Bimodal grain microstructure development during hot compression of a cast-homogenized Mg-Zn-Zr alloy

Hadadzadeh, Amir; Mokdad, F.; Amirkhiz, Babak Shalchi; Wells, Mary A.; Williams, Bruce W.; Chen, D.L.

doi:10.1016/j.msea.2018.03.112

Cited by 38 publications

(8 citation statements)

References 41 publications

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“…It can be preliminarily concluded that there are at least three kinds of phases including α-Mg, MgZn 2 , and CaMgSn. This result is consistent with the investigations in other literature [ 30 , 31 , 32 ].…”

Section: Resultssupporting

confidence: 94%

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

et al. 2018

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In this paper, a new type of low-cost Mg-3.36Zn-1.06Sn-0.33Mn-0.27Ca (wt %) alloy ingot with a diameter of 130 mm and a length of 4800 mm was fabricated by semicontinuous casting. The microstructure and mechanical properties at different areas of the ingot were investigated. The microstructure and mechanical properties of the alloy under different one-step and two-step homogenization conditions were studied. For the as-cast alloy, the average grain size and the second phase size decrease from the center to the surface of the ingot, while the area fraction of the second phase increases gradually. At one-half of the radius of the ingot, the alloy presents the optimum comprehensive mechanical properties along the axial direction, which is attributed to the combined effect of relatively small grain size, low second-phase fraction, and uniform microstructure. For the as-homogenized alloy, the optimum two-step homogenization process parameters were determined as 340 °C × 10 h + 520 °C × 16 h. After the optimum homogenization, the proper size and morphology of CaMgSn phase are conducive to improve the microstructure uniformity and the mechanical properties of the alloy. Besides, the yield strength of the alloy is reduced by 20.7% and the elongation is increased by 56.3%, which is more favorable for the subsequent hot deformation processing.

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Section: Resultssupporting

confidence: 94%

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

et al. 2018

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“…The higher amount of Zn and Zr in the dendritic zones is probably due to the presence of sub-micrometric and nanometric Zn-Zr based precipitates. These findings are in agreement with other authors [17,[27][28][29], showing that during the recrystallization of Zn-Zr magnesium alloys, fine grains nucleate near the previous casting grain boundaries, while in the grain core, finely dispersed Zn-Zr submicrometric and nanometric precipitates can pin dislocations and prevent the nucleation and growth of the new recrystallized grains. This process results in a "necklace" structure, caused by an incomplete dynamic recrystallization.…”

Section: Microstructuresupporting

confidence: 93%

“…The area fraction of recrystallized grains is about 60%. This grain structure is probably ascribable to the synergic effect of localized plastic flow during forging [26] and to elements segregation in the dendrites [28,29]. Moreover, SEM-EDS analyses pointed out the presence of micrometric Zn-Zr intermetallics at the dendrite boundaries (white in Figure 5a) and different amounts of Zn and Zr in the recrystallized equiaxed grains and un-recrystallized dendrites.…”

Section: Microstructurementioning

confidence: 90%

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Influence of Plasma Electrolytic Oxidation on Fatigue Behaviour of ZK60A-T5 Magnesium Alloy

et al. 2020

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Magnesium alloys are used in the motorsport and aerospace fields because of their high specific strength. However, due to their low corrosion resistance, protective surface treatments, such as conversion coating or electroless plating, are necessary when they are used in humid or corrosive environments. The present study aimed at evaluating the effect of plasma electrolytic oxidation (PEO), followed by the deposition of a polymeric layer by powder coating, on the rotating bending fatigue behaviour of the wrought magnesium alloy ZK60A-T5. The specimens were extracted from forged wheels of racing motorbikes and were PEO treated and powder coated. Microstructural characterization was carried out by optical (OM) and scanning electron microscopy (SEM) to analyse both the bulk material and the multilayer, consisting of the anodic oxide interlayer with the powder coating top layer (about 40 µm total thickness). Rotating bending fatigue tests were carried out to obtain the S–N curve of PEO-treated specimens. The results of the rotating bending tests evidenced fatigue strength equal to 104 MPa at 106 cycles and 90 MPa at 107 cycles. The results of the investigation pointed out that PEO led to a reduction in fatigue strength between 14% and 17% in comparison to the untreated alloy. Fracture surface analyses of the fatigue specimens, carried out by SEM and by 3D digital microscopy, highlighted multiple crack initiation sites at the interface between the PEO layer and substrate, induced by the concurrent effects of coating defects, local tensile stresses in the substrate, and increased roughness at the substrate–coating interface.

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“…With the recrystallized grains increase, the softening degree caused by recrystallized grains also increases. Therefore, DRX also contributes to the increase in alloy elongation (Hadadzadeh et al, 2018). In summary, with the deformation temperature increases, the atomic diffusion rate increases.…”

Section: Effect Of Deformation Temperature On Microstructure Of Alloymentioning

confidence: 93%

Hot Tensile Deformation Behavior of Mg-4Li-1Al-0.5Y Alloy

Yang

Wang

et al. 2021

Front. Mater.

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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.

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Bimodal grain microstructure development during hot compression of a cast-homogenized Mg-Zn-Zr alloy

Cited by 38 publications

References 41 publications

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

Microstructure and Mechanical Properties of the As-Cast and As-Homogenized Mg-Zn-Sn-Mn-Ca Alloy Fabricated by Semicontinuous Casting

Influence of Plasma Electrolytic Oxidation on Fatigue Behaviour of ZK60A-T5 Magnesium Alloy

Hot Tensile Deformation Behavior of Mg-4Li-1Al-0.5Y Alloy

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