Natural formation of bcc Co: Initial stage of Co precipitation in supersaturated Au90Co10

被引:6
作者
Bauer, R. [1 ]
Bischoff, E. [2 ]
Mittemeijer, E. J. [1 ,2 ]
机构
[1] Univ Stuttgart, Inst Mat Sci, D-70569 Stuttgart, Germany
[2] Max Planck Inst Met Res, D-70569 Stuttgart, Germany
来源
PHYSICAL REVIEW B | 2010年 / 81卷 / 09期
关键词
AU-CO; PHASE-TRANSFORMATION; ALLOTROPIC TRANSFORMATION; MAGNETIC-PROPERTIES; EPITAXIAL-GROWTH; COBALT; ALLOYS; FCC; MICROSTRUCTURE; SUPERLATTICES;
D O I
10.1103/PhysRevB.81.094113
中图分类号
T [工业技术];
学科分类号
08 ;
摘要
Natural formation of the bcc modification for Co was demonstrated to occur upon precipitation of Co in supersaturated Au90Co10 alloy. The microstructural evolution was investigated by high-resolution transmission electron microscopy. Co precipitation starts with the formation of very thin coherent plates along {100}(Au). This initially precipitated Co was shown to be a hitherto unknown metastable bcc modification of Co exhibiting a Bain-type orientation relationship with the matrix: (100)(Au,fcc)parallel to(100)(Co,bcc) and [001](Au,fcc)parallel to[011](Co,bcc) (three variants). Prolonged annealing causes the bcc Co to transform according to a Bain-type transformation into face-centered-cubic (fcc) Co, exhibiting the (cube-on-cube) orientation relationship (100)(Au,fcc)parallel to(100)(Co,fcc) and [001](Au,fcc)parallel to[001](Co,fcc) (three variants), in association with loss of coherency and a morphological change from Co platelets to equiaxed Co particles. A delicate balance of interface energy and bulk energy upon precipitation and subsequent growth/coarsening governs the successive appearance of the bcc and fcc modifications of Co.
引用
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页数:6
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