Hot Deformation Behavior and Microstructure Evolution of Cu-Ni-Co-Si Alloys.

Feng Liu,Jimiao Ma,Xujun Mi,Haofeng Xie,Guojie Huang,Wenjing Zhang,Lijun Peng

doi:10.3390/ma13092042

Abstract

The Cu-1.7Ni-1.4Co-0.65Si (wt%) alloy is hot compressed by a Gleeble-1500D machine under a temperature range of 760 to 970 °C and a strain rate range of 0.01 to 10 s−1. The flow stress increases with the extension of strain rate and decreases with the rising of deformation temperature. The dynamic recrystallization behavior happens during the hot compression deformation process. The hot deformation activation energy of the alloy can be calculated as 468.5 kJ/mol, and the high temperature deformation constitutive equation is confirmed. The hot processing map of the alloy is established on the basis of hot deformation behavior and hot working characteristics. With the optimal thermal deformation conditions of 940 to 970 °C and 0.01 to 10 s−1, the fine equiaxed grain and no holes are found in the matrix, which can provide significant guidance for hot deformation processing technology of Cu–Ni–Co–Si alloy.

Highlights

Cu–Ni–Si alloy is an ideal material for integrated circuit lead frames, connectors, elastic components and power conversion, which has high tensile strength, high softening temperature, and excellent electrical and thermal conductivity
According to the trinary phase diagram of Cu–Ni–Si, Ni2 Si intermetallic is precipitated at temperature 880 ◦ C and the addition of Co to this system results in the formation of Materials 2020, 13, 2042; doi:10.3390/ma13092042
Since the phase transition temperature and stress of (Ni, Co)2 Si phases are higher than those of the Ni2 Si phase, the deformation behavior, microstructure and microstructure evolution of the Cu–Ni–Co–Si alloy during hot processing may be different from those of the Cu–Ni–Si alloy, which have a great effect on the formability and comprehensive performance of the alloy

Summary

Introduction

Cu–Ni–Si alloy is an ideal material for integrated circuit lead frames, connectors, elastic components and power conversion, which has high tensile strength, high softening temperature, and excellent electrical and thermal conductivity. The addition of the Co element to Cu–Ni–Si alloy can form a dispersive and high heat-resistance stability (Ni, Co) Si precipitation phase in the matrix, which can significantly improve the strength and high temperature softening resistance without sacrificing the conductivity of the alloy [6,7]. Lei [8] has studied the thermal compression deformation behavior of the Cu-6.0Ni-1.0Si-0.5Al-0.15Mg-0.1Cr alloy under a temperature range of 700–970 ◦ C and a strain rate range of 0.001–1 s−1 , established the stress–strain constitutive equation and acquired the reasonable hot processing deformation parameters: 850–875 ◦ C and 0.001–0.01 s−1. Since the phase transition temperature and stress of (Ni, Co) Si phases are higher than those of the Ni2 Si phase, the deformation behavior, microstructure and microstructure evolution of the Cu–Ni–Co–Si alloy during hot processing may be different from those of the Cu–Ni–Si alloy, which have a great effect on the formability and comprehensive performance of the alloy. The constitutive relationship of hot deformation and thermal processing maps were established to reveal the microstructure evolution and deformation mechanism in the process of hot deformation, and to provide guidance for the establishment of a hot working process for the Cu–Ni–Co–Si alloy

Materials and Methods

The True Stress–True Strain Curve

The value of of

7.62. Figure

Microstructure

Conclusions