间接超声振动制备A356铝合金半固态浆料的机理

摘要

The process of semi-solid A356 alloy slurry prepared by indirect ultrasonic vibration (IUV) and its mechanism,combined with water simulation experiment of visual tracer particles, was investigated. The results show that the non-dendritic primary particles can be produced after A356 alloy IUV treated for 20 s at the bottom of container, and after treated for 40 s, the semi-solid slurry with grain shape coefficient of 0.6 and average grain diameter of 70 μm can be obtained. In the process of indirect ultrasonic vibration, there are obvious characteristics of ultrasonic vibration, such as acoustic streaming, cavitation and thermal effects and the high-frequency mechanical vibration characteristics, such as vigorous surface agitation, the increase of the nucleation induced by falling off solid particles formed on the crucible wall.The melt is IUV treated, the combined action of ultrasonic and high-frequency mechanical vibration are rather than single mechanical vibration effect.%采用间接超声振动方法制备出晶粒尺寸细小、形貌圆整的铝合金半固态浆料,并结合可视化的示踪粒子水模拟实验对其制浆机理进行探讨.结果表明:在容器底部对A356铝合金熔体进行间接超声振动处理20 s即可获得明显的非枝晶初晶颗粒;作用40 s后可获得晶粒形状系数为0.6、平均晶粒直径为70 μm的半固态浆料;在制浆过程中,有明显的超声波作用的特征,即透过容器底部在熔体内部有明显的声流效应、空化效应以及热效应;同时具有高频机械振动的特征,液面搅动较大,凝结于杯壁的固相颗粒剥落,使晶核数量增加;因此,间接超声振动作用于金属熔体时,并不是单纯的机械振动作用效果,而是超声波和高频机械振动的共同作用.