Macrosegregation and thermosolutal convection-induced freckle formation in dendritic mushy zone of directionally solidified Sn-Ni peritectic alloy  

作　　者：Peng Peng Anqiao Zhang Jinmian Yue Xudong Zhang Yuanli Xu 

机构地区：[1]Institute of Materials Science and Engineering,Lanzhou University,Lanzhou,730000,China [2]School of Physical Science and Technology,Lanzhou University,Lanzhou,730000,China

出　　处：《Journal of Materials Science & Technology》2021年第16期21-26,共6页材料科学技术（英文版）

基　　金：financially supported by the National Natural Science Foundation of China(No.51871118);the 2018 joint Foundation of Ministry of Education for Equipment Pre-research(No.6141A020332);the Key Research and Development Plan of Gansu Province(No.18YF1GA102);the Fundamentalx Research Funds for the Central Universities(No.lzujbky-2019-sp03);the Fund of Science and Technology Project of Lanzhou City(No.2019-1-30);the Fund of State Key Laboratory of Special Rare Metal Materials(No.SKL2020K003)。

摘　　要：Compared with the growing applications of peritectic alloy,none research on the freckle formation during peritectic solidification has been reported before.Observation on the dendritic mushy zone of Sn-36 at.%Ni peritectic alloy during directional solidification at different growth velocities shows that the freckles are formed in two different regions:region I before peritectic reaction and region II after peritectic reaction.In addition,more freckles can be observed at lower growth velocities.Examination on the experimental results demonstrates that both the temperature gradient zone melting(TGZM)and Gibbs-Thomson(G–T)effects have obvious influences on the morphology of dendritic network during directional solidification.The current theories onKI Rayleigh number Racharacterizing the thermosolutal convection of dendritic mushy zone to predict freckle formation through the maximum of Ra can only explain the existence of region I while the appearance of region II after peritectic reaction cannot be predicted.Thus,a new Rayleigh number RaP is proposed in consideration of evolution of dendritic mushy zone by both effects and peritectic reaction.Theoretical prediction of RaPalso shows a maximum after peritectic reaction in addition to that before peritectic reaction,thus,agreeing well with the freckle formation in region II.In addition,more severe thermosolutal convection can be predicted by the new Rayleigh number RaP at lower growth velocities,which further demonstrates the reliability of RaP in describing the dependence of freckle formation on growth velocity.

关 键 词：Directional solidification Thermosolutal convection Dendritic solidification Peritectic microstructures 

分 类 号：TG131[一般工业技术—材料科学与工程]