The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior...The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior room,temperature strength and modulus, as well as good elevated temperature properties were obtained as comparison with that of pure Al.展开更多
Microstructure and properties of SiCw/2124Al composite fabricated by powder metallurgy technique were systematically investigated.The results indicate that the matrix in the composite preserves the microstructural cha...Microstructure and properties of SiCw/2124Al composite fabricated by powder metallurgy technique were systematically investigated.The results indicate that the matrix in the composite preserves the microstructural characteristics of microcrystalline aluminum powder.SiC whiskers are uniformly distributed in the matrix and the interFacial bonding is excellent.Because of the addition of SiC whisker the strength and modulus of the composite increase by 45%and 76%respectively,and the coefticient of thermal expansion decreases by 35%.展开更多
(B4C+Al2O3)/Al composite designed for the dry storage of spent nuclear fuels was fabricated and then subjected to friction stir welding, at a welding speed of 100 mm/min and rotation rates of 400–800 r/min. Sound joi...(B4C+Al2O3)/Al composite designed for the dry storage of spent nuclear fuels was fabricated and then subjected to friction stir welding, at a welding speed of 100 mm/min and rotation rates of 400–800 r/min. Sound joints were obtained under all welding parameters;however, significant softening occurred in the nugget zone(NZ) for all the joints. Therefore, all the joints exhibited significantly decreased strength at both room temperature and high temperature compared with the base metal, with the joints fracturing in the NZs. Rotation rate exhibited no obvious effect on the tensile strength of the joints, but led to increased elongation as the result of the broadened NZs. The detailed microstructural examinations indicated that the welding thermomechanical effect broke up the near 3D amorphous Al2O3 netlike structure distributed at the Al grain boundaries, caused the coarsening of Al grains, and the agglomeration and crystallization of amorphous Al2O3, thereby resulting in the softening of the NZs and the reduction in the joint strength. Consequently, inhibiting the breakup and crystallization of 3D amorphous Al2O3 netlike structure is the key factor to improve the joint strength of the(B4C+Al2O3)/Al composite.展开更多
The raw and pre-smashed(PS)carbon nanotube(CNT)reinforced 6061Al composites(CNT/6061Al)with different CNT contents were respectively fabricated by powder metallurgy technology.It was found that reducing the CNT cluste...The raw and pre-smashed(PS)carbon nanotube(CNT)reinforced 6061Al composites(CNT/6061Al)with different CNT contents were respectively fabricated by powder metallurgy technology.It was found that reducing the CNT cluster size by presmashing processing could sharply reduce the friction coefficient,and significantly improve the density,hardness,and wear resistance of the CNT/6061Al composites.For the raw-CNT/6061Al composites,the wear rate increased approximately linear trend while the CNT content was over 1 wt.%.The plastic deformation,deep grooves,and serious delamination were presented on the wear surface.The wear process was gradually transformed from Al-copper base counterpart wear into Al-Al wear for the higher adhesion-binding energy between aluminum and copper base counterpart.While for the PS-CNT/6061Al composites,the wear rate gradually decreased as the CNT content increased from 0 to 2 wt.%.This was mainly because the generation of the thinner mechanically mixed layer(MML)and the PS-CNT prevented the direct contact between specimen and copper base counterpart,which effectively inhibited the adhesive wear.But excessive PS-CNTaddition(~3 wt.%)would weaken the bonding between CNT and 6061Al,and thus the wear resistance of the composite was reduced apparently.展开更多
Neutron absorbing materials(NAMs)are necessary in the nuclear industry for the storage and transportation of spent fuel.Among all the NAMs,B_(4)C/Al composites are widely used because of the specific neutron absorptio...Neutron absorbing materials(NAMs)are necessary in the nuclear industry for the storage and transportation of spent fuel.Among all the NAMs,B_(4)C/Al composites are widely used because of the specific neutron absorption capacity[1–4].Compared with traditional low-strength functional NAMs such as B_(4)C/1100Al and B_(4)C/6061Al,NAMs with enough high-temperature(350℃)strength are competent for further structural usage and exhibit huge advantages in the dry storage of spent fuel because of heat transfer ability and weight reduction[5].展开更多
