超声处理对2219大规格铝锭微观组织与宏观偏析的影响

在半连续铸造过程中施加超声,成功制备了Φ1250 mm 2219铝合金铸锭.利用光学显微镜、扫描电镜、能谱仪及直读光谱仪等仪器对铸锭的组织与成分分布进行检测与分析,探究超声对铸锭组织与偏析的内在作用机制.研究结果表明:超声振动引起的空化和声流效应能明显均匀组织结构,细化晶粒,尤其是心部晶粒细化率达到39.6%.超声促进铸锭晶间第二相呈枝丫状断续分布,晶内析出物点状弥散分布.同时,超声有效减小近表面负偏析,降低边部与心部之间的溶质浓度差异,弱化整个横截面的浓度波动,从而改善宏观偏析.

Effect of ultrasonication on the microstructure and macrosegregation of a large 2219 aluminum ingot

By applying ultrasonication during direct chill casting, a 2219 ingot with a diameter of 1250 mm was successfully produced. To study ultrasonic inner mechanism of ingot, the microstructure and macrosegregation of ingots cast after ultrasonication were analyzed by optical microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and direct-reading spec-trometry. The results show that the cavitation and acoustic streaming effects brought by ultrasonic vibration can obviously regulate the structure and refine the grain size of the resulting ingots. The central grain refinement rate observed is 39. 6%. Ultrasonication promotes the formation of branched intergranular secondary phases with a discontinuous distribution, and transgranular precipitates present a dispersed distribution with dot. Ultrasonication also effectively decreases negative segregation near the surface of the ingots, reduces the difference solute concentration between their edge and center, and weakens fluctuations in concentration over the entire cross section of the samples, thereby improving the macrosegregation properties of the final products.