Effect of eutectic Si on surface nanocrystallization of Al-Si alloys by surface mechanical attrition treatment
Effect of eutectic Si on surface nanocrystallization of Al-Si alloys by surface mechanical attrition treatment
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DOI：
10.1016/j.msea.2011.09.090
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发表时间：
2011-12
期刊：
影响因子：
6.4
通讯作者：
H.W. Chang;P. Kelly;Y.-N. Shi;Mingxing Zhang
中科院分区：
文献类型：
--
作者：
H.W. Chang;P. Kelly;Y.-N. Shi;Mingxing Zhang
采用表面机械摩擦处理（SMAT）对纯Al （AA196）和Al - si （A356）合金进行了表面纳米化处理。透射电镜观察了铝基和硅颗粒在应变诱导下的微观组织演变，包括晶粒细化。在纯Al和A356合金中，Al基体的纳米晶化是通过在原始粗晶或细分的亚晶中形成由密集的位错壁和位错缠结隔开的位错细胞而发生的。在SMAT过程中，脆性Si相优先通过直接断裂得到细化。分散的Si小颗粒极大地促进了Al基体的细化过程，因为这些颗粒不仅可以作为位错运动的障碍，而且可以促进位错的产生和增殖。与纯Al相比，Al - si合金的纳米晶区更厚，稳定的纳米晶粒更小。由于低温下Si在Al基体中的扩散速率较低，在SMAT过程中Si颗粒没有明显的再溶解到Al中。
Pure Al (AA196) and Al–Si (A356) alloy were subjected to surface nanocrystallization through surface mechanical attrition treatment (SMAT). Strain induced microstructure evolution, including grain refinement of Al matrix and Si particles, was examined using transmission electron microscopy. Nanocrystallization of Al matrix in both pure Al and A356 alloy occurs through formation of dislocation cells separated by dense dislocation walls and dislocation tangle within the original coarse grains or subdivided subgrains. During SMAT, the brittle Si phase is preferentially refined through direct breakage. The Al matrix refinement process is greatly facilitated by the dispersed small Si particles, because such particles can not only act as obstacles for dislocation movement, but also promote dislocation generation and multiplication. Comparing to pure Al, thicker nanocrystalline zone can be obtained with much smaller stabilized nano-metered grains in the Al–Si alloy. Due to the low diffusion rate of Si in Al matrix at low temperature, there is no obvious re-dissolve of Si particles into Al during SMAT process.