Research on Growing Front Microstructure of Quenched PMP Samples and Liquid Ingredient
Abstract：
In order to understand the kinetic character of 123 phase formation in PMP samples, the front microstructure of the peritectic reaction was investigated by SEM and a plate form growth was found. As the elevation speed ranges from 1 to 4 mm·h -1 , the sample can grow in planar form. The fine 211 phase particles are piled up evenly in front of the growing front. The concentration of Y in the liquid phase near the 211 phase particles is considerably higher than the average value in the liquid phase. The slower the elevation speed is, the more tidily the reaction front grows, the larger the 211 phase particles are at the same time. Because, when the elevation speed is low, the sample needs longer time to pass through the melt zone, which leads more liquid phase lost and thus the 211 phase particles can grow easier. Along the c axis direction, the interface between 123 phase and liquid phase is not as tidy as ab plane. Near the 123 base in liquid phase, a "temporary" phase was found, in which, the concentration of Y is various, but it is higher than in the liquid and lower than that in the 123 phase. The front stage growing form was found for the first time and it is very thin about 2～3 μm.To analyse the concentration of Y in the liquid phase, the line scan method was used between the 211 phase particles and liquid phase. It was found that the original concentration of Y in the liquid phase in PMP sample is very low. As the melting time extends, the concentration increases considerably. Keeping the PMP samples in a certain temperature for enough time, the concentration of Y in the liquid is even. The diffusion distance is about 1 μm and the 123 phase may nucleate within this distance. When the diffusion gets balance, further increasing the melting temperature does little effect on the concentration of Y in the liquid.
