Thermal stability of bimodal microstructure in magnesium alloy AZ91 processed by ECAP

The changes in microstructure of equal channel angular pressing (ECAP) processed magnesium alloy AZ91 during thermal exposure were studied in this paper. The microstructure stability was investigated by means of electron backscatter diffraction (EBSD), which allowed to measure the changes in grain s...

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Bibliographic Details
Published in:Materials characterization 2015-09, Vol.107, p.167-173
Main Authors: Pantělejev, Libor, Štěpánek, Roman, Man, Ondřej
Format: Article
Language:English
Subjects:
AZ91 magnesium alloy
BACKSCATTERING
Boundaries
Distortion
Electron back scatter diffraction
Electron backscatter diffraction (EBSD)
ELECTRON DIFFRACTION
Equal channel angular pressing
Equal channel angular pressing (ECAP)
GRAIN SIZE
Grains
Kernel average misorientation (KAM)
KERNELS
Lattices
MAGNESIUM ALLOYS
Magnesium base alloys
MATERIALS SCIENCE
Microstructural stability
Microstructure
MODIFICATIONS
PRECIPITATION
PRESSING
STABILITY
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Summary:The changes in microstructure of equal channel angular pressing (ECAP) processed magnesium alloy AZ91 during thermal exposure were studied in this paper. The microstructure stability was investigated by means of electron backscatter diffraction (EBSD), which allowed to measure the changes in grain size, mutual ratio of low-angle boundaries (LABs) to high-angle ones (HABs) and local lattice distortion evaluated by the kernel average misorientation (KAM) parameter. It was found experimentally that the threshold temperature at which significant grain coarsening takes place is 350°C. No modification to mean grain diameter occurs below this temperature, nonetheless, some changes in LAB and HAB fraction, as well as in local lattice distortion, can be observed. •Thermal stability of bimodal UFG AZ91 alloy was assessed by means of EBSD.•Threshold temperature for pronounced grain coarsening was found at 350°C.•Below 350°C increase in LAB fraction and local lattice distortion takes place.•Local lattice distortion (LLD) can be well described using KAM approach.•LLD is influenced by coarsening and precipitation of Mg17Al12 particles.
ISSN:1044-5803
1873-4189
DOI:10.1016/j.matchar.2015.07.009