Abstract
An alloy of composition (wt-%) Cu-15Ni-8Sn produced by the Osprey process has been examined after a range of thermomechanical treatments with the aim of achieving high strength combined with reasonable ductility. Extensive cold working and an anneal in a two phase region for recrystallisation, followed by spinodal decomposition, leads to a high strength with reasonable tensile elongation because of the small grain size. Yield stresses in excess of 1100 MPa are obtained by contributions of grain size hardening, spinodal hardening by the internal strain amplitudes created during decomposition, and progressive ordering at tin rich sites. Alternatively, very short high temperature anneals or medium short low temperature anneals for recovery or partial recrystallisation of the cold worked state lead to materials with very high yield stresses, between 1250 and 1450 MPa, maintaining similar values of tensile elongation.
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