Effect of Changing Plastic Work on Macroscopic Properties

Titanium alloys are the widely used to manufacture aero-engine components due to their capability to withstand harsh thermal and mechanical environments. Recent understanding developed on the characterisation of Titanium alloy has shown that plastic work imparted in the alloys during the manufacturing process can have long-lasting effects on the material properties. While this usually affects the global properties (e.g. the bulk hardness), the advancement of novel manufacturing and processing techniques, such as additive manufacturing and laser-shock peening, has shown promising results in altering local material properties to achieve the required performance in a component.

The aim of this project is to investigate the effect of changing plastic work on the macroscopic properties of Titanium alloys. This research incorporates experimental investigations and multiscale modelling to correlate specific microstructural features to macroscopic elasto-plastic properties, which then leads to the development of new methods and tools for predicting and ultimately prescribing the desired behaviours to these alloys through various manufacturing and processing techniques.

The experiments will involve applying varying degree of severe plastic deformation on Titanium alloys, which will then be subjected to a wide range of mechanical testing to probe the effects of stress-state, temperature and strain-rate on yield and flow behaviour. Details of the initial and final defect states and stress relaxation mechanisms will be provided by microstructural analysis prior to and after testing. These experimental results will then used to connect the crystal plasticity to bulk-scale continuum strength models. These models will expand our knowledge in component-level simulations and extend the multiscale modelling workflow. A similar workflow is currently being developed for Magnesium, which will act as the basis of the framework for this research to build upon. Experimentally-validated numerical models for the Titanium alloy of interest will be created and be used to populate the library of elasto-plastic anisotropic continuum models. By exploiting the understand of the effect of plastic work, these models can be selectively assigned to different regions of a structure during the manufacturing process to optimise the performance of next-generation components.

This research project is supported by Rolls-Royce as the knowledge gained and the methods developed will aid the company in further understanding the underlying phenomena of changing plastic work and its implications for improving its engine component design. This project also falls within the EPSRC Research Areas of Engineering Design and Manufacturing Technologies as the developed methods will improve the material modelling capability for current and future products, as well as identify specific processing routes to achieve microstructural optimisation of complex engineering structures.