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Cyclic twin nucleation in tin-based solder alloys / L.P. Lehman in Acta materialia, Vol. 58 N° 10 (Juin 2010) 

Public ISBD [article]  in Acta materialia > Vol. 58 N° 10 (Juin 2010) . - pp. 3546–3556 Titre : Cyclic twin nucleation in tin-based solder alloys Type de document : texte imprimé Auteurs : L.P. Lehman, Auteur ; Y. Xing, Auteur ; T. R. Bieler, Auteur Année de publication : 2011 Article en page(s) : pp. 3546–3556 Note générale : Métallurgie Langues : Anglais (eng) Mots-clés : Undercooling  solidification  Nucleation  Twinning  Single  crystal  growth  Electron  backscattering  diffraction  (EBSD)  Solidification  microstructure Résumé : The microstructure and Sn crystal orientations of lead-free solder alloys such as near-eutectic SnAgCu have a significant influence on the mechanical response of a solder joint to service conditions. Thus solidification processes were examined in SnAgCu solder joints. Distinct evidence of sixfold cyclic growth twinning of Sn during solidification from the melt was observed in Sn–Ag, SAC and Sn–Cu solders. Three orientations of Sn grains, each having a common 〈1 0 0〉 direction, were found in each of these systems, though the morphologies of these cyclic twinned microstructures differed. Analysis of dendrite arm spacing in cyclically twined structures with a beach ball morphology implies that the common 〈1 0 0〉 axis intersects with the region of the nucleation event. Models are presented for two pseudo/metastable hexagonal unit cells based upon {1 0 1} or {3 0 1} twins that introduce the cyclic twinning structure at the nucleation stage. Formation of these hexagonal unit cells may be facilitated by the presence of alloy elements. Subsequent epitaxial growth of the tetragonal unit cell on this nucleus can account for all three types of morphologies observed in microstructures of Sn-rich solder alloys. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410000443 [article] Cyclic twin nucleation in tin-based solder alloys [texte imprimé] / L.P. Lehman, Auteur ; Y. Xing, Auteur ; T. R. Bieler, Auteur . - 2011 . - pp. 3546–3556. Métallurgie Langues : Anglais (eng) in Acta materialia > Vol. 58 N° 10 (Juin 2010) . - pp. 3546–3556 Mots-clés : Undercooling  solidification  Nucleation  Twinning  Single  crystal  growth  Electron  backscattering  diffraction  (EBSD)  Solidification  microstructure Résumé : The microstructure and Sn crystal orientations of lead-free solder alloys such as near-eutectic SnAgCu have a significant influence on the mechanical response of a solder joint to service conditions. Thus solidification processes were examined in SnAgCu solder joints. Distinct evidence of sixfold cyclic growth twinning of Sn during solidification from the melt was observed in Sn–Ag, SAC and Sn–Cu solders. Three orientations of Sn grains, each having a common 〈1 0 0〉 direction, were found in each of these systems, though the morphologies of these cyclic twinned microstructures differed. Analysis of dendrite arm spacing in cyclically twined structures with a beach ball morphology implies that the common 〈1 0 0〉 axis intersects with the region of the nucleation event. Models are presented for two pseudo/metastable hexagonal unit cells based upon {1 0 1} or {3 0 1} twins that introduce the cyclic twinning structure at the nucleation stage. Formation of these hexagonal unit cells may be facilitated by the presence of alloy elements. Subsequent epitaxial growth of the tetragonal unit cell on this nucleus can account for all three types of morphologies observed in microstructures of Sn-rich solder alloys. DEWEY : 669 ISSN : 1359-6454 En ligne : http://www.sciencedirect.com/science/article/pii/S1359645410000443