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In this study, a new energy efficient welding method called flux bands constricting arc (FBCA) welding was presented. A real-time electrical signal acquisition system and a high-speed camera system were proposed to understand the arc stability in FBCA welding. In ultra-narrow gap groove, the arc voltage and welding current in gas metal arc welding and FBCA welding experiments with various groove gaps (4–10 mm) were acquired. The dynamic characteristics, probability distributions, scatter graphs, and coefficients of variations of voltage and current during welding were adopted to determine the arc stability. Results indicate that flux bands considerably improve the arc stability in the ultra-narrow gap (

A new energy-efficient welding method, flux bands constricting arc (FBCA) welding, is proposed to solve the fabrication of metal sandwich panels. This method is suitable for welding T-joints in special structures where the welding gun is unable to reach the welding position, such as welding thick face-plate metal sandwich panels. The characteristics of FBCA welding, key welding technologies, and corresponding defects and resolutions are discussed. Pull-out tests between T-joints welded by laser and FBCA welding were conducted. Results indicate that complete penetration and good fusion of three-sided T-joint can be produced by FBCA welding. The typical cross section morphology is unlike other common welding methods. T-joints without defects, such as weld asymmetry, root leakage, slag inclusion, and pores, show better ultimate tensile strength than T-joints welded by laser welding. The FBCA welding method can compensate for shortage of insufficient weld width of laser welding.

The new type of Al-Ti-C-La master alloy was prepared by commercial pure Al, Ti powder, graphite powder, Al powder and La2O3 powder by aluminum melt in-situ reaction method. The microstructure and the effect on commercial pure aluminum of Al-Ti-C-La master alloy have been studied by means of X-ray diffraction (XDR), scanning electron microscopy (SEM) equipped with energy-dispersive spectrometry (EDS). The synthesis thermodynamics and kinetics of Al-Ti-C-La master alloy were analyzed. The experiment shows that Al-Ti-C-La master alloy is composed of Al, Al3Ti, TiC and Ti2Al20La. The refining performance of the prepared Al-Ti-C-La master alloy is obviously better than that of Al-Ti-C master alloy when the addition of rare earth oxide La2O3 is 10 wt% and the preparation temperature is 930 °C. The analysis of thermodynamic calculation and the process of kinetics demonstrate that, in the preparation process of Al-Ti-C-La master alloy, firstly, Al reacts with Ti to produce Al3Ti, C reacts with Ti and Al3Ti to form TiC based on the aluminothermy reaction. Rare earth oxide La2O3 and C powder react with Ti powder and O2 in the air occur to generate CO, TiC, [La] atoms and LaC2. [La] atoms adsorb on the surface of Al3Ti to form the new rare earth compounds Ti2Al20La.

A new welding method, flux bands constricting arc (FBCA) welding, is proposed to compensate for the shortage of insufficient weld width of laser welding T-joints in high steel sandwich panels. The arc behavior (arc burning position, arc shape, arc heat, and arc stability) before and after sticking the flux bands (GMAW and FBCA welding) to the ultra-narrow gap groove was tested. Results indicate that flux bands have solid-wall constricting effect (SWCE) and thermo-compression effect (TCE) on the arc and self-producing slag and gas function in FBCA welding. In ultra-narrow gap groove, the arc burning position climbing up phenomenon (APCP) occurs without flux bands. The SWCE of flux bands on the arc effectively suppresses the APCP because of the insulation of flux bands. In the FBCA welding process, the effective heating area of the arc is increased by at least 5 mm2 compared with that in GMAW. When the groove gap decreases, flux bands not only compress the arc from an inverted bell shape to a rectangular shape, but also make the 660 &deg, C isotherm on the core-plate to increase from 3 mm to 8 mm. In the end, the proportion of unstable arc burning time is reduced by 86.85%, the fluctuation of arc voltage and welding current are also significantly reduced by the flux bands because of their SWCE on the arc.

It is well known that the mechanical properties of hypoeutectic Al–7%Si alloys are influenced by the size, morphology, and distribution of primary α-Al and eutectic Si crystals. In the present work, a novel Al–Ti–C–Ce master alloy was prepared by the pure molten aluminum thermal explosion reaction, and its effects on the microstructure and mechanical properties of hypoeutectic Al–7%Si alloy were investigated. The results show that the Al–Ti–C–Ce master alloy containing α-Al, granular TiC, lump-like TiAl3, and block-like Ti2Al20Ce has excellent refining and modification properties for hypoeutectic Al–7%Si alloy. When 1.5 wt.% Al–Ti–C–Ce master alloy is added, the coarse dendritic α-Al in hypoeutectic Al–7%Si alloy is refined into equiaxed grains. The secondary dendritic arm spacing (SDAS) was also reduced, and the coarse needle-flake eutectic Si phase was transformed into a fibrous and granular phase. It was found that the ultimate tensile strength and elongation increased by 59% and 56%, respectively, due to the decrease in the SDAS of primary α-Al dendrites and the modification of eutectic Si crystals. Moreover, the change of mechanical properties corresponds to the evolution of microstructure.

For solving the problem of automated robot ultra-narrow gap welding, based on flux bands constricting arc ultra-narrow gap welding experiments, a robot ultra-narrow gap welding system and real-time arc signal acquisition system were established. The paper elaborates the effect of robot kinematic accuracy on the welding process, and through studying the arc signal in different groove types and with different welding wire position in the groove to put forward an arc characteristic that can be used for weld tracking in ultra-narrow gap welding. Results of this study indicate that robot kinematic accuracy should be controlled less than ±1mm in flux bands constricting arc ultra-narrow gap welding. The narrower the groove gap is, the higher the requirement of robot kinematic accuracy is. As the welding torch deviation distance from center of groove increase, the arcing voltage is significantly reduced, the voltage drop is also reduced, but the peak current and short-circuit transition frequency are significantly increased. The arc signal reflects the arc state and welding wire position in the groove. The difference in the arc signal when the welding torch is near to and away from the side-wall, which can be used to track the center of the groove.

