A versatile automated sample changer for texture measurements on the high pressure-preferred orientation neutron diffractometer

Dessieux

et al. 2018

QuBS

The time-of-flight neutron diffraction data collected in-situ on Oak Ridge National Laboratory’s (ORNL, Oak Ridge, TN, USA) VULCAN and Los Alamos National Laboratory’s (LANL, Los Alamos, NM, USA) High-Pressure-Preferred-Orientation (HIPPO) diffractometers have been analyzed complementarily to show the texture evolution during annealing of a cold-rolled Al-2%Mg alloy. The texture analysis aimed to identify the components present in the initial rolling (or deformation) texture and in the thermally-activated recrystallization texture, respectively. Using a quasi-Monte-Carlo (QMC) approach, a new method has been developed to simulate the weighted texture components, and to obtain inverse pole figures for both rolling and normal directions. As such, distinct recrystallization pathways during annealing in isochronal conditions, can be revealed in terms of the evolution of the texture components and their respective volume fractions. Moreover, the recrystallization kinetics associated with the cube and random texture components are analyzed quantitatively using a similar approach developed for differential scanning calorimetry (DSC).

Section: Methodsmentioning

confidence: 99%

Section: Neutron Diffraction Texture Characterizationsmentioning

confidence: 99%

Distinct Recrystallization Pathways in a Cold-Rolled Al-2%Mg Alloy Evidenced by In-Situ Neutron Diffraction

Dessieux

et al. 2018

QuBS

“…The samples were mounted on sample holders and measured at rotation angles of 0, 45, 67.5 and 90 degrees around the sample cylinder axis using an automated sample changer [32]. Neutrons were detected by 3 He detector tubes grouped on 30 detector panels arranged on three rings with nominal diffraction angles of 140, 90 and 40 degrees.…”

Section: Texture Measurementmentioning

confidence: 99%

Anisotropy in hexagonal close-packed structures: improvements to crystal plasticity approaches applied to magnesium alloy

Oppedal

Kadiri

Tomé

et al. 2013

Philosophical Magazine

Due to its polarity, {1 01 2} twinning in strongly textured hexagonal close packed (HCP) structures can be maximized or minimized under particular loading conditions. The resulting anisotropy can be dramatically demonstrated for magnesium with a [0 0 0 1] fibre, for example. The stress-strain behaviour from compression loading parallel to the fibre produces a 'parabolic' stress-strain curve, but a 'sigmoidal' curve when loaded normal to the fibre. When modelling anisotropy in HCP structures with crystal plasticity, contemporary researchers usually fit hardening parameters to only these two extreme cases, i.e., maximized or minimized twinning activity, presuming that the same parameters would interpolate the correct behaviour under any other transitional stress direction. A comparison with experiments presented in this paper demonstrates that this assumption is not fully accurate, whether using the phenomenological Voce hardening model or the dislocation density based hardening model in the VPSC (visco-plastic selfconsistent) framework. This indicates that slip-twin interactions are not properly captured in these models. Through a simple phenomenological implementation, we show that dislocation transmutation by twinning is an important aspect of sliptwin interactions that improve the predictability of the above crystal plasticity models for HCP structures.

“…As an example, Figure 6 shows the texture evolution in Zr-2.5Nb measured on the HIPPO diffractometer [77,78] using a high-temperature deformation furnace [79]. The texture of the 6 mm diameter and 20 mm long sample was measured at room temperature before and after the high-temperature deformation on a robotic sample changer [80] as a benchmark. During the furnace experiment, the texture was measured at 250 ∘ C, 625 ∘ C, 815 ∘ C, and 975 ∘ C, and then the sample was compressed by 20%, followed again by texture measurements at the same temperatures during cooling.…”

Section: Deformation Studiesmentioning

confidence: 99%

A Review of Neutron Scattering Applications to Nuclear Materials

Vogel

2013

ISRN Materials Science

The growing demand for electric energy will require expansion of the amount of nuclear power production in many countries of the world. Research and development in this field will continue to grow to further increase safety and efficiency of nuclear power generation. Neutrons are a unique probe for a wide range of problems related to these efforts, ranging from crystal chemistry of nuclear fuels to engineering diffraction on cladding or structural materials used in nuclear reactors. Increased flux at modern neutron sources combined with advanced sample environments allows nowadays, for example, studies of reaction kinetics at operating temperatures in a nuclear reactor. Neutrons provide unique data to benchmark simulations and modeling of crystal structure evolution and thermomechanical treatment. Advances in neutron detection recently opened up new avenues of materials characterization using neutron imaging with unparalleled opportunities especially for nuclear materials, where heavy elements (e.g., uranium) need to be imaged together with light elements (e.g., hydrogen, oxygen). This paper summarizes applications of neutron scattering techniques for nuclear materials. Directions for future research, extending the trends observed over the past decade, are discussed.