The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morpholo...The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.展开更多
By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimens...By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimension of die leg （D）, process velocity and initial billet temperature were used in FE simulations so as to determine the conditions in which better longitudinal welding quality can be obtained. According to K criterion, the local welding parameters such as welding pressure, effective stress and welding path length on the welding plane are linked to longitudinal welds quality. Simulation turns out that pressure-to-effective stress ratio （ρ/σ） and welding path length （L） are the key factors affecting the welding quality, Higher welding chamber best and sharper die leg give better welding quality. When H=10 mm and D=0.4 mm, the longitudinal welds have the best quality. Higher process velocity decreases welds quality. The proper velocity is 10 mm/s for this simulation. In a certain range, higher temperature is beneficial to the longitudinal welds. It is found that both 450 and 465℃ can satisfy the requirements of the longitudinal welds.展开更多
The 4-lobe aluminum alloy helical surface rotors are widely applied in industry,such as superchargers.Generally,the conventional manufacturing processes of aluminum alloy helical surface are time consuming and costly....The 4-lobe aluminum alloy helical surface rotors are widely applied in industry,such as superchargers.Generally,the conventional manufacturing processes of aluminum alloy helical surface are time consuming and costly.To make the manufacturing processes more flexible and economical,the forward hot extrusion process is proposed to form the 4-lobe aluminum alloy helical surface rotors.In this work,we implement both simulations and experiments to the forming process of the helical surface,of which the material is 6063 aluminum alloy.The forward hot extrusion process is simulated with finite element method in DEFORM-3D.Based on the simulation method,the influences of different extrusion parameters,such as extrusion temperature,extrusion speed and extrusion ratio,on the extrusion process are studied.According to the numerical simulation results,the optimal case is chosen to carry out the experiment.Furthermore,the experimental results show that the surface is smooth;the toothed fill is full;the twist angle in the length direction is evenly distributed;the value of twist angle is roughly in line with the design angle,which is mainly due to the modified die structure,having a positive and significant effect on the increment of twist angle.Therefore,the twist angle has an increase of about 76%,which verifies the modified die structure.展开更多
The aluminum alloys belonging to the 7000 series are high-strength alloys used in a wide variety of products for weight reduction.They are primarily used in the field of transportation and aerospace.Among these,the A7...The aluminum alloys belonging to the 7000 series are high-strength alloys used in a wide variety of products for weight reduction.They are primarily used in the field of transportation and aerospace.Among these,the A7075 alloy has the highest strength and is expected to be applicable in a wide range of fields,such as aircraft components and sports equipment.However,it has high deformation resistance and is prone to surface defects,which is called tearing.Tearing typically occurs at high temperatures and high ram speeds,and adversely affects productivity.The localized melting of Zn and additive compounds,due to the heat generated during the process,is considered to cause tearing.In this study,the effect of friction,heat,and tearing at the tool-metal interface was mitigated by improving the die surface quality.The reduced friction eliminated recrystallization by preventing the temperature from increasing to recrystallization temperature.In addition,an AlCrN coating was adopted instead of nitriding to improve the die surface quality.The tearing size and heat generated when using the AlCrN coating were found to be limited.Moreover,the grain size observed in the tearing region on the extruded surface was small.The simulations using the shear friction coefficient m observed from friction tests indicate that the use of the AlCrN coating improved the material flow.Thus,the AlCrN coating is considered effective for reducing friction at the interface and preventing the recrystallization of the extruded surface.From the aforementioned results,it can be inferred that a die coating can reduce the tearing sensitivity and increase the productivity of the A7075 alloy.展开更多
基金Project(U1664252)supported by the National Natural Science Foundation of China
文摘The effect of dynamic recrystallization(DRX)on the microstructure and mechanical properties of 6063 aluminum alloy profile during porthole die extrusion was studied through experiment and simulation.The grain morphology was observed by means of electron backscatter diffraction(EBSD)technology.The results show that,at low ram speeds,increasing the ram speed caused an increase in DRX fraction due to the increase of temperature and strain rate.In contrast,at high ram speeds,further increasing ram speed had much less effect on the temperature,and the DRX faction decreased due to high stain rates.The microhardness and fraction of low angle boundaries in the welding zones were lower than those in the matrix zones.The grain size in the welding zone was smaller than that in the matrix zone due to lower DRX fraction.The decrease of grain size and increase of extrudate temperature were beneficial to the improvement of microhardness.
