Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely us...Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).展开更多
Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pu...Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.展开更多
Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micr...Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micro-electromechanical systems,micro-sensors,and field-effect transistors.However,SiC,being a brittle and hard material,poses challenges for traditional machining methods like micro-groove machining and chemical etching,including subsurface damage,short tool life,and low processing efficiency.This paper investigates the processing characteristics of femtosecond laser machining of SiC micro-grooves and compares them with those of single-crystal Si.The results indicate that femtosecond laser ablation of SiC primarily leads to melting and vaporization,forming modification,melted,and ablation areas in the affected area.Femtosecond laser processing of SiC micro-grooves involves three processes:heat absorption and melting,vaporization,and chipping,with vaporization as the primary material removal mechanism.The depth and width of SiC micro-grooves are positively correlated with pulse energy(E_(p)),pulse overlap rate(PO),and number of passes(N_(pass)).The bottom roughness of the micro-grooves is positively correlated with E_(p),negatively correlated with PO,and less affected by changes in the N_(pass).These findings further elucidate the material removal and micro-groove formation mechanisms of SiC under femtosecond laser irradiation,providing theoretical insights for high-quality and high-efficiency processing of SiC micro-grooves.展开更多
Annelid-inspired robots exhibit excellent motion adaptability and structural compliance,enabling them to navigate con-lfined,hazardous,or complex environments such as pipelines,soil,or the gastrointestinal tract.This ...Annelid-inspired robots exhibit excellent motion adaptability and structural compliance,enabling them to navigate con-lfined,hazardous,or complex environments such as pipelines,soil,or the gastrointestinal tract.This review summarizes key developments in their bionic part design,actuation methods,material selection,and performance characteristics.Comparative analyses show that different actuation strategies(e.g.,pneumatic,shape memory alloys,and electroactive polymers,ete.)need to be weighed in terms of their advantages,limitations,and applicable environments.Materials likesilicone rubber and SMA are evaluated for their strength,flexibility,and energy performance.Quantitative benchmarks of velocity,load capacity,and energy consumption are presented to highlight design-performance correlations.Prospective research directions include the integration of multifunctional adaptive materials,real-time feedback sensing systems,and scalable architectures for autonomous operation in unstructured environments.展开更多
Diamond is a highly valuable material with diverse industrial applications,particularly in the fields of semiconductor,optics,and high-power electronics.However,its high hardness and chemical stability make it difficu...Diamond is a highly valuable material with diverse industrial applications,particularly in the fields of semiconductor,optics,and high-power electronics.However,its high hardness and chemical stability make it difficult to realize high-efficiency and ultra-low damage machining of diamond.To address these challenges,several polishing methods have been developed for both single crystal diamond(SCD)and polycrystalline diamond(PCD),including mechanical,chemical,laser,and ion beam processing methods.In this review,the characteristics and application scope of various polishing technologies for SCD and PCD are highlighted.Specifically,various energy beam-based direct and assisted polishing technologies,such as laser polishing,ion beam polishing,plasma-assisted polishing,and laser-assisted polishing,are summarized.The current research progress,material removal mechanism,and infuencing factors of each polishing technology are analyzed.Although some of these methods can achieve high material removal rates or reduce surface roughness,no single method can meet all the requirements.Finally,the future development prospects and application directions of different polishing technologies are presented.展开更多
While the use of low-melting-point metals as sintering aids for high-entropy carbide(HEC)ceramics has been well established,their existence can compromise hardness due to residual metallic inclusions.This study demons...While the use of low-melting-point metals as sintering aids for high-entropy carbide(HEC)ceramics has been well established,their existence can compromise hardness due to residual metallic inclusions.This study demonstrates an innovative strategy to meet this challenge,where(Ti,Zr,Nb,Ta,Mo)C high-entropy carbide ceramics with ultrafine grains and enhanced hardness are obtained through chromium(Cr)-metal-assisted spark plasma sintering(SPS)at a temperature as low as 1600℃.The results show that the addition of 5 vol%Cr promotes the formation of highly densified single HEC phase ceramics with a high relative density(98.4%)and an ultrafine-grained microstructure(0.17μm).This low-temperature densification mechanism can be attributed to Cr’s solid-solution effect within the matrix and the increased carbon vacancies generated during sintering.The grain size of the(Ti,Zr,Nb,Ta,Mo)C ceramics with 5 vol%Cr metal addition is significantly smaller than that of Cr-free(Ti,Zr,Nb,Ta,Mo)C ceramics sintered at 2000℃(3.03μm)or via traditional low-temperature liquid-phase sintering(1.3–1.5μm).Importantly,the addition of 5 vol%Cr substantially increased the hardness of the ceramics,with a remarkable increase from 23.57 to 28.16 GPa compared to that of the pure(Ti,Zr,Nb,Ta,Mo)C ceramics,owing to the fine-grain strengthening and solid-solution strengthening mechanisms.This work highlights the uniqueness of Cr metal as a sintering aid in achieving densification and hardness improvements in(Ti,Zr,Nb,Ta,Mo)C ceramics,offering a promising strategy for improving the properties of HEC materials for further development in the near future.展开更多
