Increasing the reliability of welded joints in high-strength V-1461 aluminium–lithium alloy

Filler materials for welding V-1461 alloy, ensuring high cracking resistance, corrosion resistance and mechanical properties, are selected. The results of tests of the welded joints in static tensile loading and bending and the impact toughness of the weld metal and low-cycle fatigue strength are presented. The experimental results show that the application of impact ultrasound treatment increases by an order of magnitude the values of low-cycle fatigue resistance of the welded joints as a result of the formation of the nanostructured surface layers. The level of residual stresses in welded joints is determined.     

Investigation of the strength of steel–titanium diffusion welded joints

The results of investigation of the structure and mechanical properties in tensile loading and structural strength at 20°C of diffusion welded joints between 08Cr18Ni10Ti steel and PT-3V and PT-5V are presented.     

Application of the local approach to the fatigue assessment for welded joints

The fatigue behavior of welded structures is currently determined by means of recommendations defined in terms of S-N curve corresponding to the detail classes of welded joints without taking account of the actual geometry of the weld. A new fatigue strength assessment method based on Dang Van multiaxial fatigue limit criterion was introduced, which is named the local approach and presented by lnstitut de Soudure recently. The local approach has advantages in taking welding residual stresses and the geometry of the weld toe and weld root into consideration. The application of the local approach to the fatigue strength assessment of low carbon steel Q235B welded joints was studied. The fatigue tests and finite element analysis results show that the local approach parameters recommended by lnstitut de Soudure were incorrectly for low carbon steel Q235B welded joints. With aluminum alloy welded joints being used widely, the parameters of the local approach used for aluminum alloy welded joints were obtained and verified on bases of the fatigue tests and finite element analysis.     

Microstructures of 2219 twin wire welded joints

0IntroductionAs a kind of efficient welding method,twin wirewelding has many merits such as big deposition rate,littleheat input and narrow heat-affected zone.What’s more,the defects such as incomplete penetration,discontinuousseam or undercut can be avo…     

Research on the properties of laser welded joints of aluminum killed cold rolled steel

Aluminum killed cold rolled steel used for automobiles was welded in this paper by using CO2 laser with wavelength 10.6μm.The experiment shows that high quality of welding can be realized at welding speed of 4500mm/min by optimizing the parameters.The strenth and hardness of laser welded joints for aluminum killed cold rolled steel increased compared to those of the base metal while the formability decreased.Forming limit diagram of joint material indicated that the laser weld seam should avoid the maximum deformation area of automobile parts during the designing period for the position of weld seam.     

Improving the fatigue performance of longitudinal welded joints by low transformation temperature electrodes

0　IntroductionAfatigueisoneofthemainfailurescausesofweldedstructures.Manyexperimentshaveshownthatfatiguestrengthsofweldedjointsaremuchlowerthanthoseofbasemetal.Thefatiguecrackmainlyinitiatesatweldtoe ,becausetherearetensileresidualstressesandstressconcentrationinthisregion ,sothatthefatiguestrengthcanbeincreasedbybothmodifyingstressdistributionatweldtoeanddecreasingstressconcentration .Therearemanymethodstoimprovethefatiguestrengthsofweldedjoints[1,2 ] ,forexample ,TIGdress ing,hammerpeenin…     

Effect of the orientation of defects on the load‐carrying capacity of welded joints weakened by soft interlayers

The results of the investigations of the effect of the shape of the current decrease curve at the moment of completion of welding on the thermal cycle of welding up the crater and the shape of the surface of the shrinkage cavity are presented. The kinematics of solidification of the weld pool during the final stage of welding is investigated. The optimum shape of the current decrease curve for minimizing the dimensions and optimizing the shape of the shrinkage cavity is determined.     

Effect of cooling rate on the microstructure of electron beam welded joints of two-phase TiAl-based alloy

The analysis of the microstructural characterization and phase composition of electron beam welded joint zones of Ti- 43Al-9V-O. 3Y alloy has been done in this study. The welded seam is mainly composed of B2 phase, the partial γ ＋ α2 twophase lamellar structure and granular γm phase. And the lanthanon Y existed as YAl2 phase and served as grain refined. The impact of different cooling rates on joint microstructure, fracture characteristic and tensile strength were investigated. The high cooling rate restrained the structural transformation and resulted in the ordering structure. The fracture of the joint was brittle cleavage fracture because the ordering structure went against restraining the crack propagation. With the decrease of cooling rate, the transformation amounts of lamellar structure increased, and the fracture presented the layered and crosslayered characteristic.     

Microstructural characterization of electron beam welded joints of TiAl-based intermetallic compound

The feasibility to use election beam welding to join the nominal composition Ti-48Al-2Cr-2Nb (at.%) alloy was assessed. The microstructure characterization and cracking susceptibility of the joints were evaluated by means of OM, SEM, XRD, and microhardness.It was found that the welded microstructure exhibited columnar and     

Microstructurai characterization of electron beam welded joints of TiAl-based intermetallic compound

The feasibility to use electron beam welding to join the nominal composition Ti-48Al-2Cr-2Nb (at.%) alloy was assessed. The microstructure characterization and cracking susceptibility of the joints were evaluated by means of OM,SEM, XRD, and microhardness. It was found that the welded microstructure exhibited columnar and dendritic structures.Microstructural constituents in the fusion zone were a massive gamma structure and some amount of lamellar structure consisting of alternating platelets of α2 and γ. The major contributing factor to the susceptibility to solidification cracking was microsturctural change in this study for the suppression of α phase decomposition leading to produce more retained α2 britfie phase. Compared with transgranular cleavage fracture in the base metal, the weld metal exhibited mainly translamellar fracture.     

