Grain boundary serration in nickel alloy inconel 600: Quantification and mechanisms

Abstract

The serration of grain boundaries in Inconel 600 caused by heat treatment is studied systematically. A new method based on Fourier transforms is used to analyse the multiple wave-like character of the serrated grain boundaries.A new metric -the serration index -is devised and utilised to quantify the degree of serration and more generally to distinguish objectively between serrated and non-serrated boundaries. By considering the variation of the serration index with processing parameters, a causal relationship between degree of serration and solution treatment/cooling rate is elucidated. Processing maps for the degree of serration are presented. Two distinct formation mechanisms arise which rely upon grain boundary interaction with carbides: (i) Zener-type dragging which hinders grain boundary migration and (ii) a faceted carbide growth-induced serration.

Global DIC approach guided by a cross-correlation based initial guess for HR-EBSD and on-axis HR-TKD

“…The performances are tested using the standard EBSD technique as well as the newly developed on-axis TKD configuration for which a global DIC approach is applied for the first time. This echoes the recent works by Yu et al [28] and Tang et al [29], who first applied the 'local' HR-EBSD technique to "off-axis" and "on-axis" TKD, respectively. Besides the investigated techniques, another originality of this work also stems from the chosen materials, whose thermomechanical treatments have caused significant plastic strains.…”

“…The HR-EBSD technique measures lattice rotation and elastic strain with an accuracy up to 10 À4 (0,006°) on single crystals such as GaN and SiGe [26] or silicon subjected to four-point bending [27]. It was also applied for the first time to "off-axis" TKD [28] in 2018 to map the strain field in the vicinity of a single dislocation in tungsten or more recently to "on-axis" TKD [29]. In the HR-EBSD method, at least four non-collinear regions of interest (ROI) are picked up across two highresolution EDP (typically 1000 £ 1000 pixels), one reference EDP and one target EDP.…”

Profilometry-based indentation plastometry to obtain stress-strain curves from anisotropic superalloy components made by additive manufacturing

“…An accelerating voltage of 30 kV was used, with a 2 nA probe current. Further details are available elsewhere [34].…”

Effect of sample thinning on strains and lattice rotations measured from Transmission Kikuchi diffraction in the SEM

“…More recently, a new hardware setup was introduced [20], where the phosphor screen in the setup is parallel to the plane of the thin sample and directly underneath. This setup, known as on-axis TKD, has an added advantage of obtaining Kikuchi patterns with much lesser gnomonic distortion than the t EBSD setup, higher signal levels and consequently less sensitive to beam drift [21,22] due to shorter scan times.…”

“…A similar cross-correlation approach can be used as in HR-EBSD to measure shifts and rotations in TKD patterns, thereby extending the ability of the technique [22]. In addition to this, the forescatter (FSD) diodes on the setup can be used to obtain TEM like Bright-Field and Dark-Field images [23] to a point where dislocations and their pile-ups are clearly visible [22].…”