# Study on the Softening Behavior of Cu–Cr–In Alloy during Annealing

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## Abstract

**:**

## 1. Introduction

## 2. Experimental Procedure

## 3. Results

#### 3.1. Hardness Properties

#### 3.2. Microstructure Evolution

_{s}is the shape factor (0.9) [17,18], D is the lattice size, N is a constant (0.263) [17], b is the Burgers vector, ρ is the dislocation density, and K is obtained from $K=2sin\theta /\lambda $, in which θ and λ are the Bragg angle of the particular peak and the wavelength of Cu-Kα radiation (0.15405 nm). As shown in Equation (1), $\sqrt{\mathsf{\rho}}$ is the slope of the linear fit of the $\Delta K$ – $NbK$ plot.

## 4. Discussion

#### 4.1. Softening Mechanism

#### 4.2. Static Recrystallization Kinetics

_{V}is the recrystallized volume fraction, HV

_{D}is the initial hardness of the deformed alloy, HV

_{t}is the hardness after a given annealing time t and HV

_{Rex}is the hardness of the fully recrystallized material.

_{V}can be presented in the form of ln[−ln(1 − X

_{V})] vs. lnt, which is linear. As shown in Figure 8b, a high linear fitting degree exists between ln[−ln(1 − X

_{V})] and lnt, and the slope of each line is the value of n at each temperature. The Avrami indices n of the Cu–Cr–In alloy with 60% cold deformation and annealed at 600 °C, 625 °C, 650 °C, 675 °C, and 700 °C are 1.06, 0.72, 0.78, 0.69, and 0.58, respectively. The JMAK function at each temperature can be obtained and curves of the JMAK functions with a high fitting degree are shown as solid lines in Figure 8b.

_{R}is the annealing time at a given recrystallized volume fraction, A is a constant, R is the universal gas constant, Q

_{R}is the activation energy of recrystallization, and T is the absolute temperature.

_{R}can be evaluated when 50% recrystallization occurred at the relevant temperature. The plot of ln(1/t

_{R}) versus 1000/T is linear, and the linear fitting correlation is R

^{2}= 0.96273, as shown in Figure 9. Q

_{R}can be calculated from the slope. The activation energy of recrystallization of the 60% cold-drawn Cu0.54Cr0.17In alloy is Q

_{R}= 188.29 ± 18.44 kJ/mol, which is similar to the activation energy of the self-diffusion activation energy of Cu with 197 kJ/mol [24], and indicates that the recrystallization mechanism of the alloy is attributed mainly to Cu self-diffusion. The activation energy of the recrystallization of the Cu–Cr–In alloy is significantly higher than that of 70% cold-rolled pure Cu with 58 kJ/mol [25] and 60% cold-drawn Cu–Cr–Sn alloy with 117.958 kJ/mol [26], which indicates that elemental In addition can improve the activation energy of recrystallization of Cu–Cr alloys, and has a more obvious effect on delaying recrystallization than Sn addition. Mainly because of the big atomic radius of indium atoms, the atoms that are solutioned into the Cu lattice cause serious lattice distortion, which hinders dislocation movement and delays the recovery and recrystallization of the Cu–Cr–In alloy.

