The microstructure evolution of Mg-Al-Ca alloys modified by the addition of strontium was investigated. It was found that Sr addition leads to the coarsening of α-Mg matrix. However, with the Sr content increasing fr...The microstructure evolution of Mg-Al-Ca alloys modified by the addition of strontium was investigated. It was found that Sr addition leads to the coarsening of α-Mg matrix. However, with the Sr content increasing from 0.1% to 0.5%, the grain size decreases from 83.9 to 65.8 μm. The addition of Sr ranging from 0.1% to 0.3% refines the Al2Ca phase. It changes the morphology of the Al2Ca phase from bone-shaped to granular or banding, and increases its volume fraction. The decrease of grain size of the α-Mg matrix is due to the increase of the effective undercooling degree of the melt and the constitutional undercooling in a diffusion layer ahead of the advancing solid/liquid interface in the alloy modified by the Sr additions. The modification mechanism of Al2Ca is attributed to the adsorption of Sr additions to the Al2Ca crystal. When the Sr content increases to 0.5%, the alloy is over-modified.展开更多
Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding （FSW） was investigated through pole figure measurement and X-ray diffraction （XRD） pattern analysis. It was found that at the top and bottom sur...Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding （FSW） was investigated through pole figure measurement and X-ray diffraction （XRD） pattern analysis. It was found that at the top and bottom surfaces of friction stir zone （FSZ）, （0002） basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and （0002） basal planes showed a random distribution.展开更多
The structure of the quaternary Al?(2?4)wt.%Ca?Ni?La system near the aluminum corner has been studied using computational analysis in the Thermo-Calc program and experimental studies(electron microscopy,microprobe ana...The structure of the quaternary Al?(2?4)wt.%Ca?Ni?La system near the aluminum corner has been studied using computational analysis in the Thermo-Calc program and experimental studies(electron microscopy,microprobe analysis and X-ray diffraction).Based on the phase equilibria data obtained,the experimental projection of the liquidus surface and solid state phase-field distribution of the Al?Ca?Ni?La system have been proposed.Microstructure studies reveal that the alloys with the 2?4 wt.%Ca,2?4 wt.%Ni and 1?3 wt.%La ranges have an ultra-fine hypoeutectic structure with 30%volume fraction of eutectic intermetallics,which allows one to classify these alloys as natural Al-matrix composites.The ultra-fine eutectic structure produces significant strengthening,the magnitude of which can be well described using the modified Orowan looping mechanism model.Small additives of Zr and Sc(0.2 and 0.1 wt.%,respectively)lead to significant strengthening(by^25%)due to the formation of L12 type phase(Al3(Zr,Sc))nanoparticles during annealing of the alloy at 350?400℃.Due to the high volume fraction of eutectic intermetallics,the new alloys have low coefficients of thermal expansion and high thermal stability of the structure and mechanical properties.展开更多
基金financially supported by the Russian Science Foundation(No.20-19-00746)(SEM,DSC,thermodynamic calculations)the federal academic leadership program Priority 2030 of NUST MISIS(DFT,XRD)。
基金Project(51075132)supported by the National Natural Science Foundation of ChinaProject(9451806001002350)supported by Guangdong Science Fund+2 种基金Project(30815007)supported by the Science Fund of State Key Laboratory of Advanced Design and Manufacturing for Vehicle BodyProject(09JJ1007)supported by Hunan Science Fund for Distinguished Young ScholarsProject(20090161110027)supported by the Doctoral Fund of Ministry of Education of China
文摘The microstructure evolution of Mg-Al-Ca alloys modified by the addition of strontium was investigated. It was found that Sr addition leads to the coarsening of α-Mg matrix. However, with the Sr content increasing from 0.1% to 0.5%, the grain size decreases from 83.9 to 65.8 μm. The addition of Sr ranging from 0.1% to 0.3% refines the Al2Ca phase. It changes the morphology of the Al2Ca phase from bone-shaped to granular or banding, and increases its volume fraction. The decrease of grain size of the α-Mg matrix is due to the increase of the effective undercooling degree of the melt and the constitutional undercooling in a diffusion layer ahead of the advancing solid/liquid interface in the alloy modified by the Sr additions. The modification mechanism of Al2Ca is attributed to the adsorption of Sr additions to the Al2Ca crystal. When the Sr content increases to 0.5%, the alloy is over-modified.
文摘Macro-texture of an Mg-Al-Ca alloy prepared by friction stir welding （FSW） was investigated through pole figure measurement and X-ray diffraction （XRD） pattern analysis. It was found that at the top and bottom surfaces of friction stir zone （FSZ）, （0002） basal planes of magnesium tend to be arranged parallel to the plate surface. In the cross section of FSZ, no obvious texture had evolved and （0002） basal planes showed a random distribution.
基金financial support of the grant of the Russian Science Foundation(Project No.18-79-00345)(preparation of alloys,electron microscopy(SEM,EMPA,TEM),tensile tests)Ministry of Science and Higher Education of the Russian Federation in the framework of Increase Competitiveness Program of MISiS(No.P02-2017-2-10)(thermodynamic calculations,dilatometry,DSC and XRD).
文摘The structure of the quaternary Al?(2?4)wt.%Ca?Ni?La system near the aluminum corner has been studied using computational analysis in the Thermo-Calc program and experimental studies(electron microscopy,microprobe analysis and X-ray diffraction).Based on the phase equilibria data obtained,the experimental projection of the liquidus surface and solid state phase-field distribution of the Al?Ca?Ni?La system have been proposed.Microstructure studies reveal that the alloys with the 2?4 wt.%Ca,2?4 wt.%Ni and 1?3 wt.%La ranges have an ultra-fine hypoeutectic structure with 30%volume fraction of eutectic intermetallics,which allows one to classify these alloys as natural Al-matrix composites.The ultra-fine eutectic structure produces significant strengthening,the magnitude of which can be well described using the modified Orowan looping mechanism model.Small additives of Zr and Sc(0.2 and 0.1 wt.%,respectively)lead to significant strengthening(by^25%)due to the formation of L12 type phase(Al3(Zr,Sc))nanoparticles during annealing of the alloy at 350?400℃.Due to the high volume fraction of eutectic intermetallics,the new alloys have low coefficients of thermal expansion and high thermal stability of the structure and mechanical properties.
