Different from other alloys,the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn...Different from other alloys,the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn−Ni peritectic alloys.In addition,the experimental results demonstrate that the dendritic morphology is influenced by the temperature gradient zone melting and Gibbs−Thomson effects.A new Rayleigh number(Ra_(P))is proposed in consideration of both effects and peritectic reaction.The prediction of Ra_(P) confirms the freckle formation in two regions during peritectic solidification.Besides,heavier thermosolutal convection in samples with larger diameter is also demonstrated.展开更多
Visualizations of the solidification process were obtained by means of X-ray radioscopy within a Hele-Shaw cell filled with a Ga-25wt%In alloy.Therrno-solutal convection in the solidifying melt gives rise to the devel...Visualizations of the solidification process were obtained by means of X-ray radioscopy within a Hele-Shaw cell filled with a Ga-25wt%In alloy.Therrno-solutal convection in the solidifying melt gives rise to the development of vertical segregation channels( 'chimneys').The probability of chimney formation depends sensitively on variations of both the concentration and temperature distribution.A forced melt flow perpendicular to the growth direction accelerates the growth of the secondary dendrite arms on the upstream side and suppresses the development of secondary arms on the downstream side.The primary dendrite arm spacing is increased,whereas the secondary arm spacing remains unaffected. Flow-induced modifications of the local composition were observed within the mushy zone which may contribute to the formation of spacious segregation pattern.展开更多
基金the National Natural Science Foundation of China(No.51871118)the Basic Scientific Research Business Expenses of the Central University and Open Project of Key Laboratory for Magnetism and Magnetic Materials of the Ministry of Education,Lanzhou University,China(No.LZUMMM2021005)+1 种基金the Science and Technology Project of Lanzhou City,China(No.2019-1-30)the State Key Laboratory of Special Rare Metal Materials,China(No.SKL2020K003).
文摘Different from other alloys,the observation in this work on the dendritic mushy zone shows that the freckles are formed in two different regions before and after peritectic reaction in directional solidification of Sn−Ni peritectic alloys.In addition,the experimental results demonstrate that the dendritic morphology is influenced by the temperature gradient zone melting and Gibbs−Thomson effects.A new Rayleigh number(Ra_(P))is proposed in consideration of both effects and peritectic reaction.The prediction of Ra_(P) confirms the freckle formation in two regions during peritectic solidification.Besides,heavier thermosolutal convection in samples with larger diameter is also demonstrated.
基金Item Sponsored by Deutsche Forschungsgemeinschaft (DFG) in frame of the SFB 609"Electromagnetic Flow Control in MetallurgyCrystal Growth and Electrochemistry"
文摘Visualizations of the solidification process were obtained by means of X-ray radioscopy within a Hele-Shaw cell filled with a Ga-25wt%In alloy.Therrno-solutal convection in the solidifying melt gives rise to the development of vertical segregation channels( 'chimneys').The probability of chimney formation depends sensitively on variations of both the concentration and temperature distribution.A forced melt flow perpendicular to the growth direction accelerates the growth of the secondary dendrite arms on the upstream side and suppresses the development of secondary arms on the downstream side.The primary dendrite arm spacing is increased,whereas the secondary arm spacing remains unaffected. Flow-induced modifications of the local composition were observed within the mushy zone which may contribute to the formation of spacious segregation pattern.
