Evolution of Microstructure and Properties of an Ultrahigh Strength Cu-Ni-Sn Alloy with Low Sn Content During the Multi-Stage Thermomechanical Treatment

Abstract

An ultrahigh strength Cu-9Ni-1.5Sn-0.8Si-0.1Al alloy was designed, and the effect of multi-stage thermomechanical treatment on the microstructure and properties of the alloy was investigated. The alloy treated by cold rolled (60%)-pre-aging (400 °C /30 min)-cold rolled (50%)-450 °C/120min-cold rolled (50%)-330 °C/120 min had a yield strength of 1093 MPa, tensile strength of 1150 MPa, and remained a conductivity of 18.1%IACS. The nanoscale β’-Ni 3 Sn, β-Ni 3 Si, γ’-Ni 3 Al precipitates formed during the thermomechanical treatment. The orientation relationship (OR) between the matrix and the precipitates was [111]Cu//[111]β’//[111]β//[111]γ’ and [200]Cu//[200]β’//[200] β//[220] γ’.The super-high strength of the designed alloy was mainly attributed to the precipitation strengthening, solid solution strengthening and sub-structure strengthening. Compared with single stage aging treatment, multi-stage thermomechanical treatment further improved the mechanical and electrical properties of the alloy, due to the nanoparticles that form during the aging treatment and the dislocation configuration that forms during cold rolling further promotes precipitation in the matrix.

Keywords: a low Sn-content Cu-Ni-Sn alloy, super-high strength, treatment, precipitate