Phase selection and microstructure characteristics of directionally solidified Gd ₅Ge ₄ alloy by laser zone re-melting

The Gd ₅Ge ₄ alloy with the peritectic reaction during solidification was prepared by the arc-melt method under protection of argon atmosphere. The as-cast alloys were cut and directionally solidified with the help of laser rapid solidification technique. Microstructure characteristics and phase selection of Gd ₅Ge ₄ during the rapid directional solidification by laser zone re-melting were investigated. The microstructure originating from steady-state growth was evaluated with the help of optical microscope (OM) and X-ray diffraction (XRD). The alloy after laser zone directional solidification possesses obvious preferred orientation and the amorphization occurs under this condition. The cellular spacing could be expressed as a function of the laser scanning velocity during the rapid solidification. An acceptable combination is found between the experimental results and the classical J-H numerical solidification model for a rapid cellular/dendritic growth.