Study on the Microstructures and Properties of Ti-Mo base Composites Processed by Vacuum Sintering

• Main Authors: Cheng Liang, 梁誠
• Other Authors: Shun-Tien Lin
• Format: Others
• Language: en_US
• Published: 2017
• Online Access: http://ndltd.ncl.edu.tw/handle/5jb3f8

博士 === 國立臺灣科技大學 === 機械工程系 === 105 === The aim of this study is to explore the titanium-molybdenum matrix composites, using vacuum sintering to optimize the properties. The characteristics of titanium- molybdenum matrix composites, has lightweight, strong mechanical properties, and good resistance to corrosion. In this study, we investigated the microstructure, mechanical properties and corrosion resistance of Ti-8Mo-xNi composites after sintering at different temperatures. Significant Widmanstätten-like structures formed on the β titanium matrix of the Ti-8Mo-xNi composites. The acicular TiNi intermetallic compound precipitates within the Widmanstätten-like structure increased as the added amount of Ni increased. the Ti-8Mo-6Ni composites possessed a relatively high relative density (94.9%) and hardness (42 HRC), but the highest TRS value of 1177 MPa was reached after sintering at 1175°C for 1 h. Ti-8Mo-xNi specimens formed a passive film, which contributed to better anti-corrosion properties. The effects with NbC carbides added in the microstructural evolution, the mechanical and corrosion properties of Ti-8Mo-6Ni composites were also investigated, through the vacuum sintering process at various temperatures were determined the best results. After sintering at 1275°C for 1 hour, the sintered density (99.7%) and hardness (48 HRC) of the NbC-1 wt% sample were obtained. The lowest Icorr (3.21ⅹ10-7 A•cm-2) and highest Rp (29172 Ω•cm2) appeared in the NbC-1 specimens after sintering at 1275°C for 1 h, which effectively improved the corrosion resistance. We also investigated the microstructure, mechanical properties and corrosion resistance of Ti-8Mo-xCu composites after sintering at different temperatures. Ti-12Cu-8Mo sintered alloys exhibited the excellent mechanical properties after sintered at 1200°C. Ti2(Cu, Mo) hypereutectoid phase was obviously observed in the sintered alloys. The titanium alloy for the corrosion resistance in sodium chloride is very excellent; it will be fully applied to the atmospheric environment. And then Titanium-based composites also use the addition of carbides to achieve the effect of dispersive precipitation strengthening. The experimental results show that, Adding different carbides (WC, TaC and ZrC), are combined with titanium to form titanium carbide and stable β phase, with the increasing of various carbide contents and sintering temperature, the relative density of microstructure increasing. Hardness and mechanical properties are also significantly improved. The addition of 5 wt% zirconium carbide (ZrC) has a most exceptional effect, The sintering density (98.9%), hardness (45 HRC) and transverse rupture strength (1068 MPa) were significantly improved. Adding different carbides (WC, TaC and ZrC), are combined with titanium to form titanium carbide and stable β phase, Such reaction after sintering at high temperature, revealed the mechanisms of in-situ precipitation strengthening, are the reaction as 2Ti + MC = TiC + Ti (M), (M = Ta, W, Zr).