Special features of using backing tapes for shaping the ‘root’ layer of welded joints

The results of investigation of the formation of the ‘root’ layer of welded joints in different spatial positions using backing tapes as temporary shaping devices are presented. The parameters of the welding conditions and measures for producing high-quality welded joints preventing the formation of unacceptable defects are determined.     

Investigation on characteristic of J integral parameter in welded joints

The J integral parameter and its application feasibility in welded joints with different weldmatchings in yield strength (overmatching weld and undermatching weld), different material constitutive laws (material with a Ludes yield plateau and power hardening) and under different fracture types (ligament yielding fracture and general yielding fracture) are investigated. First the condition of J integral path independent has been studied based upon finite element analysis by using ADINA procedure on welded joints. It was shown that the J integral is path dependent for the cases studied in this paper. Then experiments were carried out to study availability of J integral as a plastic singularity parameter at the tip of the notch in welded joints. The results show that J dominance in most cases studied is not validated in v and u displacement fields. From both considerations mentioned above it can be concluded that J-integral as controlling parameter used to estimate the safety of welded structures is not alw     

Effects of strength matching and crack depth on the fracture parameters for welded joints

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Micro-mechanical properties of 2219 welded joints with twin wire welding

Nanoindentation method was adopted to investigate the distribution regularities of micro-mechanical properties of 2219 twin wire welded joints, thus providing the necessary theoretical basis and guidance for joint strengthening and improvement of welding procedure. Experimental results show that in weld zone, micro-mechanical properties are seriously uneven. Both hardness and elastic modulus distribute as uneven sandwich layers, while micro-mechanical properties in bond area are much more uniform than weld zone;In heat-affected zone of 2219 twin wire welded joint, distribution regularity of hardness is similar to elastic modulus. The average hardness in quenching zone is higher than softening zone, and the average elastic modulus in solid solution zone is slightly higher than softening zone. As far as the whole welded joint is concerned, metal in weld possesses the lowest hardness. For welded specimens without reinforcement, fracture position is the weld when tensioning. While for welded specimens with reinforcement, bond area is the poorest position with joint strength coefficient of 61%. So, it is necessary to strengthen the poor positions--weld and bond area of 2219 twin wire welded joint in order to solve joint weakening of welding this kind of alloy.     

Effect of modifying microadditions on the corrosion resistance of welded joints in low‐alloy steel

Results of investigation of the effect of the cooling rate on the structure and mechanical properties of metal in plasma quenching are presented.     

Bending properties of friction stir welded joints – Studies on characteristics of friction stir welded joints in structural aluminum alloys (report 4)

The objective of this work is to determine the best parameters for brazing ceramic joints of pre-metallized Al₂O₃ with Ti by a plasma process using amorphous ribbons of Cu₄₉Ag₄₅Ce_x alloy as the addition metal. The alloys were prepared in an arc oven, and later processed by melt spinning, varying Cerium content by 4–6%. Brazing took place in a vacuum oven and the following variables were analysed: deposition time of the Ti film and temperature and brazing time, which were related to the flex resistance in three points of the brazed joint. A linear regression equation was obtained, and the interaction between these factors was verified. The metallized ceramic surfaces showed excellent uniformity and the brazed joints demonstrated very good adhesion, achieving flex resistance values of up to176.8 MPa.     

Increasing the load‐carrying capacity of spot welded joints in low‐carbon steels

It is shown to be possible to produce a heat-resisting coating for an intermetallic titanium alloy with the hardening ortho phase preventing changes in the surface layer of the alloy as a result of the build-up of oxide corrosion products, which can soften the component at working temperatures of 700–800°C. The results of investigation of the heat resistance properties, evolution of the composition and structure of the alloyed ion-plasma coatings on the titanium alloy with the hardening ortho-phase at working temperatures show that the deposition of the coating greatly reduces the depth in which the surface layer of the alloy changes and the thickness of this layer does not exceed 5 μm.     

Properties and structure of friction stir welded joints in 1424 and V-1461 (Al–Li) alloys*

The effect of the friction stir welding (FSW) conditions on the structure of welded joint and mechanical properties of 1424 and V-1461 alloys is investigated. FSW is accompanied by the formation of a recrystallized fine-grain microstructure in the welded joint. It is shown that the increase of the heat input to the welded sheets does not increase the average grain size in the weld zone (the average grain size is 1.5–2.2 μm). The tensile strength of the welded joints depends on the welding conditions for both alloys. Special features of the microstructure formed in the zone of the welded joint are discussed and the effect of the microstructure on the mechanical properties of the welded joints and evolution under the effect of heat treatment after FSW are determined.     

Micro-mechanical properties of 2219 welded joints with twin wire welding 

0IntroductionWith the rapid developmentof modern manufacturing,applications of aluminum alloy welded structures with bigthickness are becoming more and more widely. As a kindof efficient welding method, twin wire welding has suchmerits as big deposition rate, little heat input and narrowheat-affected zone. At the same time, the defects such asincomplete penetration, discontinuous beam or undercutcan be avoided effectively[1 -5]. 2219 aluminum alloy hasthe wider application foreground due to it…     

Improving fatigue performance of welded joints of X65 pipeline steel by UIT

0IntroductionAs well known,ocean steel structures are most madeby welding.It is quite possible for ocean engineeringstructures,especially submarine oil and gas pipelines to bedestroyed by fatigue failure,because these structures al-ways endure cyclic load…