A double layer Rare Earth Metal (REM) conversion coating process of Al 6061/SiCp metal matrix composites (MMC) was studied.The corrosion resistance of REM conversion coating was examined by electrochemical impedance s...A double layer Rare Earth Metal (REM) conversion coating process of Al 6061/SiCp metal matrix composites (MMC) was studied.The corrosion resistance of REM conversion coating was examined by electrochemical impedance spectroscopy (EIS).REM conversion coating produced very corrosion resistant surface of Al 6061/SiCp MMC.The X ray diffraction (XRD) analysis revealed that REM conversion coatings exhibited non crystalline structure.The composition of REM conversion coating was studied by X ray photoelectron spectroscopy (XPS).The coatings consisted of cerium oxide and hydrated cerium oxide.Some of Ce3+were oxidized to Ce4+during the formation of the first layer coating in the solution containing Ce3+.During the course of exposing the specimens in open air,some of the residual Ce3+were oxidized to Ce4+.REM conversion coating formed in the solution containing Ce4+consisted entirely of Ce4+compounds.展开更多
To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning(SPDT)by studying influence of the p...To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning(SPDT)by studying influence of the precipitates generation of Al6061 on surface integrity and surface roughness.Based on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg_(2)Si and the scratches on the machined surface mostly come from the iron-containing phase(α-, β-AlFeSi).Moreover, the generated Mg_(2)Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg_(2)Si with the medium size(more than 1 μm and less than 2 μm) in Al6061.展开更多
This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile...This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum,and the tensile specimens fractured at the matrix after exceeding 1 Pa.Non-equilibrium grain boundaries were formed at the hot-rolled interface,and a large amount of Mg_(2)Si particles were linearly precipitated along the interfacial grain boundaries(IGBs).During subsequent heat treatment,Mg_(2)Si particles dissolved back into the matrix,and Al_(2)O_(3) film remaining at the interface eventually evolved into MgO.In addition,the local IGBs underwent staged elimination during HRB,which facilitated the interface healing due to the fusion of grains at the interface.This process was achieved by the dissociation,emission,and annihilation of dislocations on the IGBs.展开更多
目的利用搅拌摩擦加工技术制备纳米SiC铝基复合材料,研究经过纳米粒子的添加和FSP作用后,其耐腐蚀性能的变化及原因。方法室温条件下,在3.5%NaCl溶液中,通过电化学阻抗谱和动电位极化曲线对试样的耐腐蚀性能进行检测分析。利用电子背散...目的利用搅拌摩擦加工技术制备纳米SiC铝基复合材料,研究经过纳米粒子的添加和FSP作用后,其耐腐蚀性能的变化及原因。方法室温条件下,在3.5%NaCl溶液中,通过电化学阻抗谱和动电位极化曲线对试样的耐腐蚀性能进行检测分析。利用电子背散射衍射技术和透射电镜对3种试样的显微组织进行表征,研究耐腐蚀性能的变化机理。结果经搅拌摩擦加工后,样品的阻抗值明显提高,动电位极化曲线测试结果显示,母材、FSP试样和复合材料试样的自腐蚀电位分别为–1.517、–1.338、–1.339V,而腐蚀电流密度分别为0.48、0.11、0.12 m A/cm^(2)。FSP加工试样的晶粒由平均晶粒尺寸为8.7μm左右的等轴晶粒构成,并且大部分析出相因高温作用发生溶解,而纳米SiC粒子的加入,使晶粒尺寸进一步降低至4.1μm左右。结论所制备Al6061/SiC复合材料的耐腐蚀性能相较于母材明显改善,但弱于FSP试样。SiC和基体之间电位差的存在构成腐蚀微电池,降低材料的耐腐蚀性能,而晶界数量的增加造成点阵空位等缺陷增加,导致电荷转移的阻力增加,耐腐蚀性能得到改善。展开更多
文摘A double layer Rare Earth Metal (REM) conversion coating process of Al 6061/SiCp metal matrix composites (MMC) was studied.The corrosion resistance of REM conversion coating was examined by electrochemical impedance spectroscopy (EIS).REM conversion coating produced very corrosion resistant surface of Al 6061/SiCp MMC.The X ray diffraction (XRD) analysis revealed that REM conversion coatings exhibited non crystalline structure.The composition of REM conversion coating was studied by X ray photoelectron spectroscopy (XPS).The coatings consisted of cerium oxide and hydrated cerium oxide.Some of Ce3+were oxidized to Ce4+during the formation of the first layer coating in the solution containing Ce3+.During the course of exposing the specimens in open air,some of the residual Ce3+were oxidized to Ce4+.REM conversion coating formed in the solution containing Ce4+consisted entirely of Ce4+compounds.
