Laser micro sintering (LMS) is a promising technique for micro-additive manufacturing. During LMS of metallic powder, the material property variation and the heat input energy profile are important to understand physical phenomena involved. This paper presents a finite element temperature distribution profile in LMS of nickel powder on 304 stainless steel substrate. The simulation considered the transition of powder-to-dense sub-model which involves effective thermal conductivity, volumetric enthalpy, and absorptance change; and a moving volumetric Gaussian distribution heat source sub-model. It is found that, for a specified cross section, the mechanism of preheating the nickel powder changes for the heat source from previous laser-irradiated substrate region to molten nickel as the laser beam approaches, while the center of molten pool slice is slightly shifted toward the reverse direction of laser scanning when the laser moves away due to the thermal accumulation effect. Simulated sintered widths showed very good agreement with experimental measurement, and relative prediction errors are below 16 % within the process window.

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A coupled finite volume-element method is developed to simulate the transient thermal deformation of water-cooled mirror by considering fluid flow and convective heat transfer. The simulation process consists of two steps: the 3D finite volume models of fluid flow and heat transfer equation are solved to obtain the time-dependent temperature field by using CFD; then, the obtained temperature field used as final temperature field is unidirectionally coupled to the finite element model for solving the thermoplastic equation. It is concluded that fluid flow not only affects the magnitude of temperature rise and thermal deformation, but also affects the distribution of temperature and thermal deformation. The temperature gradient in the thickness direction (z direction) is found to be much larger than that in transverse direction. It is found that the temperature and the consequent deformation of water-cooled mirror increase significantly in the first seconds and gradually become steady state in the subsequent time. Experiments are conducted to estimate the precision of numerical models, and the experimental results agree well with the simulated results.

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