Fabrication of homogeneous Mo-Cu composites using spherical molybdenum powders prepared by thermal plasma spheroidization process

In this work, spherical and dense molybdenum particles with the average particle size of 16.6 mu m were synthesized by thermal plasma spheroidization process, and further used to fabricate homogeneous Mo-25 wt% Cu composites by infiltration method. The influence of infiltration temperature and holding time on the microstructure and properties of obtained Mo-Cu composites was investigated, and experimental results show that homogeneous Mo-Cu composites with high densification are obtained and the smooth surface of pores could facilitate the infiltration process. Specially, 98.6% of relative density of Mo-Cu composites is achieved and less than 10% irregular particles existing in spherical powders induce closed or half-connected pores in porous Mo skeleton, which shows adverse effect on full dense Mo-Cu composites obtaining. In addition, the highest microhardness of Mo-Cu composites (199 +/- 3.6 Hv) is obtained when infiltrated at 1300 degrees C for 1 h. Moreover, the maximum value of thermal conductivity (TC) of Mo-Cu composites is 154 W/(m.K), and this is lower than that predicted by theoretical models, which may be due to the small amounts of carbon in Mo-Cu composites and non-full dense of Mo-Cu composites. Furthermore, the carbon in porous skeleton could be well removed by controlling the atmosphere of sintering process. Importantly, Mo-25 wt% Cu composites fabricated by irregular particles exhibit non-uniform microstructure and low TC compared to that prepared by spherical particles, which would be due to the uneven pore distribution and closed pores in porous skeleton fabricated by irregular particles. These results well illustrate the superiority of spherical molybdenum particles on fabrication homogeneous Mo-Cu composites.