基金Funded by Natural Science Foundation of Guangdong Province,China (No.2017A030313330)Science and Technology Program of Guangzhou (No.201804020040)。
文摘To improve the surface quality for aluminum alloy 6061(Al6061) in ultra-precision machining, we investigated the factors affecting the surface finish in single point diamond turning(SPDT)by studying influence of the precipitates generation of Al6061 on surface integrity and surface roughness.Based on the Johnson-Mehl-Avrami solid phase transformation kinetics equation, theoretical and experimental studies were conducted to build the relationship between the aging condition and the type, size and number of the precipitates for Al6061. Diamond cutting experiments were conducted to machine Al6061 samples under different aging conditions. The experimental results show that, the protruding on the chip surface is mainly Mg_(2)Si and the scratches on the machined surface mostly come from the iron-containing phase(α-, β-AlFeSi).Moreover, the generated Mg_(2)Si and α-, β-AlFeSi affect the surface integrity and the diamond turned surface roughness. Especially, the achieved surface roughness in SPDT is consistent with the variation of the number of AlFeSi and Mg_(2)Si with the medium size(more than 1 μm and less than 2 μm) in Al6061.
基金This work was financially supported by the National Key Research and Development Program of China(No.2018YFA0707300)the Key Research and Development Program projects of Shandong(No.2020CXGC010304).
文摘This work aims to investigate the mechanical properties and interfacial characteristics of 6061 Al alloy plates fabricated by hotroll bonding(HRB)based on friction stir welding.The results showed that ultimate tensile strength and total elongation of the hot-rolled and aged joints increased with the packaging vacuum,and the tensile specimens fractured at the matrix after exceeding 1 Pa.Non-equilibrium grain boundaries were formed at the hot-rolled interface,and a large amount of Mg_(2)Si particles were linearly precipitated along the interfacial grain boundaries(IGBs).During subsequent heat treatment,Mg_(2)Si particles dissolved back into the matrix,and Al_(2)O_(3) film remaining at the interface eventually evolved into MgO.In addition,the local IGBs underwent staged elimination during HRB,which facilitated the interface healing due to the fusion of grains at the interface.This process was achieved by the dissociation,emission,and annihilation of dislocations on the IGBs.
文摘目的利用搅拌摩擦加工技术制备纳米SiC铝基复合材料,研究经过纳米粒子的添加和FSP作用后,其耐腐蚀性能的变化及原因。方法室温条件下,在3.5%NaCl溶液中,通过电化学阻抗谱和动电位极化曲线对试样的耐腐蚀性能进行检测分析。利用电子背散射衍射技术和透射电镜对3种试样的显微组织进行表征,研究耐腐蚀性能的变化机理。结果经搅拌摩擦加工后,样品的阻抗值明显提高,动电位极化曲线测试结果显示,母材、FSP试样和复合材料试样的自腐蚀电位分别为–1.517、–1.338、–1.339V,而腐蚀电流密度分别为0.48、0.11、0.12 m A/cm^(2)。FSP加工试样的晶粒由平均晶粒尺寸为8.7μm左右的等轴晶粒构成,并且大部分析出相因高温作用发生溶解,而纳米SiC粒子的加入,使晶粒尺寸进一步降低至4.1μm左右。结论所制备Al6061/SiC复合材料的耐腐蚀性能相较于母材明显改善,但弱于FSP试样。SiC和基体之间电位差的存在构成腐蚀微电池,降低材料的耐腐蚀性能,而晶界数量的增加造成点阵空位等缺陷增加,导致电荷转移的阻力增加,耐腐蚀性能得到改善。
