B,Sr联合处理Al-7Si合金及细化变质效果评估

COMBINED TREATMENT OF Sr AND B AND EVALUATION OF REFINMENT-MODIFICATION LEVELS FOR Al-7Si CASTING ALLOY

采用定量金相及化学分析方法研究了B,Sr联合处理对亚共晶Al-7Si合金凝固组织的影响．Al-7Si合金熔体经B, Sr联合处理时, Sr对合金的细化处理效果无明显影响．而B的出现减少了熔体中有效Sr含量,降低了合金的变质处理效果．在此基础上,结合冷却曲线模式识别技术研究了合金熔体状态与冷却曲线凝固段整体形状的关系．随着表征曲线相似程度的综合偏差值Ω趋近于零,相应的变质级别差值及晶粒尺寸差值也同时向零收敛．冷却曲线凝固段的整体形状可以表征B,Sr联合处理后合金的熔体状态．通过建立基于大量实验结果累积的数据库,有望实现B,Sr联合处理Al-7Si合金细化变质效果的在线评测．

The effects of B and Sr combined addition on the solidified structures of hypoeutectic Al-7Si alloys have been studied by quantitative metallography and chemical analysis. The results show that the addition of Sr has no remarkable effect on the grain refinement of the alloys, but the addition of B reduces the effective content of Sr in the melt Al-7Si alloys and thus decreases the modification level of Al-7Si alloys. Based on these, the relationship between the shape of solidification segment in the cooling curve and the features of melt hypoeutectic A1-Si alloys has been studied by computeraided cooling curve analysis. It is indicated that both the grain size difference and the modification level difference converge to zero when the comprehensive parameter Ω, which expresses the difference between cooling curves, approached to zero. The shape of the solidification segment in the cooling curve can characterize the features of the Al-7Si alloy melt by combined addition of B and Sr. Based on a database established from a large amount of experimental results, it is possible that the on-line prediction of modification level of eutectic Al-7Si can be realized.