Adam Clare

Metal paste extrusions processes have found widespread application and are typically thought of as facile techniques to create metal components without the need for energy sources typically used in direct energy deposition and powder bed fusion processes. Despite recent advances in achieving net shape and improvements to material/component integrity, these processes are characterized by performance limiting defects which often emerge as a result of deposition strategy and are retained post sintering. Understanding these and devising strategies to minimize their formation will be essential for wider acceptance of the technology and utilization in more demanding applications.In this study, metal paste extrusion is explored from the first principle of depositing and understanding the formation of ‘inter-track’ and ‘in-track’ pores which manifest in fully sintered parts. To evaluate the contribution of these to undermining material integrity, tensile tests of linear and circular deposition strategies are undertaken. Experiments show that track interface length plays a major role in determining elongation to failure and tensile strength. To study post deposition defect behavior through the sintering cycle, X-Ray Computed Tomography is performed. This allows the evolution of defects to be observed through heat treatment. It is found that there are pores larger than the D90 metal particles introduced upon deposition that cannot be closed upon sintering. It is concluded that the limitation on the mechanical properties of metal paste extrusion components originates from the emergence of defects and their characteristics after the completion of the processing, as opposed to being influenced by the metallurgy prior or post sintering.

View record