摘要
目的 利用无针搅拌头对2024铝合金表面进行搅拌摩擦加工(FSP)处理,探究行进速度对铝合金改性层性能的影响。方法 采用HT-JC6×8/2搅拌摩擦焊接设备对合金表面进行改性处理。采用电火花线切割在改性层表面截取测试试样(均来自细晶区)。采用5%(体积分数)氟硼酸对改性层试样进行阳极覆膜,以便观察改性层金相组织。通过光学显微镜(OM)、扫描电子显微镜(SEM)、透射电镜(TEM)等,分析了改性层的显微组织、形貌及性能。采用电化学测试,研究不同行进速度下改性层在3.5%(质量分数)Na Cl溶液中的腐蚀行为。结果 改性层晶粒得到显著细化,未发现气孔、裂纹等缺陷。改性层分为细晶区(FG)、变形晶区(TG)和粗晶区(CG)。其中,FG厚度在1 024.3~1 247.3μm。当行进速度为100 mm/min时,改性层的性能最优,其屈服强度(σ_(0.2))、抗拉强度(σ_(b))相比于母材(BM)分别提升了19.2%和24.5%,伸长率(δ)最高可达20.3%;改性层以韧性断裂为主。同时,相较于BM,改性层的耐腐蚀性能最佳,其腐蚀电位(E_(corr))提升至–0.539 V,腐蚀电流密度(J_(corr))降低至2.448×10^(-6) A/cm^(2)。结论 通过对不同行进速度下改性层组织及性能的分析,发现改性层的力学性能和抗腐蚀性能,随着行进速度的增加,均呈现先增强后减弱的趋势。当行进速度达到100 mm/min时,改性层的性能最佳。
FSP is a green,environmentally friendly,and efficient surface modification technology.It can reduce the generation of cracks,porosity,and other defects on the alloy surface and improve its surface properties.To increase the depth of the stirring area,traditional FSP generally uses a stirring head with a stirring pin.Nevertheless,inserting the stirring pin into the alloy matrix may destroy the microstructure,which could subsequently lead to a reduction in the overall performance and an accelerated deterioration to the service life of alloy components.To circumvent the issues mentioned,the work aims to utilize a pin-less stirring head to facilitate FSP modification treatment on the surface of the 2024 aluminum alloy(BM).Furthermore,the effect of the traverse speed on the properties of the modified layer of the alloy is investigated.The 2D stirring friction welding equipment model HT-JC6×8/2 was employed to implement a pin-less stirring friction modification treatment on the surface of the aluminum alloy.The process parameters were as follows,including the spindle speed of 1000 r/min,and the traverse speed of 40 mm/min,60 mm/min,80 mm/min,100 mm/min,and 120 mm/min.Tensile and corrosion specimens(from the FG)were extracted from the surface of the modified layer by EDM wire cutting.Anode film of the modified layer specimens was conducted in a 5%HBF4 solution at room temperature to facilitate observation of the metallographic microstructure of the modified layer.The DC voltage was set to 18 V for 150 s.The microstructure,polarized corrosion morphology,tensile fracture morphology,and tensile mechanical properties of the modified layer were analyzed by OM,SEM,TEM,and a YYF/slow strain rate stress corrosion tester.Additionally,a three-electrode system was employed for electrochemical testing of the modified layer to study the corrosion behavior of the modified layer in 3.5%NaCl solution under different traverse speed conditions.An analysis of the tensile and electrochemical corrosion properties of the modified layer specimens showed that the performance of the modified layer peaked at a traverse speed of 100 mm/min.The cross section of the modified layer was bowl-shaped,and the surface grains were significantly refined,with no defects such as porosity and cracks.The modified layer could be divided into three distinct zones according to the size and shape of the grains,including FG,TG,and CG.The thickness of the FG was between 1024.3μm and 1247.3μm.When the traverse speed was 100 mm/min,compared with the BM,theσ_(0.2) andσ_(b) were enhanced by 19.2%and 24.5%,respectively,and theδcould be up to 20.3%.The fracture form of the modified layer was dominated by ductile fracture.At this juncture,the modified layer had the best corrosion resistance.In comparison to the BM,the E_(corr) of the modified layer was enhanced from-1.283 V to-0.539 V,while the J_(corr) was diminished from 6.680×10^(-5) A/cm^(2) to 2.448×10^(-6) A/cm^(2).Concurrently,in the Nyquist curve,the capacitive arc radius was the largest.In the polarized corrosion morphology,there were almost no large corrosion spots,which corroborated the exceptional corrosion resistance of the material.The pin-less FSP modification uses the shoulder of the stirring head to contact the surface of the alloy.Under the combined effect of frictional heat and stress,the alloy undergoes plasticization and intense plastic deformation,which refines the microstructure of the alloy surface(grains,S-phase).The refined S-phase is uniformly dispersed in the modified layer through the rotation of the stirring head,thereby achieving the effect of dispersion strengthening.The synergistic effect of fine grain and dispersion strengthening allows the modified layer to obtain excellent comprehensive performance.
作者
张浩
王优强
段继周
ZHANG Hao;WANG Youqiang;DUAN Jizhou(School of Mechanical and Automotive Engineering,Qingdao University of Technology,Shandong Qingdao 266520,China;Key Laboratory of Marine Environmental Corrosion and Bio-fouling,Institute of Oceanology,Chinese Academy of Sciences,Shandong Qingdao 266071,China;Open Studio for Marine Corrosion and Protection,Qingdao National Laboratory for Marine Science and Technology,Shandong Qingdao 266237,China;Center for Ocean Mega-Science,Chinese Academy of Sciences,Shandong Qingdao 266071,China)
出处
《表面技术》
北大核心
2025年第8期96-106,共11页
Surface Technology
基金
国家自然科学基金(42076044)。
关键词
无针搅拌摩擦
2024铝合金
表面改性
力学性能
耐腐蚀
行进速度
FSP
2024 aluminum alloy
surface modification
mechanical properties
corrosion resistance
traverse speed
