Microstructural evolution and superplastic behavior of a fine-grained Mg–Gd alloy processed by constrained groove pressing

In the current study, microstructural evolution and superplasticity of an extruded Mg–2wt% Gd sheet were studied after the constrained groove pressing (CGP) process. Microstructural observations by scanning electron microscopy and electron backscattered diffraction revealed that after 4 cycles of CG...

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Bibliographic Details
Published inMaterials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 754; pp. 390 - 399
Main Authors Hoseini-Athar, M.M., Mahmudi, R., Prasath Babu, R., Hedström, P.
Format Journal Article
LanguageEnglish
Published Lausanne Elsevier B.V 29.04.2019
Elsevier BV
Subjects
Constrained groove pressing
Deformation mechanisms
Electron backscatter diffraction
Evolution
Extrusion
Gadolinium
Grain boundaries
Grain boundary diffusion
Grain boundary sliding
Grain size
Grooves
Heat treating
Magnesium base alloys
Mg-Gd alloy
Microstructure
Pressing
Scanning electron microscopy
Shear punch test
Shear strain
Strain rate sensitivity
Superplasticity
Mg–Gd alloy
Superplasticity
Shear punch test
Constrained groove pressing
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Summary:In the current study, microstructural evolution and superplasticity of an extruded Mg–2wt% Gd sheet were studied after the constrained groove pressing (CGP) process. Microstructural observations by scanning electron microscopy and electron backscattered diffraction revealed that after 4 cycles of CGP, a rather homogeneous fine-grained microstructure with an average grain size of 4.3 μm, and a large fraction of high angle grain boundaries was obtained. By performing shear punch tests (SPT) at different temperatures and various shear strain rates, a peak strain rate sensitivity index (m-value) of 0.49 was obtained after 4 cycles of CGP process at 673 K, while peak m-values of 0.31 and 0.36 were obtained for the as-extruded and 2 cycle CGP process conditions, respectively. An m-value of 0.49 and an activation energy of 113 kJ/mol, obtained for the fine-grained material after 4 cycles of CGP, suggest that the dominant deformation mechanism in the superplastic regime is grain boundary sliding (GBS) controlled by grain boundary diffusion.
ISSN:0921-5093
1873-4936
1873-4936
DOI:10.1016/j.msea.2019.03.082