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着重研究了颗粒增强Al基复合材料的搅拌法制备工艺及凝固过程。 通过对熔体搅拌法制备颗粒增强金属基复合材料的工艺优化进行探讨,最终用最简单的工艺过程制备出组织致密、颗粒分布均匀、界面结合良好的SiC、Al_2O_3、SiO_2颗粒增强Al-4％Mg复合材料。 SiC、Al_2O_3、SiO_2颗粒增强Al-4％Mg复合材料在等轴晶凝固条件下,颗粒被等轴晶排斥,出现颗粒推移,晶粒直径越大,颗粒分布越不均匀。在试验分析基础上,提出了颗粒推移的强烈程度由晶粒与颗粒的质量比决定的观点:同种颗粒,其直径越大,颗粒推移越不强烈;同样直径不同种类的颗粒,其密度越大,颗粒推移越不强烈。 AlO_3颗粒增强 Al-4％Mg复合材料的凝固组织中的显微缩孔是由颗粒加入导致熔体粘度增加、颗粒堵塞枝晶间的补缩流动通道以及颗粒与基体合金的热膨胀系数的差异三种因素引起的。由于气孔易在SiC颗粒表面形核,或者SiC颗粒与基体结合较弱,使得SiC颗粒增强Al-4％Mg复合材料比Al_2O_3颗粒增强Al-4％Mg复合材料易形成显微缩孔。对SiO_2颗粒增强Al-4％Mg复合材料来说,SiO_2颗粒与基体间发生了界面反应,一定量的Si溶入了基体,增大了基体的凝固潜热,从而提高了基体合金凝固时的补缩流动能力,所以SiO_2(P)/Al-4％Mg复合材料的凝固组织比同样条件下Al_2O_3(P)
The preparation process and the solidification process of particle reinforced Al matrix composites are emphatically studied. Through the optimization of the process of preparation of the particle reinforced metal matrix composites by the melt agitation method, finally the SiC, Al 2 O 3 and SiO 2 particles reinforced with compact structure, uniform particle distribution and good interfacial bonding were prepared by the simplest process. Mg composite material. Under the condition of equiaxed solidification, the particles are repelled by equiaxed grains and the particles are pushed by the SiC, Al_2O_3 and SiO_2 particle reinforced Al-4% Mg composites. The larger the grain diameter, the more uneven the particle distribution. On the basis of the experimental analysis, we put forward the viewpoint that the intensity of particle passing is determined by the mass ratio of the crystal grains to the particles: the same type of particles, the larger the diameter is, the less intense the particles are. The same diameter of different types of particles, Large, particles less intense. The microscopic shrinkage in the solidified microstructure of the AlO 3 granule reinforced Al-4% Mg composites is caused by the addition of particles resulting in the increase of the melt viscosity, the shrinkage flow channel between the clogging of the particles and the difference between the thermal expansion coefficients of the particles and the matrix alloy Cause of a variety of factors. Al-4% Mg composites reinforced Al-4% Mg composites were easier to form microscopic cavities than those with Al-4% Mg composites due to the easy nucleation of SiC particles on the surface of SiC particles or the weak bonding between SiC particles and matrix. For SiO 2 particle reinforced Al-4% Mg composites, interfacial reaction occurs between the SiO 2 particles and the matrix, a certain amount of Si dissolves into the matrix and increases the latent heat of solidification of the matrix, thereby enhancing the complement of the matrix alloy during solidification (P) / Al-4% Mg composite solidification microstructure than under the same conditions Al 2 O 3 (P)