To provide insight into the effect of grain size on the precipitation behavior ofγstrengthening super-alloy Inconel 718,a gradient nanostructure with a large grain size span(from 9 nm to tens of microns)along the dep...To provide insight into the effect of grain size on the precipitation behavior ofγstrengthening super-alloy Inconel 718,a gradient nanostructure with a large grain size span(from 9 nm to tens of microns)along the depth direction was achieved by mean of surface mechanical grinding treatment,followed by annealing upon 700-1000℃ for 1 h.The results reveal significant differences in the type and size of precipitates in samples with different grain sizes.Noγprecipitate was detected inside the grains as the grain size was refined down to 40 nm(NG-40)and 9 nm(NG-9).Forδphase,a significantly accelerated precipitation along grain boundary was observed in NG-40 upon 700℃ annealing.Interestingly,with the grain size drops to 9 nm,the precipitation ofδwas suppressed,with some nanosized MC carbides appearing upon annealing.The grain size effect of precipitation behavior endows NG-9 an ultra-high RT-hardness(5.2 GPa)after 1000℃ thermal exposure and an ultra-high hot-hardness(3.2 GPa)at 800℃.展开更多
A composite coating of nitrogen-doped carbon dots(N–CDs)and polydopamine(PDA)was prepared on magnesium alloy by combining electrodeposition with dip coating methods.The microstructure of the N–CDs/PDA composite coat...A composite coating of nitrogen-doped carbon dots(N–CDs)and polydopamine(PDA)was prepared on magnesium alloy by combining electrodeposition with dip coating methods.The microstructure of the N–CDs/PDA composite coating,including composition,surface morphology,and crystalline structure,is characterized by Raman spectroscopy,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion protection performances of the composite coating are evaluated by potentiodynamic polarization tests,electrochemical impedance spectroscopy,and salt spray tests.The effect of the particle size of the N–CDs on the corrosion performance is also investigated.The results show that the corrosion performance of the N–CDs coatings are enhanced with the increase of the particle sizes.Furthermore,an obvious self-healing performance is observed on the surface of the N–CDs/PDA composite coating.These results indicate that N–CDs/PDA composite coating can improve the corrosion performance of the Mg alloy,and open a new design direction for the protective coating of metallic materials.展开更多
基金supported by the Strategic Pri-ority Research Program of the Chinese Academy of Sciences(No.XDB0510400)the National Natural Science Foundation of China(No.52225102)the Youth Innovation Promotion Association CAS(No.2023201).
文摘To provide insight into the effect of grain size on the precipitation behavior ofγstrengthening super-alloy Inconel 718,a gradient nanostructure with a large grain size span(from 9 nm to tens of microns)along the depth direction was achieved by mean of surface mechanical grinding treatment,followed by annealing upon 700-1000℃ for 1 h.The results reveal significant differences in the type and size of precipitates in samples with different grain sizes.Noγprecipitate was detected inside the grains as the grain size was refined down to 40 nm(NG-40)and 9 nm(NG-9).Forδphase,a significantly accelerated precipitation along grain boundary was observed in NG-40 upon 700℃ annealing.Interestingly,with the grain size drops to 9 nm,the precipitation ofδwas suppressed,with some nanosized MC carbides appearing upon annealing.The grain size effect of precipitation behavior endows NG-9 an ultra-high RT-hardness(5.2 GPa)after 1000℃ thermal exposure and an ultra-high hot-hardness(3.2 GPa)at 800℃.
基金National Natural Science Foundation of China(grants 51771121)the fund provided by Science and Technology Committee of Shanghai Municipality(20ZR1437500)financial supports from Shanghai Municipal Education Commission(2019-01-07-00-07-E00015)。
文摘A composite coating of nitrogen-doped carbon dots(N–CDs)and polydopamine(PDA)was prepared on magnesium alloy by combining electrodeposition with dip coating methods.The microstructure of the N–CDs/PDA composite coating,including composition,surface morphology,and crystalline structure,is characterized by Raman spectroscopy,scanning electron microscopy,transmission electron microscopy,and X-ray photoelectron spectroscopy,respectively.The corrosion protection performances of the composite coating are evaluated by potentiodynamic polarization tests,electrochemical impedance spectroscopy,and salt spray tests.The effect of the particle size of the N–CDs on the corrosion performance is also investigated.The results show that the corrosion performance of the N–CDs coatings are enhanced with the increase of the particle sizes.Furthermore,an obvious self-healing performance is observed on the surface of the N–CDs/PDA composite coating.These results indicate that N–CDs/PDA composite coating can improve the corrosion performance of the Mg alloy,and open a new design direction for the protective coating of metallic materials.
