Enhancement of strength and ductility of Cu-Sn-Zn alloy by iron addition

Effects of iron addition to Cu-Sn-Zn alloy on the microstructures and mechanical properties were investigated. The Cu-Sn-Zn-Fe alloy, aged at 500 °C for 4 h, showed a peak hardness and an excellent combination of strength and ductility; e.g. a yield strength of 264 MPa, an ultimate tensile strength of 514 MPa and a fracture elongation of around 50%. The precipitates responsible for the strengthening are identified as bcc Fe with diameters ranging from 20 to 60 nm, and the interfacial relationship between the precipitate and copper matrix is (002)M//(110)P. It is discussed that Orowan dislocation bypassing can be a dominant strengthening mechanism; quantitative calculations for strengthening due to precipitation and grain refinement are roughly similar to the experimental results of the present Cu alloy. Additionally, the high work-hardening rate in a peak aged condition can be responsible for high tensile ductility of the alloy.