DSouza_et_al(2020)Accepted.pdf (2.62 MB)
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Relating micro-segregation to site specific high temperature deformation in single crystal nickel-base superalloy castings

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journal contribution
posted on 25.02.2020, 10:08 by Neil D'Souza, Bryan Roebuck, David M Collins, Geoff D West, Chinnapat Panwisawas
Thermo-mechanical deformation of the solid on cooling following solidification has been studied quantitatively in a Ni-base single crystal superalloy, CMSX-4 used in turbine blade applications. In the as-cast state, the alloy has location specific properties due to micro-segregation of alloying elements during solidification; this effect become increasingly important with smaller specimen cross-section in thermo-mechanical tests. Accordingly, normalised resistance/resistivity tests have been used to classify samples with varying micro-segregation, given the different γ and γ′ phase resistivities. Increased normalised resistance corresponds to increased local solvus temperature, which determines the plastic strain and stress evolution during cooling. Upon cooling from above the γ′ solvus temperature, dislocation creep occurs within the γ phase accompanied by a small increase in stress. A critical precipitation γ′ volume fraction is reached as the material cools, leading to precipitation hardening as measured by a dramatic resistance change and thereby stress increase at lower temperatures. Short-term creep tests capturing the history-dependent deformation, as demonstrated by controlled cooling experiments, gives steady-state creep, enabling parameter measurement for a Norton-type constitutive equation in a given temperature range. Implications of these results to modelling of plastic strain and stress during cooling from close to solvus temperature during casting has been discussed.

History

Citation

Materials Science and Engineering: A, Volume 773, 31 January 2020, 138862

Author affiliation

School of Engineering

Version

AM (Accepted Manuscript)

Published in

Materials Science and Engineering: A

Volume

773

Pagination

138862 - 138862

Publisher

Elsevier BV

issn

0921-5093

Acceptance date

21/12/2019

Copyright date

2020

Publisher version

https://www.sciencedirect.com/science/article/pii/S0921509319316430#!

Language

en