2D single crystal Bragg-dip mapping by time-of-flight energy-resolved neutron imaging on IMAT@ISIS

Abstract

The cold neutron imaging and diffraction instrument IMAT, at the second target station of the pulsed neutron and muon source ISIS, is used to investigate bulk mosaicity within as-cast single crystal CMSX-4 and CMSX-10 Ni-base superalloys. Within this study, neutron transmission spectrum is recorded by each pixel within the microchannel plate image detector. The movement of the lowest transmission wavelength within a specified Bragg-dip for each pixel is tracked. The resultant Bragg-dip shifting has enabled crystallographic orientation mapping of bulk single crystal specimens with good spatial resolution. The total acquisition time required to collect sufficient statistics for each test is ~ 3 h. In this work, the influence of a change in bulk solidification conditions on the variation in single crystal mosaicity was investigated. Misorientation of the (001) crystallographic plane has been visualised and a new spiral twisting solidification phenomena observed. This proof of concept work establishes time-of-flight energy-resolved neutron imaging as a fundamental characterisation tool for understanding and visualising mosaicity within metallic single crystals and provides the foundation for post-mortem deduction of the shape of the solid/liquid isotherm.

The Influence of the Cooling Bores on Crystal Orientation and Lattice Parameter in Single-Crystalline Cored Turbine Blades

“…The collimated incident beam covered an area of 0.8 mm in diameter on the tested surface. It was assumed that the unit vector ( Figure 1 a) arranged parallel to the [001] direction defines the growth direction of the primary dendrite arms [ 1 , 14 , 30 ].…”

“…Therefore, the lattice parameters of γ and γ′ solid-solutions may also be different in the areas of size about the diffusion length of alloying elements in the molten phase, which is about millimeters [ 13 ]. It may be related to the fact that the value of the γ′-phase lattice parameter in as-cast CMSX-4 superalloy can vary in a relatively wide range from 0.3587 nm [ 9 ] to 0.3579 nm [ 14 , 15 ]. Therefore, it is essential to examine the distribution of the lattice parameter of γ and γ′ in macroscopic areas of a few millimeters’ width around the blade bores.…”

Microstructural Characterization of a Single Crystal Copper Rod Using Monochromatic Neutron Radiography Scan and Tomography: A Test Experiment

“…In case large size single crystal grains are present within a sample, the wavelength scan analysis of the areas in which they are present shows an intensity attenuation profile, which is affected by the strong scattering effect of a few selected neutron wavelengths interacting with the specifically oriented lattice planes of the single crystal. Since such single crystal areas only interact with specific neutron wavelengths, the transmitted beam exhibits an almost flat profile showing the presence of dips at specific wavelengths corresponding to the Bragg scattering conditions of the lattice planes, according to their 2θ orientation with respect to the primary beam direction [10][11][12][13][14].…”

Non-destructive characterization of the spatial variation of γ/γ′ lattice misfit in a single-crystal Ni-based superalloy by energy-resolved neutron imaging

“…Neutron diffraction imaging (Woracek et al, 2018) is a relatively novel technique that can provide information about the spatial variation of microstructure of crystalline materials. It has recently been applied to single-crystal superalloys to study the relationship between dendrite growth and mosaicity within a directionally solidified single-crystal turbine blade (Strickland et al, 2020(Strickland et al, , 2021. Here, we use this technique to measure the misfit of a nickel-based superalloy single-crystal specimen, by performing time-of-flight (TOF) neutron imaging experiments at a spallation neutron source.…”