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
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.
