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The microstructural characteristics and Young’s modulus of the as-cast Ti–15Ta–15Nb alloy are reported in this study. On the basis of the examined XRD and TEM results, the microstructure of the current alloy is essentially a mixture (α + β+ α′ + α″ + ω + H) phase. The new H phase has not previously been identified as a known phase in the Ti–Ta–Nb alloy system. On the basis of examination of the Kikuchi maps, the new H phase belongs to a tetragonal structural class with lattice parameters of a = b = 0.328 nm and c = 0.343 nm, denoting an optimal presentation of the atomic arrangement. The relationships of orientation between these phases would be {0001}_α//{110}_β//{<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>2<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>0}_ω//{10<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>}_H and (01<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>0)_α//(1<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>2)_β//(<inline-formula><math display="inline"><semantics><mover accent="true"><mn>1</mn><mo stretchy="false">¯</mo></mover></semantics></math></inline-formula>010)_ω//(121)_H. Moreover, the Young’s modulus of the as-cast Ti–15Ta–15Nb alloy is approximately E = 80.2 ± 10.66 GPa. It is implied that the Young’s modulus can be decreased by the mixing of phases, especially with the presence of the H phase.