基金Key-Area Research and Development Program of Guangdong Province(2023B0909020004)Project of Innovation Research Team in Zhongshan(CXTD2023006)+1 种基金Natural Science Foundation of Guangdong Province(2023A1515011573)Zhongshan Social Welfare Science and Technology Research Project(2024B2022)。
文摘Laser powder bed fusion(LPBF)is highly suitable for forming 18Ni300 mold steel,thanks to its excellent capability in manufacturing complex shapes and outstanding capacity for regulating microstructures.It is widely used in fields such as injection molding,die casting,and stamping dies.Adding reinforcing particles into steel is an effective means to improve its performance.Nb/18Ni300 composites were fabricated by LPBF using two kinds of Nb powders with different particle sizes,and their microstructures and properties were studied.The results show that the unmelted Nb particles are uniformly distributed in the 18Ni300 matrix and the grains are refined,which is particularly pronounced with fine Nb particles.In addition,element diffusion occurs between the particles and the matrix.The main phases of the base alloy are α-Fe and a small amount of γ-Fe.With the addition of Nb,part of the α-Fe is transformed into γ-Fe,and unmelted Nb phases appear.The addition of Nb also enhances the hardness and wear resistance of the composites but slightly reduces their tensile properties.After aging treatment,the molten pools and grain boundaries become blurred,grains are further refined,and the interfaces around the particles are thinned.The aging treatment also promotes the formation of reverted austenite.The hardness,ultimate tensile strength,and volumetric wear rate of the base alloy reach 51.9 HRC,1704 MPa,and 17.8×10^(-6) mm^(3)/(N·m),respectively.In contrast,the sample added with fine Nb particles has the highest hardness(56.1 HRC),ultimate tensile strength(1892 MPa)and yield strength(1842 MPa),and the volume wear rate of the sample added with coarse Nb particles is reduced by 90%to 1.7×10^(-6) mm^(3)/(N·m).
基金Supported by Guangdong Major Project of Basic and Applied Research,China(Grant No.2019B030302010)National Natural Science Foundation of China (Grant Nos.51735003,52205456)
文摘Avoiding crystallization while maintaining the original microstructure and mechanical properties of the material are long-term goals of laser welding of Zr-based bulk metallic glass(BMG).In this paper,the effect of pulsed laser welding parameters on the microstructure,crystallization degree,and mechanical properties of Zr57Nb5Cu15.4Ni12.6Al10 BMG is investigated.Non-crystallized welding forming of a zirconium-based amorphous alloy is achieved by optimizing the process parameters of pulsed laser welding.The crystallization degree of Zr-based BMG is mainly determined by the welding speed and power.The welding depth and crystallization area fraction increase with an increase in the effective peak power density.The optimized welding process can effectively reduce the heat accumulation of the weld,thus avoiding crystallization.The flexural strength of the weld can be maintained at 96.5%of the matrix.
基金Supported by National Natural Science Foundation of China(Grant No.52122510)the School-enterprise Cooperation Project Funded by Dongguan Strong Laser Advanced Equipment Co.,Ltd.(Grant No.21HK0214)。
文摘Silicon carbide(SiC)is widely used in fields such as new energy,military radar,and aerospace due to its outstanding physical and chemical properties.The surface micro-grooves of SiC can enhance the performance of micro-electromechanical systems,micro-sensors,and field-effect transistors.However,SiC,being a brittle and hard material,poses challenges for traditional machining methods like micro-groove machining and chemical etching,including subsurface damage,short tool life,and low processing efficiency.This paper investigates the processing characteristics of femtosecond laser machining of SiC micro-grooves and compares them with those of single-crystal Si.The results indicate that femtosecond laser ablation of SiC primarily leads to melting and vaporization,forming modification,melted,and ablation areas in the affected area.Femtosecond laser processing of SiC micro-grooves involves three processes:heat absorption and melting,vaporization,and chipping,with vaporization as the primary material removal mechanism.The depth and width of SiC micro-grooves are positively correlated with pulse energy(E_(p)),pulse overlap rate(PO),and number of passes(N_(pass)).The bottom roughness of the micro-grooves is positively correlated with E_(p),negatively correlated with PO,and less affected by changes in the N_(pass).These findings further elucidate the material removal and micro-groove formation mechanisms of SiC under femtosecond laser irradiation,providing theoretical insights for high-quality and high-efficiency processing of SiC micro-grooves.
