The Effect of Impurity Kinds and Content on Phase Constituent and the Microstructure of LaSi Alloy

LaSi alloy with 1:1 atomic ratio was prepared by vacuum arc melting process, and different content impurities of Fe, Ni and Cu were added into the LaSi alloy. The phase constituent and microstructure of LaSi alloy with different impurities were studied using XRD and SEM, respectively. Experimental results showed that the LaSi alloy exhibited a new phase LaSi _2-x when the added Fe content reached more than 300ppm. And the main diffraction peak of LaSi phase was shifted to a lower angle with the increase of Fe content. Similar to the effect of Fe impurities, the phase LaSi _2-x appeared when the Ni impurity was added into LaSi alloy, while the diffraction intensity of main peak reduced by about 5 times compared to high-pure LaSi alloy. There was no LaSi _2-x phase when the Cu was added into LaSi alloy, and the diffraction intensity of the main peak of LaSi increased by 2 times compared to the high-purity LaSi alloy. The microstructure of LaSi with Fe and Ni impurities displayed dark grey network. The LaSi alloy exhibited almost single-phase microstructure when the Cu impurity content reached 1526ppm. The Fe and Ni impurities exerted an obvious effect on phase and microstructure of LaSi alloy, while the Cu impurities played little effect on the phase and microstructure of LaSi alloy.