High stereographic resolution texture and residual stress evaluation using time-of-flight neutron diffraction

Area of Science:

• Materials Science
• Solid State Physics
• Crystallography

Background:

• Neutron diffraction provides bulk averaged textures and microstructure information, including crystallographic parameters, phase fraction, crystallite size, and strain.
• Accurate texture and residual stress analysis are crucial for understanding material properties and performance.
• Existing neutron diffraction beamlines offer established methods for texture measurement.

Purpose of the Study:

• To establish a procedure for combined high stereographic resolution texture and residual stress evaluation using neutron diffraction.
• To verify the reliability of simultaneous Rietveld analysis of multiphase textures and macro stress tensors.
• To investigate phase stress partitioning in martensite-austenite multilayered steel.

Main Methods:

• Utilized the TAKUMI engineering materials diffractometer at J-PARC, dividing neutron detector panel regions for combined measurements.
• Performed pole figure evaluation on a limestone standard sample to assess texture measurement precision.
• Employed a high-strength martensite-austenite multilayered steel for simultaneous multiphase texture and macro stress tensor analysis.
• Applied a texture-weighted geometric mean micromechanical (BulkPathGEO) model for macro stress tensor analysis.

Main Results:

• Texture measurement precision was found to be comparable to established neutron beamlines (HIPPO, D20).
• Simultaneous Rietveld analysis successfully determined multiphase textures and macro stress tensors in layered steel.
• Analysis revealed significant in-plane stress differences between martensite (compressive) and austenite (tensile) layers.
• Phase stress partitioning was attributed to martensite transformation volume expansion and layer misfit during quenching.

Conclusions:

• The developed procedure enables precise, simultaneous evaluation of texture and residual stress.
• This method is reliable for analyzing complex, multiphase materials like advanced steels.
• Understanding phase stress partitioning is key to predicting the mechanical behavior of layered materials.