Two heat treatments of A356 alloys with combined addition of rare earth and strontium were conducted.T6 treatment is a long time treatment（solution at 535 ℃ for 4 h ＋ aging at 150 ℃ for 15 h）.The other treatment ...Two heat treatments of A356 alloys with combined addition of rare earth and strontium were conducted.T6 treatment is a long time treatment（solution at 535 ℃ for 4 h ＋ aging at 150 ℃ for 15 h）.The other treatment is a short time treatment（solution at 550 ℃ for 2 h ＋ aging at 170 ℃ for 2 h）.The effects of heat treatment on microstructure and tensile properties of the Al-7%Si-0.3%Mg alloys were investigated by optical microscopy,scanning electronic microscopy and tension test.It is found that a 2 h solution at 550 ℃ is sufficient to make homogenization and saturation of magnesium and silicon in α（Al） phase,spheroid of eutectic Si phase.Followed by solution,a 2 h artificial aging at 170 ℃ is almost enough to produce hardening precipitates.Those samples treated with T6 achieve the maximum tensile strength and fracture elongation.With short time treatment（ST）,samples can reach 90% of the maximum yield strength,95% of the maximum strength,and 80% of the maximum elongation.展开更多
Mesozoic multi-stage tectono-magmatic events produced widely distributed granitoids in the South China Block. Huangshadong(HSD) is located in south-eastern South China Block, where closely spaced hot springs accompany...Mesozoic multi-stage tectono-magmatic events produced widely distributed granitoids in the South China Block. Huangshadong(HSD) is located in south-eastern South China Block, where closely spaced hot springs accompany outcrops of Mesozoic granites. New data on whole-rock geochemistry, zircon U-Pb geochronology, and zircon Lu-Hf isotopes are presented, to study the petrogenesis and tectonic evolution of the granites, and to explore the relationship between granites and geothermal anomalies. Zircon U-Pb isotopes display three periods of granites in the HSD area: Indosinian(ca. 253 Ma, G4) muscovite-bearing monzonitic granite, early Yanshanian(ca. 175–155 Ma, G5 and G3) monzonitic granite and granodiorite, and late Yanshanian(ca. 140 Ma, G1 and G2) biotite monzonitic granite. In petrogenetic type, granites of the three periods are I-type granite. Among them, G1, G2, G3, and G4 are characterized by high fractionation, with high values of SiO2, alkalis, Ga/Al, and Rb/Sr, and depletion in Sr, Ba, Zr, Nb, Ti, REEs, with low(La/Yb)N, Nb/Ta, and Zr/Hf ratios and negative Eu anomalies. In terms of tectonic setting, 253 Ma G4 may be the product of partial melting of the ancient lower crust under post-orogenic extensional tectonics, as the closure of the Paleo-Tethys Ocean resulted in an intracontinental orogeny. At 175 Ma, the subduction of the Pacific Plate became the dominant tectonic system, and low-angle subduction of the Paleo-Pacific Plate facilitated partial melting of the subducted oceanic crust and basement to generate the hornblende-bearing I-type granodiorite. As the dip angle of the subducting plate increased, the continental arc tectonic setting was transformed to back-arc extension, inducing intense partial melting of the lower crust at ca. 158 Ma and resulting in the most frequent granitic magmatic activity in the South China hinterland. When slab foundering occurred at ca. 140 Ma, underplating of mantle-derived magmas caused melting of the continental crust, generating extensive highly fractionated granite展开更多
6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and tim...6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200℃, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints.展开更多
基金Project(2008B80703001) supported by Guangdong Provincial Department of Science and Technology,ChinaProject(09A45031160) supported by Guangzhou Science and Technology Commission,ChinaProject(ZC2009015) supported by Zengcheng Science and Technology Bureau,China
文摘Two heat treatments of A356 alloys with combined addition of rare earth and strontium were conducted.T6 treatment is a long time treatment（solution at 535 ℃ for 4 h ＋ aging at 150 ℃ for 15 h）.The other treatment is a short time treatment（solution at 550 ℃ for 2 h ＋ aging at 170 ℃ for 2 h）.The effects of heat treatment on microstructure and tensile properties of the Al-7%Si-0.3%Mg alloys were investigated by optical microscopy,scanning electronic microscopy and tension test.It is found that a 2 h solution at 550 ℃ is sufficient to make homogenization and saturation of magnesium and silicon in α（Al） phase,spheroid of eutectic Si phase.Followed by solution,a 2 h artificial aging at 170 ℃ is almost enough to produce hardening precipitates.Those samples treated with T6 achieve the maximum tensile strength and fracture elongation.With short time treatment（ST）,samples can reach 90% of the maximum yield strength,95% of the maximum strength,and 80% of the maximum elongation.
