The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured ...The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.展开更多
A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580...A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580 to 640℃.X-ray computed tomography was used to visualize pores,and crystal plasticity finite element simulation was adopted for deformation analysis.The microstructure characterizations reveal a hierarchical cell feature composed of α-Mg and eutectic phases.With the increase of injection temperature,large cell content in the material decreases,while the strength of the alloy increases.The underlying mechanism about strength change is that coarse-grained solids experience smaller stress even in hard orientations.The sample fabricated at a moderate temperature of 620℃ exhibits the highest elongation,least quantity and lower local concentration of pores.The detachment and tearing cracks formed at lower injection temperature and defect bands formed at higher injection temperature add additional crack sources and deteriorate the ductility of the materials.展开更多
The regulation of sintering temperature in spark plasma sintering enables the achievement of grain refinement,phase control,and performance enhancement in the preparation of AZ91D magnesium alloy.This study investigat...The regulation of sintering temperature in spark plasma sintering enables the achievement of grain refinement,phase control,and performance enhancement in the preparation of AZ91D magnesium alloy.This study investigates the influence of sintering temperature on microstructural evolution and mechanical properties of the AZ91D alloy.Microstructural analysis was conducted using scanning electron microscopy,electron backscatter diffraction,and X-ray diffraction.Microscopic structures and mechanical behaviors were examined through hardness and tensile tests.Elevated sintering temperatures resulted in reduced secondary phase content,leading to a decrease in mechanical performance.The alloy exhibited optimal mechanical properties at 320℃.The nanoparticle coarsening process and particle evolution during sintering were simulated using phase field methods.By optimizing the sintering temperature,precise control over microstructural and textural evolution can be achieved,facilitating the attainment of desired hardness levels and mechanical properties.展开更多
基金supported by the National Natural Science Foundation of China(52205382,52225503)National Key Research and Development Program(2023YFB4603300)+1 种基金Key Research and Development Program of Jiangsu Province(BZ2024019,BE2022069)International Joint Laboratory of Sustainable Manufacturing,Ministry of Education and the Fundamental Research Funds for the Central Universities(NG2024014,XCA2300501)。
文摘The addition of ceramic reinforcements provides a promising approach to achieving high-performance magnesium matrix composites.In this work,AZ91D magnesium alloys and 2 wt.%TiC/AZ91D composites have been manufactured by laser powder bed fusion(LPBF)with variations of laser processing parameters.The effect of TiC reinforcement addition on the laser absorption behaviors,forming quality,microstructure evolution and mechanical properties of the magnesium alloys is investigated.The TiC addition improves the interactions of laser with alloy powder and laser absorption rate of alloy powder,and decreases powder spatter of powder bed.The results show that high relative density of~99.4%and good surface roughness of~12μm are obtained for the LPBF-fabricated composites.The TiC addition promotes the precipitation of β-Mg_(17)Al_(12)in the alloys and the transformation of coarse columnar to fine equiaxed grains,where the grains are refined to~3.1μm.The TiC/AZ91D composites exhibit high microhardness of 114.6±2.5 HV_(0.2),high tensile strength of~345.0 MPa and a uniform elongation~4.1%.The improvement of tensile strength for the composites is ascribed to the combination of grain refinement strengthening and Orowan strengthening fromβ-Mg_(17)Al_(12)precipitates and Al_8Mn_5 nanoparticles.In the composites,the unmelted TiC particles can act as an anchor for the network structure of β-Mg_(17)Al_(12)precipitates,effectively impeding crack propagation and enhancing their performance.This work offers an insight to fabricating high-performance magnesium matrix composites by laser additive manufacturing.
基金supported by the National Natural Science Foundation of China(Nos.51825101,52001202)the National Key Research and Development Program of China(No.2021YFA1600900)。
文摘A comprehensive analysis of the microstructure and defects of a thixomolded AZ91D alloy was conducted to elucidate their influences on mechanical properties.Samples were made at injection temperatures ranging from 580 to 640℃.X-ray computed tomography was used to visualize pores,and crystal plasticity finite element simulation was adopted for deformation analysis.The microstructure characterizations reveal a hierarchical cell feature composed of α-Mg and eutectic phases.With the increase of injection temperature,large cell content in the material decreases,while the strength of the alloy increases.The underlying mechanism about strength change is that coarse-grained solids experience smaller stress even in hard orientations.The sample fabricated at a moderate temperature of 620℃ exhibits the highest elongation,least quantity and lower local concentration of pores.The detachment and tearing cracks formed at lower injection temperature and defect bands formed at higher injection temperature add additional crack sources and deteriorate the ductility of the materials.
基金supported by the National Natural Science Foundation of China(Nos.52074246,22008224,52275390,52205429,52201146)National Defense Basic Scientific Research Program of China(Nos.JCKY2020408B002,WDZC2022-12)+2 种基金Key Research and Development Program of Shanxi Province(202102050201011,2022ZDYF035)Science and Technology Major Project of Shanxi Province(20191102008,20191102007)Guiding Local Science and Technology Development Projects by the Central Government(YDZJSX2022A025,YDZJSX2021A027).
文摘The regulation of sintering temperature in spark plasma sintering enables the achievement of grain refinement,phase control,and performance enhancement in the preparation of AZ91D magnesium alloy.This study investigates the influence of sintering temperature on microstructural evolution and mechanical properties of the AZ91D alloy.Microstructural analysis was conducted using scanning electron microscopy,electron backscatter diffraction,and X-ray diffraction.Microscopic structures and mechanical behaviors were examined through hardness and tensile tests.Elevated sintering temperatures resulted in reduced secondary phase content,leading to a decrease in mechanical performance.The alloy exhibited optimal mechanical properties at 320℃.The nanoparticle coarsening process and particle evolution during sintering were simulated using phase field methods.By optimizing the sintering temperature,precise control over microstructural and textural evolution can be achieved,facilitating the attainment of desired hardness levels and mechanical properties.
