Structure Regulation And Synchrotron Radiation Imaging Onthe Solidification Of Sn-Cu Peritectic Alloy

Peritectic reaction widely occurs in the fabrication process of engineering and functional materials.The process condition of peritectic reaction can influence the morphology and volume fraction of the two phases,and then affects the mechanical and physical properties of materials.At present,the researches concerning the peritectic reaction mainly focus on the alloy systems with the solid solution as the primary phase.However,the cases of the intermetallic compounds(IMCs)as the primary phase are scarcely studied.The growth of IMCs usually exhibit an anisotropic facet mode which can easily form the coarsen microstructure and different morphologies.Due to existing two nucleation and growth processes in the peritectic alloys,the solidification process is very complex.If we can in situ observe and characterize the solidification process of the faceted peritectic alloy,and obtain the most direct and accurate experimental data,these will bring great convenience to the study of the solidification mechanism of the faceted peritectic alloy.In this paper,the growth behavior of the IMCs in the Sn-Cu peritectic alloys was researched under the electric fields(DC,ECP and vertical interaction fields)by the synchrotron radiation X-ray real-time imaging technology.Meanwhile,the growth behavior of the IMCs was captured in a series of imaging experiments by the synchrotron radiation imagingtechnology,and the intermetallic compoundsCu3 Sn and Cu6Sn5 were confirmed by the XRD and SEM detection methods.The effect of cooling rate on the solidification structure of the Sn-Cu peritectic alloy is also investigated by synchrotron radiation imaging.This paper has made some conclusions as follow:(1)the solidification process of Sn-10%Cu peritectic alloy was in situ observed.The peritectic phase precipitated directly from liquid phase and the nucleation of primary phase was inhibited when the DC fields of 20 A/cm2 and 200 A/cm2 were applied.Meanwhile,the growth and remelting behaviors of secondary dendritic arm for the peritectic phase were real-time observed.(2)The peritectic phase precipitated directly from liquid phase,and the nucleation of primary phase was inhibited under the ECP fields action.The peritectic phase was obviously refined under the ECP fields action compared with that of the DC fields.(3)The peritectic phase precipitating directly from liquid phase and the nucleation of primary phase being inhibited occurred once againunder the vertical electric fields interaction.The bifurcation of X-like and petals-like peritectic phase was in situ observed,X-like peritectic phase trended to petals-like peritectic due to the bifurcation of dendrite arm.(4)When the cooling rate was 3 ?/min,the primary phase was changed from the strip into the bulky lath,and the rod-like primary phase was also observed.The growth orientations of X-like peritectic phase were changed,the linear dendrite arm was bent.When the cooling rate was 1 ?/min,the primary phase was in the form of the massive and short rod shape,and the strip primary phase disappeared.The size of primary phase of Sn-20%Cu alloy was very big in the cooling rate of 1 ?/min.The growth orientations of primary phase was also changed,and the bifurcation phenomenon of primary phase was also observed.The peritectic phase Cu6Sn5 was in the presence of dendritic form without X-likeand petals-like.The solidification process of Sn-Cu peritectic alloys was in situ observed by synchrotron radiation imaging technology.The effects of the DC,ECP,vertical interaction electric field and cooling rate on the primary and peritectic phases were investigated,and their mechanisms was also explained.In order to further perfect the solidification mechanism of the faceted peritectic alloy,the most direct and accurate experimental data will bring great convenience to the study of the solidification mechanism of peritectic alloys.