Direct rolling of Ti-6Al-4V-0.1B alloy sheets in the β phase region

The microstructures and tensile properties of Ti-6Al-4V-0.1B alloys with lamellar structures after direct rolling were investigated systematically. When sheet is rolled in the β phase region, boron-containing alloys with fine grains show good ductility. No crack is found in the macrostructure when examined. By scanning electron microscopy, the observation shows that TiB whiskers are mainly at the grain boundary in as-cast microstructure, while in as-rolled microstructure the whiskers become smaller and arrange along the rolling direction. Electron backscatter diffraction analysis shows that the matrix microstructure of the as-rolled alloys has a low degree of distortion, and remains lamellar (α lath width is reduced to 1.73±0.42 μm). The microstructure refinement causes the change of mechanical properties that both the room temperature tensile properties and the high temperature strength of as-rolled alloys are obviously higher than those of as-cast alloys. TiB whiskers debond with matrix alloys when the temperature is high, which causes the high temperature ductility of as-rolled alloys are relatively low.