A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments （RRA）. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and tensil...A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments （RRA）. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and tensile tests were used to investigate the effects of RRA treatment on the microstructures and properties. DSC test reveals the reversion temperature range of the strengthening δ＇ （Al3Li） phase. The results show that the microstructure consists of δ＇ （Al3Li） phase, T1 （Al2CuLi） phase and θ″/θ′（Al2Cu） phase for 2A97 alloy treated by a triple-aging of a retrogression and re-aging treatment in the following order： （1） at 165℃×30 min, （2） at 220 ℃ or 240℃ × 15 min, （3） at 165℃×24 h. The plastic deformation, incorporated into the treatment after secondary high temperature aging, promotes the T1 precipitation during final re-aging. The tensile properties of the alloy treated by the retrogression and re-aging treatment reach the peak level of alloy single-aged at 165℃ in T6 temper.展开更多
The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and stren...The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and strength of samples of nine groups under duplex aging conditions and three retrogression and reaging heat treatments were also measured. Incorporating the microstructure and property, we found that when the condition of the first order aging kept identical, the fracture toughness and stress corrosion cracking resistance increase with aging time and the second aging temperature. The optimal treatment conditions are （ 115℃×7h ＋ 185 ℃×13h） among all tested two-stage aging treatments. Although the 7475 alloy treated by RRA method shows the highest strength and its stress corrosion cracking resistance after twenty minutes retrogression can also reach the same level as those by the optimal treatment of （115℃×7h＋ 185℃×13h ）, the fracture toughness is even low.展开更多
The effect of various retrogression and re-aging(RRA)treatments on mechanical properties and corrosion behavior of a new type Al-Zn-Mg-Cu-Er-Zr alloy was investigated by microhardness testing,tensile testing,intergran...The effect of various retrogression and re-aging(RRA)treatments on mechanical properties and corrosion behavior of a new type Al-Zn-Mg-Cu-Er-Zr alloy was investigated by microhardness testing,tensile testing,intergranular corrosion(IGC)and exfoliation corrosion(EXCO)testing.The results show that the RRA treatment can effectively improve the IGC and EXCO resistance with less strength sacrificing because the grain interior precipitates and the grain boundary precipitates are similar to that of T6 temper and T73 temper.Meanwhile,as the microhardness of the retrogressed alloy reaches the peak value during the retrogression at 170℃,the corresponding RRA-treated alloy possesses the better strength,but the corrosion resistance is poor in comparison with that of the retrogression at 190℃.The optimal combination of strength,IGC and EXCO resistance is obtained after retrogression at 180℃for 60 min.Moreover,for different heat treatment tempers,the corresponding micros true tural evolution of the precipitates including Al_(3)(Er,Zr)particles was also discussed in detail.展开更多
基金"973" Key Project of Chinese National Programs for Fundamental Research and Development (2005CB623705)
文摘A new high strength 2A97 Al-Cu-Li-X alloy was subjected to triple-aging of retrogression and re-aging treatments （RRA）. Transmission electron microscopy （TEM）, differential scanning calorimetry （DSC）, and tensile tests were used to investigate the effects of RRA treatment on the microstructures and properties. DSC test reveals the reversion temperature range of the strengthening δ＇ （Al3Li） phase. The results show that the microstructure consists of δ＇ （Al3Li） phase, T1 （Al2CuLi） phase and θ″/θ′（Al2Cu） phase for 2A97 alloy treated by a triple-aging of a retrogression and re-aging treatment in the following order： （1） at 165℃×30 min, （2） at 220 ℃ or 240℃ × 15 min, （3） at 165℃×24 h. The plastic deformation, incorporated into the treatment after secondary high temperature aging, promotes the T1 precipitation during final re-aging. The tensile properties of the alloy treated by the retrogression and re-aging treatment reach the peak level of alloy single-aged at 165℃ in T6 temper.
文摘The effects of two-stage aging and retrogression and reaging heat treatment on the fracture toughness and stress corrosion cracking resistance of 7475 alloy were studied. The fracture toughness, conductivity and strength of samples of nine groups under duplex aging conditions and three retrogression and reaging heat treatments were also measured. Incorporating the microstructure and property, we found that when the condition of the first order aging kept identical, the fracture toughness and stress corrosion cracking resistance increase with aging time and the second aging temperature. The optimal treatment conditions are （ 115℃×7h ＋ 185 ℃×13h） among all tested two-stage aging treatments. Although the 7475 alloy treated by RRA method shows the highest strength and its stress corrosion cracking resistance after twenty minutes retrogression can also reach the same level as those by the optimal treatment of （115℃×7h＋ 185℃×13h ）, the fracture toughness is even low.
基金financially supported by the National Key Basic Research&Development Plan Project(No.2012CB619503)。
文摘The effect of various retrogression and re-aging(RRA)treatments on mechanical properties and corrosion behavior of a new type Al-Zn-Mg-Cu-Er-Zr alloy was investigated by microhardness testing,tensile testing,intergranular corrosion(IGC)and exfoliation corrosion(EXCO)testing.The results show that the RRA treatment can effectively improve the IGC and EXCO resistance with less strength sacrificing because the grain interior precipitates and the grain boundary precipitates are similar to that of T6 temper and T73 temper.Meanwhile,as the microhardness of the retrogressed alloy reaches the peak value during the retrogression at 170℃,the corresponding RRA-treated alloy possesses the better strength,but the corrosion resistance is poor in comparison with that of the retrogression at 190℃.The optimal combination of strength,IGC and EXCO resistance is obtained after retrogression at 180℃for 60 min.Moreover,for different heat treatment tempers,the corresponding micros true tural evolution of the precipitates including Al_(3)(Er,Zr)particles was also discussed in detail.
