混合方式及过热温度对过共晶Al-Si合金中初生Si的影响

Effect of Mixing Ways and Overheating Temperature on Primary Silicon in Hypereutectic Al-Si Alloys by CDS Casting

采用受控扩散凝固技术(CDS)制备过共晶Al-18Si、Al-20Si、Al-22Si合金,研究了不同混合方式及Al-25Si合金在不同过热温度下对受控扩散凝固目标合金初生Si相的尺寸、形貌和分布的影响。结果表明,液-液混合对初生Si的改善效果较液-固混合好;随着过热温度增大,初生Si相尺寸减小,形貌逐渐变得圆整且分布均匀;相同过热温度下,随着合金Si含量的增加,初生Si相尺寸增大,形貌变化不明显。特别是在过热温度为900℃的Al-25Si合金与660℃的液态纯Al液-液混合得到Al-18Si合金中的初生Si相尺寸仅为34.3μm,长宽比为1.48。

The hypereutectic Al-18Si,Al-20Si,Al-22Si（weight fraction） alloys were prepared by the controlled diffusion solidification（CDS）,and effects of different mixing ways and high silicon alloy overheating temperatures on the size,morphology and distribution of primary silicon in hypereutectic Al-Si alloys were investigated.The results show that effect of liquid-liquid mixing way is superior to liquid-solid mixing way in improving primary Si.With the increase of the overheating temperature,the size of primary silicon is decreased with round morphology and uniform distribution.At the same overheating temperature,with increasing in the content of silicon in the alloys,the size of primary silicon is increased with the slightly change of morphology.Especially,the microstructure of liquid Al-25Si alloy with 900 ℃ overheating mixing with liquid pure Al at 660 ℃ exhibits desirable,where the primary silicon size is only 34.3 μm,and the length-width ratio is 1.48.