Effect of Mg/Si ratio on the microstructure and hardness-conductivity relationship of ultrafine-grained Al-Mg-Si alloys
Effect of Mg/Si ratio on the microstructure and hardness-conductivity relationship of ultrafine-grained Al-Mg-Si alloys
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DOI：
10.1007/s10853-016-0691-0
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发表时间：
2017-04-01
影响因子：
4.5
通讯作者：
Li, X. M.
中科院分区：
文献类型：
--
作者：
Han, Y.;Shao, D.;Li, X. M.
采用挤压和冷拔法制备了Mg/Si比分别为0.75、1.10、1.48和1.94的Al-Mg-Si超细晶合金。用透射电镜观察了时效过程中组织的演变。分别测定了时效处理前后合金的硬度和电导率。实验结果表明，四种时效合金均有β "析出物分散在晶粒内部。Mg/Si比对析出相尺寸不敏感，但Mg/Si比对析出相数密度和析出相间距有较大影响。优化后的Mg/Si比为1.48，析出密度最大，硬度最高，同时电导率最高。考虑到超细晶长度尺度下的析出行为及其对硬度-电导率关系的影响，这些发现是合理的。提出了晶粒尺寸、位错、固溶原子和析出相对超细晶AlMg- Si合金硬度的综合强化模型。计算结果与实验结果吻合较好。同样，采用模型定量描述了多种微观结构特征对电导率的影响。结果表明，析出对Al- mg - si超细晶合金的硬度和电导率都有显著的影响，这将为高性能的超细晶Al合金的材料设计提供依据。
Ultrafine-grained Al-Mg-Si alloys with four different Mg/Si ratios (= 0.75, 1.10, 1.48, and 1.94) were prepared by using extrusion and cold-drawing. The microstructural evolution during aging treatment was examined by using transmission electron microscopy. Hardness and electrical conductivity of the alloys were, respectively, measured before and after aging treatment. Experimental results showed that beta '' precipitates were dispersed within the grain interior in all the four aged alloys. Although the precipitate size was insensitive to the Mg/Si ratio, the precipitate number density as well as the inter-precipitate spacing was greatly dependent on the Mg/Si ratio. The optimized Mg/Si ratio within present work was 1.48, which led to the densest precipitation, and resulted in the highest hardness and simultaneously greatest conductivity. These findings are rationalized by considering the precipitation behaviors in the ultrafine-grained length scale and their effect on the hardness-conductivity relationship. A strengthening model was proposed for the ultrafine-grained AlMg- Si alloys, which accounted for the multiple contributions from grain size, dislocations, solid solution atoms, and precipitates to the hardness. The calculations were in good agreement with the experimental results. Similarly, the effect of multiple microstructural features on the electrical conductivity was also quantitatively described by adopting a model. The contribution of precipitation to both the hardness and conductivity is well demonstrated for the ultrafinegrained Al-Mg-Si alloys, which will be helpful for material design of advanced ultrafine-grained Al alloys with enhanced performance.