TY  - JOUR
A1  - Laquai, René
A1  - Schaupp, Thomas
A1  - Griesche, Axel
A1  - Müller, Bernd R.
A1  - Kupsch, Andreas
A1  - Hannemann, Andreas
A1  - Kannengiesser, Thomas
A1  - Bruno, Giovanni
T1  - Quantitative analysis of hydrogen-assisted microcracking in duplex stainless steel through X-ray refraction 3D imaging
JF  - Advanced engineering materials
N2  - While the problem of the identification of mechanisms of hydrogen-assisted damage has and is being thoroughly studied, the quantitative analysis of such damage still lacks suitable tools. In fact, while, for instance, electron microscopy yields excellent characterization, the quantitative analysis of damage requires at the same time large field-of-views and high spatial resolution. Synchrotron X-ray refraction techniques do possess both features. Herein, it is shown how synchrotron X-ray refraction computed tomography (SXRCT) can quantify damage induced by hydrogen embrittlement in a lean duplex steel, yielding results that overperform even those achievable by synchrotron X-ray absorption computed tomography. As already reported in the literature, but this time using a nondestructive technique, it is shown that the hydrogen charge does not penetrate to the center of tensile specimens. By the comparison between virgin and hydrogen-charged specimens, it is deduced that cracks in the specimen bulk are due to the rolling process rather than hydrogen-assisted. It is shown that (micro)cracks propagate from the surface of tensile specimens to the interior with increasing applied strain, and it is deduced that a significant crack propagation can only be observed short before rupture.
KW  - 2101 duplex stainless steel
KW  - computed tomography
KW  - fractography
KW  - hydrogen
KW  - embrittlement
KW  - microcracking
KW  - synchrotron radiation
KW  - X-ray refraction
Y1  - 2022
U6  - https://doi.org/10.1002/adem.202101287
SN  - 1527-2648
VL  - 24
IS  - 6
PB  - Wiley-VCH
CY  - Weinheim
ER  - 
TY  - JOUR
A1  - Laquai, Rene
A1  - Gouraud, Fanny
A1  - Müller, Bernd Randolf
A1  - Huger, Marc
A1  - Chotard, Thierry
A1  - Antou, Guy
A1  - Bruno, Giovanni
T1  - Evolution of Thermal Microcracking in Refractory ZrO2-SiO2 after Application of External Loads at High Temperatures
JF  - Materials
N2  - Zirconia-based cast refractories are widely used for glass furnace applications. Since they have to withstand harsh chemical as well as thermo-mechanical environments, internal stresses and microcracking are often present in such materials under operating conditions (sometimes in excess of 1700 °C). We studied the evolution of thermal (CTE) and mechanical (Young’s modulus) properties as a function of temperature in a fused-cast refractory containing 94 wt.% of monoclinic ZrO2 and 6 wt.% of a silicate glassy phase. With the aid of X-ray refraction techniques (yielding the internal specific surface in materials), we also monitored the evolution of microcracking as a function of thermal cycles (crossing the martensitic phase transformation around 1000 °C) under externally applied stress. We found that external compressive stress leads to a strong decrease of the internal surface per unit volume, but a tensile load has a similar (though not so strong) effect. In agreement with existing literature on β-eucryptite microcracked ceramics, we could explain these phenomena by microcrack closure in the load direction in the compression case, and by microcrack propagation (rather than microcrack nucleation) under tensile conditions.
KW  - electro-fused zirconia
KW  - microcracking
KW  - synchrotron x-ray refraction radiography (SXRR)
KW  - thermal expansion
Y1  - 2019
U6  - https://doi.org/10.3390/ma12071017
SN  - 1996-1944
VL  - 12
IS  - 7
PB  - MDPI
CY  - Basel
ER  -