Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grai...Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grains became finer and the tensile strength was improved with the increase of Y content in Mg-Y-1.5LPC-0.4Zr alloy.The results show that the formed precipitates responsible for age hardening change from fine hexagonal-shaped equilibrium Mg12RE phase to metastableβ′phase with orthorhombic-bc crystal structure when Y is added into Mg-1.5LPC-0.4Zr alloy,and the volume fraction of precipitate phases also increases.The cubic-shapedβ-Mg24Y5 precipitate phases were also observed at grain boundaries in Mg-6Y-1.5LPC-0.4Zr alloy. The distribution of prismatic shapedβ′phases and cubic shapedβ-Mg24Y5 precipitate phases in Mg matrix may account for the remarkable enhancement of tensile strength of Mg-Y-LPC-Zr alloy.The Mg-6Y-1.5LPC-0.4Zr alloy exhibits maximum tensile strength at peak-aged hardness,and the values are 250 MPa at room temperature and 210 MPa at 250°C.展开更多
The influence of trace Y on the microstructure evolution and mechanical properties of Mg_(100−x)Y_(x)(x=0.25,_(0.75),1.5,3,4,5,at.%)alloys during solidification process was investigated via molecular dynamics(MD)simul...The influence of trace Y on the microstructure evolution and mechanical properties of Mg_(100−x)Y_(x)(x=0.25,_(0.75),1.5,3,4,5,at.%)alloys during solidification process was investigated via molecular dynamics(MD)simulations.The results show that the Mg_(100−x)Y_(x) alloys are mainly characterized by a face-centered cubic(FCC)crystal structure;this is different from pure metal Mg,which exhibits a hexagonal close packed(HCP)structure at room temperature.Among these alloys,Mg_(99.25)Y_(0.75) has a larger proportion of FCC cluster structures,with the highest fraction reaching 56.65%.As the content of the Y increases up to 5 at.%(Mg95Y5 alloy),the amount of amorphous structures increases.The mechanical properties of the Mg_(100−x)Y_(x) alloys are closely related to their microstructures.The Mg_(99.25)Y_(0.75) and Mg_(97)Y_(3) alloys exhibit the highest yield strengths of 1.86 and 1.90 GPa,respectively.The deformation mechanism of the Mg−Y alloys is described at the atomic level,and it is found that a difference in the FCC proportion caused by different Y contents leads to distinct deformation mechanisms.展开更多
After substituting partial Cu and Mg with Zn or Al elements for Mg65Cu25Y10 alloy,respectively,the metallic glass plate samples with thickness of 2-3 mm were prepared by water-quenching,their respective glass-forming ...After substituting partial Cu and Mg with Zn or Al elements for Mg65Cu25Y10 alloy,respectively,the metallic glass plate samples with thickness of 2-3 mm were prepared by water-quenching,their respective glass-forming ability and thermal stability were studied by using differential thermal analysis(DTA) and X-ray diffraction(XRD). Using Kissinger equation,the activation energies of crystallization of these metallic glasses heated with a constant rate were calculated. The results show that Al element is greatly harmful to the glass-forming ability of Mg-Cu-Y alloys and cannot acquire bulk amorphous alloys;nevertheless,the effect of Zn element addition is indeterminate for various components. The magnitudes of thermal stability are also revealed.展开更多
Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry...Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry(XRD),environmental scanning electron microscopy(ESEM) and atomic force microscopy(AFM) were used to study the amorphization and morphology of the prepared alloy. Under micro condition,the sample alloy is composed of amorphous structure with cauliflorate shape,primary CuMg2 dendrite phase,mixed primary CuMg2 and Cu2Y crystalline phases,as well as Mg phase with small size. Further study under sub-micro condition shows that,the planar amorphous structure of cauliflorate shape is composed of the three-dimensional sub-micro morphology of "bulge-concavity" pattern,which extends into the space in terms of certain period. It is estimated that the major factors influencing the micro and sub-micro morphologies of amorphous alloy are its super-cooling liquid structure,rapid quenching transformation,as well as the melting conditions.展开更多
基金Project(2010A6100153)supported by Natural Science Foundation of Ningbo,China
文摘Ageing hardening,microstructure and mechanical properties of Mg-xY-1.5LPC-0.4Zr（x=0,2,4,6）alloys（LPC represents La-based rare earth metal）were investigated.It was found that the age hardening was enhanced,the grains became finer and the tensile strength was improved with the increase of Y content in Mg-Y-1.5LPC-0.4Zr alloy.The results show that the formed precipitates responsible for age hardening change from fine hexagonal-shaped equilibrium Mg12RE phase to metastableβ′phase with orthorhombic-bc crystal structure when Y is added into Mg-1.5LPC-0.4Zr alloy,and the volume fraction of precipitate phases also increases.The cubic-shapedβ-Mg24Y5 precipitate phases were also observed at grain boundaries in Mg-6Y-1.5LPC-0.4Zr alloy. The distribution of prismatic shapedβ′phases and cubic shapedβ-Mg24Y5 precipitate phases in Mg matrix may account for the remarkable enhancement of tensile strength of Mg-Y-LPC-Zr alloy.The Mg-6Y-1.5LPC-0.4Zr alloy exhibits maximum tensile strength at peak-aged hardness,and the values are 250 MPa at room temperature and 210 MPa at 250°C.
