The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensi...The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensitivity of the 7xxx Al alloys were studied.The alloys with high Zn content and Sc addition exhibited higher hardness than the 7085 alloy at the position 3 mm away from the quenching end.The density ofηand T phases increased with the increase in Zn and Cu contents,and the Sc addition led to the formation of the Y phase and moreηphases at the position 120 mm away from the quenching end.Compared with the 7085 alloy,the high Zn−high Cu and Sc-added alloys exhibited higher quench sensitivity,while the simultaneous increase in Zn content and decrease in Cu content could enhance the hardness and reduce the quench sensitivity of the 7085 alloy.展开更多
The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included...The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included a braking pressure of 1.25 MPa and an initial braking speed(IBS) of 200-350 km/h in a braking process of high-speed train according to the scale-conversion rules. The tribo-couple materials were characterized using scanning electron microscopy(SEM), X-ray diffractometry(XRD), and energy-dispersive X-ray spectrometry(EDS). It is found that the matching tribo-couple features low friction surface temperature, reliable friction factor, and high durability. The continuous lubricating mechanically-mixed layer(MML) forms gradually on the worn surfaces of ring in the friction process. The MML is heterogeneous, which greatly controls wear rate and coefficient of friction(COF) of the composites. The wear mechanism of SiC3D/Al is typically abrasive wear at an IBS of 200-300 km/h. When the IBS increases to 350 km/h, oxidation wear and delamination are observed. The friction behavior of the tribo-couple predicted using Solidwork simulation software agrees well with the experimental results. The tribo-couple meets the requirement of emergency braking of high-speed train.展开更多
In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of Ti...In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of TiC.The effects of TiC content on the microstructure,mechanical properties,and corrosion resistance of the alloy were investigated.It was found that the precipitation morphologies of TiC changed from lamellar eutectic to needle structure with the increase of TiC content,and finally formed mixed needled and bulk TiC particles.TiC appears as a dissolution−precipitation phenomenon in the CoCrNi alloy,which is important for the mechanical properties and corrosion resistance of the CoCrNi/(TiC)_(x) alloy.The strength of alloy was enhanced obviously after the addition of TiC.The compressive yield strength of CoCrNi/(TiC)_(0.4) alloy reached 746 MPa,much larger than that of the CoCrNi medium entropy alloy,108 MPa.Additionally,the addition of TiC was found to improve the corrosion resistance of CoCrNi medium entropy alloy in the salt solution.展开更多
A transient numerical model was applied to simulating the axial-directional crystallization purification(ADCP) process of gallium(Ga) raw material at different coolant temperatures(Tc), and the evolutions of melt/crys...A transient numerical model was applied to simulating the axial-directional crystallization purification(ADCP) process of gallium(Ga) raw material at different coolant temperatures(Tc), and the evolutions of melt/crystal(m/c) interface shape, temperature distribution and thermal stresses were simulated and analyzed. The results showed that the m/c interface shape, temperature distribution, and thermal stress in the Ga material were determined by the Tc in the crystallizer during the ADCP process. The temperature gradient and thermal stress in the grown Ga crystal increased with decreasing Tc. At Tc=15 ℃, the m/c interface shape was flat, and the temperature gradient was ideal. Therefore, the Ga materials with lower thermal stresses and suitable m/c interface shape, and an ideal efficiency of impurity removal were obtained. The purity of Ga reached 6 N standard by using ADCP process repeated 6 times at Tc of 15 ℃. The results of the simulation showed good agreement with the experimental results.展开更多
基金The authors are grateful for the financial supports from the Science and Technology Major Project of Guangxi,China(GKAA17202007).
文摘The Zn,Cu,and Sc contents of 7xxx Al alloys were adjusted according to the chemical composition of a 7085 Al alloy,and the effects of Zn and Cu contents and Sc addition on the microstructures,hardness,and quench sensitivity of the 7xxx Al alloys were studied.The alloys with high Zn content and Sc addition exhibited higher hardness than the 7085 alloy at the position 3 mm away from the quenching end.The density ofηand T phases increased with the increase in Zn and Cu contents,and the Sc addition led to the formation of the Y phase and moreηphases at the position 120 mm away from the quenching end.Compared with the 7085 alloy,the high Zn−high Cu and Sc-added alloys exhibited higher quench sensitivity,while the simultaneous increase in Zn content and decrease in Cu content could enhance the hardness and reduce the quench sensitivity of the 7085 alloy.
