Effect of Multi-Pass Compression Deformation on Microstructure Evolution of AZ80 Magnesium Alloy
LI Zhenliang(), ZHANG Xinlei, TIAN Dongkuo
School of Materials and Metallurgy, Inner Mongolia University of Science and Technology, Baotou 014010, China
Cite this article:
LI Zhenliang, ZHANG Xinlei, TIAN Dongkuo. Effect of Multi-Pass Compression Deformation on Microstructure Evolution of AZ80 Magnesium Alloy. Acta Metall Sin, 2024, 60(3): 311-322.
Magnesium alloy has a hexagonal close-packed crystal structure, and its plasticity is poor at room temperature. This is primarily due to the small number of movable slip systems at room temperature, which is prone to deformation texture. Therefore, temperature and compression deformation play an important role in the regulation of plastic deformation. In this work, AZ80 magnesium alloy was subjected to multi-pass compression deformation at a constant temperature and step-down temperature. The microstructure of the AZ80 magnesium alloy with different deformation degrees and deformation paths was observed and analyzed using EBSD. In addition, the grain boundary, dislocation density, Schmid factor, and polar figure evolution of the AZ80 magnesium alloy during hot compression deformation were primarily studied. Results show that the comprehensive effect of grain size, twinning, and texture on the plastic regulation of AZ80 magnesium alloy is better than that of single dynamic recrystallization. Moreover, three-time constant-temperature deformation (ε = 0.6) promotes dynamic recrystallization, whereas three-time step-cooling deformation (ε = 0.6) promotes plastic deformation. More 86°{102} <110> tensile twins are produced by reduced grain orientation difference, increased number of low-angle grain boundaries, and increased geometrically necessary dislocation density, which are important factors affecting the plastic regulation of three-time step-cooling deformation (ε = 0.6).
Fig.1 Process maps of three-step deforming process with constant-temperature (a) and three-step deforming process with step-cooling (b) (P—pass, ε—strain)
Fig.2 Microstructure evolutions of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d)
Fig.3 Average grain sizes (a) and average grain shape aspect ratios (b) of constant-temperature and step-cooling deformation processes
Fig.4 Grain boundaries distributions of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (The green lines represent subgrain boundaries, and the grain boundaries indicated by the red arrows are the bow-bend grain boundaries)
Fig.5 Grain size diagrams of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (The colored small grains are dynamically recrystallized grains, the red grains are basal orientation, and the other colored grains are non-basal orientation)
Fig.6 Grain boundary ratios (a) and dynamic recrystallization ratios (b) of constant-temperature and step-cooling deformation processes
Fig.7 Misorientation distributions of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d)
Fig.8 Geometrically necessary dislocation (GND) density distribution maps of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (The green is the dislocation concentration area, and the blue is the dislocation-free area)
Fig.9 Geometrical necessary dislocation density (ρGND) statistical maps of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d)
Fig.10 Schmid factor distribution maps of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (The blue is hard orientation, the red is soft orientation, and other colors are between hard orientation and soft orientation)
Fig.11 Schmid factor statistical maps of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d)
Fig.12 Pole figures of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (ED—extrusion direction, TD—transverse direction)
Fig.13 Orientation distribution function (ODF) maps of constant-temperature deformation process at ε = 0.2 (a), ε = 0.4 (b), and ε = 0.6 (c); and step-cooling deformation process at ε = 0.6 (d) (The red area is strong texture, the blue area is weak texture, and the texture intensity of the green area is between them; φ2—Euler angle)
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