在金属材料激光增材制造过程中,预测出热历史的变化,可有效地提高成形质量,确保成形零件的尺寸高精度。采用网格激活和边界调整的有限差分方法,建立了能在线预测激光定向能量沉积(laser directed energy deposition,LDED)温度场随时间...在金属材料激光增材制造过程中,预测出热历史的变化,可有效地提高成形质量,确保成形零件的尺寸高精度。采用网格激活和边界调整的有限差分方法,建立了能在线预测激光定向能量沉积(laser directed energy deposition,LDED)温度场随时间和空间变化的三维瞬态数学模型。预测出熔池中心温度和熔池中心后方不同处的温度。最后通过沉积实验对模型计算出的温度进行了验证,模拟耗时仅为实际加工时间的83.5%。展开更多
Gadolinium(Gd)is one of the most effective strengthening elements for magnesium alloys.The development of commercially available Mg-Gd alloys with high Gd content and the optimization of their preparation processes ha...Gadolinium(Gd)is one of the most effective strengthening elements for magnesium alloys.The development of commercially available Mg-Gd alloys with high Gd content and the optimization of their preparation processes have been a major focus in magnesium alloy research.In this study,a Mg-23Gd-2Zn-0.4Zr alloy with ultra-high Gd content is designed,and high-quality fabrication is achieved using laser-directed energy deposition(LDED)technology.Through heat treatment and microstructure control,a balance between tensile strength(425 MPa)and elongation(3.4%)is achieved.The ultra-high strength of the LDED-T6 VZ232K alloy is primarily attributed to precipitation strengthening caused by the ultra-high density(2.4×10^(4)μm^(-2))ofβphase.The high ductility is mainly due to the modification of the fracture mode,facilitated by the introduction of a substantial number of stacking fault structures during solution heat treatment.The extended hardness plateau(exceeding 138 Hv)and high yield strength(exceeding 300 MPa)are associated with the three-directional cross-interlocked structure of theβphase in the over-aged state at 220℃ and 250℃.The analysis of the LDED-VZ232K alloy indicates that reduced heat input during the additive manufacturing(AM)process is critical for the defect-free fabrication of alloys with ultra-high Gd content.展开更多
Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstrea...Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.展开更多
The intrinsic brittleness of ceramic materials and the complex temperature field used during laser directed energy deposition(LDED)inevitably lead to the formation of surface and internal defects in the fabricated com...The intrinsic brittleness of ceramic materials and the complex temperature field used during laser directed energy deposition(LDED)inevitably lead to the formation of surface and internal defects in the fabricated components,which significantly affect their subsequent deposition accuracy and mechanical properties.This study systematically investigates the influence of the laser surface remelting(LSR)process on the forming quality of Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)eutectic ceramics prepared via LDED and reveals the underlying mechanisms with the support of finite element method(FEM)simulations and an infrared thermal imager.The new LSR strategy achieves a remarkable reduction of up to 82%in surface roughness by forming a secondary molten pool and mitigating heat accumulation effects.Moreover,the internal crack density and porosity are reduced by 41%and 86%,respectively.Through redistribution and precise control of the energy input,the originally incomplete eutectic microstructure is successfully transformed into an ultrafine eutectic microstructure,thereby effectively mitigating microstructural inhomogeneity,with the eutectic spacing refined to as small as 102 nm.Additionally,the reduction in surface and internal defects increases the relative density of the samples from 89.3%to 95.9%,whereas the microhardness shows maximum improvements of 18%and 11%in the transverse and longitudinal sections,respectively.On this basis,by integrating the LSR process,this study successfully prepared a bulk eutectic ceramic free of obvious macroscopic defects,with dimensions of 45 mm×20 mm×30 mm.The results provide critical insights into the scientific mechanism of the LSR in terms of defect suppression,microstructure evolution regulation,and mechanical property enhancement of eutectic ceramics.This approach is expected to offer a new technical pathway for improving the formation quality of LDED-ed large-size complex oxide eutectic ceramics,as well as other brittle material systems.展开更多
文摘在金属材料激光增材制造过程中,预测出热历史的变化,可有效地提高成形质量,确保成形零件的尺寸高精度。采用网格激活和边界调整的有限差分方法,建立了能在线预测激光定向能量沉积(laser directed energy deposition,LDED)温度场随时间和空间变化的三维瞬态数学模型。预测出熔池中心温度和熔池中心后方不同处的温度。最后通过沉积实验对模型计算出的温度进行了验证,模拟耗时仅为实际加工时间的83.5%。
基金financially supported by the National Key Research and Development Pragram of China(Grant No.2023YFB4603300)。
文摘Gadolinium(Gd)is one of the most effective strengthening elements for magnesium alloys.The development of commercially available Mg-Gd alloys with high Gd content and the optimization of their preparation processes have been a major focus in magnesium alloy research.In this study,a Mg-23Gd-2Zn-0.4Zr alloy with ultra-high Gd content is designed,and high-quality fabrication is achieved using laser-directed energy deposition(LDED)technology.Through heat treatment and microstructure control,a balance between tensile strength(425 MPa)and elongation(3.4%)is achieved.The ultra-high strength of the LDED-T6 VZ232K alloy is primarily attributed to precipitation strengthening caused by the ultra-high density(2.4×10^(4)μm^(-2))ofβphase.The high ductility is mainly due to the modification of the fracture mode,facilitated by the introduction of a substantial number of stacking fault structures during solution heat treatment.The extended hardness plateau(exceeding 138 Hv)and high yield strength(exceeding 300 MPa)are associated with the three-directional cross-interlocked structure of theβphase in the over-aged state at 220℃ and 250℃.The analysis of the LDED-VZ232K alloy indicates that reduced heat input during the additive manufacturing(AM)process is critical for the defect-free fabrication of alloys with ultra-high Gd content.
