TY  - JOUR
A1  - Müller, B. R.
A1  - Cooper, R. C.
A1  - Lange, A.
A1  - Kupsch, Andreas
A1  - Wheeler, M.
A1  - Hentschel, M. P.
A1  - Staude, A.
A1  - Pandey, A.
A1  - Shyam, A.
A1  - Bruno, Giovanni
T1  - Stress-induced microcrack density evolution in beta-eucryptite ceramics
BT  - experimental observations and possible route to strain hardening
JF  - Acta materialia
N2  - In order to investigate their microcracking behaviour, the microstructures of several beta-eucryptite ceramics, obtained from glass precursor and cerammed to yield different grain sizes and microcrack densities, were characterized by laboratory and synchrotron x-ray refraction and tomography. Results were compared with those obtained from scanning electron microscopy (SEM). In SEM images, the characterized materials appeared fully dense but computed tomography showed the presence of pore clusters. Uniaxial tensile testing was performed on specimens while strain maps were recorded and analyzed by Digital Image Correlation (DIC). X-ray refraction techniques were applied on specimens before and after tensile testing to measure the amount of the internal specific surface (i.e., area per unit volume). X-ray refraction revealed that (a) the small grain size (SGS) material contained a large specific surface, originating from the grain boundaries and the interfaces of TiO2 precipitates; (b) the medium (MGS) and large grain size (LGS) materials possessed higher amounts of specific surface compared to SGS material due to microcracks, which decreased after tensile loading; (c) the precursor glass had negligible internal surface. The unexpected decrease in the internal surface of MGS and LGS after tensile testing is explained by the presence of compressive regions in the DIC strain maps and further by theoretical arguments. It is suggested that while some microcracks merge via propagation, more close mechanically, thereby explaining the observed X-ray refraction results. The mechanisms proposed would allow the development of a strain hardening route in ceramics.
KW  - Beta-eucryptite
KW  - Microcracked ceramics
KW  - X-ray refraction
KW  - Tensile load
KW  - Strain hardening
Y1  - 2017
U6  - https://doi.org/10.1016/j.actamat.2017.10.030
SN  - 1359-6454
SN  - 1873-2453
VL  - 144
SP  - 627
EP  - 641
PB  - Elsevier
CY  - Oxford
ER  -