An Unusual Extrusion Texture in Mg–Gd–Y–Zr Alloys

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

doi:10.1002/adem.201500516

Cited by 65 publications

(21 citation statements)

References 28 publications

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“…The SPT curves were then plotted as shear stress against normalized punch displacement. and textural evolutions of this alloy in the extruded condition were already described in an earlier report [33]. Similar microstructural information for the material processed by 4 ECAP passes at 623 K is presented in Fig.…”

Section: Experimental Materials and Proceduressupporting

confidence: 81%

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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Section: Experimental Materials and Proceduressupporting

confidence: 81%

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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“…Details of the melting and extrusion processes were described earlier [14,24] but, briefly, the required metal was melted in an electric resistance furnace under a protective flux cover, poured into a steel die preheated to 300 °C using a tilt-casting system to minimize casting defects and melt turbulence and then extruding at 400 °C with an extrusion ratio of 19:1. The hot shear deformation was assessed using SPT and again the details were given earlier [25].…”

Section: Experimental Materials and Proceduresmentioning

confidence: 99%

“…These micrographs show there are no elongated grains in either the ED or TD and it is reasonable to conclude that the DRX is complete. Regarding the DRX mechanism of the alloy during the extrusion process, it was shown earlier [14] that new DRX grains form at the original grain boundaries during hot deformation and therefore it was concluded that the DRX can be considered as the main mechanism of recrystallization. The microstructure of the Mg-5Gd-4Y-0.4Zr alloy, extruded with lower extrusion ration of 8:1, is shown in Fig.…”

Section: Microstructure Before Sptmentioning

confidence: 99%

“…These differences are attributed to the role of the RE elements in delineating the onset temperature of recrystallization, the amount of stored energy [32], and the crystallographic texture of the newly-formed DRX grains [14,33].As an example, while DRX occurs at grain boundaries of an AZ31 alloy at 300 °C, there was no evidence for the presence of recrystallized grains in the microstructure of an Mg-Gd alloy at this temperature [32]. Accordingly, it is concluded that 350 °C is the temperature for the onset of recrystallization in the present Mg-Gd-Y-Zr alloy as observed in Fig.…”

Section: Microstructural and Textural Evolution After Sptmentioning

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%

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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 Evolution and Mechanical Properties of the As‐Cast and Extruded Mg–Gd Alloys

et al. 2015

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The microstructure, hardness, and shear strength of two Mg-Gd alloys with 1 and 2 wt% Gd were studied in both as-cast and extruded conditions. In the as-cast condition, the addition of Gd has no significant effect on the grain size, but it results in a high volume fraction of Mg5Gd precipitates. Gd addition decreased the grain size of the extruded materials, by retarding recrystallization during hot deformation through solute drag effect of Gd atoms in Mg. The enhancements in strength and hardness of the cast materials are due to the formation of Mg5Gd particles, while in the extruded materials the severe grain refinement achieved after extrusion is responsible for such improvements.

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An Unusual Extrusion Texture in Mg–Gd–Y–Zr Alloys

Cited by 65 publications

References 28 publications

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

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

Microstructural Evolution and Mechanical Properties of the As‐Cast and Extruded Mg–Gd Alloys

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