In situ observation on the solidification of Sn-10Cu hyperperitectic alloy under direct current field by synchrotron microradiography

The structural evolution of peritectic solidification under the direct current (DC) field action, mainly on the morphological evolution of primary phase ε (Cu3Sn) and peritectic phase η (Cu6Sn5), is in situ observed by high resolution X-ray real-time imaging with synchrotron radiation. The ultimate solidification microstructures after experiencing the imaging experiment are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS). It is found that the η phase precipitates directly from parent liquid phase without experiencing corresponding peritectic reaction when the DC field of 20 A/cm2 or 200 A/cm2 is imposed during the solidification process of the Sn-10%Cu alloy. It means that the DC field has altered the phase transformation sequence and suppressed the nucleation of primary ε phase. Meanwhile, the growing and dissolving behaviors of secondary dendrite arm for intermetallic compound Cu6Sn5 under the DC field action are also in situ observed and discussed.