In the present work,the friction stir back extrusion(FSBE)process was used as a novel method for the fabrication of AA6063 aluminum alloy wire.Scanning electron microscopy(SEM)equipped with energy dispersive spectrosc...In the present work,the friction stir back extrusion(FSBE)process was used as a novel method for the fabrication of AA6063 aluminum alloy wire.Scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),tensile and hardness tests were performed.The FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains,and the mean grain size decreased from 179.0μm to 15.5μm due to the occurrence of dynamic recrystallization(DRX).Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated particles.The minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min,respectively.The 475-r/min sample had the maximum hardness value due to having the lowest grain size(i.e.,15.5μm)and the presence of many fine Mg2Si precipitates in the aluminum matrix.With increasing rotational speed up to 600 r/min,the hardness decreased,owing to the growth of both grains and precipitates.The FSBE process with a rotational speed of 475 r/min increased the tensile strength(from 150 to 209 MPa)and ductility(from 21.0%to 30.2%)simultaneously.展开更多
This article has been retracted:please see Elsevier Policy on Article Withdrawal(https:/www.elsevier.com/about/our-business/policies/articlewithdrawal).This article has been retracted at the request of the Editor.The ...This article has been retracted:please see Elsevier Policy on Article Withdrawal(https:/www.elsevier.com/about/our-business/policies/articlewithdrawal).This article has been retracted at the request of the Editor.The authors have plagiarized part of a paper by Omid Abouali and Goodarz Ahmadi that had already appeared in Journal of Nanoparticle Research(2005)7:75-88(https:/link.springer.com/article/10.1007/s11051-004-7910-3).展开更多
In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was ...In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was to investigate the effects of working parameters such as pressure ratio （50 〈 Po]Pb 〈 800）, nozzle diameters （D=0.23, 0.27, 0.45 mm）, nozzle to plate distance （0.5 〈L/D〈 50）, particle diameter （1 nm〈 dp 〈 100 nm ） and angle between two nozzles. A single-phase 3D unsteady-state model was implemented by the software. For this purpose, a user-defined function （UDF） was employed to implement nanoparticles for different assumptions of Cunningham correction factor. An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature; Lagrangian particle trajectory analysis was used for particle motion. Using the variable Cunningham cor- rection factor showed suitable agreement with experimental data in comparison with other methods. Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number, the distance between bow shock and impaction plate, and the collection efficiency. Maximum jet velocity, distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic imoactors.展开更多
基金financially supported by Grant program from Babol Noshirvani University of Technology (Nos.BNUT/370725/98 and BNUT/393044/98)
文摘In the present work,the friction stir back extrusion(FSBE)process was used as a novel method for the fabrication of AA6063 aluminum alloy wire.Scanning electron microscopy(SEM)equipped with energy dispersive spectroscopy(EDS),tensile and hardness tests were performed.The FSBE via the rotational speed of 475 r/min resulted in fine equiaxed grains,and the mean grain size decreased from 179.0μm to 15.5μm due to the occurrence of dynamic recrystallization(DRX).Heat generated by the FSBE changed the size and volume fraction of the Mg2Si precipitated particles.The minimum particle size and maximum volume fraction obtained in the sample were processed by rotational speeds of 475 and 600 r/min,respectively.The 475-r/min sample had the maximum hardness value due to having the lowest grain size(i.e.,15.5μm)and the presence of many fine Mg2Si precipitates in the aluminum matrix.With increasing rotational speed up to 600 r/min,the hardness decreased,owing to the growth of both grains and precipitates.The FSBE process with a rotational speed of 475 r/min increased the tensile strength(from 150 to 209 MPa)and ductility(from 21.0%to 30.2%)simultaneously.
文摘This article has been retracted:please see Elsevier Policy on Article Withdrawal(https:/www.elsevier.com/about/our-business/policies/articlewithdrawal).This article has been retracted at the request of the Editor.The authors have plagiarized part of a paper by Omid Abouali and Goodarz Ahmadi that had already appeared in Journal of Nanoparticle Research(2005)7:75-88(https:/link.springer.com/article/10.1007/s11051-004-7910-3).
文摘In this study, numerical simulation of flow field in a supersonic/hypersonic impactor with one or two nozzles was carried out using a commercial computational fluid dynamics （CFD） software FLUENT. The objective was to investigate the effects of working parameters such as pressure ratio （50 〈 Po]Pb 〈 800）, nozzle diameters （D=0.23, 0.27, 0.45 mm）, nozzle to plate distance （0.5 〈L/D〈 50）, particle diameter （1 nm〈 dp 〈 100 nm ） and angle between two nozzles. A single-phase 3D unsteady-state model was implemented by the software. For this purpose, a user-defined function （UDF） was employed to implement nanoparticles for different assumptions of Cunningham correction factor. An axisymmetric form of the compressible Navier-Stokes and energy equations was used for both fluid flow and temperature; Lagrangian particle trajectory analysis was used for particle motion. Using the variable Cunningham cor- rection factor showed suitable agreement with experimental data in comparison with other methods. Results show that increase of the distance between nozzle and impaction plate causes increase of Mach number, the distance between bow shock and impaction plate, and the collection efficiency. Maximum jet velocity, distance between bow shock and impaction plate and collection efficiency increase by using two nozzles in supersonic and hypersonic imoactors.
