Abstract
The hot deformation behavior of Cu-20.0Ni-5.0Sn-0.25Zn-0.22Mn was investigated using a Gleeble-3500 thermal simulator with a temperature range from 720 °C to 880 °C and a strain rate range from 0.001 s−1 to 1 s−1. The results show that the flow stress increased with the increase of the strain rate and the decrease of the temperature. The constitutive equation of the alloy was established based on the peak flow stress. Figures of the power dissipation efficiency and flow instability with the variable of the true strain from 0.2 to 0.8 displayed the dynamic change of power dissipation efficiency and the instability area. The domain of 730–770 °C and 0.001–0.01 s−1 possessed a power dissipation efficiency over 40% throughout the whole deformation. The flow instability always appeared at a high strain rate from 0.1 s−1 to 1 s−1 during the whole deformation process. The nucleation site of the dynamic recrystallization generally appeared along the grain boundaries, indicating the discontinuous dynamic recrystallization mechanism. The appropriate conditions for deformation with a true strain of 0.9 is in a safe domain (820–860 °C with a strain rate of 0.001–0.01 s−1). There were four kinds of variation tendencies of the power dissipation efficiency with the increase of the true strain under various conditions, suggesting a changing situation for the main softening mechanisms.
Highlights
Copper alloys with ultra-high strength have been widely used in electronic and electrical engineering due to their excellent elasticity and good electrical conductivity.Copper-beryllium alloy is a commonly used elastic copper alloy
The flow stress value is usually concerned with the competitive relationship between work hardening caused by dislocation accumulation and softening from dynamic recovery (DRV) and dynamic recrystallization (DRX)
At the domain of the temperature range from 720 ◦ C to 800 ◦ C and a strain rate range from 0.1 s−1 to 1 s−1, the values of η were all below 23%. This was because the low temperature and high strain rate could not provide sufficient energy or time for dynamic recrystallization, which is bad for the hot deformation process
Summary
Copper alloys with ultra-high strength have been widely used in electronic and electrical engineering due to their excellent elasticity and good electrical conductivity. Copper-beryllium alloy is a commonly used elastic copper alloy. The beryllium vapor generated during the production process is hypertoxic, and copper-beryllium alloys have the disadvantage of poor stress relaxation resistance [1,2,3]. As a typical spinodal decomposition-strengthening copper alloy, the environmentally friendly Cu-Ni-Sn alloy has been increasingly applied as a substitute for the copper-beryllium alloy [4]. Cu-NiSn alloys have a good combination of mechanical properties, electrical properties, stress relaxation resistance, corrosion resistance, and wear resistance after reasonable composition design and thermomechanical treatment [5,6,7]. The yield strength of the Cu15Ni-8Sn-0.8Nb alloy was up to 1230 MPa when the sample was vortically swaged by a
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