Numerical and physical simulation of rapid microstructural evolution of gas atomised Ni superalloy powders

Li, Zhou; Grant, P. S.; Zheng, Liang; Lee, T. L.; Liu, Na; Liu, Zhou; Zhang, Guoqing; Mi, J.; Grant, Patrick

Abstract

The rapid microstructural evolution of gas atomised Ni superalloy powder compacts over timescales of a few seconds was studied using a Gleeble 3500 thermomechanical simulator, finite element based numerical model and electron microscopy. The study found that the microstructural changes were governed by the characteristic temperatures of the alloy. At a temperature below the γ' solvus, the powders maintained dendritic structures. Above the γ' solvus temperature but in the solid-state, rapid grain spheroidisation and coarsening occurred, although the fine-scale microstructures were largely retained. Once the incipient melting temperature of the alloy was exceeded, microstructural change was rapid, and when the temperature was increased into the solid + liquid state, the powder compact partially melted and then re-solidified with no trace of the original structures, despite the fast timescales. The study reveals the relationship between short, severe thermal excursions and microstructural evolution in powder processed components, and gives guidance on the upper limit of temperature and time for powder-based processes if desirable fine-scale features of powders are to be preserved.

Citation

Li, Z., Grant, P. S., Zheng, L., Lee, T. L., Liu, N., Liu, Z., Zhang, G., Mi, J., & Grant, P. (2017). Numerical and physical simulation of rapid microstructural evolution of gas atomised Ni superalloy powders. Materials & design, 117, 157-167. https://doi.org/10.1016/j.matdes.2016.12.074

• Acceptance Date: Dec 23, 2016
• Online Publication Date: Dec 27, 2016
• Publication Date: Mar 5, 2017
• Deposit Date: Jan 28, 2017
• Publicly Available Date: Jan 9, 2018
• Journal: Materials & Design
• Print ISSN: 0261-3069
• Electronic ISSN: 0264-1275
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 117
• Pages: 157-167
• DOI: https://doi.org/10.1016/j.matdes.2016.12.074
• Keywords: Ni superalloys, Rapid heating and cooling, Powder consolidation, Electron microscopy, Finite element modelling
• Public URL: https://hull-repository.worktribe.com/output/447696
• Publisher URL: http://www.sciencedirect.com/science/article/pii/S0264127516316008
• Additional Information: This article is maintained by: Elsevier; Article Title: Numerical and physical simulation of rapid microstructural evolution of gas atomised Ni superalloy powders; Journal Title: Materials & Design; CrossRef DOI link to publisher maintained version: http://dx.doi.org/10.1016/j.matdes.2016.12.074; Content Type: article; Copyright: © 2016 Elsevier Ltd. All rights reserved.
• Contract Date: Jan 28, 2017