Effect of Ag on Properties, Microstructure, and Thermostability of Cu-Cr Alloy.

Yuqing Sun,Haofeng Xie,Lijun Peng,Guojie Huang,Xujun Mi,Xue Feng,Xinhua Liu,Gaolei Xu

doi:10.3390/ma13235386

Abstract

Cu–Cr-based alloys exhibit excellent electrical conductivity and strength, but their poor thermal stability limits their application in industry. In this paper, Cu–0.2Cr (at. %) and Cu–0.2Cr–0.12Ag (at. %) alloys were prepared to study the effect of Ag on the properties, microstructure, and thermal stability of the Cu–Cr alloy. Microstructure and precipitation were observed by an optical microscope (OM) and a transmission–electron microscope (TEM). After cold-drawing by 99.9% and aging at 450 °C for 2 h, the peak hardness and electric conductivity of the Cu–Cr alloy were 120.3 HV and 99.5% IACS, respectively, and those of the Cu–Cr–Ag alloy were 135.8 HV and 98.3% IACS, respectively. The softening temperature of the Cu–Cr alloy was 500~525 °C, and that of the Cu–Cr–Ag alloy was about 550 °C. The creep strains of the Cu–Cr and Cu–Cr–Ag alloys at 40 MPa and 400 ℃ for 50 h were 0.18% and 0.05%, respectively. Ag elements improved the thermal stability of the Cu–Cr alloy. Recovery and recrystallization occurred before the coarsening of precipitates during the softening process. Ag atoms mainly improved the softening resistance of the alloy by delaying recrystallization, and mainly increased creep resistance by preventing the increase in mobile-dislocation density.

Highlights

Cu–Cr-based alloys are typical precipitation-strengthening alloys with good electrical conductivity and mechanical properties, and they are used in integrated–circuit lead frames, connectors, and electrical equipment [1,2,3,4,5]
Ag elements improved the thermal stability of the Cu–Cr alloy
The aging time of the Cu–Cr alloy reaching value was alloy reaching peak value was prolonged by Ag, which was ascribed to Ag inhibiting the growth of prolonged by Ag, which was ascribed to Ag inhibiting the growth of precipitates [27,28]

Summary

Introduction

Cu–Cr-based alloys are typical precipitation-strengthening alloys with good electrical conductivity and mechanical properties, and they are used in integrated–circuit lead frames, connectors, and electrical equipment [1,2,3,4,5]. These alloys include Cu–Cr–Zr [6], Cu–Cr–Zr–Mg [7], Cu–Cr–Ag [8], and Cu–Cr–Mg [9]. A small number of Ag elements are readily soluble in the Cu matrix under atmospheric smelting [10], and lead to obvious solid-solution strengthening [11] and precipitation strengthening [12], so the Cu–Cr–Ag alloy interests many researchers. The Ag element was uniformly distributed in the Cu matrix

Methods

Results

Conclusion