The aging behaviors of Al 1.42%Li 2.41%Cu 0.93%Mg 0.073%Zr 0.17%Sc(mass fraction, the same below) alloy at room temperature, 160 ℃ , and 160 ℃ after 8% pre deformation were studied respectively by hardness measureme...The aging behaviors of Al 1.42%Li 2.41%Cu 0.93%Mg 0.073%Zr 0.17%Sc(mass fraction, the same below) alloy at room temperature, 160 ℃ , and 160 ℃ after 8% pre deformation were studied respectively by hardness measurement. The microstructure of the alloy in various aging conditions was observed by TEM. The results show that the main precipitations of the alloy in quenching condition are the particles containing Sc and Zr which have certain coherent relation with the matrix. Addition of Sc in Al Li Cu Mg Zr alloy will be favorable to promoting precipitation. The particles can serve as preferred nucleation sites for δ′ phases which accelerate the aging hardening rate at initial aging. The main hardening phases of the alloy aged at 160 ℃ are δ′ and δ′/β′ composite precipitates. The size of the composite precipitates is very small (nanometer size). The composite precipitates will preclude efficiently the formation concentrative slip location and will improve the mechanical properties of the alloy. S′ phase will occur in the alloy aged at 160 ℃ after 8% pre deformation. It is found that 8% pre deformation has no obvious influence on the precipitation of the composite phase.展开更多
The influence of grain structure and Ce on the strength ductility combination for aluminum lithium alloy was investigated. The strength ductility combination of pancake shape unrecrystallized grains is superior to...The influence of grain structure and Ce on the strength ductility combination for aluminum lithium alloy was investigated. The strength ductility combination of pancake shape unrecrystallized grains is superior to that of recrystallized grains. A significant improvement in strength ductility combination can be achieved by adding Ce to alloy 2090. According to the research results about fracture and properties of monotonic tension for Al Li alloys 2090 and 2090+Ce, the relationship among grain structure, strength differences between grain within and grain boundary, stress localization degree at grain boundary and extrinsic strengthening effect was researched. The method and mechanisms of optimizing strength ductility were discussed, including grain structure, subgrain, T 1 phase, rare earth element Ce and aging procedure.展开更多
The effect of electric current pulse on the grain growth in the superplastic deformation of 2091 Al Li alloy was investigated. Optical metallographic microstructure observation and average linear intercept measuring r...The effect of electric current pulse on the grain growth in the superplastic deformation of 2091 Al Li alloy was investigated. Optical metallographic microstructure observation and average linear intercept measuring results show that at same strain, the grain size in the superplastic deformation loaded with electric current pulse is smaller than that unemploying electric current pulse, and so does the grain growth rate. TEM observation shows that the dislocation density at grain boundary in the superplastic deformation applied with electric current pulse is lower than that unemploying electric current pulse.It indicates that electric current pulse increases the rate of dislocation slip and climb in grain boundary, which leads to a decrease of both the density of the dislocation slipping across grain boundary at same strain rate and the driving force for grain growth, therefore the rate of grain growth decreases.The established model for grain growth shows an exponential relation of grain size with strain.展开更多
基金The Key Program of the 9th Five year Plan of China!(No .95 YS 0 0 1)
文摘The aging behaviors of Al 1.42%Li 2.41%Cu 0.93%Mg 0.073%Zr 0.17%Sc(mass fraction, the same below) alloy at room temperature, 160 ℃ , and 160 ℃ after 8% pre deformation were studied respectively by hardness measurement. The microstructure of the alloy in various aging conditions was observed by TEM. The results show that the main precipitations of the alloy in quenching condition are the particles containing Sc and Zr which have certain coherent relation with the matrix. Addition of Sc in Al Li Cu Mg Zr alloy will be favorable to promoting precipitation. The particles can serve as preferred nucleation sites for δ′ phases which accelerate the aging hardening rate at initial aging. The main hardening phases of the alloy aged at 160 ℃ are δ′ and δ′/β′ composite precipitates. The size of the composite precipitates is very small (nanometer size). The composite precipitates will preclude efficiently the formation concentrative slip location and will improve the mechanical properties of the alloy. S′ phase will occur in the alloy aged at 160 ℃ after 8% pre deformation. It is found that 8% pre deformation has no obvious influence on the precipitation of the composite phase.
文摘The influence of grain structure and Ce on the strength ductility combination for aluminum lithium alloy was investigated. The strength ductility combination of pancake shape unrecrystallized grains is superior to that of recrystallized grains. A significant improvement in strength ductility combination can be achieved by adding Ce to alloy 2090. According to the research results about fracture and properties of monotonic tension for Al Li alloys 2090 and 2090+Ce, the relationship among grain structure, strength differences between grain within and grain boundary, stress localization degree at grain boundary and extrinsic strengthening effect was researched. The method and mechanisms of optimizing strength ductility were discussed, including grain structure, subgrain, T 1 phase, rare earth element Ce and aging procedure.
文摘The effect of electric current pulse on the grain growth in the superplastic deformation of 2091 Al Li alloy was investigated. Optical metallographic microstructure observation and average linear intercept measuring results show that at same strain, the grain size in the superplastic deformation loaded with electric current pulse is smaller than that unemploying electric current pulse, and so does the grain growth rate. TEM observation shows that the dislocation density at grain boundary in the superplastic deformation applied with electric current pulse is lower than that unemploying electric current pulse.It indicates that electric current pulse increases the rate of dislocation slip and climb in grain boundary, which leads to a decrease of both the density of the dislocation slipping across grain boundary at same strain rate and the driving force for grain growth, therefore the rate of grain growth decreases.The established model for grain growth shows an exponential relation of grain size with strain.
