(清华大学 机械工程系， 北京 100084)
摘 要: 利用自行研制的双向多级速电磁搅拌装置， 研究“熔体处理＋双向电磁搅拌”半固态浆料复合制备技术。 结果表明： 该技术制备浆料效率较高， 可实现A356.2合金半固态浆料的在线制备。 在冷速较快的情况下， 降低浇注温度可以大大缩短半固态浆料的制备时间； 在冷却速度较快、 搅拌速度较低的情况下， 提高搅拌频率不但有助于改善晶粒形貌， 而且具有相当的晶粒细化作用。 选取如下技术参数： 加入0.03%Ti(Al-5Ti-B)(质量分数)和0.04%Sr(Al-10Sr)进行熔体处理、 正-反无间歇双向搅拌、 浇注温度640 ℃、 搅拌频率25~30 Hz、 输出电压220 V、 单向搅拌时间5 s、 搅拌时间67 s， 可获得形状系数大于0.8、 初生晶粒尺寸在80~90 μm之间的A356.2半固态浆料。
关键字: A356.2合金； 在线制备； 熔体处理； 双向电磁搅拌；流变成形
（ Department of Mechanical Engineering, Tsinghua University, Beijing 100084, China）
Abstract: Using the self-developed reversible multilevel-speed electromagnetic stirrer, the multiple semi-solid preparation technology of melt treatment and reversible electromagnetic stirring was studied. The results show that the technology, with high preparation efficiency, can realize the on-line preparation of semi-solid slurry of A356.2 alloy, i.e. the preparation efficiency fits the subsequent die casting procedure. With the faster cooling rate, the slurry preparation time can be largely reduced by decreasing pouring temperature. Under the condition of the faster cooling rate and smaller stirring speed, elevated stirring frequency not only strongly promotes to modify the morphologies of α(Al) grains, but also has considerable effects on grain refinement. Following the processing parameters below, the A356.2 alloy slurry with grain diameter of 80-90 μm and shape factor of 0.8 or more can be obtained: melt treatment with the additions of 0.03%Ti(Al-5Ti-B) (mass fraction) and 0.04%Sr(Al-10Sr), reversible two-way stirring without interval, pouring temperature of 640 ℃, stirring frequency of 25-30 Hz, output voltage of 220 V, one-way stirring time of 5 s, total stirring time of 67 s.
Key words: A356.2 alloy; on-line preparation; melt treatment; reversible electromagnetic stirring; rheoforming
