Controlling of IMCs layers formation sequence, bond strength and electrical resistance in Al[sbnd]Cu bimetal compound casting process

Abstract

This research aimed to produce Al/Cu bimetal through the compound casting process. The control of the thickness and type of IMCs layers at Al/Cu interface were investigated by controlling of Al melts pouring temperature and Cu preheating temperatures. By these methods it was tried to reach an increase in Al/Cu bond strength and electrical conductance of the produced bimetal. The microstructure and mechanism of IMCs formation at the Al/Cu interface were evaluated by Optical Microscope (OM) and Electron Probe Micro-Analysis (EPMA). From the experiments, it was observed that the interface comprised three major layers including, Layer I: α-Al/Al2Cu (α+θ) eutectic structure, Layer II: the intermediate intermetallic compound of Al2Cu (θ), and finally the solid state diffusion Layer III which included several IMCs such as AlCu, Al3Cu4, Al2Cu3, and Al4Cu9. From experiential evidences it was concluded that the control of the preheat temperature of solid copper was far more influential on the formation, thickness, and type of intermetallic phases than the controlling the melt pouring temperature of aluminum. According to the experimental results, Al2Cu3 and Al3Cu4 phases with a higher hardness and lower toughness in comparison with Al2Cu, AlCu, and Al4Cu9 phases, had a more destructive effect on the bond strength.