Microstructural Control of Ti-Al-Nb-W-B Alloys

In this work, new TiAl alloys containing W, B, and Nb have been developed. Fine uniform microstructures, with colony size smaller than 50 μm, can be conveniently obtained after hot-isostatic pressing (HIP) and homogenization treatment without any grain-refining processes using hot deformation. The effects of tungsten and boron on the microstructure of the TiAl alloys, including the colony size and lamellar spacing, were analyzed. This work shows that a small additional amount of W can refine the grain size of the Ti-Al-Nb-W-B alloys. The lamellar spacing also decreases with increasing W concentration. When the amount of W is greater than 0.4 at. pct, the β phase is stabilized and remains at room temperature, which can degrade the ductility of the alloy. Mechanical properties, such as the hardness of the alloy, can be increased by the addition of the alloying element through the solution strengthening and refinement of the grain size.