超声波对铝合金熔体的有效细化区域

Efficient refining zone of ultrasonic sonication on the industrial aluminum alloy melt

为了探讨凝固组织的超声细化区域范围,在液相线温度至575℃区间内对铝合金熔体施加超声振动,待铸锭冷却至室温,经腐蚀处理后观察其宏观和微观组织.试验结果表明,在工具杆端面位置处靠近铸锭边缘有一明显的作用区域分界线,分界线两端组织呈现截然不同的特征,端面以下组织均得到了有效的细化,而端面以上组织晶粒粗大,呈枝晶状分布.超声在熔体中产生空化和声流效应,理论计算表明,熔体中的有效空化范围为端面下30mm区域内,超声在熔体中产生的声流效应遍及整个熔体可流动区域,通过声流和空化的双重作用,工具杆端面以下的组织均受到超声的作用,并得到细化.

In order to discuss the extent of grain refinement on the solidification structure,ultrasonic vibration was imposed on aluminum alloy melt during the liquid temperature and 575 ℃. The experimental results show that there is an obvious borderline in the area from the radiator′s face to the boundary of the ingot. The structure of one side of the borderline is absolutely different from the other′s. Structures below the radiator′s face are all well refined while those of the other side are coarse and of dendritic. Ultrasound induces cavitation and acoustic streaming in the melt. Calculation results indicate that the area of 30 mm below the radiator′s face is the efficient cavitation area in the melt. The acoustic streaming tranferes the effective nuclei and equiaxed grains from the cavitation area to other areas and brings the melt in those areas back,thus forming equiaxed grains and more effective nuclei. Subjected by the duple action of cavitation and acoustic streaming,the structures below the face are all refined at last.