The Effect of Molybdenum on the Creep Behavior of Orthorhombic Titanium Aluminides
D A. Shepherd, V K. Vasudevan
The effect of molybdenum additions on the creep properties of two orthorhombic titanium aluminide materials, Ti-22Al-26Nb and Ti-22Al-24.5Nb-1.5Mo (at.%), has been investigated. Heat treatments below the beta transus temperature followed by a 16-hour ageing treatment produced similar microstructures. Using the similar microstructures (consisting of O laths in a B2 matrix with a2 dispersed at B2 grain boundaries) for the two compositions, tensile creep testing was conducted under stresses of 68, 160, and 197 MPa at temperatures of 590 and 760oC. The creep results demonstrated the favorable effect of Mo on creep reistance in these orthorhombic titanium aluminides. Due to similar microstructures, results also suggested that improvements have been substructural, rather than purely microstructural, in nature.