电磁分离技术制备过共晶Al-Si合金自生功能梯度材料

由于初生相与熔体的导电性差异，在通电熔体及外磁场作用下，初生相颗粒在熔体内受到某一方向的合力，从而在熔体中做有规律的运动．因此，适当地控制铸件凝固过程及初生相颗粒的移动速度，使初生相颗粒在铸件中呈现有规律分布，可以获得自生功能梯度材料．对初生相颗粒在熔体内受力及运动情况的分析结果表明：颗粒的大小、形状及浓度对颗粒的运动状态及速度都有很大的影响．用电磁分离技术成功制备了过共晶A1-25Si功能梯度材料试样，从试样一端到另一端初生Si颗粒的含量、尺寸和形状均呈现梯度的变化．

Study on Hypereutectic Al-Si Functionally Graded Materials by Electromagnetic Separation

A new processing method of in-situ functionally graded materials (FGMs) by electromagnetic separation was proposed. Some electromagnetic force is imposed on the primary particles when the melt is exposed to an electromagnetic field induced by static magnetic field and direct current, and the primary particles move in some direction under the electromagnetic force due to the difference in electrical conductivity between the primary phase and the melt. By appropriate controlling of the melt solidification and electromagnetic field, the primary particles can be regularly distributed and FGM is obtained. The electromagnetic forces imposed on the primary particles and the movement of the primary particles were analyzed. The results indicate that the size and shape of the primary particles and the particle volume fraction affect the movement of primary particles. In the hypereutectic Al-25% Si sample produced by electromagnetic separation, the volume fraction, the size, and the shape of the Si primary particles are gradually transitional from one side of the sample to the other, which suggests that the hypereutectic Al-Si functionally graded materials can be directly produced by appropriate controlling during the course of casting exposed to the electromagnetic field.