The as-cast and as-extruded Mg–9Li–1Al–xCa alloys(x=0,0.2;wt%)were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The microstructures of the as-cast and as-extruded...The as-cast and as-extruded Mg–9Li–1Al–xCa alloys(x=0,0.2;wt%)were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The microstructures of the as-cast and as-extruded Mg–9Li–1Al–xCa alloys were observed to investigate the effect of calcium(Ca)element on the Mg–9Li–1Al(LA91)alloy,and the crystallographic calculations between Al_(2)Ca and the matrix(α-Mg andβ-Li phases)were examined on the basis of the edge-to-edge matching model.The experimental results indicate that the addition of 0.2 wt%Ca into LA91 alloy reduce the size of theα-Mg phases in the as-cast alloy and that ofβ-Li phases in the as-extruded alloy due to the Al_(2)Ca particles distributed inside the matrix.Crystallographic calculation results suggested that there is a good crystallographic matching between the matrix and Al_(2)Ca,which confirmed that Al_(2)Ca particles can act as a heterogeneous nucleation site for bothα-Mg andβ-Li phases and were effective grain refiners for LA91 alloy.展开更多
The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and ...The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture.展开更多
The corrosion behaviors of T5 （225 ℃, 6.5 h） and T6 （460 ℃, 2 h ＋ 225 ℃, 12 h） peak-aged Mg-7Gd- 5Y-1Nd-0.5Zr alloys with oxide films were investigated by optical microscope （OM）, scanning electron microsco...The corrosion behaviors of T5 （225 ℃, 6.5 h） and T6 （460 ℃, 2 h ＋ 225 ℃, 12 h） peak-aged Mg-7Gd- 5Y-1Nd-0.5Zr alloys with oxide films were investigated by optical microscope （OM）, scanning electron microscopy （SEM）, and energy-dispersive spectroscopy （EDS）. The weight loss rates and electrochemical tests were also analyzed. The thicknesses of T5 and T6 oxide films are roughly 0.6 and 1.0 μm, respectively. The components of oxide films mainly consist of O, Mg, Y, Nd, and Gd, and the T6 oxide film results in surfaces with larger peaks than T5 oxide film. In addition, Y, Nd, and Gd peaks are all higher than those of Mg-7Gd-5Y- 1Nd-0.5Zr alloys, but Mg peak is consistently far below than that of the alloys. The specimens could be arranged in de- creasing order of corrosion rates and corrosion current densi- ties： T6 oxide film 〈 T5 oxide film 〈 T6 without oxide film 〈 T5 without oxide film. The oxide films are compact to increase the corrosion resistance for Mg-7Gd-5Y-1Nd-0.5Zr alloys, which will provide a guiding insight into the corrosion and protection of Mg-RE alloys in atmospheric environments.展开更多
基金The authors are grateful for the financial supports from National Natural Science Foundation of China(51171212)Chongqing Science and Technology Commission(CSTC2012JJJQ50001,CSTC2013jcyjC60001,cstc2012ggB 50003)+1 种基金The National Science and Technology Program of China(2013DFA71070)the Fundamental Research Funds for the Central Universities(CDJZR13138801).
文摘The as-cast and as-extruded Mg–9Li–1Al–xCa alloys(x=0,0.2;wt%)were prepared by a simple alloying process followed by hot extrusion with an extrusion ratio of 28.2.The microstructures of the as-cast and as-extruded Mg–9Li–1Al–xCa alloys were observed to investigate the effect of calcium(Ca)element on the Mg–9Li–1Al(LA91)alloy,and the crystallographic calculations between Al_(2)Ca and the matrix(α-Mg andβ-Li phases)were examined on the basis of the edge-to-edge matching model.The experimental results indicate that the addition of 0.2 wt%Ca into LA91 alloy reduce the size of theα-Mg phases in the as-cast alloy and that ofβ-Li phases in the as-extruded alloy due to the Al_(2)Ca particles distributed inside the matrix.Crystallographic calculation results suggested that there is a good crystallographic matching between the matrix and Al_(2)Ca,which confirmed that Al_(2)Ca particles can act as a heterogeneous nucleation site for bothα-Mg andβ-Li phases and were effective grain refiners for LA91 alloy.
基金Project supported by the National Natural Science Foundation of China(51571084 and 51171059)Project of Scientific And Technological Research In Henan Province(152102210072)
文摘The effects of Sm on the microstructure and mechanical properties of Mg-11 Gd-2 Y-0.6 Al alloy were investigated by X-ray diffraction,optical microscopy,scanning electron microscopy,energy dispersive spectrometry and high resolution transmission electron microscopy.Based on the theory of edge—edge matching and electronegativity theory,the mechanism of grain refinement is discussed.The strengthening mechanism is expounded conveniently from fine grain strengthening,coherent strengthening,precipitation strengthening and grain boundary strengthening.The results show that the micro structure of Mg-11 Gd-2 Y-0.6 Al alloy is mainly composed of a-Mg matrix,Mg5 Gd and Mg24Y5 phases.The addition of Sm forms Mg41Sm5 phase in the alloy and refines the alloy.The addition of Sm significantly improves the mechanical properties of the alloy at room and high temperatures.When the addition of Sm is 3 wt%,the tensile strengths of the alloy at room temperature and high temperature(200℃)reach the maximum value 292 and 321 MPa,respectively.The fracture mode of the alloy at different temperatures is mainly brittle fracture and intercrystalline fracture.
基金financially supported by the National Natural Science Foundation of China(No.51204020)the National Basic Research Program of China(Nos.2013CB632202 and 2013CB632205)
文摘The corrosion behaviors of T5 （225 ℃, 6.5 h） and T6 （460 ℃, 2 h ＋ 225 ℃, 12 h） peak-aged Mg-7Gd- 5Y-1Nd-0.5Zr alloys with oxide films were investigated by optical microscope （OM）, scanning electron microscopy （SEM）, and energy-dispersive spectroscopy （EDS）. The weight loss rates and electrochemical tests were also analyzed. The thicknesses of T5 and T6 oxide films are roughly 0.6 and 1.0 μm, respectively. The components of oxide films mainly consist of O, Mg, Y, Nd, and Gd, and the T6 oxide film results in surfaces with larger peaks than T5 oxide film. In addition, Y, Nd, and Gd peaks are all higher than those of Mg-7Gd-5Y- 1Nd-0.5Zr alloys, but Mg peak is consistently far below than that of the alloys. The specimens could be arranged in de- creasing order of corrosion rates and corrosion current densi- ties： T6 oxide film 〈 T5 oxide film 〈 T6 without oxide film 〈 T5 without oxide film. The oxide films are compact to increase the corrosion resistance for Mg-7Gd-5Y-1Nd-0.5Zr alloys, which will provide a guiding insight into the corrosion and protection of Mg-RE alloys in atmospheric environments.
