Solidification structure evolution and crystal growth mechanism of Mg-Sn eutectic alloy

Abstract

Optical microscope, X-ray diffractometer, scanning electron microscope and energy dispersive spectrometer were used to study the microstructure, phase growth morphology and phase composition of free solidified Mg-Sn eutectic in-situ composites at different solidification stages.The crystal growth mechanism of Mg-Sn eutectic in-situ composite and the effect of cooling rate on the microstructure of the alloy were investigated.The results show that the solidification structure of Mg-Sn hypoeutectic alloy is hexagonal rose-like primary α-Mg phase and eutectic Mg/Mg2Sn lamellar mixed structure. The solidification structure of Mg-Sn hypereutectic alloy is a mixed structure of angular primary Mg2Sn intermetallic compound phase and eutectic Mg/Mg2Sn lamellar structure.With the increase of Sn content, the quantity of primary α-Mg phase decreased and the content of eutectic phase increased. With the increase of cooling rate, the microstructure of the alloy is obviously refined.The α-Mg primary phase is a non-faceted phase, and the primary Mg2Sn intermetallic compound phase is a faceted phase.

Keywords

• hypoeutectic alloy
• eutectic in-situ composites
• faceted phase
• non-faceted phase