Effect of imposed strain and annealing temperature on uniform elongation in A5052 alloy processed by accumulative roll bonding

Abstract

The relation between strain and uniform elongation, and the effect of low-temperature annealing, were examined using an Al-Mg alloy (A5052) processed by accumulative roll bonding (ARB). Specimens were deformed by ARB for 1 to 7 cycles at room temperature, and then subjected to isochronal annealing for 30 min at temperatures ranging from 100 to 300 °C. Tensile properties, hardness, and grain boundary structure before and after annealing were investigated. The uniform elongation of ARB-processed specimens decreases with increasing ARB cycles. However, the elongation is improved by low-temperature annealing for specimens processed by ARB of 3 or more cycles. Higher strain in the ARB process results in higher uniform elongation after annealing, even though the specimens have the same value of 0.2% proof stress. This improvement of the uniform elongation by annealing is caused by annihilation of dislocations inside ultra-fine grains, which are developed by ARB of 3 or more cycles.

Texture and Mechanical Properties of Al–Mg Alloy with Unimodal and Bimodal Grain-Structures Formed by Accumulative Roll Bonding and Annealing

“…9, which were reported in our previous study, using the same A5052 aluminum alloy specimens ARB-processed and annealed. 14) Compared with the starting material before ARB, the as-ARB-processed specimens (the specimens 1c 7c) indicated significant increases in the tensile strength and drastic decreases in the uniform elongation with increasing the number of ARB cycles. The result corresponded well with those reported in previous researches of SPD.…”

“…Fig. 9 Stress-strain curves for the A5052 specimens ARB-processed by 1, 3, 5, and 7 cycles and the specimens ARB-processed and annealed at either 250°C or 300°C (reconstructed from data in the previous study 14) ). The stress-strain curves for the starting material (SM) and the as-ARBprocessed specimens are indicated by black lines, and those for the ARBed and annealed specimens are described in accordance with the color legend.…”

“…the higher strain, resulted in the higher elongation after the low temperature annealing. 14) In order to improve ductility while maintaining high strength in SPD processed metals, some research groups have focused on the bimodal fine grain-structures, of which grain size distribution has two peaks. 1518) For example, Wang et al reported a dramatic improvement in ductility without reducing tensile strength in pure copper specimens having bimodal grain-sizes, which were 1 µm3 µm coarse grains and 200 nm fine grains.…”

Review - Materials Design for Improving Mechanical Properties of Ultra-Lightweight Mg-Li Based Alloys

“…In lightweight structural metals, the balance between strength and density is important. Figure 8(b) illustrates the correlation between yield strength and the density of a range of Mg and Al alloys [14,35,[36][37][38][39][40][41]. The symbols 'p' and 's' within the figure denote precipitation-strengthened and solid solution-strengthened alloys, respectively.…”