Effect of Ru additions on microstructure and mechanical properties of Cr–TaCr 2 alloys

Abstract

Early work indicated that Ru reduced the ductile-to-brittle transition temperature of Cr even at small concentrations. To evaluate the potential of Ru as a beneficial alloying element in the two-phase Cr–TaCr 2 alloys, a number of Cr–8 at.%Ta alloys with 0–10 at.%Ru were prepared, and their microstructures and mechanical properties were evaluated. The Ru addition was found to move the eutectic point of Cr–TaCr 2 to a higher Ta level, as compared to the binary Cr–Ta system. Ru partitioned preferentially in the Laves phase over in the Cr matrix, with a partitioning ratio of 2–5:1, depending on the Ru addition level. Ru was also found to mainly occupy the Cr site in the TaCr 2 Laves phase. The hardness of both the primary Cr matrix and the eutectic microconstituent increased slightly with the increase in Ru addition. At a higher Ru addition level (i.e. 10 at.%), the hardness of the primary Cr matrix increased significantly, probably due to the precipitation of extremely fine Laves-phase precipitates. The Ru addition did not noticeably affect the fracture toughness of the two-phase alloys.