Speaker
Description
Neutron Bragg-edge imaging, offering high spatial resolution for visualizing crystallographic information, has become a useful tool for material research. Magnesium (Mg) and its alloy, as one of the light structural materials, have been widely applied in various industries. Deformation twinning plays an important role in the deformation processes of Mg alloys with a hexagonal-close-packed (HCP) structure. Our study focuses on understanding the mecha-nisms of deformation twinning in Mg and its alloy using neutron Bragg-edge imaging and diffraction techniques. Two types of samples were designed: Pure Mg with coarse grains, for direct observation of deformation twins using energy/wavelength-dependent neutron trans-mission imaging; and Mg-6Zn alloy with fine grains, for extracting the volume fraction of de-formation twins via Bragg-edge transmission spectra analysis. Rectangular-shaped pure Mg and Mg-6Zn (6 wt.% Zn) alloy samples were prepared. Compression tests were carried out using a loading machine with different strains. Ex-situ pulsed neutron transmission imaging experiments were conducted at BL22 RADEN of the MLF/J-PARC [1]. A µNID detector was used to obtain 2D neutron Bragg-edge spectra of the samples after compression [2], and GUI-RITS software was used for Bragg-edge spectral analysis [3].
As shown in Fig. 1, the transmission spectra of the Mg-6Zn sample along the compression direction exhibit evident changes with increasing strain, especially for the three prominent Bragg edges. The height of the {0002} edge increases with strain, while the {10-10} edge de-creases simultaneously, indicating texture evolution due to twinning. The volume fraction changes of {10-12} <10-11> twins were quantitatively assessed through Bragg-edge spectral analysis. Additionally, direct visualization of twin formation and growth during compression of coarse-grained pure Mg was achieved using wavelength-dependent imaging. Comparative analyses with in-situ neutron diffraction data from BL19 TAKUMI, MLF/J-PARC, will also be presented.
References
[1] T. Shinohara et al., Rev. Sci. Instrum. 91, 043302 (2020)
[2] J.D. Parker et al., JPS Conf. Proc. 22, 011022 (2018)
[3] K. Oikawa et al., J. Phys. Conf. Ser. 2605, 012013 (2023)
| Abstract Topic | Application studies |
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