材料期刊网

通过超声熔体处理技术制备细晶 AC7A 锭坯，为后续变形提供原料。采用直接或间接超声技术对熔融合金进行超声振动处理。研究浇铸温度(740~660°C)、处理时间(12~2 min)等参数的影响。超声处理从液态延续到半固态。结果表明，两种超声熔体处理技术都能获得理想的显微组织。适宜的熔体处理条件如下：处理时间2~3 min，对于间接超声处理技术，浇铸温度为660~615°C，对于直接超声处理技术，浇铸温度为660~635°C。沿铸锭高度方向3个位置的显微组织为非枝晶α(Al)细晶，晶粒大小为几百微米，而传统铸锭的晶粒大小为几千微米。超声处理可使金属间化合物细化，形貌得到改善。讨论和分析超声处理改变铸锭显微组织的机理。

The objective of the current study was to investigate the use of ultrasonic melt treatment technology in the production of grain-refined billets of the AC7A alloy, which was intended for subsequent use as a feedstock in forming operations. The experiments included the application of ultrasonic vibrations to the molten alloys via direct and indirect techniques. Several process parameters such as pouring temperatures (several temperatures between 740 and 660 °C), and treatment time (from 12 min down to 2 min) were investigated. The experiment included continuous ultrasonic treatment from the liquid to the semisolid states. The results showed that both treatment techniques were viable for producing billets with the desirable microstructural characteristics. The optimum treatment conditions were the short treatment time (2 to 3 min), from about 660 °C down to 615 °C for the indirect treatment technique, and from 660 °C to 635 °C for the direct treatment technique. The resulting microstructures, at three positions along the height of the ingot, were characterized by fine, non-dendritic α(Al) grains in the order of a hundred microns, as compared to few thousands of microns for the conventional cast ingots. The intermetallic particles were also refined in size and modified in morphology by the ultrasonic treatment. The operating mechanisms by which the ultrasonic vibrations altered the ingot microstructures were discussed and analyzed.