TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler1 → Correlation between RF, laser, US results → Properties – microstructure relationships, mechanisms → In view of identifying additional suitable material – temper states → Fatigue behaviour of copper in the VHCF regime dominated by crack initiation and surface evolution (replica techniques) Fatigue studies for CLIC, aim and perspectives → Large amount of test data: over 95 sonotrodes tested, some of them to the CLIC lifetime → Ranking of materials defined among a preliminary selection → Laser and US test results plotted on a common Wöhler curve Slip band, as observed in 99.98% Cu. Loading with Δσ/2 = 62.6 MPa. 5×10 6 cycles and 5×10 8 cycles, respectively (Stanzl- Tschegg et al., 2007) a)Original, SEM b)Replica, SEM courtesy of Stanzl-Tschegg

TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler2 New high resolution analytical TEM (Tecnai F20 G2 Supertwin) Fatigue studies for CLIC, strategy → Markus Aicheler, 27, PhD student from Bochum (Prof. Eggeler) since May, 1 st → Dipl. Eng. in mechanical engineering – material science of the Ruhr-Universität Bochum LEO 1530 VP Scanning Electron Microscope

TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler3 Fatigue studies for CLIC, first results expected → Evolution of the sample geometry for US fatigue testing → Compare fatigue performance of "hard" and "soft" temper state for tested metals and alloys → Understand the effect of surface conditioning (machining) on fatigue performance Al-alloys, solution annealed and quenched + machined Al-alloys, solution annealed and aged + machined Pure Al, CW 5% + machined

TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler4 Fatigue studies for CLIC o Role of the grain size (UFG Coppers)

Hall & Petch relationship (CLIC meeting 10/06/2005) Hall-Petch relationship for copper with grain sizes of 3 µm- 1 mm (Kozlov, 2002): σ = σ 0 +k·d −1/2, k = 0.14 ± 0.05 MPa·m 1/2  Δσ (25 µm.. 70 µm)  ~ 7 MPa.. 15 MPa 25 µm 70 µm

TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler6 Fatigue studies for CLIC, first results expected o Role of the grain size (UFG Coppers, new ODS Coppers, MMC...) Ultrafine-grained oxide dispersion strengthened copper prepared by cryomilling (Cu + 3 vol.% CaO) D. V. Kudashova et al., Materials Science and Engineering A (2004) , also M. Heilmaier, patent DE C1 (2001)

TS day on CLIC 5 July 2007S. Sgobba, M. Aicheler7 Fatigue studies for CLIC, planning