Component interaction in the Zr-Cr-Sb system at 870 K

Abstract

The component interaction in the Zr - Cr - Sb ternary system was studied at 870 K over the whole concentration range using methods of X-ray diffraction and metallographic analysis. The alloys for investigation were prepared by direct arc melting the stoichiometric amounts of the constituent elements under high purity Ti-gettered argon atmosphere on a water-cooled copper hearth. The arc-melted ingots were then annealed at 870 K in evacuated quartz glass tubes for 720 hours and subsequently cold water quenched. The 3-5 wt. % excess of Sb was required to compensate the evaporative losses during arc-melting. The synthesized and annealed samples are stable in atmospheric conditions. For the characterization of the annealed samples X-ray powder diffraction on DRON-2.0m diffractometer with Fe K α radiation was performed. The chemical and phase compositions of the obtained samples were examined by Scanning Electron Microscopy (SEM) using Carl Zeiss DSM 962 and REMMA-102-02 electron microscopes. In the Cr–Sb and Zr–Sb systems a formation of the all binaries reported in the literature was confirmed. In the Zr-Cr system аt 870 K ZrCr 2 binary was realized in high-temperature hexagonal modification with MgZn 2 structure type. According to EPMA data the homogeneity range of the ZrCr 2 binary is limited by the Zr 33.05 Cr 66.95 and Zr 37.59 Cr 62.41 compositions ( а = 0.5113(2)-0.5110(1), с = 0.8289(7)-0.8292(7) nm). At the temperature of investigation phase relations in Zr-Cr-Sb system are characterized by existence of one ternary compound Zr 5 Cr 0 . 5 Sb 2 . 5 with W 5 Si 3 structure type (space group I 4/ mcm ; a = 1.1097(1), c = 0.5566(2) nm). The substitutional solid solution Zr 5 Sb 4- x Cr x up to 5 at. % Cr based on the binary antimonide Zr 5 Sb 4 with Ti 5 Ga 4 structure type ( а =0.8532(4)-0.8482(2), с =0.5858(4)-0.5820(1) nm) was observed. Solubility of Sb in ZrCr 2 compound (MgZn 2 -type) is up to 6 at. % ( а = 0.5113(2)-0.5127(1), с = 0.8289(7)-0.8354(9) nm) along isoconcentrate of 33 at. % Zr. Solubility of the third component in other binary compounds is less than 1-2 at. %. Analysis of the Zr-Cr-Sb system and studied early Zr-M-Sb (M = Mn, Fe, Co, Ni, Cu) showed that the ternary compounds with W 5 Si 3 structure type appear in all these systems. The reduced number of the ternary phases in the Zr-Cr-Sb system comparing with related Zr-M-Sb systems shows an important influence of d -metal on the formation and structure of intermediate ternary phases. Keywords : intermetallics, ternary system, phase equilibria.