During the tungsten inert gas(TIG)welding process of Ti_(2)AlNb alloy,high heat input leads to the formation of coarse grains,which are detrimental to the mechanical properties of welded joints.To address this problem...During the tungsten inert gas(TIG)welding process of Ti_(2)AlNb alloy,high heat input leads to the formation of coarse grains,which are detrimental to the mechanical properties of welded joints.To address this problem,Ta microalloyed welding wires were developed to enhance the strength of the welded joints.The Ta-modifed fusion zone(FZ)exhibited a well-defned structure with a smooth,defect-free surface.Systematic analysis of the microstructure evolution and mechanical properties of the welded joints revealed that the Ta element completely dissolves into the FZ.During solidifcation,a signifcant constitutional undercooling efect occurs,promoting the columnar-to-equiaxed transition(CET)and reducing grain size from 187.42 to 133.49μm.Mechanical properties tests indicated that with increased Ta content,the strength of the welded joints initially increased and then decreased.When the Ta content in the welding wire was 1 wt%,the joints showed the best performance,with a tensile strength of 909.36 MPa and an elongation of 1.21%.Compared to the welded samples without Ta,the tensile strength and elongation increased by 153.01 MPa and 0.53%,respectively.Grain refnement and increased dislocation density were the main reasons for the improved mechanical properties.However,excessive Ta content led to signifcant the intragrain misorientation,increasing the joint’s anisotropy and causing uneven deformation during tensile testing.Therefore,further addition of Ta did not substantially enhance the tensile properties of the joint.Additionally,the paper provides a detailed analysis of the low elongation observed in the joint.After welding,dislocations were neatly arranged in the FZ,forming numerous parallel dislocation walls,leading to local stress concentration and accelerating crack initiation and propagation.Consequently,the elongation at the weld was lower than that of the base metal(BM).This research ofers a new approach to improve the mechanical properties of Ti2AlNb alloy during welding.展开更多
Electrospinning has drawn wide attention for its powerful capacity to produce ultrafne nanofbers(UNFs)from various materials.These UNFs demonstrated signifcantly enhanced performance,such as ultra-high surface area,mo...Electrospinning has drawn wide attention for its powerful capacity to produce ultrafne nanofbers(UNFs)from various materials.These UNFs demonstrated signifcantly enhanced performance,such as ultra-high surface area,more porosity and stronger mechanical properties.Here,we comprehensively review their basic principles,state-of-the-art methods and preponderant applications.We begin with a brief introduction to the refnement theory of polymer jets,followed by discussion of factors afecting fber refnement.We then discuss the refning strategies from the aspects of solution properties,spinning parameters,auxiliary force and post-treatment.Afterward,we highlight the most relevant and recent applications associated with the remarkable features of UNFs,including fltration materials,supercapacitors,biomedical materials and other applications.At the end,we ofer perspectives on the challenges,opportunities,and new directions for future development of electrospun UNFs.展开更多
In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each componen...In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each component function of a compactly supported refinable vector satisfying an inhomogeneous matrix refinement equation with finitely supported masks.展开更多
基金supported by the National Natural Science Foundation of China(No.52171041)the Science and Technology Special Project(K19168).
文摘During the tungsten inert gas(TIG)welding process of Ti_(2)AlNb alloy,high heat input leads to the formation of coarse grains,which are detrimental to the mechanical properties of welded joints.To address this problem,Ta microalloyed welding wires were developed to enhance the strength of the welded joints.The Ta-modifed fusion zone(FZ)exhibited a well-defned structure with a smooth,defect-free surface.Systematic analysis of the microstructure evolution and mechanical properties of the welded joints revealed that the Ta element completely dissolves into the FZ.During solidifcation,a signifcant constitutional undercooling efect occurs,promoting the columnar-to-equiaxed transition(CET)and reducing grain size from 187.42 to 133.49μm.Mechanical properties tests indicated that with increased Ta content,the strength of the welded joints initially increased and then decreased.When the Ta content in the welding wire was 1 wt%,the joints showed the best performance,with a tensile strength of 909.36 MPa and an elongation of 1.21%.Compared to the welded samples without Ta,the tensile strength and elongation increased by 153.01 MPa and 0.53%,respectively.Grain refnement and increased dislocation density were the main reasons for the improved mechanical properties.However,excessive Ta content led to signifcant the intragrain misorientation,increasing the joint’s anisotropy and causing uneven deformation during tensile testing.Therefore,further addition of Ta did not substantially enhance the tensile properties of the joint.Additionally,the paper provides a detailed analysis of the low elongation observed in the joint.After welding,dislocations were neatly arranged in the FZ,forming numerous parallel dislocation walls,leading to local stress concentration and accelerating crack initiation and propagation.Consequently,the elongation at the weld was lower than that of the base metal(BM).This research ofers a new approach to improve the mechanical properties of Ti2AlNb alloy during welding.
基金This work was partly supported by the Fundamental Research Funds for the Central Universities(2232020D-15,2232020A-08,2232020G-01,2232020D-14 and 2232019D3-11)grants(51773037,51973027,51803023,52003044 and 61771123)from the National Natural Science Foundation of China+3 种基金This work has also been supported by the Chang Jiang Scholars Program and the Innovation Program of Shanghai Municipal Education Commission(2019-01-07-00-03-E00023)to Prof.Xiaohong Qinthe Shanghai Sailing Program(19YF1400700)the Opening Project of State Key Laboratory of High Performance Ceramics and Superfne Microstructure(SKL201906SIC)Young Elite Scientists Sponsorship Program by CAST and DHU Distinguished Young Professor Program to Prof.Liming Wang.
文摘Electrospinning has drawn wide attention for its powerful capacity to produce ultrafne nanofbers(UNFs)from various materials.These UNFs demonstrated signifcantly enhanced performance,such as ultra-high surface area,more porosity and stronger mechanical properties.Here,we comprehensively review their basic principles,state-of-the-art methods and preponderant applications.We begin with a brief introduction to the refnement theory of polymer jets,followed by discussion of factors afecting fber refnement.We then discuss the refning strategies from the aspects of solution properties,spinning parameters,auxiliary force and post-treatment.Afterward,we highlight the most relevant and recent applications associated with the remarkable features of UNFs,including fltration materials,supercapacitors,biomedical materials and other applications.At the end,we ofer perspectives on the challenges,opportunities,and new directions for future development of electrospun UNFs.
基金Supported by National Natural Science Foundation of China (Grant Nos. 10771190, 10471123)
文摘In this paper, we investigate the support of a refinable vector satisfying an inhomoge- neous refinement equation. By using some methods introduced by So and Wang, an estimate is given for the support of each component function of a compactly supported refinable vector satisfying an inhomogeneous matrix refinement equation with finitely supported masks.
