The hot-stamped steel with ultrahigh strength is a promising material for the fabrication of automotive components.However,the coating on the sheet surface leads to a softening problem in the welded joint.Instead of t...The hot-stamped steel with ultrahigh strength is a promising material for the fabrication of automotive components.However,the coating on the sheet surface leads to a softening problem in the welded joint.Instead of the costly coating removal process,heat treatment is an economical and effective method for the diffusion process,which can decrease the Al concentration in the coating.In this study,a preheating treatment was carried out on Al-Si-coated 22MnB5 hot-stamped steels for the homogeneity of Al,followed by laser welding and hot stamping.The effects of the preheating on the microstructure and mechanical properties of the laser-welded joints were investigated.With the preheating treatment,the Al-Si coating transformed into an Fe-Al intermetallic compound and the difference in Al content between the coating and substrate was reduced.The Al content in the weld of the specimen with the preheating treatment was reduced,compared with that without the preheating treatment.The amount ofδ-ferrite in the weld after laser welding was reduced largely.The distribution of long-bland-like segregation was changed to a fine and uniform distribution.With the preheating treatment,the tensile strength of the welded joint was significantly improved and comparable to that of the decoated joint.In conclusion,the preheating treatment before the welding is an effective method to suppress the formation ofδ-ferrite and improve the mechanical properties of the welded joint.展开更多
Conventional strategies to strengthen alloys are usually accompanied by drastic sacrifice in ductility,which is known as the strength-ductility trade-off.New metallurgical processing approaches are required to defeat ...Conventional strategies to strengthen alloys are usually accompanied by drastic sacrifice in ductility,which is known as the strength-ductility trade-off.New metallurgical processing approaches are required to defeat this longstanding dilemma.Here we report a novel solid-state powder manufacturing route to overcome this challenge enabling the architecting of a complex multiphase constituent composite using readily available metal powder as a feedstock.The materials design philosophy is successfully verified in a system mixing conventional austenitic stainless steel and ferritic steel powder and consolidating it by hot isostatic pressing.Significant strengthening and work hardenability are achieved at no expense of ductility compared to the ferrite and austenite on their own.Such extraordinary strength-ductility synergy is attributed to the well-architected compositional gradients across different phases resulting in soft and hard regions at the scale of the original powder without sharp interfaces.Accordingly,plasticity progresses from soft to hard regions during mechanical loading,which is the key to mitigating the deformation incompatibility and enabling remarkable ductility.Our study provides a new concept for materials design with synergistic properties that used to be trade-offs in conventional materials,which is applicable to a broad range of material systems with unprecedented multifunctionality.展开更多
Mg(and Mg alloys)and Ti(and Ti alloys)are two important classes of metallic implant materials which are respectively completely degradable and non-degradable after implantation.Making composites composed of them offer...Mg(and Mg alloys)and Ti(and Ti alloys)are two important classes of metallic implant materials which are respectively completely degradable and non-degradable after implantation.Making composites composed of them offers the promise for combining their property advantages for bone repair.Here,we present a Mg-Ti composite fabricated by pressureless infiltration of pure Mg melt into 3D printed Ti scaffold,and demonstrate a potential of the composite for use as new partially degradable and bioactive implant materials.The composite has such architecture that the Mg and Ti phases are topologically bicontinuous and mutually interspersed in 3D space,and exhibits several advantages over its constituents,such as higher strengths than as-cast pure Mg and Ti scaffold along with lower Young’s modulus than dense Ti.Additionally,the degradation of Mg phase may induce the formation and ingrowth of new bone tissues into the Ti scaffold to form mechanical interlocking between them;in this process,the Ti scaffold provides constant support and Young’s modulus adaptively decreases toward that of bone.Despite the accelerated corrosion than pure Mg,the composite remains non-cytotoxic and does not cause obvious adverse reactions after implantation as revealed by in vitro and in vivo experiments.This study may offer a new possibility for combining mechanical durability and bioactivity in implant materials,and allow for customized and targeted design of the implant.展开更多
