In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the stand...In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the standard artificial aging treatment for Al-Cu alloy followed heat treatments of solution treatment at 510-530 ℃ for 2 h,quenching in water at 60 ℃ and then artificial aging at 160-190 ℃ for 2-8 h.The effects of solution treatment and artificial aging on the microstructure and mechanical properties of Al-Cu alloy were studied by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,transmission electron microscopy（TEM） and tensile test.The results of solution treatment indicate that the mechanical properties of Al-Cu alloy increase and then decrease with the increase of solution temperature.This is because the residual phases dissolve gradually into the matrix,and the fraction of the precipitation and the size of the re-crystallized grain increased.Compared to the solution temperature,the solution holding time has less effect on the microstructure and the mechanical properties of Al-Cu alloy.The artificial aging treatments were conducted at 160-180 ℃ for 2-8 h.The results show that the ultimate tensile strength can be obtained at 180 ℃ for 8 h.Ultimate tensile strength increased with increasing time or temperature.Yield strength was found as the same as the ultimate tensile strength result.展开更多
The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for ...The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for solution treatment and aging treatment. Experimental results show that the dendritic arms are broken and a large quantity of equiaxed grains appear in the microstructure of specimens with electromagnetic stirring(EMS).With the increase of the quenching temperature(150-350℃),the solution of Mg and Al in solidβphase increases,and the Brinell hardness of the alloy increases as well.Aging peak and over aging happen becauseθ(MgLi_2Al) which precipitates in theβmatrix and strengthens the alloy is unstable and transforms to stable AlLi phase.Aging curves of EMS specimens change in a smaller amplitude.展开更多
Single aging effects on the microstructures and the room-temperature mechanical properties of Al-3.5Cu-1.5Li-0.22（Sc+Zr） alloy were observed using TEM, tensile test and hardness test at room temperature. The results...Single aging effects on the microstructures and the room-temperature mechanical properties of Al-3.5Cu-1.5Li-0.22（Sc+Zr） alloy were observed using TEM, tensile test and hardness test at room temperature. The results show that the alloy has the character of aging hardening. The aging temperature and aging time have significant effects on the amount and distribution of the major phase of precipitation and strengthening of the alloy. At both high and low temperatures, the precipitation caused by aging is few and coarse, but at high temperature, the coarse equilibrium phases are visible at grain boundaries, therefore, influencing the composite properties of the alloy. The proper artificial single-aging treatment of the alloy is 160℃, 40h. Under this condition, the alloy obtains homogeneously distributed fine T1 phases, which leads to an optimal mechanical properties, i.e. σb is 483MPa, σ 0.2 is 413MPa, and δ is 8.4% for the alloy. However, extending overaging to 50h at 160℃, the coarse equilibrium phases precipitate at grain boundaries leads to wide precipitates-free zone（PFZ） along the grain boundaries, further results in a decrease in the composite properties of the alloy.展开更多
文摘In order to achieve good mechanical properties of Al-Cu alloys such as high strength and good toughness,precipitation hardening and artificial aging treatment were applied.As defined by the T6 heat treatment,the standard artificial aging treatment for Al-Cu alloy followed heat treatments of solution treatment at 510-530 ℃ for 2 h,quenching in water at 60 ℃ and then artificial aging at 160-190 ℃ for 2-8 h.The effects of solution treatment and artificial aging on the microstructure and mechanical properties of Al-Cu alloy were studied by optical microscopy（OM）,scanning electron microscopy（SEM）,energy dispersive X-ray spectroscopy（EDS）,transmission electron microscopy（TEM） and tensile test.The results of solution treatment indicate that the mechanical properties of Al-Cu alloy increase and then decrease with the increase of solution temperature.This is because the residual phases dissolve gradually into the matrix,and the fraction of the precipitation and the size of the re-crystallized grain increased.Compared to the solution temperature,the solution holding time has less effect on the microstructure and the mechanical properties of Al-Cu alloy.The artificial aging treatments were conducted at 160-180 ℃ for 2-8 h.The results show that the ultimate tensile strength can be obtained at 180 ℃ for 8 h.Ultimate tensile strength increased with increasing time or temperature.Yield strength was found as the same as the ultimate tensile strength result.
基金Project(107031)supported by the Key Grant of Science & Technology of the Ministry of Education of China
文摘The effects of external fields such as electromagnetic field on the structure and heat treatment behavior of Mg-Li-Al alloys were studied.Mg-8Li-3Al alloys cast with and without electromagnetic stirring were used for solution treatment and aging treatment. Experimental results show that the dendritic arms are broken and a large quantity of equiaxed grains appear in the microstructure of specimens with electromagnetic stirring(EMS).With the increase of the quenching temperature(150-350℃),the solution of Mg and Al in solidβphase increases,and the Brinell hardness of the alloy increases as well.Aging peak and over aging happen becauseθ(MgLi_2Al) which precipitates in theβmatrix and strengthens the alloy is unstable and transforms to stable AlLi phase.Aging curves of EMS specimens change in a smaller amplitude.
文摘Single aging effects on the microstructures and the room-temperature mechanical properties of Al-3.5Cu-1.5Li-0.22（Sc+Zr） alloy were observed using TEM, tensile test and hardness test at room temperature. The results show that the alloy has the character of aging hardening. The aging temperature and aging time have significant effects on the amount and distribution of the major phase of precipitation and strengthening of the alloy. At both high and low temperatures, the precipitation caused by aging is few and coarse, but at high temperature, the coarse equilibrium phases are visible at grain boundaries, therefore, influencing the composite properties of the alloy. The proper artificial single-aging treatment of the alloy is 160℃, 40h. Under this condition, the alloy obtains homogeneously distributed fine T1 phases, which leads to an optimal mechanical properties, i.e. σb is 483MPa, σ 0.2 is 413MPa, and δ is 8.4% for the alloy. However, extending overaging to 50h at 160℃, the coarse equilibrium phases precipitate at grain boundaries leads to wide precipitates-free zone（PFZ） along the grain boundaries, further results in a decrease in the composite properties of the alloy.
