搅拌温度对半固态过共晶铝硅合金中初生硅形貌的影响

Influence of Stirring Temperature on Morphology of Primary Silicon in Semi-solid Hypereutectic Aluminum Silicon Alloy

采用等温搅拌法制备过共晶铝硅合金半固态浆料,研究了搅拌温度对初生硅形貌的影响。结果表明,搅拌可明显改善初生硅的形貌,使其细化、球化。搅拌温度过高,熔体内部过冷度较小,先析出的初生硅晶核较少,初生硅长大时相互间抑制作用较小,易择优长成较粗大的初生硅,这些较粗大的初生硅不易碎化、磨圆而得以保留。降低搅拌温度,熔体内过冷度增大,利于提高熔体内部的形核率,初生硅长大时相互间抑制作用较大,长成的初生硅较细小,易被碎化、磨圆细化、球化。但搅拌温度过低,尽管制备的初生硅更细小,却由于初生硅间易出现团聚,球化程度会变差。

The influence of stirring temperature on the morphology of primary silicon in semi-solid hypereutectic aluminum silicon alloy prepared by the method of isothermal stirring was studied. The results show that stirring can significantly improve the morphology of primary silicon, and make primary silicon refine and spheroidize. When stirring temperature is too high, the internal undercooling of melt is small, which makes the crystal nuclei of first precipitated primary silicon less, and the inhibition effect of primary silicon in growing with each other become minor, which results in coarser primary silicon formed. These coarser primary silicons are reserved because of hard crushed and rounded. Decreasing stirring temperature, the internal undercooling of melt increases, the nucleation rate of melt improves, which makes primary silicon grow with larger inhibition with each other and results in relatively small primary silicon formed. These relatively small primary silicon is refined and spheroidized because of easy crashed and rounded. When stirring temperature is too low, though the finer primary silicon could be obtained, spheroidization could be worse because agglomeration easily occur between primary silicon.