High-Temperature Properties of Niobium- and Molybdenum-Doped γ-TiAl Powder Materials Produced Using Titanium Hydride

Abstract

The creep-resistant γ-TiAl-based Ti₄₆Al₄₉Nb₄Mo₁ alloy, with a composition close to that of the third- generation TNM alloy, was developed with the powder metallurgy method using titanium hydride and intermetallics as starting materials. The alloy had a duplex structure, with 20–25 μm grains, consisting of 22% α₂ phase and 78% γ phase. No additional phases were detected. Mechanical properties of the powder material at temperatures up to 850°C were studied by compression and bending tests. At a temperature of 20°C, the Ti₄₆Al₄₉Nb₄Mo₁ alloy exhibited a bending strength of 800 MPa and significant high-temperature strength, remaining at a level of 670 MPa at 850°C. The alloy also showed enhanced creep resistance in compression tests, attributed to its fine-grained duplex structure. At temperatures up to 800°C, the alloy demonstrated considerably higher yield stress and strengthened more rapidly than the three-component material. Creep testing of the Ti₄₆Al₄₉Nb₄Mo₁ alloy between 750 and 800°C indicated increased high-temperature creep resistance. The strain rate sensitivity remained unchanged at both 750°C and at 800°C under all applied loads, suggesting an invariant deformation mechanism. The calculated thermal activation parameters for creep were in good agreement with data for cast alloys of this class. The mechanical properties of the Ti₄₆Al₄₉Nb₄Mo₁ alloy indicate its potential for use at temperatures up to 800°C.