Numerical simulation of heat transfer and melting of Fe-based powders in SLM processing

[摘要] Modelling of selective laser melting (SLM) of Fe and stainless steel powders has been performed to analyze unsteady heat transfer in a porous medium under conditions of rapid phase transformations. The pulsed laser heat source develops high temperature gradients that lead to large solidification velocities, which can be used in acquisition of complex microstructures in SLM manufacturing. First, the effective thermal conductivity as a function of the local porosity which is a dynamically varying parameter in SLM was evaluated numerically. It showed a high role of heat transfer through the gas phase in powders with low thermal conductivity, i.e. in stainless steel. At the porosity 65% and above, the mechanism of heat transfer drastically changed and a linear dependence of thermal conductivity on porosity frequently used in literature becomes incorrect. Second, the obtained dependence was accounted for modelling of thermal fields and powder consolidation in the powder bed. The results of simulation agree well with the obtained experimental data and show the importance of correct dynamical evaluation of the thermophysical properties in SLM processes.

[发布机构] Udmurt State University, Universitetskaya str. 1, Izhevsk; 426034, Russia^1

[效力级别] 计算机科学

[关键词] Complex microstructures;Effective thermal conductivity;High temperature gradient;Low thermal conductivity;Selective laser melting;Simulation of heat transfer;Solidification velocity;Stainless steel powders