Quantifying X-ray diffractometer precision for measurement of dislocation density and the evolution of defect structures during solidification of additive manufacturing powders

Abstract

In this work, the Phillips PW 3020 X’Pert Diffractometer and PANalytical X’Pert Pro MPD X-ray Diffractometer were used to perform in-situ monitoring of quenched microstructures to define the defect evolution of Inconel 718 additive manufacturing powder. Dislocation density analysis based on X-ray Diffraction (XRD) measurement is sensitive to XRD peak broadening. The X-ray line profile is affected by the instrumental effects of the diffractometer, so quantifying and analyzing XRD instrument performance is important for accurate dislocation density analysis. The average measurement bias of the Phillips diffractometer was found to be -1.5490·10−3 Å while the precision was found to be 6.1000·10−5 Å. The average measurement bias of the PANalytical diffractometer was found to be -1.7633·10−4 Å while the precision was found to be 7.6917·10−5 Å. The average dislocation density calculated from the data was 3.93·1014 m−2 for the smaller particle size range and 2.58·1014 m−2 for the larger particle size range. The number of diffraction peaks utilized in dislocation density analysis was found to be a more significant factor than the instrumental differences. This work confirmed that differences in defect structure density can be observed across differently sized particles sourced from additive manufacturing powder.