The effects of mischmetal Pr/Ce on microstructures and mechanical properties of ADC12 alloy were investigated by means of optical microscopy, scanning electron microscopy, and energy dispersive spectrometry. The experiment results show that the microstructures of the alloy can be refined significantly when 0.6wt.% Pr/Ce is added to the alloy. Coarse dendritic crystals of primary α-A1 phases are tiny, and some grains are round. The morphology of iron-rich phase is changed into particle-like shape from original strip-like shape or bulk-like shape, and distributed much uniformly in the boundarys of grains. The eutectic silicon phases become fine and dispersed granular shape. Mischmetal Pr/Ce can combine with Al, Si, Fe, Cu elements of the alloy to form rare-earth intermetallic compounds, which are shiny white under the scanning electron microscope, and with shapes of acicular, lumpish, granular. In addition, comprehensive mechanical properties of ADC12 alloy are better when the addition of Pr/Ce is 0.6wt.%. The tensile strength and elongation reach 251.67 MPa and 3.04%, respectively, which are 34.91%and 51.24% higher than that of the matrix, respectively. Cleavage surfaces of the alloy are lessened, and the dimples are increased in quantity, diminished in size, and well-distributed, showing obviously the characteristic of ductile fracture.%为了解混合稀土Pr/Ce变质对ADC12合金组织及性能的影响,采用光学显微镜、扫描电镜、能谱分析等手段对其进行观察和分析.结果表明:当加入质量分数0.6%的Pr/Ce时,组织中粗大的初生α-Al相枝晶已变得较为细小,甚至有些α-Al晶粒变得圆整了,富铁相则由原来的条状、块状变为颗粒状,较均匀地分布在晶粒边界上,而共晶Si相也呈细小弥散分布的颗粒状;混合稀土Pr/Ce能与该合金成分中的Al、Si、Fe、Cu 4种元素结合生成稀土金属间化合物,这些化合物在扫描电镜下呈亮白色,其形貌有针状、块状、颗粒状3种;此外,当Pr/Ce的质量分数为0.6%时,该合金具有良好的综合力学性能,其抗拉强度达到251.67 MPa,延伸率达3.04%,分别比基体合金的提高了34.91%和51.24%.
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