Optimization of Mechanical Properties of Al–Al‐Compound Castings by Adapted Heat Treatment

Aluminum–aluminum compound castings consisting of an aluminum wrought alloy sheet and an aluminum casting alloy are produced via high pressure die casting (HPDC). In order to realize a firm bonding, the sheet material is Zn‐coated prior to casting. The task of the Zn‐coating is to replace the resistant aluminum oxide layer on the surface. In addition, a smooth metal–metal interface between the insert and the casting alloy develops by the diffusion of Zn atoms into the surrounding area of the interface. Within this paper, the subsequent heat treatment of the resultant formation is investigated to enhance the strength of the firmly bonded compound. In a first step, heat treatment for two wrought alloys AlZn5.5MgCu, AlCu4MgSi, and the casting alloy AlSi10Mg(Fe) are examined. Based on these results, suitable parameters for the heat treatment of the compounds are selected and tested. Mechanical tests demonstrate a significant enhancement for the strength of the heat treated compounds. Microprobe analysis is used to examine the diffusion and dissolution of the coated Zn at the boundary layer during the solution annealing of the firmly bonded compound.