Phase Transformations in the Quenched Alloy Based on Orthorhombic Titanium Aluminide during Heating

Phase transformations in the alloy based on the orthorhombic titanium aluminide (Ti-24,3Al-24,8Nb-1,4V-1,0Zr-0,6Mo-0,3Si – at. %) were studied by differential thermal analysis. The alloy was quenched from the different phase regions (β+O, β+O+α2+(Vω), β+α2, β) and was subjected to continuous heating up to . It was found that the heating temperature of the O-alloy, which determines its phase state during quenching, affects the temperature ranges, intensity, and stages of the phase transformations during subsequent heating.

Effect of Trace Boron Addition on the Microstructure and Tensile Elongation of Ti2AlNb-Based Orthorhombic Titanium Alloys

The grain sizes of two kinds of orthorhombic alloys, namely (O+B2) Ti-22Al-11Nb-2Mo -1Fe and (O+2) Ti-27.5Al-13Nb have been successfully reduced by the addition of trace boron (B) (less than 0.12 wt.%). For example, the grain size in the B2 solution-treated condition was reduced from 1 mm to 80 m by the addition of 0.05% B for both alloys. The tensile elongation of Ti-22Al-11Nb-2Mo-1Fe at room temperature and 650C was increased from 0.3% to 4.3%, and from 8.2% to 30.3%, respectively, by the addition of 0.10% B. Ti-27.5Al-13Nb also showed an improved room temperature ductility by the minor B addition.