A Multiscale Study of Structural Integrity of High Temperature Superalloys
Multiscale and microstructure-sensitive predictive tools are critical for modelling deformation and propagation of cracks in high temperature superalloys.
Nickel-based superalloys are an important class of high temperature and highly corrosion resistant materials, which are widely used in aerospace, marine and power generation industries. They are unique as they contain a large volume fraction of ordered phase precipitates at the nano-scale embedded coherently in a metal matrix. As a structural material that is usually exposed to high static or cyclic loads in non-ambient environments, it is important to understand the resistance to both crack initiation and propagation in order to ensure structural integrity and provide guidance for future alloy development. Through systematic testing, characterisation and modelling, this research will provide a thorough understanding of microstructure-deformation interaction at a crack tip, and, more importantly, how it controls crack growth under fatigue, creep and oxidation conditions.
This project has an intrinsic multiscale nature, and will lead to novel modelling approaches for connecting crack propagation (macroscale) with oxygen diffusion (atomicscale), crystallographic slip (nano/microscale) and strain heterogeneity (mesoscale), which is currently lacking and critical for fatigue design and safe life prediction of high-temperature alloy components.
Two exemplar alloy systems, single crystal and polycrystalline alloys, will be considered. The single crystal alloys will be used to investigate the slip behaviour and crack growth in the g matrix and its particular interaction with the g’-precipitates. Polycrystalline alloys are proposed to study the combined effects of g’ precipitates and grain boundaries on slip behaviour and crack growth. Both cutting-edge experimental and computational approaches will be adopted in this project.
This project is a fundamental research programme that aims to provide new insights into the micromechanics at a crack tip and its significance in crack growth for nickel based superalloy systems. The simulation of microstructure-deformation interaction at a crack tip and the development of crack growth model are new, and will be of high value to academics and researchers worldwide working on mechanical behaviour of high temperature metallic materials. In the long term, the research is anticipated to have important applications in the research and development of future innovative aeroengines, gas turbines and nuclear reactors striving to achieve the maximum efficiency.
Professor Liguo Zhao, Professor of Solid Mechanics
"This research project has significant industrial impact, as the alloys studied here are used for safety critical components in power generation, aeroengine, oil and gas sectors."