## 5. Conclusions

## Author Contributions

## Funding

## Acknowledgments

## Conflicts of Interest

## References

- Liu, Q.; Zhang, X.; Ge, Y.; Wang, J.; Cui, J.Z. Effect of processing and heat treatment on behavior of Cu-Cr-Zr alloys to railway contact wire. Metall. Mater. Trans. A
**2006**, 37A, 3233–3238. [Google Scholar] [CrossRef] - Hatakeyama, M.; Toyama, T.; Yang, J.; Nagai, Y.; Hasegawa, M.; Ohkubo, T.; Eldrup, M.; Singh, B.N. 3D-AP and positron annihilation study of precipitation behavior in Cu–Cr–Zr alloy. J. Nucl. Mater.
**2009**, 386–388, 852–855. [Google Scholar] [CrossRef] - Chen, J.S.; Wang, J.F.; Xiao, X.P.; Wang, H.; Chen, H.M.; Yang, B. Contribution of Zr to strength and grain refinement in CuCrZr alloy. Mater. Sci. Eng. A
**2019**, 756, 464–473. [Google Scholar] [CrossRef] - Pang, Y.; Xia, C.D.; Wang, M.P.; Li, Z.; Xiao, Z.; Wei, H.G.; Sheng, X.F.; Jia, Y.L.; Chen, C. Effects of Zr and (Ni, Si) additions on properties and microstructure of Cu–Cr alloy. J. Alloys Comp.
**2014**, 582, 786–792. [Google Scholar] [CrossRef] - Watanabe, C.; Monzen, R.; Tazaki, K. Mechanical properties of Cu–Cr system alloys with and without Zr and Ag. J. Mater. Sci.
**2008**, 43, 813–819. [Google Scholar] [CrossRef][Green Version] - Fu, H.D.; Xu, S.; Li, W.; Xie, J.X.; Zhao, H.B.; Pan, Z.J. Effect of rolling and aging processes on microstructure and properties of Cu-Cr-Zr alloy. Mater. Sci. Eng. A
**2017**, 700, 107–115. [Google Scholar] [CrossRef] - Meng, A.; Nie, J.F.; Wei, K.; Kang, H.J.; Liu, Z.J.; Zhao, Y.H. Optimization of strength, ductility and electrical conductivity of a Cu–Cr–Zr alloy by cold rolling and aging treatment. Vacuum
**2019**, 167, 329–335. [Google Scholar] [CrossRef] - Purcek, G.; Yanar, H.; Demirtas, M.; Alemdag, Y.; Shangina, D.V.; Dobatkin, S.V. Optimization of strength, ductility and electrical conductivity of Cu–Cr–Zr alloy by combining multi-route ECAP and aging. Mater. Sci. Eng. A
**2016**, 649, 114–122. [Google Scholar] [CrossRef] - Chenna Krishna, S.; Karthick, N.K.; Sudarshan Rao, G.; Jha, A.K.; Pant, B.; Cherian, R.M. High Strength, Utilizable Ductility and Electrical Conductivity in Cold Rolled Sheets of Cu-Cr-Zr-Ti Alloy. J. Mater. Eng. Perform.
**2018**, 27, 787–793. [Google Scholar] [CrossRef] - Yuan, D.W.; Wang, J.F.; Chen, H.M.; Xie, W.B.; Wang, H.; Yang, B. Mechanical properties and microstructural evolution of a Cu-Cr-Ag alloy during thermomechanical treatment. Mater. Sci. Tech-Lond.
**2018**, 34, 1433–1440. [Google Scholar] [CrossRef] - Chen, H.M.; Gao, P.Z.; Peng, H.C.; Wei, H.G.; Xie, W.B.; Wang, H.; Yang, B. Study on the Hot Deformation Behavior and Microstructure Evolution of Cu-Cr-In Alloy. J. Mater. Eng. Perform.
**2019**, 28, 2128–2136. [Google Scholar] [CrossRef] - Chen, H.; Yuan, D.; Xie, W.; Zhang, J.; Wang, H.; Yang, B. A novel route for strengthening copper rods: Non-solution heat treatment combined with pre-aging. J. Mater. Process. Tech.
**2019**, 274, 116290. [Google Scholar] [CrossRef] - Yuan, J.H.; Gong, L.K.; Zhang, W.Q.; Zhang, B.; Wei, H.G.; Xiao, X.P.; Wang, H.; Yang, B. Work softening behavior of Cu-Cr-Ti-Si alloy during cold deformation. J. Mater. Res. Technol.
**2019**, 8, 1964–1970. [Google Scholar] [CrossRef] - Wang, H.; Gong, L.K.; Liao, J.F.; Chen, H.M.; Xie, W.B.; Yang, B. Retaining meta-stable fcc-Cr phase by restraining nucleation of equilibrium bcc-Cr phase in CuCrZrTi alloys during ageing. J. Alloys Comp.
**2018**, 749, 140–145. [Google Scholar] [CrossRef] - Peng, L.J.; Xie, H.F.; Huang, G.J.; Xu, G.L.; Yin, X.Q.; Feng, X.; Mi, X.J.; Yang, Z. The phase transformation and strengthening of a Cu-0.71 wt% Cr alloy. J. Alloys Comp.
**2017**, 708, 1096–1102. [Google Scholar] [CrossRef] - Williamson, G.K.; Hall, W.H. X-ray line broadening from filed aluminium and wolfram. Acta Metall.
**1953**, 1, 22–31. [Google Scholar] [CrossRef] - HajyAkbary, F.; Sietsma, J.; Böttger, A.J.; Santofimia, M.J. An improved X-ray diffraction analysis method to characterize dislocation density in lath martensitic structures. Mater. Sci. Eng. A
**2015**, 639, 208–218. [Google Scholar] [CrossRef] - Langford, J.I.; Wilson, A.J.C. Scherrer after sixty years: A survey and some new results in the determination of crystallite size. J. Appl. Crystallogr.
**1978**, 11, 102–113. [Google Scholar] [CrossRef] - Liu, Y.; Li, Z.; Jiang, Y.X.; Zhang, Y.; Zhou, Z.Y.; Lei, Q. The microstructure evolution and properties of a Cu-Cr-Ag alloy during thermal-mechanical treatment. J. Mater. Res.
**2017**, 32, 1324–1332. [Google Scholar] [CrossRef] - Sitarama Raju, K.; Subramanya Sarma, V.; Kauffmann, A.; Hegedűs, Z.; Gubicza, J.; Peterlechner, M.; Freudenberger, J.; Wilde, G. High strength and ductile ultrafine-grained Cu–Ag alloy through bimodal grain size, dislocation density and solute distribution. Acta Mater.
**2013**, 61, 228–238. [Google Scholar] [CrossRef] - Tang, J.; Zhang, H.; Teng, J.; Fu, D.F.; Jiang, F.L. Effect of Zn content on the static softening behavior and kinetics of Al–Zn–Mg–Cu alloys during double-stage hot deformation. J. Alloys Comp.
**2019**, 806, 1081–1096. [Google Scholar] [CrossRef] - Nazari, A.; Sanjayan, J.G. Johnson–Mehl–Avrami–Kolmogorov equation for prediction of compressive strength evolution of geopolymer. Ceram. Int.
**2015**, 41, 3301–3304. [Google Scholar] [CrossRef] - Chao, H.Y.; Sun, H.F.; Chen, W.Z.; Wang, E.D. Static recrystallization kinetics of a heavily cold drawn AZ31 magnesium alloy under annealing treatment. Mater. Charact.
**2011**, 62, 312–320. [Google Scholar] [CrossRef] - Gale, W.F.; Totemeir, T.C. Smithells Metals Reference Book; Butterworth-Heinemann: Oxford, UK, 2004. [Google Scholar]
- Benchabane, G.; Boumerzoug, Z.; Thibon, I.; Gloriant, T. Recrystallization of pure copper investigated by calorimetry and microhardness. Mater. Charact.
**2008**, 59, 1425–1428. [Google Scholar] [CrossRef] - Luo, Z.Y.; Luo, F.X.; Xie, W.B.; Chen, H.M.; Wang, H.; Yang, B. A study on annealing-induced softening in cold drawn Cu−Cr−Sn alloy. Materialwiss. Werkst.
**2018**, 49, 1325–1334. [Google Scholar] [CrossRef]