基金Project(51465014)supported by the National Natural Science Foundation of ChinaProject(1099043)supported by Scientific and Technological Research Program of Guangxi,ChinaProjects(2014GXNSFAA118351,2014GXNSFAA118329,2012GXNSFBA053156)supported by the Natural Science Foundation of Guangxi,China
文摘The friction and wear properties of interpenetrating phase composites(IPC) SiC3D/Al sliding against graphite/SiC(G/SiC) composites were investigated using a sub-scale brake dynamometer. The testing conditions included a braking pressure of 1.25 MPa and an initial braking speed(IBS) of 200-350 km/h in a braking process of high-speed train according to the scale-conversion rules. The tribo-couple materials were characterized using scanning electron microscopy(SEM), X-ray diffractometry(XRD), and energy-dispersive X-ray spectrometry(EDS). It is found that the matching tribo-couple features low friction surface temperature, reliable friction factor, and high durability. The continuous lubricating mechanically-mixed layer(MML) forms gradually on the worn surfaces of ring in the friction process. The MML is heterogeneous, which greatly controls wear rate and coefficient of friction(COF) of the composites. The wear mechanism of SiC3D/Al is typically abrasive wear at an IBS of 200-300 km/h. When the IBS increases to 350 km/h, oxidation wear and delamination are observed. The friction behavior of the tribo-couple predicted using Solidwork simulation software agrees well with the experimental results. The tribo-couple meets the requirement of emergency braking of high-speed train.
基金sponsored by the National Key R&D Program of China (No.2018YFC1902401)the National Natural Science Foundation of China(No.52005053)Open Fund of Key Laboratory of New Processing Technology for Nonferrous Metal & Materials Ministry of Education,China (No.20KF-24)。
文摘In order to improve the strength and corrosion resistance of CoCrNi medium entropy alloy,TiC strengthened CoCrNi medium entropy alloy(CoCrNi/(TiC)_(x)(x=0.1,0.2,0.4))was designed by addition of different amounts of TiC.The effects of TiC content on the microstructure,mechanical properties,and corrosion resistance of the alloy were investigated.It was found that the precipitation morphologies of TiC changed from lamellar eutectic to needle structure with the increase of TiC content,and finally formed mixed needled and bulk TiC particles.TiC appears as a dissolution−precipitation phenomenon in the CoCrNi alloy,which is important for the mechanical properties and corrosion resistance of the CoCrNi/(TiC)_(x) alloy.The strength of alloy was enhanced obviously after the addition of TiC.The compressive yield strength of CoCrNi/(TiC)_(0.4) alloy reached 746 MPa,much larger than that of the CoCrNi medium entropy alloy,108 MPa.Additionally,the addition of TiC was found to improve the corrosion resistance of CoCrNi medium entropy alloy in the salt solution.
基金Project(51465014)supported by the National Natural Science Foundation of ChinaProject(Guike AA17204021-7)supported by the Innovation Driven Development Special Foundation of Guangxi,China。
文摘A transient numerical model was applied to simulating the axial-directional crystallization purification(ADCP) process of gallium(Ga) raw material at different coolant temperatures(Tc), and the evolutions of melt/crystal(m/c) interface shape, temperature distribution and thermal stresses were simulated and analyzed. The results showed that the m/c interface shape, temperature distribution, and thermal stress in the Ga material were determined by the Tc in the crystallizer during the ADCP process. The temperature gradient and thermal stress in the grown Ga crystal increased with decreasing Tc. At Tc=15 ℃, the m/c interface shape was flat, and the temperature gradient was ideal. Therefore, the Ga materials with lower thermal stresses and suitable m/c interface shape, and an ideal efficiency of impurity removal were obtained. The purity of Ga reached 6 N standard by using ADCP process repeated 6 times at Tc of 15 ℃. The results of the simulation showed good agreement with the experimental results.
