Improvement of room and high temperature mechanical properties of a Ti2AlNb-based alloy by the microstructural and compositional modifications

The ordered orthorhombic Ti2AlNb(O phase)-based alloys are considered as ca ndidate materials for high temperature application. A preliminary study was conducted to improve room and high temperature mechanical properties of an O phase-based Ti-22Al-27Nb alloy by microstructural and compositional modi fications. The spherical alpha (2) particles which were formed during the hot rolling in the (alpha (2) + B2) two phase region were found to be very stable when the hot-rolled material was reheated in the B2 single phase region, and the refore relatively small prior B2 grains ranging from 50 mum to 80 mum in di ameter were obtained by the pinning effect of these undissolved alpha (2) p articles. This fine-grained microstructure showed an excellent combination of room temperature tensile strength and ductility. The transition metal elements such as Mo, W and V were substituted for a po rtion of Nb in a Ti-22Al-27Nb alloy. The substitution was made so that the beta phase stability in the modified ahoy is equal to that in Ti-22Al-27Nb. It was found that the substitution of 2%W for 7%Nb (Namely Ti-22Al-20Nb-2W ) was quite effective in increasing the tensile strength at temperatures ab ove 923 K and reducing the steady state creep rate and primary creep strain .