采用不同的超声外场处理熔体工艺,研究了其对铸锭质量的作用机理与改善效果. 针对保温(750℃)和空冷(从750℃空冷7 min 10 s至约650℃)两种不同温控状态下的ZL205A铝合金熔体,分别进行相同参数的超声场处理,研究超声场对凝固组织的影响规律,并利用力学拉伸实验进行验证. 研究结果表明:在保温状态下对熔体施加超声处理,具有较好的除气与改善第二相组织分布的效果;在空冷状态下施加超声处理则可以消除集中缩孔,显著细化晶粒;当在保温和空冷条件下全程采用超声处理,铸锭内部质量的改善效果最佳. 力学性能的测试结果与铸锭凝固组织的变化规律具有一致性,验证了上述结论. 综上,对不同温控状态下的熔体施加超声处理,对熔体凝固过程的影响不同,对铸锭内部质量的改善效果也各有侧重.
Since the development of the aviation industry, improving the flight performance and reducing the weight of aircrafts has always been the goal pursued by aviation designers. Therefore, it becomes increasingly important to develop a new alloy material with high hardness, high strength, and light weight. To obtain excellent mechanical properties and good corrosion resistance, a new kind of alloy material, ZL205A alloy, was developed by the Beijing Institute of Aerial Materials (BAM) in the 1960s. Owing to its favorable mechanical properties and excellent corrosion resistance, ZL205A alloy has been well applied in the aviation industry. However, this kind of Al alloy still possesses some undesirable solidification defects:shrinkage, porosities, coarsening grains, and solute segregation. Ultrasonic melt treatment (UST) provides a means to eliminate or modify these defects. In the present work, the effects of UST on ZL205A alloy were investigated for two conditions, i.e., before casting and during solidification in ambient environment. Then, the effects of ultrasonication on the as-cast microstructures and the tensile properties were accordingly characterized and analyzed. For the case in which UST was only introduced before casting (holding temperature at 750℃), degassing and the distribution of secondary phases were modified. For the case in which UST was only introduced when cooling from 750℃ for 7 min 10 s to about 650℃, grain refinement and reduced porosities were generated. When UST was continuously employed for both conditions, the above properties were further improved compared with those of ingots without ultrasonic treatment. The mechanical tensile test results show that the improvement of the ingot internal structure can improve the ingot mechanical tensile properties, which proves the correctness of the above research results. Thus, UST carried out at two different conditions induced different regulatory functions and influencing mechanisms. This study shows that the UST of ZL205A aluminum alloy in different melt states has different emphases on improving the internal structure of the ingot.