Actual Problems in Machine Building 2018 Vol. 5 No. 3-4

Актуальные проблемы в машиностроении. Том 5. № 3-4. 2018 Материаловедение в машиностроении ____________________________________________________________________ 103 Fig. 2. SXRD patterns of as cast Ti-Nb alloys. The results of microhardness analysis are presented in table 1. The Ti-30Nb alloy shows a higher microhardness compared to the Ti-35Nb alloy due to the higher volume fraction of ω phase. When the percentage of Nb increases the microhardness decreases. The higher additions of Nb inhibit the formation of ω phase, which is responsible for increasing the hardness and brittleness by precipitation hardening. Conclusion Experimental results indicate that both the microstructure and the mechanical properties strongly depend on the Nb content. Upon rapid solidification in copper mold, metastable β-Ti structures with some fraction of ω phases, resulting in higher fractions of metastable ω phase for lower Nb additions were obtained. This indicates that the cooling rate upon casting is high enough to obtain metastable phases. References 1. Niinomi M. Recent metallic materials for biomedical applications // Metallurgical and Materials Transactions A. – 2002. – Vol. 33, iss. 3 – P. 477–486. – doi: 10.1007/s11661-002-0109- 2.