Microstructure and strengthening mechanisms of CuCrZr alloy by two-step thermomechanical treatment
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Microstructure and strengthening mechanisms of CuCrZr alloy by two-step thermomechanical treatment Shiha Huang1, Wei Huang2, Weibin Xie1,*, Huiming Chen1, Hang Wang1,* Bin Yang1
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Faculty of Materials, Metallurgy and Chemistry, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi, People’s Republic of China 2 Ningbo Brance of China Academy of Ordance Science, Ningbo 315000, Zhejiang, People’s Republic of China
Received: 18 June 2020
ABSTRACT
Accepted: 23 August 2020
The high strength obtained in Cu–Cr alloys is mainly attributed to the precipitation strengthening, dislocation strengthening, and grain-boundary strengthening. The precipitate size, dislocation density, and grain size are related to thermomechanical treatment. The strength of Cu–Cr alloys can be controlled by the thermomechanical treatment process. In this study, the microstructure and strengthening mechanisms of Cu–0.8Cr–0.1Zr (wt%) alloy after one-step and two-step thermomechanical treatment were studied. The results showed that after the following thermomechanical treatments, solution treated at 950 °C for 60 min, thickness reduction at first cold rolled for 60%, annealed at 450 °C for 180 min, and then 30% thickness reduction in secondary cold rolling, the microhardness, tensile strength, and conductivity reach 215 HV, 623 MPa, and 74.5% IACS, respectively. The main difference of strength between one-step and two-step thermomechanical treatment in the Cu–0.8Cr–0.1Zr alloy is due to the difference of dislocation strengthening effect. The dislocation strengthening achieved in two-step thermomechanical treatment (175.6 MPa) is 95 MPa greater than that of one-step thermomechanical treatment (80.6 MPa).
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Springer Science+Business
Media, LLC, part of Springer Nature 2020
1 Introduction The rapid development of the electrical industry has demanded more high-performance conductive materials, which is to maintain high conductivity and have high strength in the meanwhile. The key to obtain high strength and high conductivity copper
alloy is to balance strength and conductivity through the research of production process [1]. After decades of research, CuCrZr alloys have the advantages of high strength, high conductivity, and high softening temperature [2]. At present, CuCrZr alloys are used in high-speed rail contact wires, electronic lead frames, and resistance welding electrodes [3–5]. In
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https://doi.org/10.1007/s10854-020-04333-3
J Mater Sci: Mater Electron
addition, CuCrZr alloys have low-stress relaxation rate and good thermal conductivity at high temperatures, which makes the alloy also be used in nuclear reactor heat exchangers [6]. The precipitation behaviors of CuCrZr alloys have significant influence to strengthen the alloy. During the aging process, precipitates can form to hinder the dislocation movement and effectively strengthen the matrix. More importantly, precipitation during aging reduces the number of
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