Comparison of Phase Evolution and Sintering Properties of Ti-10Mo Alloys Prepared using Bulk Scrap and Blended Elemental (BE) Powder

In this study, Ti-10Mo alloy powder and sintered bodies were successfully fabricated using a three-step process of acid/organic solvent cleaning, hydrogenation/dehydrogenation (HDH) of bulk Ti-Mo scrap, and pressureless vacuum sintering of the alloy powder. This process can be used to recycle valuable Ti alloy. And unlike remelting-based recycling processes, in which elements vaporize, this process maintains the original ratio of Ti and Mo and results in no loss of elements during HDH and sintering. We note, however, that the phases in the resulting Ti-Mo alloy were changed by HDH and the sintering processes, and as a result the phases of the alloy evolved differently than those of alloys prepared by the blending of Ti and Mo powders. XRD results of the processed sintered bodies revealed different pathways for the transformation of the crystal structure. As sintering temperature increased, the dominant phase changes in the crystal structure of the sintered bodies that used commercial powders were α' → α' + α'', while the phase changes for the recycled Ti-10Mo sintered bodies were α' + α'' → α'' + β. Although the density of the sintered body using commercial materials was generally higher at a lower sintering temperature than the density of the sintered body that used recycled powder, at 1673 K their respective densities were nearly identical. Moreover, the sintered body that contained scrap showed superior Vickers hardness after the dual phase (α + β) of Ti was reached, despite its relatively low density.