TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality in...TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality inspection of the joint were studied.The results show that the microstructure of the weld consists of a large number of acicularα′andβblock.The microhardness curve shows that the microhardness value in the fusion zone(FZ)of the joint is significantly higher than that in the heat affected zone(HAZ)and the base metal(BM),and the microhardness of the base metal is the lowest.The tensile strength of the joint is equivalent to that of the base metal,and the fracture morphology shows that the fracture mechanism of the joint is mixed ductile-brittle fracture mode.The weld quality is excellent through chemical inspection,penetrant inspection and X-ray inspection.展开更多
Bead-on-plate CO2 laser welding of 1 000 MPa grade transformation induced plasticity （TRIP） steel was conducted under different welding powers, welding speeds and shield gases. The macrostructural and microstructura...Bead-on-plate CO2 laser welding of 1 000 MPa grade transformation induced plasticity （TRIP） steel was conducted under different welding powers, welding speeds and shield gases. The macrostructural and microstructural features of the welded joint were investigated. The increase of welding speed reduced the width of the weld bead and the porosities in the weld bead resulting from the different flow mode of melted metal in weld pool. The decrease of welding power or use of shield gas of helium also contributed to the reduction of porosity in the weld bead due to the alleviation of induced plasma formation, thus stabilizing the keyhole. The porosity formation intimately correlated with the evaporation of alloy element Mn in the base metal. The laser welded metal had same martensite microstructure as that of water-quenched base metal. The welding parameters which increased cooling rate all led to fine microstructures of the weld bead.展开更多
Binary TiMn 2 alloys with various compositions were arc melted in an Ar atmosphere. These alloys consist of TiMn 2 and a small amount of TiMn depending on alloy composition. Annealed Ti 59.4% Mn exhibits the greatest ...Binary TiMn 2 alloys with various compositions were arc melted in an Ar atmosphere. These alloys consist of TiMn 2 and a small amount of TiMn depending on alloy composition. Annealed Ti 59.4% Mn exhibits the greatest capacity for hydrogen absorption and the smallest degradation of capacity during repeated hydrogen absorption and desorption. No apparent macro and microstructural changes are observed in Ti 59.4% Mn by repeated hydrogenation of 30 cycles. At Mn content higher than 59.4% Mn, the formation of nano sized Ti hydride and the lattice expansion due to retained interstitial hydrogen were confirmed in repeatedly hydrogenated alloys. Pulverized powders were refined in all the alloys with increasing the number of repeated hydrogenation cycles. Many onion like cracks are introduced in annealed pure Ta with 100?μm equi axed grains by holding at 1?473?K followed by furnace cooling to room temperature in a hydrogen atmosphere, but no crack is observed after holding at 1?473?K in a hydrogen atmosphere followed by furnace cooling in an Ar atmosphere. It is concluded that the surface activation is attained in a hydrogen atmosphere at 1?473?K and multiple cracking occurs by absorbing a large amount of hydrogen at lower temperature. Volume expansion and dislocations generated by hydrogenation and hydride formation are responsible for multiple cracking. Hydrogen induced multiple cracking in Ta occurs in the following sequence: hydrogen absorption, lattice expansion, hydride formation, and crack nucleation and propagation. Powder fabrication of Ta by hydrogenation is discussed in comparison with the hydrogen pulverization of intermetallic alloys.展开更多
基金the Priority Academic Program Development of Jiangsu Higher Education Institution and Beijing Institute of Aeronautical Materials(No.KZ82171509).
文摘TIG welding experiments of TC2 titanium alloy sheet was carried out,and the well-formed weld was obtained.After welding process,the cross-section microstructure,mechanical properties,fracture morphology and quality inspection of the joint were studied.The results show that the microstructure of the weld consists of a large number of acicularα′andβblock.The microhardness curve shows that the microhardness value in the fusion zone(FZ)of the joint is significantly higher than that in the heat affected zone(HAZ)and the base metal(BM),and the microhardness of the base metal is the lowest.The tensile strength of the joint is equivalent to that of the base metal,and the fracture morphology shows that the fracture mechanism of the joint is mixed ductile-brittle fracture mode.The weld quality is excellent through chemical inspection,penetrant inspection and X-ray inspection.
文摘Bead-on-plate CO2 laser welding of 1 000 MPa grade transformation induced plasticity （TRIP） steel was conducted under different welding powers, welding speeds and shield gases. The macrostructural and microstructural features of the welded joint were investigated. The increase of welding speed reduced the width of the weld bead and the porosities in the weld bead resulting from the different flow mode of melted metal in weld pool. The decrease of welding power or use of shield gas of helium also contributed to the reduction of porosity in the weld bead due to the alleviation of induced plasma formation, thus stabilizing the keyhole. The porosity formation intimately correlated with the evaporation of alloy element Mn in the base metal. The laser welded metal had same martensite microstructure as that of water-quenched base metal. The welding parameters which increased cooling rate all led to fine microstructures of the weld bead.
文摘Binary TiMn 2 alloys with various compositions were arc melted in an Ar atmosphere. These alloys consist of TiMn 2 and a small amount of TiMn depending on alloy composition. Annealed Ti 59.4% Mn exhibits the greatest capacity for hydrogen absorption and the smallest degradation of capacity during repeated hydrogen absorption and desorption. No apparent macro and microstructural changes are observed in Ti 59.4% Mn by repeated hydrogenation of 30 cycles. At Mn content higher than 59.4% Mn, the formation of nano sized Ti hydride and the lattice expansion due to retained interstitial hydrogen were confirmed in repeatedly hydrogenated alloys. Pulverized powders were refined in all the alloys with increasing the number of repeated hydrogenation cycles. Many onion like cracks are introduced in annealed pure Ta with 100?μm equi axed grains by holding at 1?473?K followed by furnace cooling to room temperature in a hydrogen atmosphere, but no crack is observed after holding at 1?473?K in a hydrogen atmosphere followed by furnace cooling in an Ar atmosphere. It is concluded that the surface activation is attained in a hydrogen atmosphere at 1?473?K and multiple cracking occurs by absorbing a large amount of hydrogen at lower temperature. Volume expansion and dislocations generated by hydrogenation and hydride formation are responsible for multiple cracking. Hydrogen induced multiple cracking in Ta occurs in the following sequence: hydrogen absorption, lattice expansion, hydride formation, and crack nucleation and propagation. Powder fabrication of Ta by hydrogenation is discussed in comparison with the hydrogen pulverization of intermetallic alloys.
