Microstructure formation and control in additive manufacturing of metallic alloys

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Additive manufacturing (AM) of metallic alloys is rapidly emerged as a viable alternative to subtractive manufacturing. Microstructures of metallic components are a key contributory factor for resilience and reliable use with intended mechanical properties. The microstructure formation during rapid solidification of AM is however severely affected by the local temperature field near the growth interface of the melt pool. The typical thermal conditions occur during metal AM tend to promote strong grain orientations and texture; instead equiaxed microstructures are mostly preferred for wide range of engineering applications for their mechanical properties and resilience.This PhD project aims to study possible microstructure control mechanisms that can be applied to AM processes, in order to step towards the future inline process control capabilities. Potential for intensified nucleation mechanisms, which can act as control measures to reduce oriented grain structures and textures are aimed to examine. In particularly, the ways that can control the melt pool flow as tool to increased nucleation/fragmentation potential with ways to reduce effective thermal gradients at the melt pools will be one of the key focuses. Experimentally, advanced synchrotron imaging techniques will be employed to investigate the links between the evolution of the moving melt pool and the microstructure development at the solid-liquid interface. In addition, ex situ post metallographic examinations with a supportive computational framework is expected to develop to interpret and integrate experimental data into comprehensive scientific and engineering information.