Effects of annealing process on sagging resistance of cold-rolled three-layer Al alloy clad sheets
(National Engineering Research Center of Light Alloy Net Forming & State Key Laboratory of
Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240, China)
Abstract: The effects of annealing process on the hardness, microstructure, Si diffusion, and the sagging resistance of cold-rolled 4343/3003/4343 Al alloy clad sheets and their 3003 Al alloy core sheets were experimentally investigated through hardness tests, EBSD observations, EDS analysis, and sagging test. The results showed that with the increase of annealing temperature, the hardness of both clad sheet and core sheet decreased, while the sagging resistances of both clad and core sheets achieved maximum values after annealing at 380 °C for 1 h. After annealing at 380 °C, the clad layer contained fine and equiaxed recrystallized grains; the core layer was composed of fully recrystallized coarse grains elongated along the rolling direction. The Si diffusion from the clad layer to the core zone was limited. After annealing at a higher temperature of 440 °C or 550 °C, the sagging resistance of clad sheets worsened precipitously. The grains in the clad layer grew up, obscuring the interface between the clad and core layer; the recrystallized grains in the core layer became finer. Significant amount of Si penetrated into the core layer through the accelerated diffusion. Compared with the microstructure refinement, Si diffusion is the main factor influencing the sagging resistance.
Key words: aluminum alloy; microstructure; annealing; Si diffusion; sagging resistance