PECULIARITIES OF HYDROGEN INTERACTION WITH THE TAl_2–xNi_x LAVES PHASES (T = Zr, Hf)

Abstract

The effect of hydrogen treatment on the phase composition and structure of the Laves phases in the Zr(Hf)–Ni–Al systems has been studied. It is found that ball milling in a planetary mill leads to partial glass formation in the alloys, the Laves phases have nanocrystallites ≈6–14 nm in size, and a phase transition takes place in the HfAl_1.4Ni_0.6 alloy. The nanocrystallites of the Laves phases refine with increasing grinding time. It is shown that interaction of the as-cast alloys with hydrogen at 3.0 MPa and 950 °С finishes with their homogenization and formation of additional phases, such as Zr₂Al₃ and Zr₆Ni₈Al₁₅, for the zirconium alloys. Besides the original phase of MgCu₂ structural type, a phase with MgZn₂ structure appears in the hafnium alloys. The ball-milled zirconium alloys partially oxidize after the heat treatment in hydrogen.