Investigation of Joining Dissimilar Materials Using Hot Pressing Process

Abstract

Hot pressing has been increasingly applied as a joining technology for dissimilar materials because of its simple setup. However, various process parameters must be clearly defined here in order to obtain an optimum joint. In this study, an experimental hot pressing for joining an aluminium alloy sheet grade A5052 with a polybutylene terephthalate (PBT) plate was carried out. Different surface treatment on the aluminium samples were firstly employed by using both mechanical and chemical processes. Then, surface topographies of the treated samples were characterized by scanning electron microscope. The Fourier transform infrared spectroscopy analysis was carried out to examine the C=O in the carbonyl group of thermo-plastic at the joint. During the hot pressing, joining force and temperature were varied. Afterwards, tension shear tests were performed for the aluminium-PBT specimens to evaluate the resulted joint strength. It was found that the pressing force of 1-ton and a pressing temperature of 270°C were the optimum parameters for joining these investigated materials. The maximum joining strength was obtained by specimens subjected to sandblasting combined with chemical surface treatment, in which the surface roughness of aluminium sheet samples was in the range of 4-9 μm. The specimens after shear tests exhibited a cohesive failure. The depth of mechanical interlocking between surfaces of both materials was approximately 33 μm. No change of the molecular structure of PBT was observed by the direct bonding between aluminium and PBT using hot pressing.