Effects of Mo addition on precipitation in Zr–1.2Nb alloys

•Mo-modified Zr–1.2Nb alloys are firstly developed as nuclear fuel cladding materials.•Mo addition decreases α→(α+β) phase transformation temperature in Zr–Nb alloys.•Precipitate of β-(Nb, Mo, Zr) is identified in Zr–Nb–Mo alloys.•Mo retards the growth of the precipitates but increases their number density.

Mo-modified Zr–1.2Nb alloys were prepared and the effects of Mo addition on precipitation in Zr–Nb alloys were elucidated. It was found that an increase of Mo content decreased α→(α+β) phase transformation temperature in Zr–Nb alloys. A new kind of precipitate, β-(Nb, Mo, Zr), was identified in the Mo-containing alloys. These particles are formed because Mo atoms replace Nb atoms in the β-(Nb, Zr) phase. Further, it was found that Mo retarded the growth of the precipitates but increased their number density.