Dynamic recrystallization behavior and processing map of the Cu-Cr-Zr-Nd alloy.

Yi Zhang,Baohong Tian,Alex A Volinsky,Yong Liu,Zhe Chai,Ping Liu,Kexing Song,Huili Sun

doi:10.1186/s40064-016-2317-z

Abstract

Hot deformation behavior of the Cu–Cr–Zr–Nd alloy was studied by hot compressive tests in the temperature range of 650–950 °C and the strain rate range of 0.001–10 s−1 using Gleeble-1500D thermo-mechanical simulator. The results showed that the flow stress is strongly dependent on the deformation temperature and the strain rate. With the increase of temperature or the decrease of strain rate, the flow stress significantly decreases. Hot activation energy of the alloy is about 404.84 kJ/mol and the constitutive equation of the alloy based on the hyperbolic-sine equation was established. Based on the dynamic material model, the processing map was established to optimize the deformation parameters. The optimal processing parameters for the Cu–Cr–Zr–Nd alloy hot working are in the temperature range of 900–950 °C and strain rate range of 0.1–1 s−1. A full dynamic recrystallization structure with fine and homogeneous grain size can be obtained at optimal processing conditions. The microstructure of specimens deformed at different conditions was analyzed and connected with the processing map. The surface fracture was observed to identify instability conditions.

Highlights

Cu–Cr–Zr alloy has been considered as a potential material candidate for the railway contact wires, connectors and lead frame materials due to its excellent properties, such as high strength, outstanding electrical conductivity, thermal conductivity, excellent fatigue resistance and formability (Su et al 2005; Xia et al 2012; Lin et al 2011; Bi et al 2013)
The reason for this is because the dynamic recovery (DRV) and dynamic recrystallization (DRX) have enough time to complete at low strain rate, so the effect of work hardening can be offset by the softening effect
Processing maps According to the above analysis and the flow stress data obtained in the isothermal compression tests, the processing maps of the Cu–Cr–Zr–Nd alloy deformed at the strain of 0.3, 0.4, 0.5 and 0.6 are shown in Fig. 8a–d, respectively

Summary

Introduction

Cu–Cr–Zr alloy has been considered as a potential material candidate for the railway contact wires, connectors and lead frame materials due to its excellent properties, such as high strength, outstanding electrical conductivity, thermal conductivity, excellent fatigue resistance and formability (Su et al 2005; Xia et al 2012; Lin et al 2011; Bi et al 2013). Activation energy and constitutive equations During the hot deformation, the relationship between the flow stress, strain rate and deformation temperature can be represented by the Arrhenius equation expressed as (Pu et al 2014; Sellars and McTegart 1966; Zener and Hollomon 1944): εexp(Q/RT ) = A1σ n1 (4)

Results

Conclusion