Microstructure characterization on Mg-2Nd-4Zn-1Zr alloy during heat treatment
(1. School of Materials Science and Engineering, North University of China, Taiyuan 030051, China;
2. National Engineering Research Center of Light Alloy Net Forming,
Shanghai Jiao Tong University, Shanghai 200240, China)
2. National Engineering Research Center of Light Alloy Net Forming,
Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: The microstructures of Mg-2Nd-4Zn-1Zr alloy in the as-cast state and after heat treatment were investigated. Several kinds of secondary phases were found and characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). In the as-cast alloy, the existing eutectic compounds are Mg-Nd-Zn ternary phases: T phases and W phases. After the heat treatment, with increasing the temperature or time, it was found that T phase almost dissolved into the α-Mg matrix, while a large amount of W phase remained in the matrix. On the other hand, with prolonging the time, the morphology of the phase changed from continuous network to the spherical shape along the grain boundary. The density of the W phase gradually decreased and finally it was coarsened and stabilized in the treatment process.
Key words: Mg-Nd-Zn alloy; heat treatment; microstructure; T phase; W phase