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对Al-15%Y(质量分数)过共晶合金在1~100μm/s的抽拉速率下进行定向凝固实验,研究抽拉速率对组织演化及Al3Y相生长规律的影响.结果表明,铸态Al-15%Y合金主要由Al3Y先析出相和Al3Y/Al共晶体组成.在定向凝固过程中,当抽拉速率为1μm/s时,Al3Y相为不规则形状且边界清晰,为小平面的生长特性.随着抽拉速率的增加,Al3Y相的形貌逐渐转变为拉长的六棱柱形态,其中少量的Al3Y相具有中空形貌.当抽拉速率为10和20μm/s时,Al3Y相按粗大的六棱柱形态生长.进一步增加抽拉速率至100μm/s时,组织中出现“十”字形貌的Al3Y相,为2个六棱柱垂直交叉结构,类似枝晶的生长形式.在抽拉速率增加的过程中,固/液界面前沿逐渐出现领先相,且凝固速率越大,领先距离越长.
The directional solidification experiment of Al-15% Y (mass fraction) hypereutectic alloy at the drawing rate of 1 ~ 100μm / s was carried out to study the effect of drawing rate on the microstructure evolution and Al3Y phase growth.The results show that as-cast Al-15% Y alloy is mainly composed of Al3Y pre-precipitation phase and Al3Y / Al eutectic.In the process of directional solidification, the Al3Y phase is irregular with a sharp pull-out rate of 1μm / s Growth characteristics.With the increase of drawing rate, the morphology of Al3Y gradually transformed into elongated hexagonal prism shape, in which a small amount of Al3Y phase had a hollow morphology.When the pull rate was 10 and 20μm / s, Al3Y phase In the form of coarse hexagonal prism, the Al3Y phase with “10” character appears in the microstructure when the drawing rate is further increased to 100μm / s, which is a perpendicular cross structure of two hexagonal columns, similar to the growth pattern of dendrites. In the process of increasing the drawing speed, the front phase of the solid / liquid interface gradually appears the leading phase, and the larger the solidification rate, the longer the lead distance.