基金Supported by the Youth Science and Technology Innovation Program of Xiamen Ocean and Fisheries Development Special Funds(No.23ZHZB034QCB38).
文摘Annelid-inspired robots exhibit excellent motion adaptability and structural compliance,enabling them to navigate con-lfined,hazardous,or complex environments such as pipelines,soil,or the gastrointestinal tract.This review summarizes key developments in their bionic part design,actuation methods,material selection,and performance characteristics.Comparative analyses show that different actuation strategies(e.g.,pneumatic,shape memory alloys,and electroactive polymers,ete.)need to be weighed in terms of their advantages,limitations,and applicable environments.Materials likesilicone rubber and SMA are evaluated for their strength,flexibility,and energy performance.Quantitative benchmarks of velocity,load capacity,and energy consumption are presented to highlight design-performance correlations.Prospective research directions include the integration of multifunctional adaptive materials,real-time feedback sensing systems,and scalable architectures for autonomous operation in unstructured environments.
基金sponsored by the National Natural Science Foundation of China(Nos.51835004,U22A20198)the Major Science and Technology Projects in Henan Province(221100230300)the 111 Project(No.B23011)。
文摘Diamond is a highly valuable material with diverse industrial applications,particularly in the fields of semiconductor,optics,and high-power electronics.However,its high hardness and chemical stability make it difficult to realize high-efficiency and ultra-low damage machining of diamond.To address these challenges,several polishing methods have been developed for both single crystal diamond(SCD)and polycrystalline diamond(PCD),including mechanical,chemical,laser,and ion beam processing methods.In this review,the characteristics and application scope of various polishing technologies for SCD and PCD are highlighted.Specifically,various energy beam-based direct and assisted polishing technologies,such as laser polishing,ion beam polishing,plasma-assisted polishing,and laser-assisted polishing,are summarized.The current research progress,material removal mechanism,and infuencing factors of each polishing technology are analyzed.Although some of these methods can achieve high material removal rates or reduce surface roughness,no single method can meet all the requirements.Finally,the future development prospects and application directions of different polishing technologies are presented.
基金financially supported by the National Natural Science Foundation of China(Nos.52172066,52172064,and 52072077)Shikuan Sun acknowledges the Guangdong Key Platform&Programs of the Education Department of Guangdong Province(No.2021ZDZX1003)the Guangdong Science and Technology Project(No.2021B1212050004).
文摘While the use of low-melting-point metals as sintering aids for high-entropy carbide(HEC)ceramics has been well established,their existence can compromise hardness due to residual metallic inclusions.This study demonstrates an innovative strategy to meet this challenge,where(Ti,Zr,Nb,Ta,Mo)C high-entropy carbide ceramics with ultrafine grains and enhanced hardness are obtained through chromium(Cr)-metal-assisted spark plasma sintering(SPS)at a temperature as low as 1600℃.The results show that the addition of 5 vol%Cr promotes the formation of highly densified single HEC phase ceramics with a high relative density(98.4%)and an ultrafine-grained microstructure(0.17μm).This low-temperature densification mechanism can be attributed to Cr’s solid-solution effect within the matrix and the increased carbon vacancies generated during sintering.The grain size of the(Ti,Zr,Nb,Ta,Mo)C ceramics with 5 vol%Cr metal addition is significantly smaller than that of Cr-free(Ti,Zr,Nb,Ta,Mo)C ceramics sintered at 2000℃(3.03μm)or via traditional low-temperature liquid-phase sintering(1.3–1.5μm).Importantly,the addition of 5 vol%Cr substantially increased the hardness of the ceramics,with a remarkable increase from 23.57 to 28.16 GPa compared to that of the pure(Ti,Zr,Nb,Ta,Mo)C ceramics,owing to the fine-grain strengthening and solid-solution strengthening mechanisms.This work highlights the uniqueness of Cr metal as a sintering aid in achieving densification and hardness improvements in(Ti,Zr,Nb,Ta,Mo)C ceramics,offering a promising strategy for improving the properties of HEC materials for further development in the near future.
