can often exist in more than one crystal structure. The face-centred-cubic and body-centred-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions1, 2, 3, 4, 5, 6, 7 in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral4, 5) coordination environments. Here, we report an in situX-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce55Al45 metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modelling of the effects of f-electron delocalization8, 9, 10. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties11 due to different bonding and structural characteristics.}, author = {Sheng1}, citeulike-article-id = {2678867}, journal = {Nature Materials 6, 192 - 197 (2007)}, keywords = {2007, alloy, nature, shear, stz}, posted-at = {2008-04-16 21:10:24}, priority = {2}, title = {Polyamorphism in a metallic glass}, url = {http://www.nature.com/nmat/journal/v6/n3/full/nmat1839.html\#a1} }

TY - JOUR ID - citeulike:2678867 L3 - citeulike-article-id:2678867 TI - Polyamorphism in a metallic glass JF - Nature Materials 6, 192 - 197 (2007) N2 - A metal, or an alloy, can often exist in more than one crystal structure. The face-centred-cubic and body-centred-cubic forms of iron (or steel) are a familiar example of such polymorphism. When metallic materials are made in the amorphous form, is a parallel 'polyamorphism' possible? So far, polyamorphic phase transitions1, 2, 3, 4, 5, 6, 7 in the glassy state have been observed only in glasses involving directional and open (such as tetrahedral4, 5) coordination environments. Here, we report an in situX-ray diffraction observation of a pressure-induced transition between two distinct amorphous polymorphs in a Ce55Al45 metallic glass. The large density difference observed between the two polyamorphs is attributed to their different electronic and atomic structures, in particular the bond shortening revealed by ab initio modelling of the effects of f-electron delocalization8, 9, 10. This discovery offers a new perspective of the amorphous state of metals, and has implications for understanding the structure, evolution and properties of metallic glasses and related liquids. Our work also opens a new avenue towards technologically useful amorphous alloys that are compositionally identical but with different thermodynamic, functional and rheological properties11 due to different bonding and structural characteristics. KW - 2007 KW - alloy KW - nature KW - shear KW - stz AU - Sheng1 UR - http://www.nature.com/nmat/journal/v6/n3/full/nmat1839.html#a1 ER -