(1. 北華航天工業(yè)學院 材料系，廊坊 065000；
2. 北京北科德瑞冶金工程技術(shù)有限公司，北京100083；
3. 北京科技大學 科技產(chǎn)業(yè)集團，北京 100083)
摘 要: 采用水淬實驗研究熔鑄法制備的Al-25%Si 合金半固態(tài)重熔組織演變，對初生硅相的尺寸、形態(tài)和體積分數(shù)進行定量統(tǒng)計和表征。結(jié)果顯示：在共晶溫度以上保溫過程中，合金組織經(jīng)歷了共晶硅的粒狀化和溶解、初生硅相熔斷和尖角鈍化以及形態(tài)圓整化3 個階段。初生硅相在重熔過程中發(fā)生“Oswald”熟化粗化，尺寸增加，同時形狀因子增大，體積分數(shù)減小。合金在590~600 ℃保溫30~50 min，初生硅尺寸粗化速率緩慢，形態(tài)圓整并且體積分數(shù)可控，可以滿足半固態(tài)加工要求。尺寸粗化速率常數(shù)K 與合金的初始凝固冷卻速度和加熱溫度有關(guān)。其中，在鋼模中凝固的合金的K 值為23.83~38.88 μm3/s，且隨加熱溫度升高，K 值減小；銅模中凝固的合金K 值為10.91~19.87 μm3/s，溫度升高，K 值增大。
關(guān)鍵字: 鋁硅合金；初生硅；過共晶；半固態(tài)重熔；組織演變
（1. Department of Materials,North China Institute of Aerospace Engineering,Langfang 065000,China;
2. Beijing Bei Ke De Rui Metallurgy Engineering and Technology Co.,Ltd.,Beijing 100083,China;
3. Science and Technology Industry Group,University of Science and Technology Beijing,Beijing 100083,China）
Abstract:The microstructure evolution of casting Al-25%Si alloy during semi-solid remelting was studied by the water quenching experiment,and the quantitative statistics and characterization of the size,shape and volume fraction of the primary Si phase were conducted. The results show that the microstructure evolution includes three stages within the process of heating insulation above the eutectic temperature,i.e.,the eutectic Si phases getting granulated and dissolving,the primary Si phases breaking and the sharp corner passivating and the shape tending to be round. The size of primary Si phases is coarsened through the Oswald ripening,its shape factor increases and the volume fraction reduces. The alloy heating to 590-600 ℃ and holding for 30-50 min has a low size coarsening rate (K) of primary Si phase with round shape and controllable volume fraction,which satisfies the requirement of the semi-solid processing. The size coarsening rate constant K depends on the solidification velocity and heating temperature. The alloy solidified in the steel mold has high K value of 23.83-38.88μm3/s. Moreover,the K value decreases with increasing temperature. While the K value of the alloy solidified in the copper mold is lower and equal to 10.91-19.87μm3/s,which increases with increasing temperature.
Key words: Al-Si alloy; primary Si; hypereutectic; semi-solid remelting; microstructure evolution
