J. Hemptenmacher (Sp), H. Schumann, K.H. Trautmann, P.W.M. Peters, German Aerospace Center (DLR), Cologne (Germany)
SiC-fibre and W-wire reinforced copper and Cu-alloys are promising candidates for application in heat sinks e.g. in
the divertor of future fusion reactors or in the burning chamber of rocket engines. The high thermal conductivity
of Cu and CuCr1Zr (up to 400 W/(mK) at RT) on one hand and the high strength of the SiC (SCS-6)-fibre (ca.
4000 MPa) or W-wire (ca. 2000 MPa) on the other hand enables the production of composites with attractive
physical and mechanical properties. The fabrication process of the composites uses continuous fibres coated with
pure Cu or the Cu-alloy by magnetron sputtering. For an optimized bonding between the SiC (SCS-6) fibre and
the Cu-matrix a thin fibre/matrix interlayer can be applied with the aid of magnetron sputtering, too. Ti- and Cr-
Abstracts of Euromat 2007 Seite 11 von 16
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interlayers were realized with a thickness of 0.2 - 8 μm. The coated fibres were stacked into a preform and sealed
under vacuum. Finally the consolidation takes place during hot isostatic pressing (HIPing). The thickness of the
matrix coating determines the fibre volume fraction, which varies between 10% and 30% in the present work.
Push out experiments were performed to characterize the fibre matrix bond strength. The measured interfacial
friction and the ‘apparent’ interfacial shear strength of the SiC/CuCr1Zr composites fall significantly below the
values, which are known from SiC/Ti composites. The room temperature strength and the high temperature (550°
C) tensile strength are determined as a function of the fibre volume fraction. The room temperature tensile
strength of the SiC/CuCr1Zr composite (Vf = 30%) exceeds 1100 MPa and is more than twice as high as the
unreinforced CuCr1Zr-alloy. The tensile strength at 550°C amounts to ca. 800 MPa (Vf = 25%).
Fatigue experiments on reinforced and unreinforced SiC/CuCr1Zr specimens were performed at room temperature
(f = 1 Hz, R = -0.6) according to the requirements defined for an application of Cu-matrix-composites in ITER. A
mechanical preloading of specimens leads to a strong benefit. This benefit is caused by a reduction of residual
stresses in the Cu-matrix. An increase in lifetime with a factor of 100 was found for a SiC/CuCr1Zr specimen (0.2
μm Ti-interlayer) with a fibre volume fraction of Vf = 25% preloaded up to 900 MPa.