Mg68Zn28Y4 alloys with stable icosahedral quasicrystals(Zn60Mg30Y10)were prepared by cast method.By simulating the environment of ocean,the alloy was eroded in 3.5%(mass fraction)NaCl for 2,4 and 30 h.The microstructu...Mg68Zn28Y4 alloys with stable icosahedral quasicrystals(Zn60Mg30Y10)were prepared by cast method.By simulating the environment of ocean,the alloy was eroded in 3.5%(mass fraction)NaCl for 2,4 and 30 h.The microstructures of the samples and eroded alloys were analyzed by OM and SEM.The compositions and the quasiperiodic structures were identified respectively by EDS and TEM.And the corrosion potential and corrosion current density before and after immersion were measured by potentiodynamic polarization measurements in 3.5%NaCl.The results show that I-phases grow in the mode of conglomeration, piling and transfixion.The Mg7Zn3 matrix andα(Mg)solid solution are eroded badly,while W-phase is eroded partially.At the same time,the I-phases exhibit excellent corrosion resistance property.The resistance to corrosion of Mg68Zn28Y4 alloy is improved by increasing exposed I-phases.With adding element Y to Mg68Zn32 alloy,the corrosion current is decreased by one order of magnitude. And after the immersion of as-cast Mg68Zn28Y4 alloy for 30 h,the corrosion current density is reduced by two orders of magnitude compared with that of uneroded Mg68Zn32 alloy.展开更多
A series of AM60-1Ce-xCa(x=0, 0.5, 1.5, 2.5) magnesium alloys were prepared by gravity casting method and analyzed by means of XRD, DSC and SEM. The effects of Ca on normal temperature mechanical properties and high t...A series of AM60-1Ce-xCa(x=0, 0.5, 1.5, 2.5) magnesium alloys were prepared by gravity casting method and analyzed by means of XRD, DSC and SEM. The effects of Ca on normal temperature mechanical properties and high temperature creep behavior of alloys were characterized by tensile and constant creep test.Microstructure analysis indicated that Ca was preferentially combined with Al in the alloy to form the high melting point Al_2Ca phase at the grain boundary. The addition of Ca can refine the crystal grains and reduces the content of β-Mg_(17)Al_(12) phase. With the increase of Ca content in the alloy, Al_2Ca phases at the grain boundary gradually changed to the network of lamellar structure, and replaced the β-Mg_(17)Al_(12) phase as the main strengthening phase gradually. The creep resistance of the alloy continuously increases because the high-temperature stable phase Al_2Ca firmly nailed at grain boundaries impedes the sliding of grain boundaries. However, when the addition of Ca was more than 1.5%, mechanical properties of the alloy started to decrease, which was probably due to the large amount of irregularly shaped Al_2Ca phases at the grain boundary. Experimental results show that the optimal addition amount of Ca is 1.5 wt.%.展开更多
基金Project(50271054)supported by the National Natural Science Foundation of ChinaProject(2002E110)supported by the Natural Science Foundation of Shannxi Province,ChinaProject supported by the Scientific Research Foundation of the Education Department of Shaanxi Province for the Returned Overseas Chinese Scholars
文摘Mg68Zn28Y4 alloys with stable icosahedral quasicrystals(Zn60Mg30Y10)were prepared by cast method.By simulating the environment of ocean,the alloy was eroded in 3.5%(mass fraction)NaCl for 2,4 and 30 h.The microstructures of the samples and eroded alloys were analyzed by OM and SEM.The compositions and the quasiperiodic structures were identified respectively by EDS and TEM.And the corrosion potential and corrosion current density before and after immersion were measured by potentiodynamic polarization measurements in 3.5%NaCl.The results show that I-phases grow in the mode of conglomeration, piling and transfixion.The Mg7Zn3 matrix andα(Mg)solid solution are eroded badly,while W-phase is eroded partially.At the same time,the I-phases exhibit excellent corrosion resistance property.The resistance to corrosion of Mg68Zn28Y4 alloy is improved by increasing exposed I-phases.With adding element Y to Mg68Zn32 alloy,the corrosion current is decreased by one order of magnitude. And after the immersion of as-cast Mg68Zn28Y4 alloy for 30 h,the corrosion current density is reduced by two orders of magnitude compared with that of uneroded Mg68Zn32 alloy.
基金financially supported by the National Natural Science Foundation of China(Grant No.50901035)the Science and Technology Development Projects of Jilin Province(Grant No.20140204042GX)the China Postdoctoral Science Foundation(Grant No.2018M642625)
文摘A series of AM60-1Ce-xCa(x=0, 0.5, 1.5, 2.5) magnesium alloys were prepared by gravity casting method and analyzed by means of XRD, DSC and SEM. The effects of Ca on normal temperature mechanical properties and high temperature creep behavior of alloys were characterized by tensile and constant creep test.Microstructure analysis indicated that Ca was preferentially combined with Al in the alloy to form the high melting point Al_2Ca phase at the grain boundary. The addition of Ca can refine the crystal grains and reduces the content of β-Mg_(17)Al_(12) phase. With the increase of Ca content in the alloy, Al_2Ca phases at the grain boundary gradually changed to the network of lamellar structure, and replaced the β-Mg_(17)Al_(12) phase as the main strengthening phase gradually. The creep resistance of the alloy continuously increases because the high-temperature stable phase Al_2Ca firmly nailed at grain boundaries impedes the sliding of grain boundaries. However, when the addition of Ca was more than 1.5%, mechanical properties of the alloy started to decrease, which was probably due to the large amount of irregularly shaped Al_2Ca phases at the grain boundary. Experimental results show that the optimal addition amount of Ca is 1.5 wt.%.
