Assessment of bias errors caused by texture and sampling methods in diffraction-based steel phase measurements

Abstract

Many advanced high-strength steels rely on a metastable austenite phase for improvements in strength and formability. To date, no method has demonstrated the ability to provide accurate austenite phase fraction measurements in textured steels. Several techniques have been proposed, such as averaging the intensity of several peaks and/or summation of intensity from several sample orientations. The series of numerical experiments performed in this work sought to quantify the effects of texture on the measurement of the austenite phase fraction, with an emphasis on techniques suitable for laboratory X-ray diffraction. Simulated diffraction profiles were created with the following variables: texture components for the ferrite and austenite phases, the sharpness of each of the texture components, the number of peaks used for averaging in the phase fraction calculation, and the sampling scheme used for sample orientation summation in the phase fraction calculation. The resulting phase fraction calculations showed that texture, the number of peak pairs and the sampling method have a drastic effect on phase fraction measurements, causing significant bias errors. Hexagonal grids produced minimal bias errors and demonstrated a robust method of measuring phase fractions in textured materials.

Assessment of Martensitic Transformation Paths Based on Transformation Potential Calculations

“… was used. Scripts and data used in this paper are included in a companion data set . Uncertainty in the lattice parameters and variation in the local stress environment will have the strongest contributions to uncertainty in the transformation potential value but have not been quantified in this work.…”

Refinements in phase fraction determination of textured alloys from transmission diffraction data

“…Based on the experimental parameters, geometrical corrections to the intensity data due to oversampling were developed. Paralleling the prior work of Creuziger et al (2018a), synthetic textures were used to investigate the robustness of the rotated ring sampling scheme to particular texture components and applied to a reduced series of rotation angles.…”

“…These assumptions were tested in prior work by Creuziger et al (2018a). As shown by Creuziger et al (2018a,b), the series of diffraction vectors (or sampling scheme) used to measure phase fractions can cause oversampling of specific areas of the pole figure depending on the distribution of diffraction vectors.…”

“…One of the sampling schemes considered by Creuziger et al (2018a) was a diffraction ring recorded at high (infinite) energies. However, at many high-energy sources the samples may be rotated while in the beam, which results in the recording of a series of diffraction rings.…”

Competition of mechanisms contributing to the texture formation in metastable austenitic steel under compressive load

“…5. As the phase fractions were refined together with the texture coefficients of the E-WIMV model in the MAUD routine, the phase compositions are not biased by the preferred orientation of crystallites in individual phases [86]. The texture degree is depicted in terms of the maximum intensity of selected poles (Fig.…”