喷丸强化对7050铝合金微观组织和耐磨性的影响

Effect of Shot Peening on Microstructure and Wear Resistance of 7050 Aluminum Alloy

目前,有关增压喷丸对7050铝合金耐磨性能的影响研究鲜见报道。通过增压喷丸方式在7050铝合金表面制备纳米晶层;用X射线衍射仪、光学显微镜、透射电镜观察并分析了纳米晶层的组织结构,统计了晶粒尺寸大小和变形层的厚度;通过维式硬度计测量了样品喷丸前、后的显微硬度;采用钻盲孔法测试了残余应力的分布;在油润滑条件下对喷丸前、后样品进行了摩擦磨损试验,通过磨损失重和形貌对比分析了耐磨性能。结果表明:增压喷丸使7050铝合表面发生严重的塑性变形,变形层平均厚度约为140μm,表层纳米晶粒平均尺寸约为80 nm,硬度比基体提高了1.38倍,耐磨损性提高了1倍以上。试样表面经增压喷丸撞击产生的塑性变形引起的晶粒细化以及加工硬化现象的共同作用,是其显微硬度和耐磨性能提高的主要原因。

Nano - crystalline layer on the surface of 7050 Al alloy was obtained by added- pressure shot peening process. The X- ray diffraction, optical microscope and transmission electron microscopy were used to study the microstructure features of nano-crystalline layer and thickness of deformed layer. The micro-hardness of the sample before and after shot peening was measured by durometer. In addition, the distribution of re- sidual stress was tested by drilling hole method and under the condition of oil lubrication, the friction and wear test was used to study the sam- ple before and after shooting peening. The abrasion resistance was analyzed by comparing wear weightlessness and morphology. Results showed that added-pressure shot peening led to severe plastic deformation on the 7050 Al alloy surface, and the average thickness of deformed layer was about 140 μm. The average size of surface nano-crystalline was about 80 nm,and the hardness was improved 1.38 times than that of sub- strate. Moreover, and the abrasion resistance was improved more than 1 time. In general, both the grain refinement resulting from surface plas- tic deformation by added-pressure shot pending and work hardening phenomenon were the main reason for the improvement of micro-hardness and abrasion resistance.