基金financially supported by the China Geological Survey(No.1212011220014)
文摘Mesozoic multi-stage tectono-magmatic events produced widely distributed granitoids in the South China Block. Huangshadong(HSD) is located in south-eastern South China Block, where closely spaced hot springs accompany outcrops of Mesozoic granites. New data on whole-rock geochemistry, zircon U-Pb geochronology, and zircon Lu-Hf isotopes are presented, to study the petrogenesis and tectonic evolution of the granites, and to explore the relationship between granites and geothermal anomalies. Zircon U-Pb isotopes display three periods of granites in the HSD area: Indosinian(ca. 253 Ma, G4) muscovite-bearing monzonitic granite, early Yanshanian(ca. 175–155 Ma, G5 and G3) monzonitic granite and granodiorite, and late Yanshanian(ca. 140 Ma, G1 and G2) biotite monzonitic granite. In petrogenetic type, granites of the three periods are I-type granite. Among them, G1, G2, G3, and G4 are characterized by high fractionation, with high values of SiO2, alkalis, Ga/Al, and Rb/Sr, and depletion in Sr, Ba, Zr, Nb, Ti, REEs, with low(La/Yb)N, Nb/Ta, and Zr/Hf ratios and negative Eu anomalies. In terms of tectonic setting, 253 Ma G4 may be the product of partial melting of the ancient lower crust under post-orogenic extensional tectonics, as the closure of the Paleo-Tethys Ocean resulted in an intracontinental orogeny. At 175 Ma, the subduction of the Pacific Plate became the dominant tectonic system, and low-angle subduction of the Paleo-Pacific Plate facilitated partial melting of the subducted oceanic crust and basement to generate the hornblende-bearing I-type granodiorite. As the dip angle of the subducting plate increased, the continental arc tectonic setting was transformed to back-arc extension, inducing intense partial melting of the lower crust at ca. 158 Ma and resulting in the most frequent granitic magmatic activity in the South China hinterland. When slab foundering occurred at ca. 140 Ma, underplating of mantle-derived magmas caused melting of the continental crust, generating extensive highly fractionated granite
基金Projects(2019JJ70077,2019JJ50510) supported by the National Science Foundation of Hunan Province,ChinaProject(31665004) supported by Open Fund of State Key Laboratory of Advanced Design and Manufacture for Vehicle Body,ChinaProjects(18B552,18B285) supported by Scientific Research Fund of Hunan Provincial Education Department,China
文摘6061 aluminum alloy T-joints were welded by double-pulsed MIG welding process. Then, the post-weld heat treatment was performed on the welded T-joints. The weld microstructure under different aging temperature and time was investigated by transmission electron microscopy and scanning electron microscopy. The mechanical properties were examined by hardness test and tensile test. The results showed that the micro-hardness was sensitive to heat treatment temperature and time. Increasing temperature was beneficial to the shortening of peak aging time. There were a large number of dislocations and few precipitates in the welded joints. With the increase of post-weld heat treatment temperature and time, the density of dislocation decreased. Meanwhile, the strengthening phase precipitated and grew up gradually. When the post-weld heat treatment temperature increased up to 200℃, large Q' phases were observed. And they were responsible for the peak value of the micro-hardness in the welded joints.
