Microstructure of directionally solidified Gd₅Si₄ by laser zone remelting

Gd₅Si₄ alloy was prepared by the arc-melted method in argon atmosphere. The as-cast alloy was cut and directionally solidified by the laser zone remelting technique. Microstructure evolution and the influencing mechanism of the Gd-based magnetic refrigerant during the rapid directional solidification were investigated. The microstructure originating from steady-state growth was evaluated with optical microscope (OM) and scanning electron microscope (SEM). The cellular spacing could be expressed as a function of the laser scanning velocity during the rapid solidification. A reasonable agreement is found between the experimental results and the Hunt-Lu numerical model for rapid cellular/dendritic growth.