Property Evaluation of Ti Powder and Its Sintered Compacts Prepared by Ti Scrap

Abstract In this study, Ti powders were fabricated from Ti scrap by the Hydrogenation-Dehydrogenation (HDH) method.The Ti powders were prepared from the spark plasm a sintering (SPS) and their m icrostructure was investigated.Hydrogenation reactions of Ti scrap occurred at near 450 o C with a sudden increase in the reaction temperature and thedecreasing pressure of hydrogen gas during the hydrogenation process in the furnace. The dehydrogenation process was alsocarried out at 750 o C for 2 hrs in a vacuum of 10 -4 torr. After the HDH process, deoxidation treatment was carried out withthe Ca (purity: 99.5%) at 700 o C for 2 hrs in the vacuum system. It was found that the oxidation content of Ti powder thatwas deoxidized with Ca showed noticeably lower values, compared to the content obtained by the HDH process. In orderto fabricate the Ti compacts, Ti powder was sintered under an applied uniaxial punch pressure of 40 MPa in the range of900-1200 o C for 5 min under a vacuum of 10 -4 torr. The relative density of the compact was 99.5% at 1100 C and the tensilestrength decreased with increasing sintering temperature. After sintering, all of the Ti compacts showed brittle fracturebehavior, which occurred in an elastic range with short plastic yielding up to a peak stress. Ti improved the corrosionresistance of the Ti compacts, and the Pd powders were mixed with the HDH Ti powders.Key words Ti, Ti alloys, HDH process , spark plasma sintering , potentiodynamic polarization.