Effects of the Microstructure and Strengthening Mechanisms of Mo2C Powders Being Added to Ti-8Nb-4Co Alloy Via the Vacuum Sintering Process

This study utilizes Ti-8Nb-4Co alloys added to different proportions of Mo2C powders (1, 3, and 5 mass%) by the vacuum sintering process of powder metallurgy and simultaneously vacuum sinters the alloys at 1240, 1270, 1300, and 1330°C for 1 h, respectively. The experimental results indicate that when 3 mass% Mo2C powders were added to the Ti-8Nb-4Co alloys, the specimens possessed the optimal mechanical properties after sintering at 1300°C for 1 h. The relative density was 98.02%, and the hardness and TRS were enhanced to 69.6 HRA and 1816.7 MPa, respectively. In addition, the microstructure of vacuum sintered Ti-8Nb-4Co-3Mo2C alloys has both α and β-phase structures, as well as TiC precipitates. EBSD results confirm that the Mo2C in situ produced TiC during the sintering process and was uniformly dispersed in the grain boundary. Moreover, the reduced molybdenum atom acted as a β-phase stabilizing element and solid-solution in the titanium matrix.

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This research is supported by the National Science and Technology Council of the Republic of China under Grant No. MOST110-2221-E-027-014-. The authors would like to express their appreciations for ASSAB STEELS TaiwaN Co., lTD. Furthermore, thanks to prof. H.C. Lin and Mr. C.Y. Kao of Instrumentation Center, National Taiwan University for EPMA and EBSD experiments.