Advanced Materials Research Vols. 291-294

Abstract: Different physical simulation welding parameters were performed using Gleeble-3500 type thermal simulator to research the effect of thermal cycle on microstructure transition and property variation of boron steel 22MnB5. The peak temperature of welding thermal cycle was set to 1320-870°C, and cooling rates t_8/5 to 6s-100s. Then microstructure observation, hardness detection, and impact toughness tests were carried out to clarify the effect of different thermal cycles. The results show that 22MnB5 has good mechanical properties, but the toughness decreases obviously under certain thermal cycles, showing cold crack sensitivity of 22MnB5. Martensite and ferrite are the main microstructure under different peak temperature and t_8/5.

Abstract: Based on experiment, preparation method, formation mechanism and reaction process in was studied ,in which phase analysis was adoped. melting method and wet synthesis are separately used to produce ternary flux.it has been found that product will be different by using the method of steaming and filtering in the process of preparing Potassium fluoroaluminate. K₂AlF₅ is very easy to get as well as Cesium fluoroaluminate.Result of ternary flux is not the way we hoped it would be for the melting point is above 520°C.

Abstract: The effect of nano-Cu particles on mechanical bend reliability of micro-joining joint with Sn-3.5Ag lead free solder was studied in this paper. The results show that 0.5% nano-Cu composite lead free solder show significantly better shearing strength and mechanical bend fatigue properties than eutectic Sn-3.5Ag solder paste, 1.0% nano-Cu composites and 1.5% nano-Cu composites. The further analysis shows that adding nano-Cu particles make much effect on intermetallic (IMC) in the interface of micro-joint and the inside of the solder joint. The different interface of micro-joining joint induced different mechanical properties.

Abstract: The residual stress,which is unavoidable in the process of flash-butt-weld rails,plays important roles in the service life of the railway rails.However,knowledge of magnitude,direction,and sign of the residual stress is useful for maintenance and failure prevention.In this paper,we measured the residual stresses in the flash-butt weld of the U71Mn railway rail,using X-ray diffraction method.Besides,we investigated the influence of grinding on residual surface stress.This investigation showed that residual stress generated by grinding could be removed by electro-polishing,we also found that there was longitudinal compressive stress in the foot and head region,while the web region presented tensile stress,and in the transverse position,all of the three regions existed both compressive and tensile stress.

Abstract: The fatigue crack growth behavior of weld metal (WM), heat affected zone(HAZ) and base metal(BM) of Duplex Stainless Steel 2205(DSS) has been determined at high-frequency fatigue testing machine. The results show that the fatigue crack growth rate of WM is slowest and the ability to resist fatigue crack growth is highest in the three parts. Secondly, the sensitivity caused by the stress change of WM is the highest, followed by HAZ, and the BM is the weakest.

Abstract: In order to solve a problem of the low mechanical properties of Manual SHS Welding joint, a new iron-base manual SHS welding material was developed by CuO+Al and Fe₂O₃+Al being the thermit and adding iron alloy materials. The structure and properties of the welded joint were studied. The results indicated that: Cu-Fe alloy in the molten pool experiences liquid phase separation during rapid solidification, and the weld metal is macroscopically separated into one Fe-rich part and one Cu-rich part. Fe-rich phase is filled in the welding line. The higher Fe supersaturation is in the Cu-Fe weld metal, the more notablely and quickly liquid phase separates. At the same time, tensile strength of the welded joint was close to 520 MPa, and impact toughness was close to 32.1J/cm², and surface hardness was also close to HB360. It also indicated this technology can meet the need of repair of metal parts in field.

Abstract: An activated flux assisted tungsten inert gas (TIG) welding of type 316L stainless steel was investigated. SiO₂-TiO₂ mixed powder was selected as the activated flux. Mixed fluxes effect on the surface appearance, weld morphology, and ferrite structure were investigated. The results showed that TIG welds surface produced with flux contributed to the formation of residues. The 80% SiO₂+ 20%TiO₂ mixture can produce the greatest improvement function in TIG penetration. Silica-titania mixed flux assisted TIG welding can increase the ferrite content of stainless steel weld metal.

Abstract: Al₂O₃ is brazed with mild steel using 70Ag-27Cu-3Ti (wt.%) active filler alloy at 900°C for 5 min. The interfacial reaction products are analyzed with X-ray diffraction (XRD)．The interfacial phases are analyzed with EDAX. According to the experimental observations, the interfaces developed during brazing have been systematically characterized and the structure are separately Ti₃Cu₃O/Ti₃Al+ TiMn+TiFe₂ +Ag(s,s)+Cu(s,s)/TiC from alumina ceramics side to mild steel side.

Abstract: The residual stress fields can have strong influences on the integrity and performance of friction stir welded aluminum alloy structure, comprehensive insight into the residual stress distribution is the key to the Friction stir welding (FSW) engineering application for a wide range of materials and thicknesses improving the weld strength and fatigue life. In this paper, the current state of the residual stresses in the FSW aluminum alloy joints is reviewed, The focus is on recent advances of experimental research, the results of numerical simulation analysis, and the effects of the technological parameters(welding speed, rotational speed, shoulder geometry et al.) on residual stress fields was evaluated. In the end, The controlling technique of residual stresses from published literatures is summarized.

Abstract: The resistance spot welding between commercially pure titanium and stainless steel was achieved using an aluminum alloy insert. The interfacial microstructure and mechanical properties of the joint were investigated. The maximum tensile shear load of 5.38 kN was obtained from the Ti/SUS304 joint welded at the welding current of 10 KA. The results reveal that the property of the Ti/SUS304 joint can be improved by using an aluminum alloy insert between Ti and SUS304 sheet.