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Sn-38.1%Pb共晶合金在频率为35kHz的超声场中发生凝固时,随着试样高度H的降低,声场对宏观偏析的抑制效果更加显著,球状共晶团在凝固组织中所占体积分数相应增大.当H等于声波在合金熔体内的波长λ时,超声场能够扩大初生(Sn)相分布区域,缩小Sn-Pb共晶和初生(Pb)相分布区域.同时,初生(Sn)相晶粒显著细化,生长方式发生“枝晶-等轴晶”的转变.对于H=λ/2和λ/4的合金试样,超声场能够促进熔体形核,降低合金整体过冷度.分析表明,超声场中的空化效应抑制了熔体过冷,声流促进共晶生长界面前沿的温度场和浓度场呈空间对称分布,使Sn-Pb共晶以三维对称方式生长.
When the Sn-38.1% Pb eutectic alloy solidifies in the ultrasonic field with a frequency of 35 kHz, the suppression effect of the sound field on the macro-segregation is more pronounced with the decrease of the sample height H. The volume occupied by the spherical eutectic in the solidified structure When H is equal to the wavelength λ of the sonic wave in the alloy melt, the ultrasonic field can expand the distribution area of the primary phase (Sn) and reduce the distribution area of Sn-Pb eutectic and primary phase (Pb) Sn) phase grains were significantly refined and the growth mode changed “dendrite-equiaxed grains.” For the alloy samples of H = λ / 2 and λ / 4, the ultrasonic field can promote the nucleation and decrease of the melt The results show that the cavitation effect in the ultrasonic field suppresses the overcooling of the melt, and the temperature field and the concentration field at the front of the eutectic growth boundary under the acoustic flow are spatially symmetric. Symmetrical way to grow.