1) The document examines mechanical alloying and amorphization in Cu-Nb-Ag in situ composite wires studied using TEM and atom probe tomography. 2) Results show the wires contain a nanoscale mixture of Cu, Nb, and Ag phases after drawing, with some regions becoming amorphized. 3) The mixing and amorphization are believed to occur through plastic deformation mechanisms like dislocation shuffling between phases, which increase vacancy concentrations and enable diffusion even where thermodynamics do not normally allow solubility. Regions of high dislocation density and mixing are most prone to amorphization.

1. Mechanical alloying and amorphization in Cu-Nb-Ag in situ composite wires studied by TEM and atom probe tomographyS. Ohsaki*, D. Raabe, K. Hono** National Institute for Materials Science, 1-2-1 Sengen, Tsukuba 305-0047, Japan1. Dec. 2009, MRS Fall, Boston

2. ÜbersichtMotivation andMethods

3. Results

4. Discussion

5. Outlook and open questionsMotivation: High strengthresistiveconductorsHigh strengthelectricalconductors: Multiphase materials; here: Cu-5 at.% Ag-3 at.% Nb (Cu-8.2wt%Ag-4wt%Nb) in-situ composite

6. Co-deformationmechanismsat large strains (mechanicalalloying; phasedissolution; dislocations in confined geometries; hetereophasedislocationtransmission; amorphization; conductivity)

7. Melt, cast, wire; SEM, TEM, APTRaabe, Mattissen: Acta Mater 46 (1998) 5973

8. 3NbAg/CuCuWhyCu-5 at.% Ag-3 at.% Nbternarybinarynm-spacing:highstrengthlowscatteringRaabe, Mattissen: Acta Mater. 47 (1999) 769

9. ÜbersichtMotivation andMethods

10. Results

11. Discussion

12. Outlook and open questionsD. Raabe: Advanced Materials 14 (2002) p. 639

13. 5Fibres; Cu-5 at.% Ag-3 at.% Nb (Cu-8.2 wt% Ag-4 wt% Nb)h=7.5h=8.6h=10.0Raabe, Ohsaki, Hono: Acta Mater. 57 (2009) 5254

14. 6Binary vs. ternarystrategyRaabe, Mattissen: Acta Mater.47 (1999) 769

15. 7298 K, influence of the size effectExperimentModel true strainRes. conduct.; Cu-5 at.% Ag-3 at.% Nb (Cu-8.2 wt% Ag-4 wt% Nb)relative change in resistivity

16. 8Nano-beam energy dispersive x-ray spectroscopy (EDS) Point 1: Cu matrixPoint 2: Nb filamentPoints 3-6: Nb and Ag with varying fractions, partly because of the convolution effect of EDS Point 7: Ag fiber. Dominance of CuPoints 1 and 2: minor Nb contributionPoints 3-6: considerable Ag contributionStrong co-existence of Cu and Ag within the same beam probesRaabe, Ohsaki, Hono: Acta Mater. 57 (2009) 5254

17. Nbfiber: h=10.0Nb phaseCu->40~60at%Nb->20~50at%Ag->5~28at%

18. Ag fiber: h=10.0Drawing direction

19. h=10.0 Ag phaseDislocation density 4.0×1016m-2 Raabe, Ohsaki, Hono: Acta Mater. 57 (2009) 5254

20. h=10.0 Nb phase Amorphization at Cu/Nb interfaceD. Raabe, U. Hangen: Materials Letters 22 (1995) 155161; D. Raabe, F. Heringhaus, U. Hangen, G. Gottstein: Zeitschrift für Metallkunde 86 (1995) 405422; D. Raabe, U. Hangen: Journal of Materials Research 12 (1995) 30503061see also: X.Sauvage: University of Rouen

21. ÜbersichtMotivation andMethods