The effect of welding materials on 1Cr18Ni9Ti and 2Cr13 steel welded joints electrochemical properties

By method of TIG,two kinds of welding materials were filled in and under certain welding craft conditions,1Cr18Ni9Ti and 2Cr13 were welded.The microstructure of two kinds of welded joints were observed and analyzed by OM,SEM.Through seawater immersion test,polarization curves and AC impedance spectroscopy of two kinds of welding joints were obtained.The results show that 2Cr13 and 1Cr18Ni9Ti welded joints are typical columnar crystal,the microstructure is lath martensite+austenite+carbide.The welded joints that filled in 308 and H1Cr21Ni10Mn7Mo welding wires,corrosion resistance has same change rule:Austenite base metal>HAZ near Austenite>welded joint>HAZ near Martensite>Martensite base metal.The every zone contrast of two kinds of welded joint corrosion resistance obtains:the welded joints filled in 308>the welded joints filled in H1Cr21Ni10Mn7Mo.

Application and prospect of computer technology in welding materials field

This paper summarizes the application status of computer technology in welding materials field from three aspects: the CAD of welding materials, the date base system for welding materials and the expert system for welding materials .Besides, this paper explores and discusses the existing problems and the developing trend in the future.

Review on friction stir welding of dissimilar magnesium and aluminum alloys: Scientometric analysis and strategies for achieving high-quality joints

Magnesium and aluminum alloys continually attract interest as lightweight structural materials for transport applications. However, joining these dissimilar alloys is very challenging. The main obstacle that hinders progress in dissimilar Mg-Al joining is the formation of brittle intermetallic compounds(IMCs). As a solid-state joining technique, FSW is an excellent candidate to attenuate the deleterious IMC effects in dissimilar Al-Mg joining due to the inherent low heat inputs involved in the process. However, the IMCs, namely Al_(3)Mg_(2) and Al_(12)Mg_(17) phases, have also been reported to form during Al-Mg dissimilar FSW;their amount and thickness depend on the heat input involved;thus,the weld parameters used. Since the heat dissipated in the material during the welding process significantly affects the amount of IMCs,the heat input during FSW should be kept as low as possible to control and reduce the amount of IMCs. This review aims to critically discuss and evaluate the studies conducted in the dissimilar Al/Mg FSW through a scientometric analysis and also with a focus on the strategies recently applied to enhance joint quality. The scientometric analysis showed that the main research directions in Mg/Al FSW are the technological weldability of aluminum and magnesium during FSW, structural morphology, and mechanical properties of dissimilar welded joints. Considering the scope of application of the aforementioned joints, the low share of articles dealing with environmental degradation and operational cracking is surprising. This might be attributed to the need for well-developed strategies for obtaining high-quality and sustainable joints for applications. Thus, the second part of this review is conventional, focusing mainly on the new strategies for obtaining high-quality Mg/Al joints. It can be concluded that in addition to the necessity to optimum welding parameters to suppress the excessive heat to limit the amount and thickness of IMC formed and improve the overall joint quality, strategies such as using Zn interlayer, electric current assisted FSW(EAFSW), ultrasonic vibration FSW(UVa FSW), are considered effective in the elimination, reduction, and fragmentation of the brittle IMCs.

Response of structural and magnetic properties of ultra-thin FeCo–V foils to high-energy beam welding processes

Microstructural evolutions and grain-boundary-character distribution during high-energy-beam welding of ultra-thin Fe Co-V foils were studied. Detailed data about the boundaries, coincidence site lattice（CSL） relationships, grain sizes, and microstructural features were acquired from electron-backscatter diffraction（EBSD） maps. Moreover, the evolution of the magnetic properties during high-energy-beam welding was studied using vibrating sample magnetometry（VSM）. The fraction of low-angle boundaries was observed to increase in the fusion zones of both electron- and laser-beam-welded foils. The results showed that the fractions of low-Σ CSL boundaries（particularly twin boundaries, Σ3） in the fusion zones of the welded foils are higher than those in the base metal. Because the strain rates produced during high-energy-beam welding are very high（because of the extremely high cooling rate）, grain deformation by a slip mechanism is limited; therefore, deformation by grain twinning is dominant. VSM analysis showed that the magnetic properties of the welded foils, i.e., their remanence, coercive force, and energy product, changed significantly. The formation of large grains with preferred orientation parallel to the easy axis of magnetization was the main reason for the diminished magnetic properties.

