Microstructure Evolution of Mo-based Composites during Selective Laser Sintering and Thermal Processing

摘要

This paper describes a novel preparation of Mo-based composites by selective laser sintering (SLS) and post-treatment thermal processing techniques, which can be used to manufacturing refractory metal parts. Coating polymer and frozen grinding techniques investigation of polymer-coated Mo powder and its SLS parameters have been discussed. The rapid prototyping experiment was conducted in the self-developed laser sintering machine, and optimized parameters have been acquired. It is intended to investigate the effects of variation of prototyping parameters: laser power, scanning velocity, preheating temperature and layer thickness etc. At last, the post-treatment thermal processing has been developed and refractory metal parts of Mo-Cu composites were gained. During processing of this material, parts are taken from the sinterstation in a ‘green’ semi-sintered state and then go through a furnace cycle. The post-treatment processing includes polymer degreasing, high temperature sintering and melting infiltration, which is sintering Mo framework by high temperature combining with Cu impregnation method. It is found that the mechanical properties of parts have been greatly improved after the post-treatment process. The microstructure evolution of post-treatment samples was investigated by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS) analyzing means. The microstructure characterization of Mo-Cu composites is homogeneous compound structure of adhesive phase Cu linked with Mo grains. A concentration of phases is along grain boundaries and these phases distribute interaction. There is little ellipsoidal Mo grains singly existed around by Cu phase. Between Mo grains and Cu zone, there is a medium changing zone, a width of 30～50nm. It is physical combination by diffusion means in Mo-Cu composites phase interface. Post-treatment processing mechanism is Mo framework solid-state sintering and Cu liquid-phase impregnation of melting/solidification.