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Displacive-replacive phase transformation in a phase studies by HREM and microdiffraction
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| Abstract |
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| The structure of the metastable Ni2Al phase, which has long been a matter of controversy, has been carefully re-examined by means of high-resolution transmission electron microscopy (HREM) and electron microdiffraction. First, it is concluded that theas-quenched NixAl100-x(60 less-than-or-equal-to x less-than-or-equal-to 65) material already exhibits a partial omega-type collapse in a one-dimensional fashion which and is consistent with the anomalous dip in the phonon dispersion curve. Ni2Al precipitates are formed on annealing by thermal decomposition of the high-temperature NixAl100-xB2 phase and still retain the small omega-type shuffle. The amount of displacement in the well developed Ni2Al phase was estimated to be between 20 and 50% of the ideal omega collapse; this was determined by means of a combined technique of HREM and microdiffraction together with dynamical calculations of HREM images and diffraction intensities. | | |
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English
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| Source (journal) |
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Philosophical magazine: B: physics of condensed matter: electronic, optical and magnetic properties. - London, 1978 - 2002 | |
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London : 1993
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1364-2812
0141-8637
0958-6644
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67:5(1993), p. 673-689
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A1993LF72000005
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