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.
Highlights
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
On the IMAT instrument, neutron energies are deduced from their time-of-flight (TOF) from the source to the TOF imaging detector and transmission spectrum is obtained for each pixel 30
The Bragg-dips observed within the transmission spectra were indexed using the procedure outlined in Appendix A of 43
Summary
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. 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. There are some techniques for 3D reconstruction, they are time and labour intensive and provide only local reconstructions of small volumes [15,16] These methods elucidate little information regarding the influence of bulk variations in the solidification environment on resultant (001) misorientation 17. No method exists which can non-destructively visualise the variation in mosaicity within bulk single crystal metallic alloys or relate (001) misorientation to changes in the shape of solid/liquid isotherm. The principle for Bragg scattering is described through Bragg’s law:
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call