DECOMPOSITION OF SINGLECRYSTALLINE AND POLYCRYSTALLINE AL-40 WT-PERCENT ZN-2 WT-PERCENT CU ALLOYS

The decomposition process of an Al-40 wt.% Zn-2 wt.% Cu alloy has been carried out for both single and polycrystalline materials. Decomposition of the supersaturated solid solution in the single crystal started in the continuous mode and changed in the course of aging to the discontinuous one. When the decomposition was completed the microstructure of the single crystal consisted of both the lamellae and intragranular structures. The only mechanism of decomposition observed in polycrystalline material was discontinuous.