It is well known that the mechanical properties of commercial pure Al are influenced by size of α-Al dendrites. In the present work, Al-5Ti-0.62C-0.2Nd grain refiner was prepared by a pure molten aluminum thermal explosion reaction, and its effect on grain refinement and mechanical properties of commercial pure Al was investigated. Microstructure and phase composition show that Al-5Ti-0.62C-0.2Nd grain refiner consists of α-Al, granular TiC, lump-like TiAl3, and block-like Ti2Al20Nd. Grain-refining tests on commercial pure Al show that an Al-5Ti-0.62C-0.2Nd grain refiner has better refining performance compared with Al-5Ti-0.62C grain refiner. With addition of 0.2-wt.%-Al-5Ti-0.62C-0.2Nd grain refiner, the average grain size of commercial pure Al can be refined from roughly 2800 to 155±5 µm effectively, and it has higher resistance to grain-refinement fading. On account of the grain refinement, the tensile strength and elongation are increased by approximately 18.3% and 83.5%, respectively.

The effects of CeO2 on the microstructure and synthesis mechanism of Al-Ti-C alloy were investigated by quenching experiment method, while using Al powder, Ti powder, graphite powder, and CeO2 powder as main raw materials. The results showed that the addition of CeO2 was favorable for promoting the formation of TiC particles in Al-Ti-C systems. With CeO2 contents increasing, the distribution of TiC particles were more homogeneous, and the rare earth phase Ti2Al20Ce was formed. CeO2 had little effect on the synthesis of Al3Ti particles in Al-Ti-C systems, but had a significant effect on the synthesis of TiC particles. In the Al-Ti-C system, TiC is mainly formed by the reaction of dissolved [Ti] and solid C in the melt. While in the Al-Ti-C-Ce system, CeO2 reacts with C and O2 to form CeC2 firstly, and then CeC2 reacts with dissolved [Ti] to form TiC. Based on thermodynamic calculation and microstructure analysis in the process of reaction, a macroscopic kinetic model of Al-Ti-C-Ce system reactions was proposed in this paper.

This paper presents a detailed discussion of the bending properties of laser welded web-core steel sandwich plates and the influence of weld width on stiffness and strength. The over-hanging three point bending test was conducted on the laser welded web-core steel sandwich plates with various welds width by self-designed device, together with the finite element simulations. A good agreement is obtained between the 2D FE analyses and experiment results. The stiffness and strength of the sandwich plates increased with the increasing of weld width, especially for the weld width lower than 60% thickness of the core plate. It is necessary to consider the weld width in the design and evaluation of the stiffness and strength of the laser welded web-core sandwich plate. Base on the results, the FEM is the priority to analysis bending properties of laser welded web-core steel sandwich plates.

All steel laser welded sandwich plates have found their position in the marine and land vehicles. To implement such design accurately, knowledge about its strength properties and the influence of laser weld dimensions on strength is necessary. In this paper, the over-hanging three point bending tests were conducted on the laser welded web-core steel sandwich plate with various weld dimensions by self-designed device, together with the finite element simulations. The results show that the joint is formed on the first plastic hinge when the load is no longer a linear relationship with the deflection, and the joint cracking when the load reaches the maximum bearing capacity of sandwich plate. The joint yield load and the maximum bearing capacity of the sandwich plates increased with the increasing of weld width. Meanwhile, the mode of failure of sandwich plates also changed: When the weld width is smaller, the mode of failure is joint yield, When the weld width is greater than 3mm, the mode of failure is the combination of partial joint yield, face plate and core plate local yield, while the face plate and core plate yield exists in the whole weld joint. It is necessary to consider the weld width in the design and evaluation of the strength of the laser welded web-core sandwich plate.

This paper presents the influence of the weld widthroot gapand weld offset of the T-joint to the overall stiffness of sandwich plate with finite element simulations. From the results of finite element calculation and some of experimental verification we can see:(1) For this structure, welding joint damage occurs before the face plate buckling.(2) Among the factors weld widthgap and weld offset of the T-joint, the weld width affect the overall stiffness the most. (3) When root gap and weld offset lower 0.1mm and 0.12 mm, respectively, they have a little influence on the resistance of deformation ability for the sandwich plate, they can be ignore.

A numerical model has been build up to study temperature evolution and metal flow for the indirect extrusion of 6005A aluminium alloy. Model validation was carried out by comparison between experiments and simulations. Results show a good agreement with each other. The influence of the extrusion parameters on the profile temperature and metal flow were studied according to the real industrialized process. It was found that the profile temperature increases with the ram speed as well as the peak load of the total press force. However, a too slow extrusion process would cause increasing of the total force at the end of the extrusion because of heat dissipation to the environment. In addition the dead metal zone at the top of the billet was shrunk during the extrusion process. The ram speed would have little influence on the distribution and shape changing of dead metal zone. Once the extrusion went into steady stage, the strain rate of metal flow would keep a stable situation relatively.

This paper uses the small punch test (SPT) to some performance of the materials, have put forward basic method to test the material tensile mechanics performance from an inverse FE method with SPT. The research shows that some tensile mechanics performance and stress of each district of welding seam can be accurate determined by small punch test. This research has offered the theoretical foundation for characterizing of the welded joint with mechanical heterogeneity

Inhomogeneous Material Modeling and Characterization for Aluminium Alloys and Welded Joints