Abstract. Forming of micro-components from powder with fields-activated sintering technology (FAST) renders different forming and sintering mechanisms, comparing to that occurring during the forming of macro-sized components with a similar technology. Establishing a good understanding of these mechanisms would help process design and control aiming at achieving desired quality of the components to be formed. This paper presents a study and the results on the sintering kinetics of the powder during Micro-FAST for the fabrication of micro-gears (the module is 0.2 and the pitch diameter 1.6 mm) from copper powder. The results showed that the densification of copper powder is related largely to the bulk plastic-deformations of the particles and the melting of the particles at contact interfaces. Particularly, it is revealed that plastic deformations of the copper particles mainly occurred at approximately 340 °C and melting of the particle-interfaces at approximately 640 °C. Differently, in a densification process with a traditional powder sintering method, grain growth and neck growth would, normally, be two dominant mechanisms that achieve the densification of powder.

Material extrusion additive manufacturing (ME-AM) builds 3D models by extruding materials through a nozzle layer by layer. As the development of materials, an increasing demand of the high-temperature extrusion has emerged in additive manufacturing (AM). While the smooth and stable extrusion process at high temperature relies heavily on the nozzle, the optimization study on the metal nozzle is reported in this work. From current brass and steel nozzles, two optimized nozzles (a steel nozzle with brass embedded and a steel nozzle with brass encircled) have been designed and the thermal conductivity has been studied by simulation analysis. Then the thermal deformation of designed nozzles and traditional nozzles have been investigated at the temperature of 410°C. Conducting the extrusion and printing tests, the extrusion performance of the proposed nozzles has been compared to that of traditional nozzles. The results indicate that the proposed nozzles lead to the better thermal distribution as well as the stronger resistance to thermal deformation compared to the traditional brass nozzle. The designed steel nozzle with brass encircled shows the excellent extrusion performance and printing performance.