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如果在铸造过程能够细化含有稀土元素的金属间化合物,那么稀土镁合金在耐热应用方面将具有巨大的潜力。研究了半固态制浆过程中不同超声功率的超声振动对Mg-3RE-3Zn-0.7Y合金半固态微观组织以及铸态试样力学性能的影响。试验对液相线以上20~40℃镁合金熔体分别施加超声功率为800 W至1200 W的超声振动,振动时间为90 s,结束超声振动温度为液相线以下10℃左右。结果表明,超声振动可以制备出组织中具有细小圆整的初生α-Mg相的优良半固态浆料,并且经过超声功率为1000 W的超声处理后浆料组织中初生α-Mg晶粒的平均晶粒直径和平均形状系数S F分别为55μm和0.63。此外,1000 W超声处理的铸件试样比未经超声处理的试样抗拉强度提高了25.2%,伸长率提高了93.5%。可见,声空化效应和声流效应使超声振动成为一种制备具有细小圆整初生晶粒镁合金半固态浆料的有效途径。
Rare-earth magnesium alloys have great potential for heat-resistant applications if the intermetallic compounds containing rare earth elements can be refined during the casting process. The effect of ultrasonic vibration with different ultrasonic powers on the semi-solid microstructure of Mg-3RE-3Zn-0.7Y alloy and the mechanical properties of the as-cast samples during semi-solid pulping was investigated. Experiments were performed on the liquidus 20 ~ 40 ℃ above the magnesium alloy melt ultrasonic power 800W to 1200 W ultrasonic vibration, vibration time is 90 s, the end of the ultrasonic vibration temperature of about 10 ℃ below the liquidus. The results show that ultrasonic vibrations can prepare fine semisolid slurry with small round primary α-Mg phase in the microstructure and the average primary α-Mg grains in the slurry after ultrasonic treatment at ultrasonic power of 1000 W The grain diameter and average shape factor SF were 55 μm and 0.63, respectively. In addition, the cast samples of 1000 W ultrasonic treatment increased the tensile strength by 25.2% and the elongation by 93.5% compared with those without ultrasonic treatment. It can be seen that the acoustic cavitation effect and the acoustic flow effect make the ultrasonic vibration an effective way to prepare semi-solid slurry of magnesium alloy with fine rounded primary grains.