Effect of small alloying additions on behaviour of rapidly solidified Cu–Cr alloys

Abstract

The mechanical properties of as well as microstructural changes in rapidly solidified ternary Cu–Cr based alloys were studied for various ternary additions. The flow stresses of the binary and various ternary alloys are explained in terms of Orowan strengthening mechanisms. Zirconium, magnesium, and, to a lesser extent, silicon affected the age hardenability of the alloys, refining the chromium dispersion by modifying the precipitation sequence described by Tang. The coarsening kinetics was insensitive to the presence of a third alloying element, showing that these additions did not affect chromium transport within the copper matrix. Nevertheless, these additions influenced the morphology of the chromium particles during coarsening; zirconium tended to keep the particles spherical, while titanium additions increased their aspect ratio. Titanium reduced dramatically the age hardenability of the alloy by provoking heterogeneous nucleation of bcc chromium on small Ti0₂ particles present in the as cast structure, resulting in a coarser particle size distribution at peak strength.

MST/1171