Welding of dissimilar metallic materials using a scanned laser beam

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For most dissimilar metal combinations, a key challenge which must be addressed for fusion joining processes is the chemical incompatibility of the metals, which typically leads to the formation of brittle intermetallic phases and consequently, inadequate weld properties. To counteract this issue, a technique which uses a scanned laser beam has been investigated for overlap joints of 1.0mm Al6061 to 1.0 mm CW004 and 1.0mm Al6061 to 0.6mm Ti-6Al-4V. Through optimisation of the scanning profile, scan speed and laser power, tailored heat inputs were developed to control the depth of melting in the lower sheet and hence limit the formation of brittle intermetallic phases. In addition, it was found that the agitation of the weld zone by the scanned laser beam ensured any intermetallic phases formed were small and dispersed, and were partially dissolved back into the aluminium weld matrix. For both dissimilar material combinations, the resulting welds contained very little cracking and were an order of magnitude stronger than conventional continuous-wave keyhole laser welds, made using the same materials. The joint strengths achieved in the CW004 to Al6061 and Ti-6Al-4V to Al6061 overlap joints were, respectively, >90% and >80% of the joint strength achieved in homogeneous aluminium welds.For most dissimilar metal combinations, a key challenge which must be addressed for fusion joining processes is the chemical incompatibility of the metals, which typically leads to the formation of brittle intermetallic phases and consequently, inadequate weld properties. To counteract this issue, a technique which uses a scanned laser beam has been investigated for overlap joints of 1.0mm Al6061 to 1.0 mm CW004 and 1.0mm Al6061 to 0.6mm Ti-6Al-4V. Through optimisation of the scanning profile, scan speed and laser power, tailored heat inputs were developed to control the depth of melting in the lower sheet and hence limit the formation of brittle intermetallic phases. In addition, it was found that the agitation of the weld zone by the scanned laser beam ensured any intermetallic phases formed were small and dispersed, and were partially dissolved back into the aluminium weld matrix. For both dissimilar material combinations, the resulting welds contained very little cracking and were an order of magnitud...