气雾化过共晶Al-Si合金粉末的形貌和组织

Morphology and Microstructure of Gas-Atomized Hypereutectic Al-Si Alloy Powders

采用扫描电镜、差热分析仪和X射线衍射仪分析粒度对气雾化过共晶Al-Si合金粉末形貌、组织和结构的影响,并计算粉末的过冷度和冷却速度。结果表明:粉末形貌规则性随粒度减小而得到改善,但Si相分布均匀性降低;同时,初晶Si相尺寸逐渐减小,形貌由不规则状转为块状;共晶Si相由不均匀针状转为网络状。随粒度减小,Al基体衍射峰发生宽化和偏移,同时热效应前移。过冷度和冷却速度随粒度减小而增大,这是导致粉末间组织和结构差异的根本原因。

The morphology and microstructure of hypereutectic Al-Si alloy powder were analyzed as a function of particle size using scanning electron microscope, differential scanning calorimetry and X-ray diffraction. The cooling rate and undercooling of powder was calculated. The results show that the distribution homogeneity of Si phases decreases with the decrease of particle size. Size of primary Si phase decreases with the decrease of particle size and the morphology of primary Si phase becomes regular. The morphology of eutectic Si changes into a network structure. X-ray diffraction peak becomes broad and shifts with the decrease of particle size. The DSC curve features of powders with different sizes deviate at the same time. The calculated results indicate that cooling rate and undercooling increases with the decrease of particle size, which leads to the deviation of microstructure.