(1. 蘭州理工大學 省部共建有色金屬先進加工與再利用國家重點實驗室，蘭州 730050；
2. 蘭州理工大學 有色金屬合金及加工教育部重點實驗室，蘭州 730050)
摘 要: 采用受控擴散凝固(CDS)技術制備過共晶Al-18%Si合金，研究其凝固組織隨低溫母合金溫度變化的演變規(guī)律和凝固行為本質。結果表明：受控擴散凝固能抑制初生硅相的過度各向異性生長，有效改善合金凝固組織結構。采用適當溫度的Al-25%Si合金(800 ℃)和純Al(580 ℃)混合進行受控擴散凝固時，凝固組織中初生硅相分布均勻，無宏觀偏析，且其平均尺寸達到42.85 μm。當純Al溫度偏低時，凝固組織中初生硅相偏聚嚴重；當純Al溫度較高時，凝固組織中初生硅相尺寸偏大。分析表明：在受控擴散凝固過程中，固-液界面前沿形成了較小的“成分過冷”，初生硅相在過冷區(qū)內趨于平界面生長。溶質原子擴散距離的平方與平衡溫度成對數關系，溫度愈高，擴散愈充分，宏觀偏析愈少。
關鍵字: 過共晶Al-18%Si合金；受控擴散凝固；平衡溫度；溶質擴散；初生硅
（1. State Key Laboratory of Advanced Processing and Recycling of Nonferrous Metals,
Lanzhou University of Technology, Lanzhou 730050, China;
2. Key Laboratory of Nonferrous Metal Alloys and Processing, Ministry of Education,
Lanzhou University of Technology, Lanzhou 730050, China）
Abstract:Using the controlled diffusion solidification (CDS) technology, the predetermined hypereutectic Al-18%Si alloy was prepared. The solidification microstructure evolutions of Al-18%Si alloy with the changing temperatures of low–temperature precursor alloy and solidification behavior were investigated. The results show that, the anisotropy growth of primary Si phase is inhibited by the CDS during solidi？cation process, which can effectively improve the solidification microstructure of Al-18%Si alloy. Adopting an appropriate precursor alloys mixing condition, which is Al-25%Si alloy at 800 ℃ and pure Al at 580 ℃, the distribution of primary Si phase is uniformly and the average size of Si phase is 42.85mm in the solidification microstructure. When the temperature of pure Al is too low, serious segregation of primary Si phase exists in the solidi？cation microstructure, and when the temperature of pure Al is too high, the average size of primary Si phase is large. The analysis results show that, during the little constitutional supercooling forming on the interface of solid-liquid in controlled diffusion solidification process, the primary Si phase tends to planar interface growth. The relationship between diffused distance square of solute and equilibrium temperature is logarithmic, the higher the equilibrium temperature, the more sufficient the solute diffusion, and the less the segregation.
Key words: hypereutectic Al-18Si alloy; controlled diffusion solidification; equilibrium temperature; solute diffusion; primary silicon phase
