Three sample preparation techniques, focused ion beam （FIB）, ion beam （IB） etching, and ultramicrotomy （UM） were used in comparison to analyze the interphase of carbon fiber ＇epoxy composites using transmission...Three sample preparation techniques, focused ion beam （FIB）, ion beam （IB） etching, and ultramicrotomy （UM） were used in comparison to analyze the interphase of carbon fiber ＇epoxy composites using transmission electron microscopy. An intact interphase with a relatively uniform thickness was obtained by FIB. and detailed chemical analysis of the interphase was investigated by electron energy loss spectroscopy. It shows that the interphase region is 200 mn wide with an increasing oxygen-to-carbon ratio from 10% to 19% and an almost constant nitrogen-to-carbon ratio of about 3%. However, gallium implantation of FIB tends to hinder fine structure analysis of the interphase. For IB etching, the interphase region is observed with transition morphology frona amorphous resin to nano-crystalline carbon fiber, but the uneven sample thickness brings difficulty for quantitative chemical analysis. Moreover, UM tends to cause damage and/or deformation on the interphase. These results are meaningful for in-depth understanding on the interphase characteristic of carbon fiber composites.展开更多
The spatial arrangement,distribution and morphology of Fe-bearing intermetallics in AA6082 alloys depends on the manufacturing process of the alloy and thus influences the macroscopic properties.Here,the microstructur...The spatial arrangement,distribution and morphology of Fe-bearing intermetallics in AA6082 alloys depends on the manufacturing process of the alloy and thus influences the macroscopic properties.Here,the microstructure of a near industrial scale casting AA6082 Al alloy fabricated by:(a)direct chill casting,(b)Al-5 Ti-1 B grain refiner addition and(c)intensive melt shearing has been investigated by threedimensional visualization using SEM-based serial ultra microtomy tomography.The formation sequence of phases in AA6082 alloys is generally categorized into four stages:formation ofα-Al grains,Fe-bearing intermetallics,Mg_(2)Si phase,and eutectic rosettes.Results of three-dimensional visualization of the microstructure indicated that TiBparticles not only could nucleate Fe-bearingβ-intermetallics,but also could provide substrate for the formation of Fe-bearingα-intermetallics and Mg_(2)Si.A further deep analysis reveals that the essential condition for the formation of secondary phases such as Fe-bearing intermetallics and Mg_(2)Si phase is the build-up of a supersaturated solute front at theα-Al solid-liquid interface irrespective of the specific nucleation site.In addition,the results indicate that grain refinement processing causes the severe interconnectivity of Fe-bearingα-intermetallics.However,the intensive melt shearing is a better manufacturing process because the intermetallics are more evenly distributed and refined than with the addition of the grain refiner,thereby improving the properties of the alloy.展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 51273007)the Program for New Century Excellent Talents in University of China (NCET)
文摘Three sample preparation techniques, focused ion beam （FIB）, ion beam （IB） etching, and ultramicrotomy （UM） were used in comparison to analyze the interphase of carbon fiber ＇epoxy composites using transmission electron microscopy. An intact interphase with a relatively uniform thickness was obtained by FIB. and detailed chemical analysis of the interphase was investigated by electron energy loss spectroscopy. It shows that the interphase region is 200 mn wide with an increasing oxygen-to-carbon ratio from 10% to 19% and an almost constant nitrogen-to-carbon ratio of about 3%. However, gallium implantation of FIB tends to hinder fine structure analysis of the interphase. For IB etching, the interphase region is observed with transition morphology frona amorphous resin to nano-crystalline carbon fiber, but the uneven sample thickness brings difficulty for quantitative chemical analysis. Moreover, UM tends to cause damage and/or deformation on the interphase. These results are meaningful for in-depth understanding on the interphase characteristic of carbon fiber composites.
基金financially supported by the EPSRC(No.EP/N007638/1)the 2021 Jiangsu Shuangchuang(Mass Innovation and Entrepreneurship)Talent Program(No.JSSCBS20210702)。
文摘The spatial arrangement,distribution and morphology of Fe-bearing intermetallics in AA6082 alloys depends on the manufacturing process of the alloy and thus influences the macroscopic properties.Here,the microstructure of a near industrial scale casting AA6082 Al alloy fabricated by:(a)direct chill casting,(b)Al-5 Ti-1 B grain refiner addition and(c)intensive melt shearing has been investigated by threedimensional visualization using SEM-based serial ultra microtomy tomography.The formation sequence of phases in AA6082 alloys is generally categorized into four stages:formation ofα-Al grains,Fe-bearing intermetallics,Mg_(2)Si phase,and eutectic rosettes.Results of three-dimensional visualization of the microstructure indicated that TiBparticles not only could nucleate Fe-bearingβ-intermetallics,but also could provide substrate for the formation of Fe-bearingα-intermetallics and Mg_(2)Si.A further deep analysis reveals that the essential condition for the formation of secondary phases such as Fe-bearing intermetallics and Mg_(2)Si phase is the build-up of a supersaturated solute front at theα-Al solid-liquid interface irrespective of the specific nucleation site.In addition,the results indicate that grain refinement processing causes the severe interconnectivity of Fe-bearingα-intermetallics.However,the intensive melt shearing is a better manufacturing process because the intermetallics are more evenly distributed and refined than with the addition of the grain refiner,thereby improving the properties of the alloy.
