超声功率对Mg-3RE-3Zn-0.7Y合金组织和力学性能的影响（英文）

Effect of Ultrasonic Power on Microstructure and Mechanical Properties of Mg-3RE-3Zn-0.7Y Alloy

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。

The Rare Earth（RE） contained Mg cast alloys have large potential in heat-resistant applications, if the RE-rich intermetallic compounds can be refined during the casting process. In the present research, the effect of ultrasonic vibration（USV） with different powers on the microstructure and the mechanical properties of the semi-solid Mg-3RE-3Zn-0.7Y alloys has been investigated. The Mg alloy melt at temperature of 20？40 °C above the liquidus was exposed to USV for 90 s at different powers from 800 W to 1200 W, and the exposure was ended at about 10 °C below the liquidus. The results show that a good semi-solid slurry with fine and spherical α-Mg particles can be obtained, and the primary α-Mg crystals have an average particle size of 55 μm and average shape coefficient of 0.63 after USV with 1000 W power. After USV treatment with the power of 1000 W, the ultimate tensile strength and the elongation of the cast samples increase by 25.2% and 93.5%, respectively, compared with those of the samples without USV treatment. It can be concluded that ultrasonic vibration is a good method to prepare semi-solid slurry of Mg alloy with fine and relatively round primary crystals due to cavitation and acoustic streaming effects.