CDS及导流器对Al-20%Si合金初生硅相的影响

Effect of CDS and cooling channel on primary Si phase of Al-20%Si alloy

采用受控扩散凝固(CDS)技术和冷却导流器(CC)制备Al-20%Si(质量分数)合金,研究导流器角度及浇注温度对CDS制备Al-20%Si合金初生硅相的影响。结果表明:CDS和导流器均能细化初生硅相,且与常规的CDS过程相比,引入导流器可以更好地细化初生硅相,且随着导流器角度的减小,细化效果变好。采用820℃的Al-30%Si与660℃的纯铝混合,导流器角度为30°,浇注温度为630℃时,可以得到平均尺寸仅为18.8μm的初生硅相,且其分布均匀。分析认为:CDS可以减小初生硅相生长前沿的成分过冷,而导流器可以进一步促进液体的强迫对流,使熔体中温度场和浓度场更均匀,从而改善初生硅的尺寸、形貌及其分布。

Controlled diffusion solidification （CDS） and cooling channel（CC） were used to prepare hypereutectic Al-20%Si （mass fraction） alloy. The effects of cooling channel angles and the pouring temperatures during CDS process on the microstructure including the size, morphology and distribution of primary silicon were studied. The results show that the application of cooling channel after CDS can obviously refine the size of primary silicon, and the better microstructure can be obtained with the decrease of the angle. Especially, the microstructure of liquid pure Al at 660 ℃ mixing with liquid Al-30%Si alloy at 820℃ is the best when the angle of cooling channel is 30° and the pouring temperature is 630 ℃. The primary Si phase with average particle size of only 18.8 μm distribute uniformly in matrix. Analysis results suggest that CDS can reduce the constitutional supercooling in the liquid ahead of the primary Si phase and the application of the cooling channel can cause the forced convection of liquid, temperature field and concentration field in the melt more evenly, thus can improve the particle size, morphology and distribution of primary Si phase.