**Figure 1.**Vickers hardness of 60% cold-drawn Cu–Cr–In alloy annealed at different temperatures and for different times.

**Figure 2.**Microstructure of cold-drawn Cu–Cr–In alloy. (

**a**) Cross-sectional morphology, (

**b**) vertical section morphology and (

**c**) TEM micrographs, (

**d**) SADP of (c) with [011]Cu zone axis.

**Figure 3.**Structure evolution of cold-drawn Cu–Cr–In alloy after annealing. (

**a**) 450 °C, 60 min; (

**b**) 450 °C, 240 min; (

**c**) 550 °C, 60 min; (

**d**) 550 °C, 240 min; (

**e**) 650 °C, 60 min; (

**f**) 650 °C, 240 min.

**Figure 4.**TEM images of the Cu–Cr–In alloy annealed at 450 °C for various times. (

**a,b**) 60 min; (

**c,d**) 240 min.

**Figure 5.**TEM images of the Cu–Cr–In alloy annealed at 550 °C for various times. (

**a,b**) 60 min; (

**c,d**) 240 min.

**Figure 6.**TEM images of the Cu–Cr–In alloy annealed at 650 °C for various times. (

**a,b**) 60 min; (

**c,d**) 240 min.

**Figure 8.**Recrystallization kinetics of 60% cold drawn Cu–Cr–In alloy by Johnson–Mehl–Avrami–Kolmogorov plot for different annealing conditions. (

**a**) t − X

_{V}, (

**b**) lnt − ln[−ln(1 − X

_{V})].

Elements | Cr | In | Cu |
---|---|---|---|

Measured composition | 0.54 | 0.17 | Surplus |

Grain | 450 °C | 550 °C | 650 °C | |||
---|---|---|---|---|---|---|

60 min | 240 min | 60 min | 240 min | 60 min | 240 min | |

Recrystallization | 1.63 | 2.49 | 8.07 | 11.48 | 59.53 | 80.97 |

Substructure | 0.00 | 0.01 | 0.04 | 0.91 | 10.84 | 15.80 |

Deformed Structure | 98.37 | 97.50 | 91.90 | 87.61 | 29.63 | 3.23 |

Time | 450 °C | 550 °C | 650 °C |
---|---|---|---|

60 min | 1.77 × 10^{14} | 1.29 × 10^{14} | 7.71 × 10^{13} |

240 min | 1.30 × 10^{14} | 1.21 × 10^{14} | 3.08 × 10^{13} |

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**MDPI and ACS Style**

Zhu, Y.; Tang, L.; Xie, W.; Chen, H.; Wang, H.; Yang, B. Study on the Softening Behavior of Cu–Cr–In Alloy during Annealing. *Crystals* **2020**, *10*, 312.
https://doi.org/10.3390/cryst10040312

**AMA Style**

Zhu Y, Tang L, Xie W, Chen H, Wang H, Yang B. Study on the Softening Behavior of Cu–Cr–In Alloy during Annealing. *Crystals*. 2020; 10(4):312.
https://doi.org/10.3390/cryst10040312

**Chicago/Turabian Style**

Zhu, Yunqing, Linsheng Tang, Weibin Xie, Huiming Chen, Hang Wang, and Bin Yang. 2020. "Study on the Softening Behavior of Cu–Cr–In Alloy during Annealing" *Crystals* 10, no. 4: 312.
https://doi.org/10.3390/cryst10040312