摘要
研究了直接电解低钛A356合金锶变质处理及其衰退行为对合金组织及性能的影响。结果表明,熔体细化处理与变质处理存在交互作用,锶含量增加,合金晶粒细化,二次枝晶臂间距减小,并且变质效果越来越好。合金未变质或未完全变质时,共晶硅以不连续短棒状为主;锶含量增加至0.01%时,硅相形态发生突变,硅相完全变质,形态转变为细小珊瑚、蠕虫状结构。最佳锶含量范围为0.02%～0.03%,T5热处理后,硅相球化效果越好,可得到高的强韧性能指标。锶变质衰退研究表明,延长保温时间,合金晶粒明显长大,保温150min后共晶硅形态从完全变质时的珊瑚状又逐渐演变为棒状结构。表明A356合金的细化效果和Si颗粒的变质效果均出现了不同程度的衰退,这与保温过程中TiAl3质点的溶解与沉淀以及Sr的严重烧损有关。
The effect of strontium modification and its fading behavior on the microstructure and mechanical properties of the direct electrolytic A356 alloys were investigated. The results show that there exists the interaction between the modification and refinement, the grain sizes are more refined and the second dendrite arm spaces decreased with the increasing of the strontium contents, as well as the effect of modification is better and better. The morphology of silicon is plate-like shape in non-modified and transfer into the fine fibrous coral-like in modified when strontium content is super than 0.01%. The optimum content of strontium is between is 0.02%～0.03%, and the effect of silicon spheroidization is better and the outstanding mechanical properties can be achieved after T5 treatments. The result of fading behavior is that the grain size increases and the effect of modification fads with the prolonging of the holding time. When the holding time exceeds than 150 min , the silicon morphology is turned into non-modified. It may be related to the solution and deposition of TiAl 3 particles and the burning loss of strontium.
出处
《铸造技术》
CAS
北大核心
2005年第5期413-416,422,共5页
Foundry Technology
关键词
直接电解低钛A356合金
变质
细化
衰退
微观组织
Direct electrolytic A356 alloys
Modification
Grain refinement
Fading
Microstructure
