Effects of Cryorolling on Properties and Precipitation Behavior of a High-Strength and High-Conductivity Cu-1Cr-0.2Zr-0.25Nb Alloy
LI Longjian1, LI Rengeng2, ZHANG Jiajun1, CAO Xinghao1, KANG Huijun1(), WANG Tongmin1
1Key Laboratory of Solidification Control and Digital Preparation Technology (Liaoning Province), School of Materials Science and Engineering, Dalian University of Technology, Dalian 116024, China 2Key Laboratory for Light-Weight Materials, Nanjing Tech University, Nanjing 210009, China
Cite this article:
LI Longjian, LI Rengeng, ZHANG Jiajun, CAO Xinghao, KANG Huijun, WANG Tongmin. Effects of Cryorolling on Properties and Precipitation Behavior of a High-Strength and High-Conductivity Cu-1Cr-0.2Zr-0.25Nb Alloy. Acta Metall Sin, 2024, 60(3): 405-416.
The performance requirements for copper alloys are increasing with the rapid development of transportation, electrical, aerospace, and electronics in modern industry. Cu-Cr-Zr alloy has exceptional strength and electrical conductivity as typical precipitation strengthening copper alloy. Strength and conductivity are mutually exclusive properties. The goal of realizing the high strength and conductivity of copper is a crucial subject in modern copper industry development. In this study, the effects of cryorolling on the microstructure, mechanical properties, and electrical conductivity of Cu-1Cr-0.2Zr-0.25Nb alloy were examined and the effects of numerous aging processes on the type, morphology, and distribution of precipitates were investigated. The findings depict that the Cu-1Cr-0.2Zr-0.25Nb alloy primarily comprised the Cr phase, Zr-rich phase, Cr2Nb phase, and Cu matrix phase. The fcc Cr nanoprecipitates can be precipitated in Cu-1Cr-0.2Zr-0.25Nb alloy after aging at 450oC for 30 min. The bcc Cr nanoprecipitates can be formed after aging at 450oC for 300 min. After cryorolling and aging treatment, the mixed structures, such as nanoprecipitation phase, nanodeformation twins, and dislocations in the Cu-1Cr-0.2Zr-0.25Nb alloy are produced and this alloy demonstrates remarkable comprehensive properties. The tensile strength of 700 MPa and electrical conductivity of 73.29%IACS were attained for the cryorolled Cu-1Cr-0.2Zr-0.25Nb alloy after aging at 450oC for 30 min; after aging at 450oC for 300 min, the conductivity can reach 79.81%IACS, and the corresponding tensile strength, yield strength, and hardness are 646 MPa, 606 MPa, and 212 HV, respectively. Combining the experimental findings with the computations of contribution to strengthening, it can reasonably be inferred that dislocation and precipitation strengthening were the primary strengthening mechanisms of Cu-1Cr-0.2Zr-0.25Nb alloy.
Fund: National Natural Science Foundation of China(51971052);National Natural Science Foundation of China(51927801);National Natural Science Foundation of China(51690163);National Natural Science Foundation of China(52001161);Liaoning Revitalization Talents Program(XLYC2007183);Innovation Foundation of Science and Technology of Dalian City(2020JJ25CY002);Innovation Foundation of Science and Technology of Dalian City(2020JJ26GX045)
Corresponding Authors:
KANG Huijun, professor, Tel: (0411)84709500, E-mail: kanghuijun@dlut.edu.cn
Fig.1 EPMA backscattered electron images of as-cast Cu-1Cr-0.2Zr-0.25Nb sample (a) and CRⅡ-FA300 sample (b)
Fig.2 EPMA map scanning analyses of Cr2Nb phase in CRⅡ-FA300 sample (a) backscattered electron image (Inset shows the EDS analysis result of area A) (b-e) element mappings of Cu (b), Cr (c), Zr (d), and Nb (e) corresponding to Fig.2a
Fig.3 EPMA map scanning analyses of Cr and Zr phase in CRⅡ-FA300 sample (a) backscattered electron image (b-e) element mappings of Cu (b), Cr (c), Zr (d), and Nb (e) corresponding to Fig.3a (f) statistics distribution of Cr phase size (dave—average size)
Fig.4 TEM analyses of CRⅡ-FA30 sample (a) TEM image of precipitates (b) HRTEM image of precipitates (c) fast Fourier transformation (FFT) image of precipitates (d) schematic of FFT figure in Fig.4c
Fig.5 TEM analyses of precipitates in CRⅡ-FA300 sample (a) bright-field TEM image (Inset shows the SAED pattern of precipitates) (b) HRTEM image of precipitates (c, d) FFT images of precipitates of region A (c) and region B (d) in Fig.5b
Fig.6 TEM image and element maps of Cr2Nb phase in CRⅡ-FA300 sample (a) TEM image (b-e) individual element mappings of Cu (b), Cr (c), Zr (d), and Nb (e) corresponding to Fig.6a (f) combined composition map
Fig.7 TEM images of CRⅡ-FA300 sample (a) high-density dislocation (b) deformation twin
Fig.8 TEM images of RⅡ-FA300 sample (a) deformation twin and detwinning (b) precipitates and subgrain
Fig.9 Engineering stress-strain curves of the Cu-1Cr-0.2Zr-0.25Nb samples
Sample
σs
MPa
σb
MPa
C
%IACS
ρ
1014 m-2
δ
%
RⅡ
650 ± 6
694 ± 3
58.23 ± 0.08
28.9
6.3
CRⅡ
694 ± 4
740 ± 1
58.15 ± 0.06
35.9
4.9
RⅡ-FA30
631 ± 13
669 ± 8
73.67 ± 0.23
20.1
8.4
CRⅡ-FA30
654 ± 6
700 ± 2
73.29 ± 0.15
22.4
6.7
RⅡ-FA300
584 ± 8
621 ± 2
80.27 ± 0.09
16.8
8.8
CRⅡ-FA300
606 ± 9
646 ± 1
79.81 ± 0.10
18.1
8.9
Table 2 Strength, elongation, electrical conductivity, and dislocation density for Cu-1Cr-0.2Zr-0.25Nb samples
Fig.10 Fitting curves of XRD spectra for CRⅡ-FA300 sample
Parameter
Symbol
Unit
Value
Ref.
Shear modulus of Cu alloy
G
GPa
44
[35]
Taylor factor
M
3.06
[36]
Burgers vector modulus
b
nm
0.2556
[35]
Poisson's ratio
ν
0.33
[37]
Maximum volume fraction of precipitates
VCr-Max
%
0.9
This work
Minimum value of conductivity
C0
%IACS
29.30
This work
Maximum value of conductivity
CMax
%IACS
83.46
This work
Transformation fraction of precipitation for CRⅡ-FA300 sample
XCRII-FA300
%
93.26
This work
Volume fraction of the precipitates for CRⅡ-FA300 sample
fCRII-FA300
%
0.839
This work
Mean radius of the precipitates for CRⅡ-FA300 sample
rCRII-FA300
nm
6.1
This work
Table 3 Parameters used in yield strength calculation
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