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为研究搅拌摩擦加工作用机理,对铝合金表面热喷涂铝基涂层进行了4道次搅拌摩擦加工。应用SEM、EDS、TEM和显微硬度测试对加工前后的涂层进行分析。结果表明,涂层经过搅拌摩擦加工后,原本层叠状、有孔隙组织通过形变诱导位错切割机制,首先形成滑移带,同时位错密度不断增加并聚集成小角度晶界,然后逐渐转变成大角度晶界,将晶粒分解细化,最终演变成致密的超细等轴晶,尺寸达到200 nm以下。涂层和基体之间发生了相互融合,涂层和基体间的间隙消失。基体中的合金元素向涂层扩散。搅拌摩擦加工后,涂层显微硬度从62 HV上升到269 HV。
In order to study the action mechanism of friction stir processing, 4 times of friction stir processing was carried out on the thermal spraying aluminum coating on the surface of aluminum alloy. The coatings before and after processing were analyzed by SEM, EDS, TEM and microhardness test. The results show that the original lamellar and porous structure induce the dislocation cutting mechanism by the friction stir processing. At first, the slip band is formed. At the same time, the dislocation density increases and aggregates into small-angle grain boundaries, and then gradually changes to Large-angle grain boundaries, grain refinement and refinement, and eventually evolved into dense superficial equiaxed grains, the size of 200 nm or less. The fusion of the coating and the matrix occurred and the gap between the coating and the matrix disappeared. Alloying elements in the matrix diffuse into the coating. After the friction stir processing, the coating hardness increased from 62 HV to 269 HV.