Changes in Microstructure and Texture of a Multi-Stack Accumulative Roll Bonding Processed Complex Aluminum Alloy with Annealing

Abstract

Changes in the microstructure and texture with annealing temperature of a nanostructured complex aluminum alloy fabricated by multi-stack accumulative Roll Bonding (aRB) process using various al alloys are investigated in detail. The aRB process is performed up to 4 cycles without lubrication at room temperature. The specimen fabricated by the aRB is a multi-layer aluminum alloy sheet in which the aa1050, aa5052 and aa6061 al alloys are alternately stacked to each other. The average grain size of the starting material is 140 μm, but after 4 cycles of the ARB process, this is reduced to 150 nm. The complex Al alloy still shows an ultrafine grained microstructure at annealing temperatures up to 250℃, but after annealing at 300℃, it exhibits a heterogeneous structure containing both the ultrafine grains and the coarse grains due to the occurrence of discontinuous recrystallization. The specimens annealed at temperatures above 300 ℃ also show a heterogeneous microstructure even if the heterogeneities of grain size differ from each other. The texture develops abnormally at higher annealing temperatures; the deformation textures are developed as [112]//nD and [111]//nD components, even in the recrystallized specimens. as the annealing temperature increases, the number fraction of the high-angle grain boundaries gradually decreases. The changes in microstructure and texture of the specimens with increase of the annealing temperature are compared to those of the specimens processed by 2-cycle of the aRB.