基金supported by the 2022 MTC Young Individual Research Grants(Grant No.M22K3c0097)the Singapore Research,Innovation and Enterprise(RIE)2025 PlanSingapore Aerospace Programme Cycle 16(Grant No.M2215a0073)。
文摘Lightweight aluminum(Al)alloys have been widely used in frontier fields like aerospace and automotive industries,which attracts great interest in additive manufacturing(AM)to process high-value Al parts.As a mainstream AM technique,laser-directed energy deposition(LDED)shows good scalability to meet the requirements for large-format component manufacturing and repair.However,LDED Al alloys are highly challenging due to their inherent poor printability(e.g.low laser absorption,high oxidation sensitivity and cracking tendency).To further promote the development of LDED high-performance Al alloys,this review offers a deep understanding of the challenges and strategies to improve printability in LDED Al alloys.The porosity,cracking,distortion,inclusions,element evaporation and resultant inferior mechanical properties(worse than laser powder bed fusion)are the key challenges in LDED Al alloys.Processing parameter optimizations,in-situ alloy design,reinforcing particle addition and field assistance are the efficient approaches to improving the printability and performance of LDED Al alloys.The underlying correlations between processes,alloy innovation,characteristic microstructures,and achievable performances in LDED Al alloys are discussed.The benchmark mechanical properties and primary strengthening mechanism of LDED Al alloys are summarized.This review aims to provide a critical and in-depth evaluation of current progress in LDED Al alloys.Future opportunities and perspectives in LDED high-performance Al alloys are also outlined.
基金the National Key R&D Program of China(No.2024YFB3714502)the National Natural Science Foundation of China(Nos.52130204 and 52174376)+5 种基金the Guangdong Basic and Applied Basic Research Foundation(No.2024B1515120031)the Key R&D Project of Shaanxi Province(Nos.2024GX-YBXM-220,2024CY-GJHX-29,2024GX-ZDCYL-03-03,and 2024GXYBXM-400)the Ningbo Major Research and Development Plan Project(No.2025Z070)the National Advanced Rare Metal Materials Innovation Center Project(No.2024 ZG-GCZX-01(1)-01)the Foundation of the China Scholarship Council(No.202406290136)the Fund of the State Key Laboratory of Solidification Processing in NPU(No.2025-TZ-01).
文摘The intrinsic brittleness of ceramic materials and the complex temperature field used during laser directed energy deposition(LDED)inevitably lead to the formation of surface and internal defects in the fabricated components,which significantly affect their subsequent deposition accuracy and mechanical properties.This study systematically investigates the influence of the laser surface remelting(LSR)process on the forming quality of Al_(2)O_(3)/GdAlO_(3)/ZrO_(2)eutectic ceramics prepared via LDED and reveals the underlying mechanisms with the support of finite element method(FEM)simulations and an infrared thermal imager.The new LSR strategy achieves a remarkable reduction of up to 82%in surface roughness by forming a secondary molten pool and mitigating heat accumulation effects.Moreover,the internal crack density and porosity are reduced by 41%and 86%,respectively.Through redistribution and precise control of the energy input,the originally incomplete eutectic microstructure is successfully transformed into an ultrafine eutectic microstructure,thereby effectively mitigating microstructural inhomogeneity,with the eutectic spacing refined to as small as 102 nm.Additionally,the reduction in surface and internal defects increases the relative density of the samples from 89.3%to 95.9%,whereas the microhardness shows maximum improvements of 18%and 11%in the transverse and longitudinal sections,respectively.On this basis,by integrating the LSR process,this study successfully prepared a bulk eutectic ceramic free of obvious macroscopic defects,with dimensions of 45 mm×20 mm×30 mm.The results provide critical insights into the scientific mechanism of the LSR in terms of defect suppression,microstructure evolution regulation,and mechanical property enhancement of eutectic ceramics.This approach is expected to offer a new technical pathway for improving the formation quality of LDED-ed large-size complex oxide eutectic ceramics,as well as other brittle material systems.
