Friction stir riveting (FSR) of AA6061-T6 aluminum alloy and DP600 steel

Surface modification by different technologies prior to joining operations or improving tribological properties is a point of great interest. Improving surface activation by increasing the roughness of the metal is a relationship that is becoming more defined. In turn, an increase in surface wettability by evaluating contact angles indicates surface activation by obtaining a high surface free energy. Technologies such as shot blasting and laser surface texturing (LST) have generated several scientific studies where they have identified the influence of parameters on the formation of rough surfaces with defined patterns. However, the application of abrasive water jet texturing (AWJT) has been little studied as an alternative. This article compares these technologies in the texturing of a carbon steel s275 in order to identify the relationship between surface quality and surface activation. It has been determined that AWJT produces the highest Rt values close to 64 µm with a cross feed of 0.45 mm and a traverse speed of 5000 mm/min. Furthermore, LST obtains the best values of free surface energy by combining a power of 20 W with a frequency of 20 kHz and a sweeping speed of 10 mm/s. Finally, contour diagrams have been obtained which relate these variables to the texturing parameters.

Surface Quality and Free Energy Evaluation of s275 Steel by Shot Blasting, Abrasive Water Jet Texturing and Laser Surface Texturing

In this study, brazing AA6061 to Q235 steel using flame brazing was performed with 70.9 wt.% CsF-0.5 wt.% RbF-28.6 wt.% AlF3 fluxes doped with GaF3, ZnF2, Zn(BF4)2 and Ga2O3 nanoparticles, matched with a Zn-15Al filler metal, and the spreadability of the filler metal and the mechanical properties of brazed joints were investigated at the same time. The results showed suitable amounts of GaF3, ZnF2, Zn(BF4)2 and Ga2O3 doped into the base flux could strengthen the filler metal in wetting and spreading on the surface of aluminum alloy and steel to different degrees. The suitable ranges of GaF3, ZnF2, Zn(BF4)2 and Ga2O3, respectively, were 0.0075–0.01 wt.%, 0.0075–0.01 wt.%, 0.0075–0.01 wt.% and 0.009–0.01 wt.%, and the maximum spreading area was obtained via doping with GaF3. The shear strength of brazed joints reached the peak at 126 MPa when 0.075 wt.% GaF3 was added. Comparative tests proved that the activity of the CsF-RbF-AlF3 flux doped with GaF3 was the best. The reason was that the CsF-RbF-AlF3-GaF3 flux was competent in removing oxides of the base metal and decreasing the interfacial tension, in virtue of the activity of Ga3+ as well as F−.

Effect of Various Nanoparticles (GaF3, ZnF2, Zn(BF4)2 and Ga2O3) Additions on the Activity of CsF-RbF-AlF3 Flux and Mechanical Behavior of Al/Steel Brazed Joints

Metal–polymer hybrid structures have been widely used in research into their lightweight automotive applications, because of their excellent comprehensive properties. As an efficient technology for automatic connection of dissimilar materials, laser joining has great application potential and development value in the field of lightweight automotive design. However, due to the physical and chemical differences between metals and polymers, the formation quality of the hybrid joint is seriously affected by defects, low bonding strength, and poor morphology. Meanwhile, it is difficult to meet the demands for lightweight automobiles by considering only bonding strength as the target for forming quality. Therefore, the technological characteristics of metal–polymer hybrid structures for use in lightweight automotive applications are analyzed, the advantages and problems of laser-joining technology are discussed, and the characterization indexes and regulation measures of forming quality in laser joining are summarized. This paper which provides reference and guidance for reliable forming, intelligent development, and lightweight application of laser joining for polymer–metal hybrid structures.

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Research Progress on Characterization and Regulation of Forming Quality in Laser Joining of Metal and Polymer, and Development Trends of Lightweight Automotive Applications

Joining processes have gained increasing relevance and their effectiveness appears as a necessity in the production of lightweight structures. Many researchers have been investigating affordable testing solutions to assess joint performance. Herein, an easy-to-apply non-destructive technique, based on vibration analysis, is presented and evaluated by a purely numerical approach. Changes in the curvature mode shape of beam-like structures are measured and related to the extension of bonded areas of the connected parts. The preliminary results, achieved by modal analysis, provide a first proof-of-concept of the proposed technique and of its increased sensitivity compared to techniques based on frequency response functions. 

Y. S. Zhang

Papers

Current Research and Challenges in Innovative Technology of Joining Dissimilar Materials for Electric Vehicles