Recently, the paper “Remelting-induced anomalous eutectic formation during solidificationof deeply undercooled eutectic alloy melts” finished by our group membersXiuxun WEI, Qisen HUANG, Jinfu LI, Yaohe ZHOU and the collaborator Xin LIN fromNorthwestern Polytechnical University and Wanqiang XU and Michael FERRY from theUniversity of New South Wales was published in Acta Materialia (2015, Vol. 95,P44-56). The reviewers gave a very positive comment on our work.
Eutecticalloys often solidify into anomalous eutectics above a critical undercooling.After decades of study, the mechanism of anomalous eutectic formation remains ahighly controversial subject. Focused on the fact that the primary eutecticphases are supersaturated with solute and temperature recalescence isinevitable to occur during rapid solidification, the sed on the eutecticdendrite growth theory, the remelted fraction of the primary eutectic wasanalyzed systematically based on the eutectic dendrite growth theory. Theeffects of phase diagram parameters such as equilibrium solute redistributioncoefficient, slope of liquidus and eutectic composition on the remeltingtendency were revealed. In combination with the experimental results of severaltypical eutectic alloys, the mechanism for anomalous eutectic formation wascomprehensively interpreted.
Non-equilibriumsolidification is one of the main research fields of our group. The subjectsinvolved include eutectic growth theory, solidification structure evolution,solidification interface morphology and metastable phase formation. Theresearch results were mainly published in the international academic journalssuch as Acta Materialia, Metallurgicaland Materials Transaction A, Journal of Crystal Growth, etc.
Appendix:the abstract of the paper
Anomalouseutectics are argued to form due to the remelting of the primary solid duringsolidification of deeply undercooled eutectic alloy melts. As an indicator ofthe tendency for anomalous eutectic formation, the remelted fraction of the primaryeutectic was analyzed systematically based on the eutectic dendrite growththeory. For eutectic alloys with either larger equilibrium solute distributioncoefficients or gentle liquidus slopes, the primary eutectic is highlysupersaturated with solute and more prone to remelting. When the eutecticcomposition is set to different values, (e.g. the eutectic point is closer toone phase of the eutectic), the two eutectic phases under rapid growth change theircompositions simultaneously, but their remelted fractions during temperaturerecalescence do not vary significantly. Three representative binary eutectic alloysAg-39.9at.%Cu, Ni-19.6at.%P andPd-16.0at.%P¾theireutectic products are solidsolution-solid solution, solid solution-stoichiometricintermetallic compoundand stoichiometricintermetallic compound-stoichiometric intermetallic compound, respectively,were solidified at large undercooling. Anomalous eutectics were observed in thefirst two eutectic alloys whose eutectic structure consists of at least onesolid solution phase, whereby the stoichiometric intermetallic compound phase remainedhighly oriented whereas the solid solution phase had a near random distributionof orientations. For the Pd-16.0at.%P alloy, however, the primary eutecticretained its original morphology as the final solidification structureregardless of the degree of undercooling. All these experimental results validatethe argument that anomalous eutectics result from the remelting of the primarysolid.
