The effect of different homogenization treatments on the microstructure and properties of the 7N01 aluminum alloy was investigated using hardness measurements, electrical conductivity measurements, tensile and slow st...The effect of different homogenization treatments on the microstructure and properties of the 7N01 aluminum alloy was investigated using hardness measurements, electrical conductivity measurements, tensile and slow strain rate tests, electron probe microanalysis, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results revealed that three-step homogenization improved the uniformity of Zr distribution by eliminating segregation of the main alloying elements. During the second homogenization step at 350 °C for 10 h, coarse and strip-like equilibrium η phases formed which assisted the nucleation of Al3Zr dispersoids and reduced the width of the precipitate-free zone of A13Zr dispersoids. As a result, coarse recrystallization was greatly reduced after homogenization at 200 °C, 2 h ＋ 350 °C, 10 h ＋ 470 °C, 12 h, which contributed to improving the overall properties of the 7N01 aluminum alloys.展开更多
Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld meta...Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld metal and heat affected zone (HAZ) is slight. Furthermore, the ratio of fatigue crack initiation life (Ni) to fatigue life to failure(Nf) is a material dependent parameter, 26.32%, 40.21% and 60.67% for base metal, HAZ and weld metal, respectively. Total fatigue life predicted using the presented model is in good agreement with the experimental data and that using Basquin’s model. The observation results of fatigue fracture surfaces, using scanning electron microscope (SEM), demonstrate that fatigue crack initiates from smooth surface due to welding process for weld metal, blowhole in HAZ causes fatigue crack initiation, and the crushed second phase particles play an important part in fatigue crack initiation in base metal.展开更多
In this study, the in-situ synthesized ZrB_(2) nanoparticles and rare earth Sc were introduced to enhance the strength and ductility of 7N01 aluminum alloy, via the generation of high-melting and uniform nanodispersoi...In this study, the in-situ synthesized ZrB_(2) nanoparticles and rare earth Sc were introduced to enhance the strength and ductility of 7N01 aluminum alloy, via the generation of high-melting and uniform nanodispersoids. The microstructure and mechanical property evolution of the prepared composites and the interaction between ZrB_(2) and Sc were studied in detail. The microstructure investigation shows that the introduction of rare earth scandium(Sc) can promote the distribution of ZrB_(2) nanoparticles, by improving their wettability to the Al melt. Meanwhile, the addition of rare earth Sc also modifies the coarse Al Zn Mg Mn Fe precipitated phases, refines the matrix grains and generates high-melting Al_3(Sc,Zr)/Al_3Sc nanodispersoids. Tensile tests of the composites show that with the combinatorial introduction of ZrB_(2) and Sc, the strength and ductility of the composites are improved simultaneously compared with the corresponding 7N01 alloy, ZrB_(2) /7N01 composite and Sc/7N01 alloy. And the optimum contents of ZrB_(2) and Sc are 3 wt% and 0.2 wt% in this study. The yield strength, ultimate strength and elongation of(3 wt% ZrB_(2) +0.2 wt% Sc)/7N01 composite are 477 MPa, 506 MPa and 9.8%, increased about 18.1%, 12.2%and 38% compared to 7N01 alloy. Furthermore, the cooperation strengthening mechanisms of ZrB_(2) and Sc are also discussed.展开更多
The effect of grain morphology and precipitates on mechanical properties and corrosion behavior of two commercial 7 N01 alloys was studied using transmission electron microscopy(TEM) and scanning electron microscopy(S...The effect of grain morphology and precipitates on mechanical properties and corrosion behavior of two commercial 7 N01 alloys was studied using transmission electron microscopy(TEM) and scanning electron microscopy(SEM) equipped with electron backscatter diffraction(EBSD). Results showed that the recrystallization degree of the outer surface of 7 N01-I alloy was lower than that of 7 N01-II alloy. The main strengthening precipitates of two alloys were mainly η’ phases. The grain boundary precipitates(GBPs) of 7 N01-I alloy distributed discontinuously, while those of 7 N01-II alloy distributed continuously. The strength of two 7 N01 alloys was similar, but the maximum corrosion depth of 7 N01-I alloy was less than that of 7 N01-II alloy, because the discontinuous GBPs and the lower recrystallization degree of outer surface of 7 N01-I alloy were favorable for improving corrosion behavior. Different models of strengthening mechanism were discussed, and the corrosion behavior was correlated with microstructure.展开更多
基金Projects(2016YFB0300901,2016YFB0300902)supported by the National Key Research and Development Program of ChinaProject(51375503)supported by the National Natural Science Foundation of ChinaProject(2013A017)supported by Guangxi Zhuangzu Autonomous Region of China
文摘The effect of different homogenization treatments on the microstructure and properties of the 7N01 aluminum alloy was investigated using hardness measurements, electrical conductivity measurements, tensile and slow strain rate tests, electron probe microanalysis, optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results revealed that three-step homogenization improved the uniformity of Zr distribution by eliminating segregation of the main alloying elements. During the second homogenization step at 350 °C for 10 h, coarse and strip-like equilibrium η phases formed which assisted the nucleation of Al3Zr dispersoids and reduced the width of the precipitate-free zone of A13Zr dispersoids. As a result, coarse recrystallization was greatly reduced after homogenization at 200 °C, 2 h ＋ 350 °C, 10 h ＋ 470 °C, 12 h, which contributed to improving the overall properties of the 7N01 aluminum alloys.
