MICROSTRUCTURE AND MECHANICAL-PROPERTIES OF ORTHORHOMBIC ALLOYS IN THE TI-AL-NB SYSTEM

The current understanding of the metallurgy of the orthorhombic alloys in the Ti-Al-Nb system is reviewed with emphasis on tensile and creep properties of ternary alloys. It is shown that increasing the Nb cont ent of alloys from 15 to 27 at% at a constant Al level significantly i ncreases both the tensile and creep properties of equiaxed as well as lath structures, while small changes in Al content have a large effect on creep. For a given alloy composition, the amount of B2(beta) phase and its distribution and the scale of O laths influences tensile prop erties, while creep properties depend on the volume fraction of equiax ed alpha(2)/O phase present in the structure as well as the size of O laths. (C) 1998 Elsevier Science Limited. All rights reserved.