Effect of Isothermal Treatment on Microstructure of Mg-7Zn-xLa Alloys
Semi-solid billets of Mg-7Zn-xLa(x=0,0.1,0.3,0.5,wt.％)alloys were prepared by semi-solid isothermal heat treatment.The effects of the La element on the semi-solid microstructure of Mg-7Zn-xLa alloys were investigated.The influence of La element on the coarsening rate constants of solid particles was analyzed.The results show that at the same isothermal heat treatment process,the average size and shape factor of solid particles decrease firstly and then increase with the increase of La content.The optimum effect was achieved when the addition amount of La was 0.3wt.％.Meanwhile,the addition of La element could effectively decrease the coarsening rate of solid particles and restrict the growth of solid particles.It was also found that the amount and particle size of α2-Mg formed by secondary solidification increased obviously when the liquid phase increased with the partial melting of the primary solid particles.
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