Development of Microstructure, Crystallographic Texture and Residual Stress in the interference region between substrate and a layer made by additive manufacturing during hybrid manufacturing

The project will consider manufacturing parts from similar and dissimilar materials to study the extent of heterogeneities in microstructure and mechanical properties in the interface.
Additive manufacturing (AM) is a technique with growing potential to be combined with traditional forming and forging methods of manufacturing to make them efficient and economical in producing complex parts with reduced number of processing steps, that is a method of hybrid manufacturing. Manufacturing components with complicated geometries can easily be achieved by AM and this characteristic can be combined with traditional forging processes. Deposition of complex features on a component made by traditional forging however can generate also unwanted features such as flaws, micro-cracks, macro-zones and residual stress. None of these are favourable for the structural integrity of the component in service as they might make the part susceptible to different fracture mechanisms. Material behaviour and properties, especially in the joint area are crucial for the application. The principal objective of this project is to obtain sufficient data on the development of microstructure, crystallographic texture, mechanical behaviour, and residual stresses in the joint area of a part produced by a combination of traditional forging and AM. The project will consider manufacturing parts from similar and dissimilar materials to study the extent of heterogeneities in microstructure and mechanical properties in the interface.
Advanced materials characterisation techniques such as electron backscattered diffraction (EBSD) coupled with direct electron detection, optical microscopy, x-ray diffraction (XRD) and energy dispersive spectroscopy (EDS) will be utilised for studying microstructure and the development of texture. The magnitude and distribution of residual stress with different length scales across the whole parts’ cross section, in particular the interface between the substrate and the AM made layers, will be measured by the aid of different techniques including XRD, hole-drilling and contour method, as well as FIBSEM for small scale hole drilling. These measurement techniques require certain skills and knowledge that will be supported by both the academic and the NPL supervisors. Understanding of the material behaviour, interrelationship between two parts produced by different techniques, and most importantly the residual stress distribution will improve the existing knowledge of microstructure and properties of AM materials, and will provide recommendations for further application.