采用超音速微粒轰击(SFPB)和表面机械滚压处理(SMRT)相结合的混合表面纳米化方法, 在2A14铝合金上制备出梯度纳米结构(GNS)表层, 对比研究了原始样品和常温空气及低温液氮环境下混合表面纳米化样品在3.5%NaCl水溶液中的电化学腐蚀行为. 结果表明: 经混合表面纳米化处理后, 2A14铝合金晶粒尺寸由最表层约30 nm逐渐增大到基体的原始尺寸, 塑性变形层厚度约130 μm, 表面粗糙度Ra约为0.6 μm, 表面微小裂纹消失. 与原始样品相比, 经过SFPB处理的样品耐点蚀能力没有得到提高, 混合表面纳米化样品的耐点蚀能力得到提高, 其中常温空气环境下样品的自腐蚀电位和点蚀击破电位分别由-1.01228和-0.29666 V升高到-0.67445和0.026760 V, 耐点蚀能力最强. 分析表明, 表层晶粒尺寸纳米化、晶界显著增多、残余压应力以及表面粗糙度的改善有利于提高样品的耐点蚀性能.
In recent years, the surface nanocrystallization (SNC) technology has received extensive attentions in the field of metal material. The shot peening and surface mechanical rolling processing technology can form the gradient nanostructured (GNS) layer on the surface of metal. The material surface roughness is large generally. Therefore, the problem how to form the thick, smooth, flawless GNS layer is need to solve urgently. By means of the hybrid surface nanocrystallization (HSNC) method of both supersonic fine particles bombarding (SFPB) and surface mechanical rolling treatment (SMRT), a gradient nanostructured surface layer was formed on 2A14 aluminum alloy plate. The electrochemical corrosion behavior of the HSNC sample at the air of room temperature and low temperature liquid nitrogen was compared with that of the original sample in aqueous solution of 3.5%NaCl. The results showed that grain size increases from about 30 nm at the surface layer gradually to coarse grain size of the matrix when the sample was processed by HSNC. The total thickness of the plastic deformation layer is about 130 μm. The surface roughness Ra is about 0.6 μm with the surface microcrack disappeared. Compared to the original sample, the pitting corrosion resistance of the SFPB samples was not improved and the pitting corrosion resistance of the HSNC samples was improved. The self-corrosion potential and pitting corrosion potential increase respectively from -1.01228 and -0.29666 V in the original sample to -0.67445 and 0.026760 V at the air room temperature of the HSNC sample. The pitting corrosion resistance of the HSNC sample at the air of room temperature was the biggest. The analysis showed that the surface GNS grain, significant increase of the nanocrystal boundaries, the introduction of compressive residual stress and the decrease of surface roughness were beneficial to improve the pitting corrosion resistance.
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