基金Project(2007BAE38BO4) supported by the National Science and Technology Pillar Program
文摘By using the rigid-visco-plasticity finite element method, the welding process of aluminum porthole die extrusion to form a tube was simulated based on Deform-3D software. The welding chamber height （H）, back dimension of die leg （D）, process velocity and initial billet temperature were used in FE simulations so as to determine the conditions in which better longitudinal welding quality can be obtained. According to K criterion, the local welding parameters such as welding pressure, effective stress and welding path length on the welding plane are linked to longitudinal welds quality. Simulation turns out that pressure-to-effective stress ratio （ρ/σ） and welding path length （L） are the key factors affecting the welding quality, Higher welding chamber best and sharper die leg give better welding quality. When H=10 mm and D=0.4 mm, the longitudinal welds have the best quality. Higher process velocity decreases welds quality. The proper velocity is 10 mm/s for this simulation. In a certain range, higher temperature is beneficial to the longitudinal welds. It is found that both 450 and 465℃ can satisfy the requirements of the longitudinal welds.
基金Project(zzyjkt2014-09)supported by the National Key Laboratory of High Performance and Complex Manufacturing,ChinaProject(2015GK3006)supported by Key R&D Program of Science and Technology Department of Hunan Province,China
文摘The 4-lobe aluminum alloy helical surface rotors are widely applied in industry,such as superchargers.Generally,the conventional manufacturing processes of aluminum alloy helical surface are time consuming and costly.To make the manufacturing processes more flexible and economical,the forward hot extrusion process is proposed to form the 4-lobe aluminum alloy helical surface rotors.In this work,we implement both simulations and experiments to the forming process of the helical surface,of which the material is 6063 aluminum alloy.The forward hot extrusion process is simulated with finite element method in DEFORM-3D.Based on the simulation method,the influences of different extrusion parameters,such as extrusion temperature,extrusion speed and extrusion ratio,on the extrusion process are studied.According to the numerical simulation results,the optimal case is chosen to carry out the experiment.Furthermore,the experimental results show that the surface is smooth;the toothed fill is full;the twist angle in the length direction is evenly distributed;the value of twist angle is roughly in line with the design angle,which is mainly due to the modified die structure,having a positive and significant effect on the increment of twist angle.Therefore,the twist angle has an increase of about 76%,which verifies the modified die structure.
文摘The aluminum alloys belonging to the 7000 series are high-strength alloys used in a wide variety of products for weight reduction.They are primarily used in the field of transportation and aerospace.Among these,the A7075 alloy has the highest strength and is expected to be applicable in a wide range of fields,such as aircraft components and sports equipment.However,it has high deformation resistance and is prone to surface defects,which is called tearing.Tearing typically occurs at high temperatures and high ram speeds,and adversely affects productivity.The localized melting of Zn and additive compounds,due to the heat generated during the process,is considered to cause tearing.In this study,the effect of friction,heat,and tearing at the tool-metal interface was mitigated by improving the die surface quality.The reduced friction eliminated recrystallization by preventing the temperature from increasing to recrystallization temperature.In addition,an AlCrN coating was adopted instead of nitriding to improve the die surface quality.The tearing size and heat generated when using the AlCrN coating were found to be limited.Moreover,the grain size observed in the tearing region on the extruded surface was small.The simulations using the shear friction coefficient m observed from friction tests indicate that the use of the AlCrN coating improved the material flow.Thus,the AlCrN coating is considered effective for reducing friction at the interface and preventing the recrystallization of the extruded surface.From the aforementioned results,it can be inferred that a die coating can reduce the tearing sensitivity and increase the productivity of the A7075 alloy.