LDH sealing for PEO coated friction stir welded AZ31/AA5754 materials

The need to combine various metals in light-weight constructions requires the development of coatings that prevent galvanic corrosion.Layered double hydroxides(LDHs)can be an example of such coatings,which were previously successfully obtained in situ on individual materials.In addition,the possibility of LDH growth(including LDH growth in the presence of chelating agents)on the surface of plasma electrolytic oxidation(PEO)-coated metals was previously shown.This PEO+LDH combination could improve both corrosion and mechanical characteristics of the system.The possibility of LDHs formation in situ on the surface of PEO-coated friction stir welded(FSW)magnesium-aluminum materials(AZ31/AA5754 system was selected as a model one)was demonstrated in the presence of 1,3-diamino-2-hydroxypropane-N,N,N',N'-tetraacetic acid(DHPTA)as a chelating agent,which was selected based on analysis of respective metal-ligand compounds stability.LDHs growth was achieved under ambient pressure without addition of carbonates in the electrolyte.The effectiveness of the resulting coating is shown both for corrosion resistance and hardness.

An improved fatigue life prediction model based on loading sequence

Purpose–In view of the difficulty in determining the key parameters d in the Corten-Dolan model,based on the introduction of small loads,damage degrees and stress states to the Corten-Dolan model and the existing improved model,the sequential effects of the adjacent two-stage load were further considered.Design/methodology/approach–Two improved Corten-Dolan models were established on the basis of modifying the parameter d by two different methods,namely,increasing stress ratio coefficient as well as considering the effects of loading sequence and damage degree as independent influencing factors respectively.According to the test data of the welded joints of common materials(standard 45 steel),alloy materials(standard 16Mn steel)and Q235B steel,the validity and feasibility of the above two improved models for fatigue life prediction were verified.Findings–Results show that,compared with the traditional Miner model and the existing Corten-Dolan improved model,the two improved models have higher prediction accuracy in the fatigue life prediction of welding materials whether under two-stage load or multi-stage load.Originality/value–Because the mathematical expressions of the models are relatively simple and need no multi-layer iterative calculation,it is convenient to predict the fatigue life of welded structure in practical engineering.

Improving weld formability by a novel dual-rotation bobbin tool friction stir welding

A novel dual-rotation bobbin tool friction stir welding （DBT-FSW） was developed, in which the upper shoulder （US） and lower shoulder （LS） have different rotational speeds. This process was tried to weld 3.2 mm thick alunlinum-lithium alloy sheets. The metallographic analysis and torque measurement were carried out to characterize the weld formabiliW. Experimental results show that compared to conven- tional bobbin tool friction stir welding, the DBT-FSW has an excellent process stability, and can produce the defect-free joints in a wider range of welding parameters. These can be attributed to the significant improvement of material flow caused by the formation of a staggered layer structure and the unbalanced force between the US and LS during the DBT-FSW process.

Computational fluid dynamics simulation of friction stir welding:A comparative study on different frictional boundary conditions

Numerical simulation based on computational fluid dynamics （CFD） is a useful approach for quantitatively investigating the underlying thermal-mechanical conditions during FSW, such as temperature field and material deformation field. One of the critical issues in CFD simulation of FSW is the use of the frictional boundary condition, which represents the friction between the welding tool and the workpiece in the numerical models. In this study, three-dimensional numerical simulation is conducted to analyze the heat transfer and plastic deformation behaviors during the FSW of AA2024. For comparison purposes, both the boundary velocity （BV） models and the boundary shear stress （BSS） models are employed in order to assess their performances in predicting the temperature and material deformation in FSW. It is interesting to note that different boundary conditions yield similar predictions on temperature, but quite different predictions on material deformation. The numerical predictions are compared with the experimental results. The predicted deformation zone geometry by the BSS model is consistent with the experimental results while there is large difference between the predictions by the BV models and the experimental measurements. The fact that the BSS model yields more reasonable predictions on the deformation zone geometry is attributed to its capacity to automatically adjust the contact state at the tool/workpiece interface. Based on the favorable predictions on both the temperature field and the material deformation field, the BSS model is suggested to have a better performance in numerical simulation of FSW than the BV model.