Abstract
Magnesium-6 wt.% aluminum (Mg-6Al) alloy plates with a 6-millimeter thickness were processed from an initial 12-millimeter thickness by differential speed rolling (DSR), with a 0.76-millimeter thickness reduction per pass using a speed ratio of 2, preheating temperature of 315 °C, and roll temperature of 265 °C. The effects of annealing temperature of 250, 275, and 300 °C with a corresponding holding time of 15 min on the microstructure, texture, and mechanical properties were investigated. Key results show that dynamic recrystallization (DRX) occurred during the roll processing, resulting in a greatly reduced grain size. In addition, the basal pole of the as-rolled plate was inclined to the rolling direction (RD) by ~20°, due to the shear strain introduced during DSR. Subsequent annealing caused grain growth, eliminated the basal pole inclination towards the RD, and slightly increased the pole intensity. Compared with the as-rolled plate, the average of the ultimate tensile strength (UTS) and the yield strength (YS) of the annealed plates decreased, while the average elongation at fracture (εf) increased. With the annealing temperature of 275 °C, the plate achieved a good combination of mechanical properties with UTS, YS, and εf being 292.1 MPa, 185.0 MPa, and 24.9%, respectively. These results suggest that post-roll annealing is an effective way to improve the mechanical response of this Mg alloy processed by DSR.
Highlights
Accepted: 2 June 2021Magnesium (Mg) alloys have a great potential for use as structural materials, in automotive and aerospace industrial applications, owing to their low density and high specific strength [1,2]
differential speed rolling (DSR) is carried out at different rotational speeds for the upper and lower rolls, so that a shear strain can be introduced during the thickness reduction process, leading to different inclinations of the basal pole of the processed plate material from those processed by conventional rolling [8], enhancing their formability [9,10]
It is clearly seen that the second phase was almost dissolved into the Mg matrix, sporadic bright particles distributed along the grain boundaries
Summary
Accepted: 2 June 2021Magnesium (Mg) alloys have a great potential for use as structural materials, in automotive and aerospace industrial applications, owing to their low density and high specific strength [1,2]. Due to the hexagonal close-packed (HCP) crystal structure, wrought Mg alloys exhibit poor formability at room temperature. Their formability can be greatly enhanced through grain refinement and texture control with proper thermoplastic deformation processing, such as extrusion [3], equal channel angular extrusion (ECAE) [4], equal speed rolling (ESR), and differential speed rolling (DSR) [5,6,7]. The DSR method is used in materials’ processing to impart high-strength through grain refinement and to control the as-deformed texture [11]. Kim et al [12]
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