Aging treatments are the key process to obtain satisfactory strength for 7xxxAl alloys and their composites. However, traditional single-stage(SS) aging is time-consuming to reach a peak strength condition. In this st...Aging treatments are the key process to obtain satisfactory strength for 7xxxAl alloys and their composites. However, traditional single-stage(SS) aging is time-consuming to reach a peak strength condition. In this study, an efficient 120℃ + 160℃ two-stage(TS) aging treatment was proposed on a B_4C/7A04Al composite fabricated via powder metallurgy(PM) technology, which could acquire similar peak-aging strength but only took about 15% of the time compared to traditional 120℃ SS aging. The evolution of precipitation during the TS aging was investigated, as well as those of the 7A04Al alloys for comparison. In the second stage aging process, the higher aging temperature accelerated the nucleation of η′ phases inside the grains and thus increased the density of precipitates. Moreover, the short aging time limited the coarsening of precipitates and the broadening of precipitatefree zones. The above factors were beneficial for quickly obtaining satisfactory precipitation strengthening effects. The B_4C/7A04Al composite exhibited slower aging kinetics than the 7A04Al alloy in the TS aging. Mg elements consumption by the chemical reaction between B impurities introduced by B_4C particles and the Al matrix was considered to potentially retard the aging kinetics of the B_4C/7A04Al composite. Nevertheless, the precipitation sequence was not affected.展开更多
Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The...Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.展开更多
In this study,7 xxx(Al-Zn-Mg-Cu)alloys with high Zn concentrations were fabricated by increasing the Zn contents of 7085 Al alloys.The hardness,quench sensitivity,and electrical conductivity of the alloys and a 7085 A...In this study,7 xxx(Al-Zn-Mg-Cu)alloys with high Zn concentrations were fabricated by increasing the Zn contents of 7085 Al alloys.The hardness,quench sensitivity,and electrical conductivity of the alloys and a 7085 Al alloy under peak-aged state were studied.The high Zn concentration alloys had higherη′phase densities and lower quantities of Mg solid atoms than the 7085 Al alloy and thus exhibited higher hardness and electrical conductivity.The high Zn concentration alloys also exhibited slightly higher quench sensitivity than 7085 Al alloy,and the depth of the quenching layer of the alloy with 11.27 wt%Zn content reached 100 mm.This work confirmed that the novel 7 xxx alloy with high Zn concentration showed balanced performance,exhibiting enhanced hardness and conductivity and reasonable quench sensitivity compared with the 7085 commercial Al alloy.展开更多
As a classic in-situ reaction, the Al-TiO_(2) reaction is expected to prepare aluminum matrix composites with high thermal stability.In this study, it was found that the preparation method of ensuring sufficient react...As a classic in-situ reaction, the Al-TiO_(2) reaction is expected to prepare aluminum matrix composites with high thermal stability.In this study, it was found that the preparation method of ensuring sufficient reaction using higher temperatures in previous studies was not conducive to acquiring optimized high-temperature strength. With the increase of hot-pressing temperature and the extension of holding time, the in-situ reaction became more thorough, but the strength of the composites first increased and then decreased. Coarsening of the microstructure at high temperatures would lead to degradation of strength and controlling the in-situ reaction process by the hot-pressing parameters could optimize the mechanical properties of the composites. Strengthening mechanisms at room and high temperatures were studied, and it was found that the load-transfer and Orowan strengthening mechanisms are the main strengthening effects at room temperature, while the pinning effect of fine particles became more crucial at elevated temperatures. As a result, the coarsening of the reinforcing phases was more detrimental to the hightemperature strength. Therefore, an insufficient in-situ reaction led to more excellent mechanical properties, and the composite hot-pressed at 605℃ and held for 2 h exhibited the highest strength, which was 367 MPa at room temperature and 170 MPa at 350℃.展开更多
文摘The in-situ forming TiB_2 reinforced Al composite was favorably prepared by reaction- sintering of pure Al,Ti and B powders under vacuum.The TiB_2 is of submicrosize and free from lattice defect in the main.A superior room,temperature strength and modulus, as well as good elevated temperature properties were obtained as comparison with that of pure Al.
文摘Microstructure and properties of SiCw/2124Al composite fabricated by powder metallurgy technique were systematically investigated.The results indicate that the matrix in the composite preserves the microstructural characteristics of microcrystalline aluminum powder.SiC whiskers are uniformly distributed in the matrix and the interFacial bonding is excellent.Because of the addition of SiC whisker the strength and modulus of the composite increase by 45%and 76%respectively,and the coefticient of thermal expansion decreases by 35%.