文摘Fatigue characteristics of A7N01 aluminium alloy welded joint were investigated and a fatigue crack initiation life-based model was proposed. The difference of fatigue crack initiation life among base metal, weld metal and heat affected zone (HAZ) is slight. Furthermore, the ratio of fatigue crack initiation life (Ni) to fatigue life to failure(Nf) is a material dependent parameter, 26.32%, 40.21% and 60.67% for base metal, HAZ and weld metal, respectively. Total fatigue life predicted using the presented model is in good agreement with the experimental data and that using Basquin’s model. The observation results of fatigue fracture surfaces, using scanning electron microscope (SEM), demonstrate that fatigue crack initiates from smooth surface due to welding process for weld metal, blowhole in HAZ causes fatigue crack initiation, and the crushed second phase particles play an important part in fatigue crack initiation in base metal.
基金Project supported by the National Natural Science Foundation of China(U20A20274,52071158,51701085,U1664254)the Six Talents Peak Project of Jiangsu Province(2018-XCL-202)+1 种基金the Open Funds of SKLMMC of SJTU(MMC-KF18-16)the Jiangsu Province Key Laboratory of High-end Structural Materials(HSM1803,1902)。
文摘In this study, the in-situ synthesized ZrB_(2) nanoparticles and rare earth Sc were introduced to enhance the strength and ductility of 7N01 aluminum alloy, via the generation of high-melting and uniform nanodispersoids. The microstructure and mechanical property evolution of the prepared composites and the interaction between ZrB_(2) and Sc were studied in detail. The microstructure investigation shows that the introduction of rare earth scandium(Sc) can promote the distribution of ZrB_(2) nanoparticles, by improving their wettability to the Al melt. Meanwhile, the addition of rare earth Sc also modifies the coarse Al Zn Mg Mn Fe precipitated phases, refines the matrix grains and generates high-melting Al_3(Sc,Zr)/Al_3Sc nanodispersoids. Tensile tests of the composites show that with the combinatorial introduction of ZrB_(2) and Sc, the strength and ductility of the composites are improved simultaneously compared with the corresponding 7N01 alloy, ZrB_(2) /7N01 composite and Sc/7N01 alloy. And the optimum contents of ZrB_(2) and Sc are 3 wt% and 0.2 wt% in this study. The yield strength, ultimate strength and elongation of(3 wt% ZrB_(2) +0.2 wt% Sc)/7N01 composite are 477 MPa, 506 MPa and 9.8%, increased about 18.1%, 12.2%and 38% compared to 7N01 alloy. Furthermore, the cooperation strengthening mechanisms of ZrB_(2) and Sc are also discussed.
基金the National Key Research and Development Program of China (Nos. 2021YFB3704204, 2021YFB3700902, 2021YFB3704205)Beijing Natural Science Foundation, China (No. 2202009)+2 种基金the National Natural Science Foundation of China (No. 51621003)Basic Research Program of Jiangsu Province (Natural Science Foundation), China (No. BK20191148)Beijing Lab Project for Modern Transportation Metallic Materials and Processing Technology and Jiangsu Key Laboratory for Clad Materials, China (No. BM2014006)。
文摘The effect of grain morphology and precipitates on mechanical properties and corrosion behavior of two commercial 7 N01 alloys was studied using transmission electron microscopy(TEM) and scanning electron microscopy(SEM) equipped with electron backscatter diffraction(EBSD). Results showed that the recrystallization degree of the outer surface of 7 N01-I alloy was lower than that of 7 N01-II alloy. The main strengthening precipitates of two alloys were mainly η’ phases. The grain boundary precipitates(GBPs) of 7 N01-I alloy distributed discontinuously, while those of 7 N01-II alloy distributed continuously. The strength of two 7 N01 alloys was similar, but the maximum corrosion depth of 7 N01-I alloy was less than that of 7 N01-II alloy, because the discontinuous GBPs and the lower recrystallization degree of outer surface of 7 N01-I alloy were favorable for improving corrosion behavior. Different models of strengthening mechanism were discussed, and the corrosion behavior was correlated with microstructure.
