Microstructural stability and grain growth kinetics in an extruded fine-grained Mg–Gd–Y–Zr alloy

Alizadeh, Reza; Mahmudi, R.; Ngan, A.H.W.; Langdon, Terence G.

doi:10.1007/s10853-015-9041-x

Cited by 52 publications

(16 citation statements)

References 28 publications

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“…SEM micrographs of the alloy at r = 1.5 mm are shown in Fig 5 . Also, it should be mentioned that, in accordance with an earlier study [30], the EDS results confirm the presence of some small Zr-rich precipitates in the microstructure of the alloy.…”

Section: Microstructural Evolution During Hpt Processingsupporting

confidence: 90%

“…In the initial extruded condition prior to HPT, the material displayed a fairly equiaxed and uniform grain structure with an average grain size of ~8.6 m: a detailed microstructural characterization of the extruded condition was given earlier [30]. SEM micrographs of the alloy at r = 1.5 mm are shown in Fig 5 .…”

Section: Microstructural Evolution During Hpt Processingmentioning

confidence: 99%

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Superplasticity of a nano-grained Mg–Gd–Y–Zr alloy processed by high-pressure torsion

Alizadeh

Mahmudi

Ngan

et al. 2016

Materials Science and Engineering: A

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While most of the reports on Mg-Gd-Y-Zr alloys report superplasticity after extrusion or friction stir processing, it is important to investigate superplasticity in these alloys after other severe plastic deformation processes having greater grain refinement capability. Accordingly, superplasticity was studied in an Mg-9Gd-4Y-0.4Zr (GW94) alloy after different high-pressure torsion (HPT) conditions. The HPT was performed at room temperature under an applied pressure of 6.0 GPa for up to 16 turns. TEM microstructural characterization revealed that the grain size was reduced from an initial value of ~8.6 m in the extruded condition to ~95 ± 10 and ~85 ± 10 nm after 8 and 16 turns, respectively. A shear punch testing method was used for evaluation of superplasticity at 573, 623, 673 and 723 K. Maximum strain rate sensitivities of ~0.51 ± 0.05 and ~0.48 ± 0.05 were obtained at 623 K for the material processed through 16 and 8 turns, respectively. This strain rate sensitivity and an activation energy of ~100 ± 5 kJ mol -1 suggests the occurrence of grain boundary sliding in the superplastic region.

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Section: Microstructural Evolution During Hpt Processingsupporting

confidence: 90%

Section: Microstructural Evolution During Hpt Processingmentioning

confidence: 99%

Superplasticity of a nano-grained Mg–Gd–Y–Zr alloy processed by high-pressure torsion

Alizadeh

Mahmudi

Ngan

et al. 2016

Materials Science and Engineering: A

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“…Accordingly, attempts have been made to improve their thermal stability through the addition of different alloying elements. It was reported that the addition of gadolinium (Gd) and other rare earth (RE) elements can lead to a remarkable improvement in the thermal stability of microstructure and mechanical properties at high temperatures due to solution hardening and precipitation strengthening [13,14].…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques

Alizadeh

Mahmudi

Pereira

et al. 2017

Materials Science and Engineering: A

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Mg-Gd-Y-Zr alloys have attracted much attention recently due to their ability to exhibit stable fine-grained microstructures and their potential superplastic behavior. However, the microstructure and superplasticity of these alloys processed by severe plastic deformation (SPD) methods remain less understood. In this work, the microstructure and superplastic behavior of an Mg-5Gd-4Y-0.4Zr (GW54) alloy were investigated after processing using extrusion and the SPD processes of equal-channel angular pressing (ECAP) and high-pressure torsion (HPT).Microstructural characterization by transmission electron microscopy and electron backscattered diffraction showed that nano-sized grains of ~72 ± 5 nm were obtained after 8 HPT turns whereas the grain sizes were about ~4.6 ± 0.2 and ~2.2 ± 0.2 m after extrusion and 4 ECAP passes, respectively. Shear punch tests revealed that the optimum temperature for superplasticity is 623 K for the HPT samples and 723 K for the ECAP and extrusion samples, at which the strain rate sensitivity were measured as about 0.42 ± 0.05, 0.46 ± 0.05 and 0.50 ± 0.05 for the extrusion, ECAP and HPT samples, respectively, and the corresponding activation energies were about 117, 101 and110 ± 5 kJ/mol for these three processing conditions. These results suggest that grain boundary sliding controlled by grain boundary diffusion is the dominant mechanism of deformation at the optimum temperatures for superplastic flow.

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“…For example, there are reports that rareearth (RE) elements can greatly improve the microstructural stability of Mg alloys at high temperatures [1][2][3][4]. Among the newly-developed Mg-RE based alloys are Mg-Gd-Y alloys which exhibit superior strength [5][6][7] and creep resistance [8,9].…”

Section: Introductionmentioning

confidence: 99%

“…These exceptional properties originate primarily from the influence of RE elements on the restoration processes and the textural evolution of Mg alloys at elevated temperatures [14,15] and also from the presence of RE-rich precipitates having superior thermal stability [4]. These results suggest that it would be valuable to investigate the hot deformation of Mg-Gd-Y alloys to obtain a better understanding of the dominant flow mechanisms at these high temperatures.…”

Section: Introductionmentioning

confidence: 99%

Microstructural evolution during hot shear deformation of an extruded fine-grained Mg–Gd–Y–Zr alloy

et al. 2017

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Abstract:Mg-Gd-Y-Zr alloys are among recently developed Mg alloys having superior mechanical properties at elevated temperatures. Dynamic recrystallization (DRX) and rare earth (RE)-rich particles play important roles in enhancing the high temperature strength of these alloys. Accordingly, the microstructural evolution of a fine grained extruded Mg-5Gd-4Y-0.4Zr alloy was investigated after hot shear deformation in the temperature range of 350-450 °C using the shear punch testing (SPT) method. The results reveal the occurrence of partial dynamic recrystallization at the grain boundaries at 350 °C while the fraction of DRX grains increases with increasing deformation temperature. A fully-recrystallized microstructure was achieved after SPT at 450 °C. The Gd-rich and Y-rich cuboid particles, having typical sizes in the range of ~50 nm to ~3 m, show excellent stability and compatibility after hot shear deformation and these particles enhance the high temperature strength during hot deformation at elevated temperatures. The textural evolution, examined using electron backscattered diffraction (EBSD), revealed a non-fibrous basal DRX texture after SPT which is different from the conventional deformation texture.

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Microstructural stability and grain growth kinetics in an extruded fine-grained Mg–Gd–Y–Zr alloy

Abstract: The grain growth kinetics of an extruded finegrained Mg-9Gd-4Y-0.4Zr (wt%) alloy was investigated by static annealing in the temperature range of 673-773 K.

Cited by 52 publications

References 28 publications

Superplasticity of a nano-grained Mg–Gd–Y–Zr alloy processed by high-pressure torsion

Superplasticity of a nano-grained Mg–Gd–Y–Zr alloy processed by high-pressure torsion

Microstructural evolution and superplasticity in an Mg–Gd–Y–Zr alloy after processing by different SPD techniques

Microstructural evolution during hot shear deformation of an extruded fine-grained Mg–Gd–Y–Zr alloy

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