The pre-alloyed TiB_(2)/AlSi10Mg composite,a new high-strength aluminum alloy developed for laser pow-der bed fusion(LPBF)technology,offers promising applications in lightweight and multi-scaled structures.However,the...The pre-alloyed TiB_(2)/AlSi10Mg composite,a new high-strength aluminum alloy developed for laser pow-der bed fusion(LPBF)technology,offers promising applications in lightweight and multi-scaled structures.However,thermal behavior during LPBF is markedly scale-dependent,leading to microstructural varia-tions that significantly affect the load-bearing capacity of multi-scaled structures.Therefore,this study systematically investigates the scale-dependent behavior of microstructure characteristics of this com-posite.Utilizing a hatching scanning strategy,it was found that the marginal zones of samples are pre-dominantly composed of coarse Al cell and Al grain structures,contrasting with the fine microstructures in the central zones.With increasing structure scale,cell and grain structures in both the marginal and central zones become more refined,with cell sizes reducing by 49%-72%(∼3.02μm→0.86-1.55μm).Particularly,the minimum-scaled structures also feature broken eutectic Si particles and nanopores.The essence is primarily due to the low heat dissipation with higher peak temperature and longer duration time at high temperatures in both the small-scale structures and marginal zones.Additionally,smaller structures correlate with reduced microhardness and tensile strength,accompanied by the“softening”of the marginal zones.The strength of the minimum-scaled structure is only half that of the standard sample.Our findings suggest a scale threshold of 2.0 mm for researching scale effect.Encouragingly,in-corporating additional contour scanning significantly counteracts the adverse influence of the scale effect.Owing to the combined influence of extended inter-layer time and laser remelting,all samples demon-strate a distinctly refined microstructure.This results in consistently high levels of microhardness and strength,with the“hardening”of the marginal zones.Eventually,the relationship between mechanical properties and microstructure sizes is established.This study provides valuable insights into the innova-tive designs and engineering applications of multi-scaled structures in LPBF using various materials.展开更多
The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal...The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal stability and vibration damping capabilities.However,basic research on Invar/MnCu FGM is still lacking,hindering its potential applications.To address this gap,this study was conducted using mixed powders and consistent process parameters to print experiments for Invar/MnCu FGM and homogeneous samples.Phases,microstructures,compositions,and thermal expansion properties were thoroughly examined.Three types of defects were detected in the Invar/MnCu FGM sample:unmelted Invar 36 powders,cracks,and pores.The mechanism of unmelted powders was deeply discussed,attributing it to material properties influencing laser absorptivity,the required time for melting powder,and effects on solidus temperature.The mechanism of cracks was also discussed,attributing it to theγ-Fe dendritic structure causing low melting point metal to form an intergranular liquid film,harmful secondary phases mismatched with the terminal alloy,and obvious tensile stresses during the DED process.Additionally,an effective strategy was proposed to reduce defects in Invar/MnCu FGM.After optimization,the specimens exhibited excellent tensile properties,with a yield strength of 262±5 MPa,an ultimate tensile strength of 316±7 MPa,and an elongation of 3%±1%.This research provides valuable references and insights for subsequent work,offering robust support for better understanding and designing other FGM.展开更多
基金supported by the National Key Research and Development Program of China(Nos.2022YFB4600300 and 2022YFB4600301)the Research Fund of the State Key Laboratory of Solidification Processing(NPU)(No.2023-QZ-04)+3 种基金the ND Basic Research Funds of NPU(No.G2022WD)the National Natural Science Foundation of China(No.52175364)the Shenzhen Science and Technology Plan Project(No.JCYJ20180508151903646)the Science and Technology Plan of Xi’an City(No.2023JH-ZCGJ-0141).
文摘The pre-alloyed TiB_(2)/AlSi10Mg composite,a new high-strength aluminum alloy developed for laser pow-der bed fusion(LPBF)technology,offers promising applications in lightweight and multi-scaled structures.However,thermal behavior during LPBF is markedly scale-dependent,leading to microstructural varia-tions that significantly affect the load-bearing capacity of multi-scaled structures.Therefore,this study systematically investigates the scale-dependent behavior of microstructure characteristics of this com-posite.Utilizing a hatching scanning strategy,it was found that the marginal zones of samples are pre-dominantly composed of coarse Al cell and Al grain structures,contrasting with the fine microstructures in the central zones.With increasing structure scale,cell and grain structures in both the marginal and central zones become more refined,with cell sizes reducing by 49%-72%(∼3.02μm→0.86-1.55μm).Particularly,the minimum-scaled structures also feature broken eutectic Si particles and nanopores.The essence is primarily due to the low heat dissipation with higher peak temperature and longer duration time at high temperatures in both the small-scale structures and marginal zones.Additionally,smaller structures correlate with reduced microhardness and tensile strength,accompanied by the“softening”of the marginal zones.The strength of the minimum-scaled structure is only half that of the standard sample.Our findings suggest a scale threshold of 2.0 mm for researching scale effect.Encouragingly,in-corporating additional contour scanning significantly counteracts the adverse influence of the scale effect.Owing to the combined influence of extended inter-layer time and laser remelting,all samples demon-strate a distinctly refined microstructure.This results in consistently high levels of microhardness and strength,with the“hardening”of the marginal zones.Eventually,the relationship between mechanical properties and microstructure sizes is established.This study provides valuable insights into the innova-tive designs and engineering applications of multi-scaled structures in LPBF using various materials.
基金supported by the National Key Research and Development Program of China(Nos.2022YFB4600300 and 2022YFB4600301)the National Natural Science Foundation of China(No.52175364)+1 种基金the ND Basic Research Funds of NPU(G2022WD)the Research Fund of the State Key Laboratory of Solidification Processing(NPU),China(No.2023-QZ-04).
文摘The fabrication of Invar/MnCu functionally graded material(FGM)through directed energy deposition(DED)can satisfy the demands for precision devices in aerospace,providing lightweight properties and integrating thermal stability and vibration damping capabilities.However,basic research on Invar/MnCu FGM is still lacking,hindering its potential applications.To address this gap,this study was conducted using mixed powders and consistent process parameters to print experiments for Invar/MnCu FGM and homogeneous samples.Phases,microstructures,compositions,and thermal expansion properties were thoroughly examined.Three types of defects were detected in the Invar/MnCu FGM sample:unmelted Invar 36 powders,cracks,and pores.The mechanism of unmelted powders was deeply discussed,attributing it to material properties influencing laser absorptivity,the required time for melting powder,and effects on solidus temperature.The mechanism of cracks was also discussed,attributing it to theγ-Fe dendritic structure causing low melting point metal to form an intergranular liquid film,harmful secondary phases mismatched with the terminal alloy,and obvious tensile stresses during the DED process.Additionally,an effective strategy was proposed to reduce defects in Invar/MnCu FGM.After optimization,the specimens exhibited excellent tensile properties,with a yield strength of 262±5 MPa,an ultimate tensile strength of 316±7 MPa,and an elongation of 3%±1%.This research provides valuable references and insights for subsequent work,offering robust support for better understanding and designing other FGM.
