The Effect of Annealing on Joint Strength and Hydroforming Properties of Cold Roll Bonded Aluminium/Copper Clad Sheets

The hydro-mechanical molding process is capable of producing more complex parts with amore uniform thickness distribution than the conventional deep drawing process. In this study,the weldability and forming of aluminium-copper double sheets were studied. The effect ofpre-rolling and secondary annealing on the strength of the intermetallic bond strength of therolled sheet was also investigated and the hydro-mechanical forming of cylindrical cups fromAl-Cu circular bilayer plates was studied. The results of hardness and T-peel tests as well asmicrostructural studies using optical microscopy showed that post-roll annealing reduced theweld strength of the rolling while secondary annealing applied the sheets improve theirductility. The maximum tensile strength of Al-Cu cups when aluminium was in contact withthe punch was equal to that of the monolayer aluminium sheet, and in the case of copper withthe punch it was lower than that of the monolayer copper sheet. Increasing the maximumforming pressure accelerated the rupture of the wall and moved the rupture area near theflange, and increased friction between the sheet and the blank-holder resulted in prematurethinning of the cup wall near the punch’s radius of curvature and reduced the maximum tensileratio.

Keywords:

Cold roll bonding , Al/Cu clad sheet , Hydro-mechanical forming , Tensile ratio