The influences of artificial aging on the microstructures and mechanical properties of an Al-1.01Mg-0.68Si-1.78Cu alloy were investigated. The detailed fracture surfaces, precipitates, and dislocation structures were ...The influences of artificial aging on the microstructures and mechanical properties of an Al-1.01Mg-0.68Si-1.78Cu alloy were investigated. The detailed fracture surfaces, precipitates, and dislocation structures were also examined through scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the tensile strengths exhibit two peak values and reach saturated values with increasing aging time, while the elongation decreases sharply to the minimum value and changes slightly later. The deformation and fracture behaviors are also closely related to the aging conditions.展开更多
The micro-porosity is usually present in the as-cast microstructure, which decreases the tensile strength and ductility and therefore limit the application of cast aluminum parts. Although much work has been done to i...The micro-porosity is usually present in the as-cast microstructure, which decreases the tensile strength and ductility and therefore limit the application of cast aluminum parts. Although much work has been done to investigate the effects of various casting parameters on the formation of porosity in various aluminum alloys, up to now, little information has been available for the relationship between micro-porosity and tensile properties of 6063 alloy. In this study, the influences of size and area fraction of micro=porosity on the tensile properties and fracture behavior of 6063 aluminum alloy were investigated by means of tensile testing, optical microscopy （OM）, and scanning electron microscopy （SEM）. The tensile tests were conducted in air at 100 ℃, 200 ℃ and 300 ℃, respectively. Results show that the large micro-porosity with sizes between 100 pm and 800μm located at the center and top of the ingot, while the small micro-porosity with size between 2 IJm and 60 μm distributed at the edge and bottom of the ingot. The area fraction of micro-porosity at the center of the ingot is much bigger than that at the edge of the ingot. When tested at 100 ℃, with the decrease in the area fraction of micro-porosity from the top of the ingot to the bottom of the ingot, the ultimate tensile strength, yield strength and the elongation are increased from 82 to 99 MPa, 32 to 66 MPa and 7% to 11%, respectively. When the temperature is no more than 200 ℃, the strain hardening exponent decreases with an increase in the area fraction of micro-porosity; while the deviation disappears when the temperature reaches 300 ℃. The fracture mode of the alloy is greatly influenced by the size and area fraction of the micro-porosity.展开更多
The ultrafine grained(UFG)1050 aluminum alloy was prepared by equal channel angular pressing at cryogenic temperature,namely cryoECAP process.The tensile behavior and microstructures of UFG 1050 aluminum alloy after a...The ultrafine grained(UFG)1050 aluminum alloy was prepared by equal channel angular pressing at cryogenic temperature,namely cryoECAP process.The tensile behavior and microstructures of UFG 1050 aluminum alloy after annealing at 90-210°C for 4 h without and with high magnetic field of 12 T were investigated by tensile tests,transmission electron microscope,and electron backscattered diffraction analyses.After cryoECAP and annealing treatments,the 1050 aluminum alloy has ultrafine grains with 0.7-1.28μm in size,the ratio of ultimate tensile strength to yield strength is less than 1.24,and the uniform elongation is less than 2.3%.With increasing the annealing temperature from 90°C to 210°C,the yield-drop phenomenon becomes more obvious due to the decrease in mobile dislocations to maintain the applied strain rate during tensile deformation.The uniform elongation decreases from 1.55%to 0.55%,the dislocation density reduces from 5.6×10^(14)m^(−2)to 4.2×10^(13)m^(−2),and the fraction of high-angle grain boundaries(HABs)increases from 63.8%to 70.8%.These phenomena cause the higher annihilation rate of dislocations,thereby leading to the degradation of strain hardening effect.During annealing under high magnetic field at 90-210°C,the low fraction of HABs(61.7%-66.2%)can provide a slower annihilation rate of dislocations,therefore resulting in the higher uniform elongation(0.64%-1.60%)and slower decrease in the flow stress after the yield peak.展开更多
基金the National High-Tech Research and Development Program of China (No. (98-A28-01-09)
文摘The influences of artificial aging on the microstructures and mechanical properties of an Al-1.01Mg-0.68Si-1.78Cu alloy were investigated. The detailed fracture surfaces, precipitates, and dislocation structures were also examined through scanning electron microscopy （SEM） and transmission electron microscopy （TEM）. The results show that the tensile strengths exhibit two peak values and reach saturated values with increasing aging time, while the elongation decreases sharply to the minimum value and changes slightly later. The deformation and fracture behaviors are also closely related to the aging conditions.
基金supported by the Fundamental Research Funds for the Central Universities of China(Grant No.N100409002)
文摘The micro-porosity is usually present in the as-cast microstructure, which decreases the tensile strength and ductility and therefore limit the application of cast aluminum parts. Although much work has been done to investigate the effects of various casting parameters on the formation of porosity in various aluminum alloys, up to now, little information has been available for the relationship between micro-porosity and tensile properties of 6063 alloy. In this study, the influences of size and area fraction of micro=porosity on the tensile properties and fracture behavior of 6063 aluminum alloy were investigated by means of tensile testing, optical microscopy （OM）, and scanning electron microscopy （SEM）. The tensile tests were conducted in air at 100 ℃, 200 ℃ and 300 ℃, respectively. Results show that the large micro-porosity with sizes between 100 pm and 800μm located at the center and top of the ingot, while the small micro-porosity with size between 2 IJm and 60 μm distributed at the edge and bottom of the ingot. The area fraction of micro-porosity at the center of the ingot is much bigger than that at the edge of the ingot. When tested at 100 ℃, with the decrease in the area fraction of micro-porosity from the top of the ingot to the bottom of the ingot, the ultimate tensile strength, yield strength and the elongation are increased from 82 to 99 MPa, 32 to 66 MPa and 7% to 11%, respectively. When the temperature is no more than 200 ℃, the strain hardening exponent decreases with an increase in the area fraction of micro-porosity; while the deviation disappears when the temperature reaches 300 ℃. The fracture mode of the alloy is greatly influenced by the size and area fraction of the micro-porosity.
基金National Natural Science Foundation of China(51574076)。
文摘The ultrafine grained(UFG)1050 aluminum alloy was prepared by equal channel angular pressing at cryogenic temperature,namely cryoECAP process.The tensile behavior and microstructures of UFG 1050 aluminum alloy after annealing at 90-210°C for 4 h without and with high magnetic field of 12 T were investigated by tensile tests,transmission electron microscope,and electron backscattered diffraction analyses.After cryoECAP and annealing treatments,the 1050 aluminum alloy has ultrafine grains with 0.7-1.28μm in size,the ratio of ultimate tensile strength to yield strength is less than 1.24,and the uniform elongation is less than 2.3%.With increasing the annealing temperature from 90°C to 210°C,the yield-drop phenomenon becomes more obvious due to the decrease in mobile dislocations to maintain the applied strain rate during tensile deformation.The uniform elongation decreases from 1.55%to 0.55%,the dislocation density reduces from 5.6×10^(14)m^(−2)to 4.2×10^(13)m^(−2),and the fraction of high-angle grain boundaries(HABs)increases from 63.8%to 70.8%.These phenomena cause the higher annihilation rate of dislocations,thereby leading to the degradation of strain hardening effect.During annealing under high magnetic field at 90-210°C,the low fraction of HABs(61.7%-66.2%)can provide a slower annihilation rate of dislocations,therefore resulting in the higher uniform elongation(0.64%-1.60%)and slower decrease in the flow stress after the yield peak.
