铜模快冷与SiC复合作用下镁合金的晶粒尺寸

Effects of Copper-mould Quenching and SiC on Grain Size in Magnesium Alloy

采用真空感应熔炼与阶梯型铜模喷铸相结合,制备出添加SiC颗粒增强亚快速凝固镁合金试样。通过等温固溶处理,定量分析了冷速及细化剂含量共同影响下镁合金晶粒尺寸变化的规律,并对相关细化机理进行了讨论。结果表明,铜模喷铸镁合金快冷组织主要由细小粒状晶组成,经400℃×2h固溶处理后转变为多边形等轴晶组织。随铜模内径降低,凝固冷速提高,有效形核分数的增大导致镁合金晶粒尺寸下降,分布趋于均匀。当添加2%的SiC时,4mm铜模内径对应的镁合金晶粒尺寸可细化到4μm,并形成整体细晶组织。

Using vacuum induction melting and multi-step copper-mould spraying casting,sub-rapid solidification of magnesium alloy containing SiC inoculants was performed.After isothermal annealing treatment,compound effects of cooling rate and inoculant content on the grain size of spraying deposited magnesium ingots were investigated.Experimental results show that microstructure of the copper-mould quenched magnesium alloy exhibits fine particle,which changes into equiaxed grain with polygon morphology after solid solution at 400 ℃for 2h.Cooling rate is enhanced with decreasing the inner diameter of copper-mould,resulting in the increase of effective nucleation fraction with uniform distribution and decrease of grain size.With addition of 2% SiC and inner diameter of 4mm,the minimum grain size reaches 4μm,and whole fine grain casting can be realized.