基金supported by the National Natural Science Foundation of China (Grant Nos. U1508216,51771194)the Youth Innovation Promotion Association,CAS (Grant No. 2016179)the National Key R&D Program of China (Grant No. 2017YFB0703104)。
文摘(B4C+Al2O3)/Al composite designed for the dry storage of spent nuclear fuels was fabricated and then subjected to friction stir welding, at a welding speed of 100 mm/min and rotation rates of 400–800 r/min. Sound joints were obtained under all welding parameters;however, significant softening occurred in the nugget zone(NZ) for all the joints. Therefore, all the joints exhibited significantly decreased strength at both room temperature and high temperature compared with the base metal, with the joints fracturing in the NZs. Rotation rate exhibited no obvious effect on the tensile strength of the joints, but led to increased elongation as the result of the broadened NZs. The detailed microstructural examinations indicated that the welding thermomechanical effect broke up the near 3D amorphous Al2O3 netlike structure distributed at the Al grain boundaries, caused the coarsening of Al grains, and the agglomeration and crystallization of amorphous Al2O3, thereby resulting in the softening of the NZs and the reduction in the joint strength. Consequently, inhibiting the breakup and crystallization of 3D amorphous Al2O3 netlike structure is the key factor to improve the joint strength of the(B4C+Al2O3)/Al composite.
基金supported by the National Key R&D Program of China(Grant No.2017YFB0703104)the Key Research Program of Frontier Sciences,CAS(Grant No.QYZDJ-SSW-JSC015)+1 种基金the National Natural Science Foundation of China(Grant Nos.51931009,51871214,51871215)the Youth Innovation Promotion Association CAS(Grant No.2020197)。
文摘The raw and pre-smashed(PS)carbon nanotube(CNT)reinforced 6061Al composites(CNT/6061Al)with different CNT contents were respectively fabricated by powder metallurgy technology.It was found that reducing the CNT cluster size by presmashing processing could sharply reduce the friction coefficient,and significantly improve the density,hardness,and wear resistance of the CNT/6061Al composites.For the raw-CNT/6061Al composites,the wear rate increased approximately linear trend while the CNT content was over 1 wt.%.The plastic deformation,deep grooves,and serious delamination were presented on the wear surface.The wear process was gradually transformed from Al-copper base counterpart wear into Al-Al wear for the higher adhesion-binding energy between aluminum and copper base counterpart.While for the PS-CNT/6061Al composites,the wear rate gradually decreased as the CNT content increased from 0 to 2 wt.%.This was mainly because the generation of the thinner mechanically mixed layer(MML)and the PS-CNT prevented the direct contact between specimen and copper base counterpart,which effectively inhibited the adhesive wear.But excessive PS-CNTaddition(~3 wt.%)would weaken the bonding between CNT and 6061Al,and thus the wear resistance of the composite was reduced apparently.
基金supported by the National Natural Science Foundation of China(Grant No.51771194)the CNNC Science Fund for Talented Young Scholars+2 种基金Ling Chuang Research Project of China National Nuclear CorporationLiao Ning Revitalization Talents Program(Grant No.XLYC1902058)the IMR Innovation Fund(Grant Nos.2021-ZD02 and 2021-PY12)。
文摘Neutron absorbing materials(NAMs)are necessary in the nuclear industry for the storage and transportation of spent fuel.Among all the NAMs,B_(4)C/Al composites are widely used because of the specific neutron absorption capacity[1–4].Compared with traditional low-strength functional NAMs such as B_(4)C/1100Al and B_(4)C/6061Al,NAMs with enough high-temperature(350℃)strength are competent for further structural usage and exhibit huge advantages in the dry storage of spent fuel because of heat transfer ability and weight reduction[5].
基金supported by the National Key R&D Program of China (Grant No. 2022YFB3707405)the National Natural Science Foundation of China (Grant Nos. U22A20114 and 52301200)+3 种基金the Guangdong Basic and Applied Basic Research Foundation (Grant No. 2021A1515110525)the Project Funded by China Postdoctoral Science Foundation (Grant No. 2023M733573)the Natural Science Foundation of Liaoning Province (Grant No. 2023-BS-020)the Liaoning Revitalization Talents Program (Grant No. XLYC2007009)。
文摘Aging treatments are the key process to obtain satisfactory strength for 7xxxAl alloys and their composites. However, traditional single-stage(SS) aging is time-consuming to reach a peak strength condition. In this study, an efficient 120℃ + 160℃ two-stage(TS) aging treatment was proposed on a B_4C/7A04Al composite fabricated via powder metallurgy(PM) technology, which could acquire similar peak-aging strength but only took about 15% of the time compared to traditional 120℃ SS aging. The evolution of precipitation during the TS aging was investigated, as well as those of the 7A04Al alloys for comparison. In the second stage aging process, the higher aging temperature accelerated the nucleation of η′ phases inside the grains and thus increased the density of precipitates. Moreover, the short aging time limited the coarsening of precipitates and the broadening of precipitatefree zones. The above factors were beneficial for quickly obtaining satisfactory precipitation strengthening effects. The B_4C/7A04Al composite exhibited slower aging kinetics than the 7A04Al alloy in the TS aging. Mg elements consumption by the chemical reaction between B impurities introduced by B_4C particles and the Al matrix was considered to potentially retard the aging kinetics of the B_4C/7A04Al composite. Nevertheless, the precipitation sequence was not affected.
