Disproportionation in Hydrogen and Recombination of the Laves Phases of Zirconium with Chromium

摘要

By the methods of differential thermal, X-ray phase diffraction, and metallographic analyses, we study the processes of conventional and solid HDDR (hydrogenation-disproportionation-de-sorption-recombination) in ZrCr_2 compound with C14- and CIS-type structures under initial pressures of hydrogen of 3 and 5MPa at temperatures of up to 1243 deg K. The ZrCr_2 compound with CIS-type structure disproportionates at 1048 and 1093 deg K for P_(H_2) = S and 3 MPa into ZrH_x and Cr and recombines in a vacuum. The temperature of disproportionation of the Laves phase with CIS-type structure is lower than for the C14 phase by 120 deg K. As the pressure of hydrogen increases, the temperature of disproportionation decreases. The application of HDDR to the reconstruction of the C14-type structure of the Laves phase in ZrCr_2 into the CIS-type structure makes it possible to decrease the temperature of treatment and its duration as compared with the case of annealing in vacuum. The procedure of HDDR forms a nanostructure in ZrCr_2.