基金the National Natural Science Foundation of China(No.51705318)the Project of LNG Shipbuilding from the Ministry of Industry and Information Technology of China。
文摘The hot-stamped steel with ultrahigh strength is a promising material for the fabrication of automotive components.However,the coating on the sheet surface leads to a softening problem in the welded joint.Instead of the costly coating removal process,heat treatment is an economical and effective method for the diffusion process,which can decrease the Al concentration in the coating.In this study,a preheating treatment was carried out on Al-Si-coated 22MnB5 hot-stamped steels for the homogeneity of Al,followed by laser welding and hot stamping.The effects of the preheating on the microstructure and mechanical properties of the laser-welded joints were investigated.With the preheating treatment,the Al-Si coating transformed into an Fe-Al intermetallic compound and the difference in Al content between the coating and substrate was reduced.The Al content in the weld of the specimen with the preheating treatment was reduced,compared with that without the preheating treatment.The amount ofδ-ferrite in the weld after laser welding was reduced largely.The distribution of long-bland-like segregation was changed to a fine and uniform distribution.With the preheating treatment,the tensile strength of the welded joint was significantly improved and comparable to that of the decoated joint.In conclusion,the preheating treatment before the welding is an effective method to suppress the formation ofδ-ferrite and improve the mechanical properties of the welded joint.
基金financially supported by the National Key R&D Program of China(No.2023YFB3712703)the Engineering and Physical Sciences Research Council(EPSRC)Rolls-Royce Plc.Michael Preuss would like to acknowledge the start-up fund from Monash University.
文摘Conventional strategies to strengthen alloys are usually accompanied by drastic sacrifice in ductility,which is known as the strength-ductility trade-off.New metallurgical processing approaches are required to defeat this longstanding dilemma.Here we report a novel solid-state powder manufacturing route to overcome this challenge enabling the architecting of a complex multiphase constituent composite using readily available metal powder as a feedstock.The materials design philosophy is successfully verified in a system mixing conventional austenitic stainless steel and ferritic steel powder and consolidating it by hot isostatic pressing.Significant strengthening and work hardenability are achieved at no expense of ductility compared to the ferrite and austenite on their own.Such extraordinary strength-ductility synergy is attributed to the well-architected compositional gradients across different phases resulting in soft and hard regions at the scale of the original powder without sharp interfaces.Accordingly,plasticity progresses from soft to hard regions during mechanical loading,which is the key to mitigating the deformation incompatibility and enabling remarkable ductility.Our study provides a new concept for materials design with synergistic properties that used to be trade-offs in conventional materials,which is applicable to a broad range of material systems with unprecedented multifunctionality.
基金supported by the National Key R&D Program of China(No.2020YFA0710404)the National Natural Science Foundation of China(Nos.51871216 and 52173269)the Youth Innovation Promotion Association CAS.
文摘Mg(and Mg alloys)and Ti(and Ti alloys)are two important classes of metallic implant materials which are respectively completely degradable and non-degradable after implantation.Making composites composed of them offers the promise for combining their property advantages for bone repair.Here,we present a Mg-Ti composite fabricated by pressureless infiltration of pure Mg melt into 3D printed Ti scaffold,and demonstrate a potential of the composite for use as new partially degradable and bioactive implant materials.The composite has such architecture that the Mg and Ti phases are topologically bicontinuous and mutually interspersed in 3D space,and exhibits several advantages over its constituents,such as higher strengths than as-cast pure Mg and Ti scaffold along with lower Young’s modulus than dense Ti.Additionally,the degradation of Mg phase may induce the formation and ingrowth of new bone tissues into the Ti scaffold to form mechanical interlocking between them;in this process,the Ti scaffold provides constant support and Young’s modulus adaptively decreases toward that of bone.Despite the accelerated corrosion than pure Mg,the composite remains non-cytotoxic and does not cause obvious adverse reactions after implantation as revealed by in vitro and in vivo experiments.This study may offer a new possibility for combining mechanical durability and bioactivity in implant materials,and allow for customized and targeted design of the implant.