基金the National Key Research and Development Program of China (No. 2017YFGX090043)the Program for New Century Excellent Talents in University, China (No. NCET-12-0170) for supporting this work。
文摘The influence of trace Y on the microstructure evolution and mechanical properties of Mg_(100−x)Y_(x)(x=0.25,_(0.75),1.5,3,4,5,at.%)alloys during solidification process was investigated via molecular dynamics(MD)simulations.The results show that the Mg_(100−x)Y_(x) alloys are mainly characterized by a face-centered cubic(FCC)crystal structure;this is different from pure metal Mg,which exhibits a hexagonal close packed(HCP)structure at room temperature.Among these alloys,Mg_(99.25)Y_(0.75) has a larger proportion of FCC cluster structures,with the highest fraction reaching 56.65%.As the content of the Y increases up to 5 at.%(Mg95Y5 alloy),the amount of amorphous structures increases.The mechanical properties of the Mg_(100−x)Y_(x) alloys are closely related to their microstructures.The Mg_(99.25)Y_(0.75) and Mg_(97)Y_(3) alloys exhibit the highest yield strengths of 1.86 and 1.90 GPa,respectively.The deformation mechanism of the Mg−Y alloys is described at the atomic level,and it is found that a difference in the FCC proportion caused by different Y contents leads to distinct deformation mechanisms.
文摘After substituting partial Cu and Mg with Zn or Al elements for Mg65Cu25Y10 alloy,respectively,the metallic glass plate samples with thickness of 2-3 mm were prepared by water-quenching,their respective glass-forming ability and thermal stability were studied by using differential thermal analysis(DTA) and X-ray diffraction(XRD). Using Kissinger equation,the activation energies of crystallization of these metallic glasses heated with a constant rate were calculated. The results show that Al element is greatly harmful to the glass-forming ability of Mg-Cu-Y alloys and cannot acquire bulk amorphous alloys;nevertheless,the effect of Zn element addition is indeterminate for various components. The magnitudes of thermal stability are also revealed.
基金Projects(0552nm028 04DZ05616) supported by Shanghai Science and Technology Committee, China
文摘Acoustic-frequency induction melting together with rapid quenching was used to prepare Mg65Cu25Y10 bulk amorphous alloy containing primary crystalline phases. Transmission electron microscopy(TEM),X-ray diffractometry(XRD),environmental scanning electron microscopy(ESEM) and atomic force microscopy(AFM) were used to study the amorphization and morphology of the prepared alloy. Under micro condition,the sample alloy is composed of amorphous structure with cauliflorate shape,primary CuMg2 dendrite phase,mixed primary CuMg2 and Cu2Y crystalline phases,as well as Mg phase with small size. Further study under sub-micro condition shows that,the planar amorphous structure of cauliflorate shape is composed of the three-dimensional sub-micro morphology of "bulge-concavity" pattern,which extends into the space in terms of certain period. It is estimated that the major factors influencing the micro and sub-micro morphologies of amorphous alloy are its super-cooling liquid structure,rapid quenching transformation,as well as the melting conditions.
