Dresden 2011 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 23: Phase Transformations I
MM 23.9: Vortrag
Mittwoch, 16. März 2011, 13:00–13:15, IFW D
Phase Formation and Martensitic Transformation of Cast Cu-Zr-Co Alloys — •Fatemeh A. Javid1, Norbert Mattern1, and Jürgen Eckert1,2 — 1IFW Dresden, Institute for Complex Materials, Dresden, Germany — 2Technical Uneversity, Dresden, Germany
The phase formation and martensitic transformation of Cu50−xZr50Cox (x=0, 2, 5, 7.5, 10, 20 at.%) melt-spun and suction-cast bulk specimens has been studied. X-ray analysis shows that cobalt affects the eutectoid reaction CuZr ↔ Cu10Zr7 + CuZr2 of the binary Cu-Zr system and shifts it to lower temperatures. The results indicate that in compositions with at least 5 at. % cobalt, the glass crystallizes directly into B2(Cu,Co)Zr and this phase is the equilibrium phase at room temperature. An extended solid solution Cu50−xZr50Cox, cobalt between 5 and 50 at.% is indicated by the lattice parameter of the B2-type phase versus Co-content. The X-ray analysis of bulk specimens shows that in compositions with more that 10 at. % of cobalt, the B2(Cu,Co)Zr phase is coming from the liquid directly and this is the main phase at room temperature while compositions with less that 10 at.% of cobalt contain monoclinic CuZr phases as the main phase. Martensitic transformation of bulk samples was investigated with differential scanning calorimeter and the results show that cobalt shifts the transformation temperatures to lower temperatures. The martensite transformation start temperature lowers from about 452 K for x=0 to room temperature for x=7.5.