New approaches for brazing temperature sensitive materials

PVD deposited copper interlayers as filler materials were used in order to manufacture TLP brazed magnesium joints. The microstructure and interface characteristics of the overlap joints were investigated by optical microscopy,scanning electron microscope with energy dispersive spectrometer and tensile testing. Sound brazed joints could be achieved. The dwell time is the main factor to control the thickness of the reaction layer. It was shown that the deposited copper filler metal clearly reacted with the magnesium substrate,resulting in the formation of a magnesium solid solution（Mg） with different amount of copper,aluminum and zinc as well as Mg₂Cu phases. With the progressing diffusion,the formation of intermetallic compounds was suppressed and the hardness distribution in the brazing seam homogenized. The joints fractured at the interface,and the maximum average tensile shear strength of overlap joints reached 85 MPa.