Alloys By Design - A Materials Modelling Approach

With this proposal, we will use modern metallurgical modelling tools to demonstrate that state of the art modern metallurgical modelling tools can complement the commonly-employed, empirical approach to alloy design. Traditionally, alloys required for metallurgical applications (e.g. within the transportation, power generation and construction industries) have been designed using rules-of-thumb, with emphasis placed on trial-and-error procedures and assessment by experiment. Application of computer-based methods will reduce the time (a new alloy can take up to ten years to design and qualify) and expense (a large number of trial alloys are fabricated and tested) which are associated with the alloy design process. We will design a new alloy - using computational methods - which is suitable for use in one of the most demanding applications: the turbine blading needed for the hottest parts of the gas turbine engine used for powering civil aircraft. The design concept for the new alloy requires it to have three key characteristics: (i) it should be thermodynamically stable during extended periods of service at high temperatures (ii) it should be resistant to degradation reactions which occur by interdiffusion with protective coatings used to protect it during operation and (iii) it must be capable of being fabricated by casting and thus resistant to the formation of melt-related defects during component fabrication. The numerical modelling work will be carried out at various scales. First, atomistic methods will be used to identify the combination of alloying additions which promote the formation of electron phases such as mu and sigma which impair key properties such as creep and fatigue. Second, microstructural modelling will be used to simulate the kinetic evolution of phase assemblies and dislocation degradation reactions which occur in these systems using techniques such as the phase field method. Third, modelling on the continuum scale will be used to assess how a component fabricated from the new alloy will perform, e.g. whether it would be prone to the formation of casting defects if it were to be cast in the foundry. The modelling tools which we will develop for this project will have considerable generality in the field of metallurgy and materials science and consequently, once this project is finished we will be in a position to use them for designing other metallurgical systems.