Magnesium Alloy, Rare Earth Phase Morphology On The Performance Impact

Magnesium alloy is the lightest metal structural material in the application now. Magnesium alloy has lots of excellent properties such as high specific strength and stiffness, strong cushioning ability, high size stability, good electromagnetic interference shielding, excellent machinability, easy recycling use and etc. The configuration of extra-nuclear electron of rare earth element is unique. Rare earth element added in magnesium alloy can purify the alloy melt, improve the alloy structure, enhance the alloy mechanical properties at room-temperature and high-temperature, strengthen anti-corrosive property of the alloy and so on. The relation is consanguineous between mechanical property and the shape of intermediate phase. Spherulitic intermediate phase is ametabolic and uncollective in the process of transmogrification. The integrated mechanical property of the alloy is excellent. It provides strength and plasticity for process of transmogrification.With different amount of rare earth La Ce Nd Gd added into AZ61 magnesium alloy, in order to improve the alloy properties by using a combination of casting and heat treatment method to obtain the second phase of spherical particle and uniform distribution. This paper focuses on the impact of morphology via researching the effect of the RE elements on microstructure and mechanical properties of cast and heat treatment alloys in order to obtain high-performance new magnesium alloys particularly for plastic processing. The results show that:With the right amount addition of La, Ce, Nd, Gd into AZ61 magnesium alloy, the structure is equable and the grain size of matrix is refined remarkably,β-Mg₁₇Al₁₂ phase is reduced and its shape is thinner. The distributing ofβ-Mg₁₇Al₁₂ phase transforms by the continual netted distribution into the separated strip and punctual distribution. The elements of rare earth react with Al to form compounds firstly by X-ray diffractometer experiment. These Al-RE phases with high melting point distribute equably at the grain boundaries and hinder dislocation migration. The mechanical properties of AZ61 magnesium alloy are improved markedly at room-temperature and high-temperature.With the right amount addition of La, Ce, Nd, Gd into AZ61 magnesium alloy, the Al₁₁La₃ phase is acicular or massive, the Al₄Ce phase is massive or claviform, the Al₂Nd phase is acicular or short claviform, the Al₂Gd phase is spherulitic. The stress concentration of the spherulitic Al₂Gd phase is small. The surface area of spherulitic intermediate phase is smallest under the similar volume. The separate function to the alloy substrate is also smallest. And spherulitic intermediate phase is ametabolic and uncollective in the transmogrification process. The integrated mechanical property of the alloy is excellent. The spherulitic intermediate phase in the alloy is beneficial to the mechanical properties. The morphology of Al-RE phase has been improved after heating treatment, however the goal of chondrules did not fully realize in this experiment.