Formation of helium-gas bubbles in the vanadium-titanium binary and ternary alloys irradiated by energetic Ni++ ions

The alloys were three V-Ti binary alloys with Ti up to 21.0 at%, six V-Ti-Be ternary alloys and six V-Ti-Zr ternary alloys with Be and Zr up to 1.0 at.%. The alloys were preimplanted with helium to 80 appM, followed by Ni2+ ion irradiation to a damage dose of 25 dpa at 7000C. TEM revealed the production of helium gas bubbles in all alloys. Neither the primary solute Ti nor the secondary solutes Be and Zr affected the bubble formation except the distribution mode. Two modes of distribution were observed: relatively uniform in mode I and highly nonuniform in mode II. The particular distribution mode that predominated in a given alloy depended upon whether or not the matrix of the alloy was free of inclusion particles and second phase precipitates. The distribution in the V-5% Ti alloy was strictly in mode I because the alloy was relatively free of oxides, whereas in the other two binary alloys with higher Ti contents, thus containing more TiO inclusions, the mode varied from I to II in different regions. In all ternary alloys, especially those containing Zr, the distribution mode was predominantly II. The Ni2+ ion irradiations induced needle-like precipitates V2Zr intermetallic with a preferential orientation in the <001> directions in the V-Ti-Zr alloys. The shape of bubbles was spherical in the as-irradiated state, but became cuboidal after a post-irradiation anneal at 10500C for 100 h