Abstract
The microstructure evolution and deformation mechanism of the as-extruded-annealed Mg-4Li-1Al-0.5Y alloy (denoted as LAY410) were investigated during the hot tensile deformation at the temperatures between 150°C and 300°C with strains from 8 × 10−5 s−1 to 1.6 × 10−3 s−1. The results show that when the strain rate decreases and/or the deformation temperature increases, the peak stress of the alloy gradually decreases, and the elongations to fracture gradually increases. The true stress–strain curves show typical dynamic recrystallization (DRX) softening characteristics. It is observed that the microstructure in the magnesium (Mg) alloy deformed at 150°C is mainly composed of the deformed grains and a few recrystallized grains. The microstructures in the Mg alloy deformed at 200°C consisted of substructures and a slightly increasing number of dynamic recrystallized grains. When the deformation temperature reaches 250°C, the number of recrystallized grains increases significantly, and the microstructures are dominated by recrystallized grains. Moreover, through theoretical calculation and result analysis, the activation energy was about 99.3 kJ/mol, and the hot tensile deformation mechanism was the alternate coordinated deformation mechanism among grain boundary slip (GBS), intragranular slip, and DRX.
Highlights
Compared with steel and aluminum (Al) alloy, Mg alloy has lower density and good thermal conductivity and machinability
Compared with pure Mg, the diffraction peak of the α-Mg phase in LAY410 alloy is shifted to the right, which indicates that the axial ratio value (c/a) of the α-Mg phase decreases as described in our previous study (Wang et al, 2020) and the results are reanalyzed in this article
With temperature increases, an obvious steadystate rheological characteristic appears at the later stage of deformation, and the fracture morphology of the alloy gradually transfers from the ductile-brittle mixed fracture mode to the ductile fracture mode
Summary
Compared with steel and aluminum (Al) alloy, Mg alloy has lower density and good thermal conductivity and machinability It has great application potential in aerospace, automobile manufacturing, and electronics industry (Luo et al, 1995; Wang, 2007; Hadadzadeh and Wells, 2013). The literatures (Al-Samman, 2009; Tang et al, 2017; Tu et al, 2020; Wang et al, 2020) found that adding Li to Mg alloys can effectively reduce the density and lattice spacing (c/a axis ratio) of Mg alloys This makes the non-basal slip system of the alloy easier to be activated during deformation, thereby effectively improving the plastic formability of the alloy. MgAlLi2 is not thermally stable and tends to be decomposed at 50–70°C, and is further
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