African Fusion July 2022

Research paves the way for stronger alloys

ibility and sustainability. An example of the company’s approach are two special setups that were developed based on the results of customer experiences. Called DP-Basic and DP-Fast, these fast cyclic parameter changes for welding processes offer users improvedpotential for process optimisation. Evaluating customer experiences, conducting welding tests and improving results is a core competence of SKS. These findings are collectedworldwide by SKS’s customer centres and welding test labs, then evaluated in the headquarters in Kaiserslautern. In a further step, the findings are trans lated into practical applications. From this process a special configuration, with the ability to extend parameter adjust ments andwiden the range and flexibility of welding processes, emerged in two versions: DP-Basic and DP-Fast. S cientists from the University of Bir mingham have described how micro scopic crystals grow and change shape in molten metals as they cool. This research is breaking new ground in alloy develop ment, paving the way for improving the tensile strength of alloys used in casting and welding. Their research, published in Acta Mate rialia, used high-speed synchrotron X-ray tomography to ‘photograph’ the changing crystal structures in molten alloys as they cool. The study shows that as aluminium copper alloy cools, the solidification pro cess starts with the formation of faceted dendrites, which are formed by a layer-by layer stacking of basic units that are just micrometres in size. These units start out as L shaped and stack on top of each other like building blocks. But as they cool, they change shape, transforming first into a U shape and then into a hollowed out cube, while some of them stack together to form beautiful dendrites. The study was led by Biao Cai, from the University of Birmingham’s School of Met allurgy and Materials, whose research has already demonstrated howmagnetic fields influence crystal growth. “The findings from this new study provide a real insight into what happens at a micro level when an alloy cools. They show the shape of the basic building blocks of crystals in molten

Tandom Metallurgical Group, which oper ates an international trading operation from its base inCongleton, Cheshire, where they produce aluminiumalloys andmaster alloys, and recycle aluminium products, scraps and dross. Cai expects to publish the results of the testing and showcase the demonstrator to industry before the end of the year, with the aim of finding industrial collaborators willing to run tests in foundry settings in combinationwithexistingproduction lines. www.birmingham.ac.uk/schools/metallurgy materials

alloys, and crystal shape determines the strength of the final alloy, so if we canmake alloys with finer crystals, we can make stronger alloys,” Cai says. “The results are in direct contrast with the classical view of dendrite formation in cooling alloys, and opens the door to de veloping new approaches that can predict and control the formation intermetallic crystals,” he adds. Cai’s previous research has resulted in a novel technology to improve the quality of recycled aluminium by removing iron frommolten alloy in a simple, inexpensive

process that uses mag nets and a temperature gradient. The technology is the subject of apatent applica tion filed by University of Birmingham Enterprise. It has also attracted funding from the Midlands Innova tion Commercialisation of Research Accelerator and the EPSRC-Impact Accel erationAccount, whichhas enabled Biao Cai to build a large-scale prototype that runs at up to 1 000 °C, and uses a 1.0 Tesla magnet. The prototype is cur rently being tested using ingots provided by the

A study led by Biao Cai from the University of Birmingham used X-ray tomography to ‘photograph’ the formation of dendrites during the solidification of molten aluminium-copper alloys.

DP-Fast for Even Better Weld Seams S KS Welding Systems is renowned in the automotive industry for flex

An aluminium weld completed using DP-Fast, which can reduce porosity when welding aluminium or coated steels and it produces a chevron effect on the weld surface.

DP stands for Dual Phase. A controlled oscillation of the weld pool is achieved with a periodic change between twowire feed speeds and/or power parameters. The resulting expansion and contraction of theweldpool ensures better gapbridg ing and improved flow properties. The controlled switching of the power ranges enables accurateheat control. This can reduce the formation of pores when joining aluminiumor coated steel materi als. The chevron weld seam appearance achieved,meets thehighdemandsplaced on visible weld seams. DP-Basic can be used for all SKS welding processes. DP-Fast can be com bined with the MIG/MAG, I- and KF-pulse processes, thus enabling a wide range of applications. By increasing the frequency to 25 Hz in the case of the DP-Fast, fine seam chevrons and good outflow of the seamedges can be achieved, even at high welding speeds. The expert mode of the weld process

controller offers even finer settings, allow ing users to come as close as possible to the optimal process. This new setup is available free of charge for all users of SKS standard sys tems to improve their welding results. www.sks-welding.com

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July 2022

AFRICAN FUSION