Fiber laser welding of copper based open cell foams

Porous metallic materials with cellular structures are well known to combine many physical and mechanical properties. This mix of different properties makes these systems very attractive for both structural and functional applications, depending on pore size, methodology of production and material characteristics. Because of their porous structure, unconventional machining and more in general unconventional processing is becoming more and more important nowadays for promoting the industrial applications of such a kind of materials. In this work a study on the fiber laser welding process, performed using a 1 kW continuous wave fiber laser, on Cu based foams is reported. The foams, whose the mean size of the pore is approximately 3.5 mm, were produced by means of infiltration of leachable space holders inside the metal in liquid state. After preliminary welding test in a bead on plate configuration performed only on the surface of the foams, samples in lap joint configuration were realized for evaluating the cross section of the welded bead. The effect of the process speed on the geometrical characteristic features of the joints was studied. The extent of the heat affected zone was evaluated directly by optical microscopy and indirectly by executing micro-hardness test. Then the heat affected zone extension was corrected to the process speed. Besides, electron scanning microscopy, coupled with electron dispersive spectroscopy, was adopted for the compositional analysis of the welded beads. It was shown that the laser joints could be achieved in lap joint configuration, allowing high reflectivity porous alloys with complex structures and average pore size of the order of millimeters to be connected.