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A crystallographic model of fcc/bcc martensitic nucleation and growth / J-B. Yang in Acta materialia, Vol. 58 N° 5 (Mars 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1599–1606 Titre : A crystallographic model of fcc/bcc martensitic nucleation and growth Type de document : texte imprimé Auteurs : J-B. Yang, Auteur ; Z.-G. Yang, Auteur ; Y. Nagai, Auteur Année de publication : 2011 Article en page(s) : pp. 1599–1606 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Martensitic  phase  transformation  Heterogeneous  nucleation  of  phase  transformations  Analytical  methods Résumé : A crystallographic model of face-centered cubic/body-centered cubic martensitic nucleation and growth has been developed in which the glissile martensitic interface is described in terms of discrete transformation and misfit dislocations within the framework of the Frank–Bilby equation. In the present model heterogeneous nucleation of a martensitic embryo occurs spontaneously by dissociation of an existing perfect dislocation under certain conditions, such as the catalysis on grain boundaries. Autocatalytic dislocation is proposed to be responsible for embryo growth, then nucleation and subsequent growth of a single embryo can be regarded as an autocatalytic process. As a natural result the crystallographic features of grown martensite are consistent with the phenomenological theory of martensite crystallography. Martensitic nucleation in this model agrees with many experimental observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007708 [article] A crystallographic model of fcc/bcc martensitic nucleation and growth [texte imprimé] / J-B. Yang, Auteur ; Z.-G. Yang, Auteur ; Y. Nagai, Auteur . - 2011 . - pp. 1599–1606. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1599–1606 Mots-clés : Martensitic  phase  transformation  Heterogeneous  nucleation  of  phase  transformations  Analytical  methods Résumé : A crystallographic model of face-centered cubic/body-centered cubic martensitic nucleation and growth has been developed in which the glissile martensitic interface is described in terms of discrete transformation and misfit dislocations within the framework of the Frank–Bilby equation. In the present model heterogeneous nucleation of a martensitic embryo occurs spontaneously by dissociation of an existing perfect dislocation under certain conditions, such as the catalysis on grain boundaries. Autocatalytic dislocation is proposed to be responsible for embryo growth, then nucleation and subsequent growth of a single embryo can be regarded as an autocatalytic process. As a natural result the crystallographic features of grown martensite are consistent with the phenomenological theory of martensite crystallography. Martensitic nucleation in this model agrees with many experimental observations. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645409007708

Positron annihilation studies of the interaction between oxygen impurities and nanovoids in neutron-irradiated vanadium / Z. Tang in Acta materialia, Vol. 58 N° 5 (Mars 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1868–1875 Titre : Positron annihilation studies of the interaction between oxygen impurities and nanovoids in neutron-irradiated vanadium Type de document : texte imprimé Auteurs : Z. Tang, Auteur ; T. Rewcharoon, Auteur ; Y. Nagai, Auteur Année de publication : 2011 Article en page(s) : pp. 1868–1875 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Positron  annihilation  (PAL)  Radiation  effects  Vacancies  Transition  metals Résumé : Vanadium samples with controlled oxygen impurity of up to 2460 at. ppm were irradiated with fast neutrons to a fluency of View the MathML source at 150 °C. The irradiation-induced nanovoids and the interaction between the defects and the oxygen impurities are studied systematically by combining the positron lifetime technique, the coincidence Doppler broadening technique and the first-principles calculations. The nanovoids are seen to be decorated with the oxygen impurities, which play a significant role in the dynamic processes of the formation of the nanovoids by irradiation and their subsequent recovery by post-irradiation annealing. The decoration with oxygen impurities not only enhances the nanovoid formation but also stabilizes them during low-temperature annealing (<400 °C). The oxygen impurities dissociate from the nanovoids by annealing above 400 °C and the irradiation-induced nanovoids recover on the annealing at 650 °C. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900809X [article] Positron annihilation studies of the interaction between oxygen impurities and nanovoids in neutron-irradiated vanadium [texte imprimé] / Z. Tang, Auteur ; T. Rewcharoon, Auteur ; Y. Nagai, Auteur . - 2011 . - pp. 1868–1875. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 5 (Mars 2010) . - pp. 1868–1875 Mots-clés : Positron  annihilation  (PAL)  Radiation  effects  Vacancies  Transition  metals Résumé : Vanadium samples with controlled oxygen impurity of up to 2460 at. ppm were irradiated with fast neutrons to a fluency of View the MathML source at 150 °C. The irradiation-induced nanovoids and the interaction between the defects and the oxygen impurities are studied systematically by combining the positron lifetime technique, the coincidence Doppler broadening technique and the first-principles calculations. The nanovoids are seen to be decorated with the oxygen impurities, which play a significant role in the dynamic processes of the formation of the nanovoids by irradiation and their subsequent recovery by post-irradiation annealing. The decoration with oxygen impurities not only enhances the nanovoid formation but also stabilizes them during low-temperature annealing (<400 °C). The oxygen impurities dissociate from the nanovoids by annealing above 400 °C and the irradiation-induced nanovoids recover on the annealing at 650 °C. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S135964540900809X