Effects of boron on the microstructure and thermal stability of directionally solidified NiAl–Mo eutectic / A. Gali in Acta materialia, Vol. 58 N° 2 (Janvier 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 421-428 Titre : Effects of boron on the microstructure and thermal stability of directionally solidified NiAl–Mo eutectic Type de document : texte imprimé Auteurs : A. Gali, Auteur ; H. Bei, Auteur ; E.P. George, Auteur Article en page(s) : pp. 421-428 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Interfaces Segregation Directional solidification Coarsening Composites Index. décimale : 669 Métallurgie Résumé : Microalloying with 0.01 at.% B decreases the range of growth speeds over which a well-aligned fibrous eutectic microstructure can be obtained in directionally solidified NiAl–Mo. Compared to the undoped alloy, the size/spacing of the Mo fibers is larger, and the fiber density smaller, in the B-doped alloy. Annealing at 1400 °C coarsens the fibers by a mechanism involving fault migration and annihilation driven by diffusion along the fiber–matrix interface. The coarsening kinetics, given by the decrease in Mo fiber density with time, is exponential, and microalloying with B decreases the coarsening rate. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...] [article] Effects of boron on the microstructure and thermal stability of directionally solidified NiAl–Mo eutectic [texte imprimé] / A. Gali, Auteur ; H. Bei, Auteur ; E.P. George, Auteur . - pp. 421-428. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 2 (Janvier 2010) . - pp. 421-428 Mots-clés : Interfaces Segregation Directional solidification Coarsening Composites Index. décimale : 669 Métallurgie Résumé : Microalloying with 0.01 at.% B decreases the range of growth speeds over which a well-aligned fibrous eutectic microstructure can be obtained in directionally solidified NiAl–Mo. Compared to the undoped alloy, the size/spacing of the Mo fibers is larger, and the fiber density smaller, in the B-doped alloy. Annealing at 1400 °C coarsens the fibers by a mechanism involving fault migration and annihilation driven by diffusion along the fiber–matrix interface. The coarsening kinetics, given by the decrease in Mo fiber density with time, is exponential, and microalloying with B decreases the coarsening rate. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science?_ob=PublicationURL&_tockey=%23TOC%235556%23 [...]

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Influence of Ni on martensitic phase transformations in NiTi shape memory alloys / J. Frenzel in Acta materialia, Vol. 58 N° 9 (Mai 2010)  

Public ISBD [article]  inActa materialia > Vol. 58 N° 9 (Mai 2010) . - pp. 3444–3458 Titre : Influence of Ni on martensitic phase transformations in NiTi shape memory alloys Type de document : texte imprimé Auteurs : J. Frenzel, Auteur ; E.P. George, Auteur ; A. Dlouhy, Auteur Année de publication : 2011 Article en page(s) : pp. 3444–3458 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : NiTi shape memory alloys Phase transformation temperatures Thermodynamics Vacuum arc melting Hysteresis width Résumé : High-precision data on phase transformation temperatures in NiTi, including numerical expressions for the effect of Ni on MS, MF, AS, AF and T0, are obtained, and the reasons for the large experimental scatter observed in previous studies are discussed. Clear experimental evidence is provided confirming the predictions of Tang et al. 1999 [19] regarding deviations from a linear relation between the thermodynamic equilibrium temperature and Ni concentration. In addition to affecting the phase transition temperatures, increasing Ni contents are found to decrease the width of thermal hysteresis and the heat of transformation. These findings are rationalized on the basis of the crystallographic data of Prokoshkin et al. 2004 [68] and the theory of Ball and James [25]. The results show that it is important to document carefully the details of the arc-melting procedure used to make shape memory alloys and that, if the effects of processing are properly accounted for, precise values for the Ni concentration of the NiTi matrix can be obtained. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001059 [article] Influence of Ni on martensitic phase transformations in NiTi shape memory alloys [texte imprimé] / J. Frenzel, Auteur ; E.P. George, Auteur ; A. Dlouhy, Auteur . - 2011 . - pp. 3444–3458. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 9 (Mai 2010) . - pp. 3444–3458 Mots-clés : NiTi shape memory alloys Phase transformation temperatures Thermodynamics Vacuum arc melting Hysteresis width Résumé : High-precision data on phase transformation temperatures in NiTi, including numerical expressions for the effect of Ni on MS, MF, AS, AF and T0, are obtained, and the reasons for the large experimental scatter observed in previous studies are discussed. Clear experimental evidence is provided confirming the predictions of Tang et al. 1999 [19] regarding deviations from a linear relation between the thermodynamic equilibrium temperature and Ni concentration. In addition to affecting the phase transition temperatures, increasing Ni contents are found to decrease the width of thermal hysteresis and the heat of transformation. These findings are rationalized on the basis of the crystallographic data of Prokoshkin et al. 2004 [68] and the theory of Ball and James [25]. The results show that it is important to document carefully the details of the arc-melting procedure used to make shape memory alloys and that, if the effects of processing are properly accounted for, precise values for the Ni concentration of the NiTi matrix can be obtained. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410001059

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