内冷搅拌法细化AZ系镁合金半固态浆料初生相的研究

RESEARCH ON GRAIN REFINEMENT OF PRIMARY PHASE OF SEMI-SOLID SLURRY OF AZ SERIES MAGNESIUM ALLOY USING INTERNAL COOLING STIRRING(ICS)METHOD

提升镁及其合金强度和室温韧性是扩展镁及其合金应用的关键技术,对镁合金凝固过程半固态处理是改善微观组织、提高产品质量的一个重要工艺途径。因此,本文提出内冷搅拌法制备非枝晶AZ系镁合金半固态浆料,采用快速淬火研究内冷搅拌过程AZ系镁合金半固态浆料初生相演变规律。通过观察金相微观组织发现,在金属熔体与平衡体质量比为3:1、平衡体温度为室温、熔体温度高于液相线20oC时,随着平衡体旋转速度增加,熔体整体温度梯度减小,凝固组织从粗大枝晶逐渐变为细小近球晶;随着旋转平衡体搅拌时间延长,浆料组织分散变得均匀,后续由于晶粒生长,晶粒出现团聚;Al元素含量增加能够细化自然凝固初生相α-Mg,而内冷搅拌法对AZ系镁合金半固态处理发现,Al元素含量虽然一定程度上细化初生相α-Mg,随着内冷搅拌条件引入,Al元素含量增加细化程度较小,而内冷搅拌条件是细化初生相α-Mg的主要因素。

It is a key technology to improve the strength and room temperature toughness of magnesium for expanding the application of magnesium and its alloys,and it is also an important technological way for semi-solid treatment to improve microstructure and product quality during solidification of magnesium alloy.Therefore,a new rheocasting process,internal rapid cooling stirring process was used to obtain a fully grain-refined spherical semisolid slurry.Rapid quenching was used to study the microstructure evolution during internal rapid cooling stirring process.By the metallographic microstructure observation,it was found that when the mass ratio of melt to balance body was 3:1,the temperature of the balance body was at room temperature,and the melt temperature was higher than liquidus around 20 oC,whose temperature was at room temperature whose temperature was above liquidus around 20oC,with the increase of the rotating speed of the balance body,the temperature gradient of the melt decreased,the whole solidification microstructure gradually changed from coarse dendrite to fine near spherulite.With the extension of the stirring time of the rotating balance body,the dispersion of the slurry structure became homogeneous,and the subsequent grain growth resulted in grain agglomeration.the results showed that the increase of Al element content could refine the nature solidified primary phaseα-Mg;however,for the internal cooling stirring condition on the semi-solid treatment of AZ magnesium alloy,which was found that although the Al element content refined the primary phaseα-Mg to a certain extent,the Al element content increased to a lesser degree with the introduction of the internal cooling stirring condition,and the internal cooling stirring condition was the main factor to refine the primary phaseα-Mg.