基金supported by the Key Research Program of Frontier Sciences,CAS (Grant No.QYZDJ-SSW-JSC015)the Project of Manned Spaceflight (Grant No.040103)+1 种基金the National Natural Science Foundation of China (Grant Nos.51931009, 51871214 and 51871215)the Youth Innovation Promotion Association CAS (Grant No.2020197)。
文摘Bimodal carbon nanotube reinforced 7055Al(CNT/7055Al) composites containing coarse grain bands and ultra-fine grain zones were fabricated by high energy ball milling, vacuum hot pressing followed by hot extrusion. The effect of extrusion temperature varied from 320℃ to 420℃ on the microstructure evolution and tensile properties were investigated. Microstructure observation indicates that the elongated coarse grain bands aligned along the extrusion direction after extrusion. The width of the coarse grain bands increased, and the length of the coarse grain bands increased firstly and then decreased with the increase of extrusion temperature. The grain size of the ultra-fine grain zones changed little after hot extrusion, but the ultra-fine grains coarsened after subsequent heat treatment, especially for the composite extruded at low temperature of 320℃. By observing the CNT distribution, it was found that the higher temperature extrusion was beneficial to the CNT orientation along the extrusion direction.Furthermore, a precipitated free zone formed at the boundary between the coarse grain band and the ultra-fine grain zone as the composite extruded at high temperature of 420℃. As the result of the comprehensive influence of the above microstructure, the tensile strength of the composite extruded at moderate temperature of 370℃ reached the highest of 826 MPa.
基金supported by the National Natural Science Foundation of China(Grant No.51601045)the Science and Technology Major Project of Guangxi(Grant No.GKAA17202007)the Guangxi“Bagui”Teams for Innovation and Research。
文摘In this study,7 xxx(Al-Zn-Mg-Cu)alloys with high Zn concentrations were fabricated by increasing the Zn contents of 7085 Al alloys.The hardness,quench sensitivity,and electrical conductivity of the alloys and a 7085 Al alloy under peak-aged state were studied.The high Zn concentration alloys had higherη′phase densities and lower quantities of Mg solid atoms than the 7085 Al alloy and thus exhibited higher hardness and electrical conductivity.The high Zn concentration alloys also exhibited slightly higher quench sensitivity than 7085 Al alloy,and the depth of the quenching layer of the alloy with 11.27 wt%Zn content reached 100 mm.This work confirmed that the novel 7 xxx alloy with high Zn concentration showed balanced performance,exhibiting enhanced hardness and conductivity and reasonable quench sensitivity compared with the 7085 commercial Al alloy.
基金supported by the National Key R&D Program of China(Grant No.2021YFA1600704)the National Natural Science Foundation of China(Grant Nos.52203385 and 52171056)+3 种基金CNNC Science Fund for Talented Young Scholarsthe IMR Innovation Fund(Grant No.2021-ZD02)the Natural Science Foundation of Liaoning Province(Grant No.2022-BS-009)Young Elite Scientists Sponsorship Program by CAST(Grant No.YESS20220225)。
文摘As a classic in-situ reaction, the Al-TiO_(2) reaction is expected to prepare aluminum matrix composites with high thermal stability.In this study, it was found that the preparation method of ensuring sufficient reaction using higher temperatures in previous studies was not conducive to acquiring optimized high-temperature strength. With the increase of hot-pressing temperature and the extension of holding time, the in-situ reaction became more thorough, but the strength of the composites first increased and then decreased. Coarsening of the microstructure at high temperatures would lead to degradation of strength and controlling the in-situ reaction process by the hot-pressing parameters could optimize the mechanical properties of the composites. Strengthening mechanisms at room and high temperatures were studied, and it was found that the load-transfer and Orowan strengthening mechanisms are the main strengthening effects at room temperature, while the pinning effect of fine particles became more crucial at elevated temperatures. As a result, the coarsening of the reinforcing phases was more detrimental to the hightemperature strength. Therefore, an insufficient in-situ reaction led to more excellent mechanical properties, and the composite hot-pressed at 605℃ and held for 2 h exhibited the highest strength, which was 367 MPa at room temperature and 170 MPa at 350℃.
