(1. 北京科技大學 鑄造研究所，北京 100083;
2. 北京聯(lián)合大學 應用技術學院，北京 100101)
摘 要: 試驗研究了在不同的冷卻速度下凝固的Al-20%Si和Al-30%Si(質(zhì)量分數(shù)，下同)合金的組織和耐磨性。 實驗結(jié)果表明,冷卻速度對過共晶鋁硅合金的凝固組織和耐磨性能有顯著的影響。隨著冷卻速度的增加，Al-20%Si和Al-30%Si合金的凝固組織組成、初生硅的形貌和尺寸都發(fā)生明顯的變化：冷卻速度小于0.1K/s的爐冷試樣和冷卻速度小于1K/s耐火磚型鑄造試樣的凝固組織由(α+Si)共晶和初生Si相組成，初生Si相呈粗大的片狀，共晶Si呈針狀；冷卻速度約10K/s的金屬型鑄造試樣的凝固組織由(α+Si)共晶、枝晶狀α相和初生Si相組成，初生Si相為塊狀或長條狀，共晶Si呈細小的針狀，并且凝固組織中出現(xiàn)的枝晶狀α相；凝固速度為(103～105)K/s的過噴粉末的凝固組織也是由(α+Si)共晶、枝晶狀α相和初生Si相組成，初生Si相為塊狀。而噴射沉積快速凝固Al-20%Si和Al-30%Si合金的沉積態(tài)組織都是由Si相和α相組成，細小的Si相均勻分布在α基體中。隨著冷卻速度的增加，Al-20%Si和Al-30%Si合金的凝固組織中初生硅的尺寸明顯減小，磨損機制發(fā)生變化，合金的耐磨性顯著增加。
關鍵字: 過共晶鋁硅合金； 冷卻速度； 凝固組織； 耐磨性
microstructures and wear resistance of
hypereutectic Al-Si alloy
JIANG Chun-mei2，ZHONG Xue-you1
（1. Foundry Institute of University， University of Science and
Technology Beijing， Beijing 100083, P.R.China;
2. College of Applied Technique， Beijing Union University，
Beijing 100101, P.R.China）
Abstract: The microstructures and wear resistance of Al-20%Si and Al-30%(Mass fraction)Si alloys solidified under different cooling rate have been researched. Results of experiments indicates that effects of the cooling rate on solidification microstructures and wear resistance of alloy are significant. When cooling rate increases，the phase constitution of solidification microstructure and the shape and sizes of primary silicon crystal in the microstructure of Al-20%Si and Al-30%Si alloys change obviously. The solidification microstructures both of the specimen solidified in furnace of which the cooling rate is less than 0.1K/s and the specimen solidified in refractory mold of which the cooling rate is less than 1K/s are composed of (α+Si) eutectic and primary Si crystal， and the coarse plateshaped primary Si crystal and needle-shaped eutectic Si crystal are inspected in the solidification microstructure. The solidification microstructures of the specimen solidified in metal mold of which the cooling rate is about 10K/s is composed of (α+Si) eutectic and primary Si crystal and the dendritic α phase， and the shape of primary Si crystal is plate or block， the eutectic Si crystal is also needle-shaped， the dendritic α phase emerged in the metal mold casting specimen. The solidification microstructures of the over-spray powder cooled by (104～106)K/s is also composed of (α+Si) eutectic and primary Si crystal and the dendritic α phase， and the shape of most of primary Si crystals are fine block. The solidification microstructures both of spray formed Al-20%Si alloy and Al-30%Si alloy are composed of Si crystal and α phase， the fine Si crystals are well-distributed in the α phase matrix. With increasing cooling rate， the size of silicon crystal diminished， the wear resistance of Al-20%Si alloy and Al-30%Si alloy increases significantly due to the wear mechanism of alloy changed.
Key words: hypereutectic Al-Si alloy； cooling rate； solidification microstructure； wear resistance
