论文部分内容阅读
采用不同凝固阶段施加低压交流电脉冲以及在模具中嵌入不同直径金属网限制熔体对流的方法,研究了低压交流电脉冲细化Al-7%Si合金宏观凝固组织的机理。结果表明,低压交流电脉冲处理620℃以上的过热熔体以及在a-Al初生相生长后半阶段施加电脉冲均不会细化合金晶粒,晶粒细化主要发生在a-Al初生相形核阶段和生长前半阶段。金属网内外晶粒均得到了细化,但网外晶粒更细小,且网内微观组织为发达的树枝晶,网外为蔷薇状组织。低压交流电脉冲孕育效应及Joule热效应不会对Al-7%Si合金晶粒细化产生明显影响,合金晶粒细化主要是电磁力诱导的熔体流动引起晶核增殖和脉冲电流作用下形核动力学改变而引起形核率增加协同作用的结果。
The mechanism of macroscopic solidification microstructure of Al-7% Si alloy by pulsed AC pulse was studied by applying low-voltage alternating current pulses in different solidification stages and embedding different diameters of metal mesh in the mold to limit melt convection. The results show that the low-voltage AC pulse processing over 620 ℃ hot melt and in the a-Al primary phase after the growth of the second half of the application of electric pulses are not refined alloy grain, grain refinement occurs mainly in the a-Al primary phase nucleation Stage and the first half of growth. The inside and outside the metal mesh have been refined, but the network outside the smaller grains, and the microstructure of the network for the developed dendrites, network for the rose-like tissue. The effects of low-voltage alternating current pulse inoculation and Joule thermal effect have no obvious effect on the grain refinement of Al-7% Si alloy. The grain refinement of the alloy is mainly caused by the electromagnetic force induced melt flow and the nucleation under the nucleation and pulse current Kinetic changes caused by increased nuclear rate of synergy results.