Multiple Wavelengths Texture Measurement Using Angle Dispersive Neutron Diffraction at WOMBAT

Abstract

In contrast to conventional angle dispersive neutron diffractometers with a single-tube detector or a small-size linear position-sensitive detector, the WOMBAT diffractometer of the Australian Nuclear Science and Technology Organisation (ANSTO) is equipped with a large-area curved position-sensitive detector, spanning 120° for the scattering angle 2θ and 15° for the azimuth η, respectively. Here, WOMBAT was employed in establishing a texture measurement environment for complex textured samples, through measuring neutron diffractograms at two selected wavelengths on a typical reference sample of martensite–austenite multilayered steel sheet. All neutron patterns were simultaneously Rietveld analyzed using the software, Materials Analysis Using Diffraction (MAUD). The shorter wavelength (λ1 = 1.54 Å, k1 = 4.08 Å−1) enabled collecting the martensite reflections α-110, α-200, α-211, α-220, α-310, and α-222, as well as the austenite peaks γ-111, γ-200, γ-220, γ-311, γ-222, and γ-331 simultaneously, by pre-setting the detector range to 2Θ = 30~150°. The longer wavelength (λ2 = 2.41 Å, k2 = 2.61 Å−1) enabled separating the overlapping strong martensite α-110 and austenite γ-111 Laue–Bragg interferences more reliably. Moreover, the detector panel division along the vertical direction has a good stereographic coverage in the azimuthal angle η,. Such a combination of multiple-wavelength neutron diffraction combined with simultaneous Rietveld texture analysis was confirmed as being very valuable for realizing high precision measurements for complex textured samples at an orientation distribution graticule of 5°, and in a much shorter beam time than the conventional angle dispersive method.

Principal Preferred Orientation Evaluation of Steel Materials Using Time-of-Flight Neutron Diffraction

“…There were two angle-dispersive neutron diffractometers RESA-2 and MUSASI-L at Japan Research Reactor No.3 (JRR-3)'s guide hall for bulk texture evaluations of metallic materials. However, unlike the recently upgraded WOMBAT neutron diffractometer, with a wide-angle (∆2θ = 120 • ), large-area, curved, position-sensitive detector located at the Open-Pool Australian Lightwater Reactor (OPAL) guide hall [8], the pole figure measurement speeds of RESA-2 (with a narrow one-dimensional position-sensitive detector) and MUSASI-L (with a single-tube detector) are very slow and not suitable for in situ time-sliced texture measurements. In view of the new era of stress and texture evaluation techniques involved in various neutron diffraction instruments from the steady-state reactor neutron source at JRR-3, the large spallation neutron source at J-PARC, and the compact neutron source at RANS, these RESA-2 and MUSASI-L instruments have been replaced by the residual stress analyzer RESA at the T2-1 neutron beamline port of JRR-3 in order to improve the cost performance.…”

“…Figure 6 primarily reveals the competitive microstructural evolution process to obtain an ultrafine-grained multiphase microstructure involved in (a) the static recrystallization of cold-rolled martensite (with broadened and flattened peaks) to obtain newly recrystallized ferrite grains with sharp and strong ferrite-110 peaks and (b) the static precipitation of austenite grains with sharp and strong austenite-111 peaks.If the main research purpose is related to the lattice structural changes and stress/strain evolution during an in situ time-of-flight neutron diffraction experiment, the engineering materials neutron diffractometers with high stereographic angles and spatial resolutions[26,27] may be recommended; if the main research purpose is related to the phase fraction and the textures, the powder diffractometers with high stereographic angle coverage[8,23,[28][29][30] are3 high-throughput candidates. The complementary use of two kinds of time-of-flight neutron diffractometer may provide us with more fruitful information for a deeper under-…”

“…Figure 6 primarily reveals the competitive microstructural evolution process to obtain an ultrafine-grained multiphase microstructure involved in (a) the static recrystallization of cold-rolled martensite (with broadened and flattened peaks) to obtain newly recrystallized ferrite grains with sharp and strong ferrite-110 peaks and (b) the static precipitation of austenite grains with sharp and strong austenite-111 peaks.If the main research purpose is related to the lattice structural changes and stress/strain evolution during an in situ time-of-flight neutron diffraction experiment, the engineering materials neutron diffractometers with high stereographic angles and spatial resolutions[26,27] may be recommended; if the main research purpose is related to the phase fraction and the textures, the powder diffractometers with high stereographic angle coverage[8,23,[28][29][30] are3 high-throughput candidates. The complementary use of two kinds of time-of-flight neutron diffractometer may provide us with more fruitful information for a deeper understanding of the microstructure and texture evolutions of advanced multiphase materials in some extreme environments.…”