Selective laser sintering (SLS) is an additive manufacturing process capable of rapidly and flexibly producing complex metallic parts. An SLS process, which is set up to manufacture micron sized components or components with micron scale features, can be called 'laser micro sintering' (LMS). One challenge associated with LMS is that fully dense metallic components are difficult to achieve. Through this award a novel double-pulse laser micro sintering process (DP-LMS) will be investigated. This new process has the potential to enhance the densification (reduce internal voids), and hence improve the mechanical properties of parts produced by LMS. The research focuses on understanding the material's transient responses during the DP-LMS process, and subsequently establishing the relevant process-structure-property relationships. The knowledge gained is also potentially relevant to other material processing and synthesis processes involving metal powder sintering. Successful implementation of the DP-LMS process has great potential to positively impact applications that may benefit from rapid and flexible fabrication of complex components with micron scale aspects such as MEMS, or micro medical devices. It is expected that both graduate and undergraduate students will be involved in the research, and that process principles and/or new findings will be incorporated directly into a current manufacturing classes and a video that will be made available to the public.
The specific research objectives are: (1) to test the hypothesis that during DP-LMS, suitably sending the two pulses can effectively help material densification with little increase of its surface roughness; (2) fundamentally understand the heat transfer, phase change, melt flow, and densification process in the target material during DP-LMS; and (3) establish the process-structure-property relationships for the DP-LMS process. The research tasks include: (1) in-situ study of the DP-LMS process using fast pyrometry, fast imaging, and emission spectroscopy to measure target temperatures, surface morphology variations, and plasma properties. (2) Development of a continuum-mechanics based model to understand the thermal and fluid transport and phase changes in the target material during the DP-LMS process. The model will be validated by the experimental measurements in task 1. And (3), characterization of the sintered material microstructures and mechanical properties through optical and electron microscopy, X-ray diffraction and hardness testing.
