# Grain Refinement Kinetics in a Low Alloyed Cu–Cr–Zr Alloy Subjected to Large Strain Deformation

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## Abstract

**:**

_{C}. The microstructural change during plastic deformation was accompanied by the formation of the microband and an increase in the misorientations of strain-induced subboundaries. We argue that continuous dynamic recrystallization refined the initially coarse grains, and discuss the dynamic recrystallization kinetics in terms of grain/subgrain boundary triple junction evolution. A modified Johnson–Mehl–Avrami–Kolmogorov relationship with a strain exponent of about 1.49 is used to express the strain dependence of the triple junctions of high-angle boundaries. Severe plastic deformation by ECAP led to substantial strengthening of the Cu–0.1Cr–0.06Zr alloy. The yield strength increased from 60 MPa in the initial state to 445 MPa after a total strain level of 12.

## 1. Introduction

_{DRX}) can be related to a strain (ε) through a modified Johnson–Mehl–Avrami–Kolmogorov equation [43,44,45],

_{DRX}= 1 − exp(−k ε

^{n}),

## 2. Materials and Methods

_{C}(90° anticlockwise rotation of the samples after each ECAP pass) at a strain rate of 1 s

^{−1}. The true strain attained at each pass was 1. ECAP processing was executed to different total strain levels, up to 12. The fine microstructure of ECAP samples was examined by a Quanta 250 Nova scanning electron microscope (FEI, Hillsboro, OR, USA) equipped with an electron backscattering diffraction (EBSD) analyzer (FEI, Hillsboro, OR, USA) using an orientation imaging microscopy (OIM) software (OIM Analysis 5.2.0, EDAX TSL, Mahwah, NJ, USA). The microstructural investigations were carried out on the Y plane, i.e., flow plane along the side face at the point of exit from the die [27]. The specimens for the EBSD analysis were electrochemically polished at 238 K using an electrolyte of HNO

_{3}:CH

_{3}OH = 1:3. The step size for the EBSD scan was t = 420 nm for the specimen deformed to a total strain of ε = 1, t = 200 nm for the specimen deformed to ε = 2, and t = 50 nm for specimens deformed to total strain levels of four to 12. The OIM images were processed by the clean-up procedures, setting a minimal confidence index of 0.1. The mean grain size (D) was measured by the linear intercept method on the OIM images as an interval between high-angle boundaries. A critical misorientation angle between low-angle and high-angle boundaries was 15°. The dislocation densities were estimated using the kernel average misorientations over a distance of 400 nm [21]. The fraction of high-angle boundaries (F

_{HAB}) and ultrafine grains (F

_{UFG}), i.e., those with D < 2 μm, were evaluated using the OIM software. The triple junctions fraction was estimated counting more than 300 junctions for each state. The tensile tests were executed at ambient temperature using an Instron 5882 (Illinois Tool Works Inc., Norwood, MA, USA) tensile machine with an initial strain rate of 2 × 10

^{−3}s

^{−1}.

## 3. Results

#### 3.1. Microstructural Evolution

_{HAB}), and the ultrafine-grain fraction (F

_{UFG}) during ECAP are shown in Figure 3. ECAP produces substantial grain refinement in the range of strain levels from one to four. After the first ECAP pass, the mean grain size drastically reduced to 8.6 μm. Further deformation promoted grain refinement, and the mean grain size after four ECAP passes was less than 1 μm. Then, the rate of grain refinement slowed down; after a total strain of ε = 12, the mean grain size attained 0.5 μm. The ECAP processing was accompanied by a significant increase in the dislocation densities, from 5 × 10

^{12}m

^{−2}in the initial state to about 9 × 10

^{14}m

^{−2}after straining to eight. It is seen in Figure 3 that the dislocation density change during ECAP clearly correlates with the reduction in grain size.

_{HAB}) and ultra-fine grain fractions (F

_{UFG}). An increase of the ultra-fine grain fraction has an incubation period corresponding to relativity low strains of zero to two. Then, the ultra-fine grain fraction significantly increased, and after a total strain of 12, attained 0.5. In contrast, the high-angle boundaries fraction gradually increased from 0.1 to its apparent saturation of about 0.7, increasing the total strain from one to 12. This behavior of ultrafine grain and high-angle boundary evolution is associated with the microbands, which are bounded by high-angle boundaries, but do not involve ultrafine grains at relatively small strain levels.

#### 3.2. Tension Behavior

_{0.2}) of 60 MPa and the ultimate tension stress (UTS) of 185 MPa, which is comparable to pure copper [16]. The hardening stage is large, and the elongation amounts to 60% in tensile tests (Figure 4). The strain imposed by ECAP to the copper alloy strongly influences its strength and ductility. The first pass results in significant strengthening; σ

_{0.2}and UTS increase by about 375% and 70%, respectively. Then, efficiency of deformation strengthening degrades; after the second ECAP pass, additional increments in the both σ

_{0.2}and UTS are 75 MPa. Upon further straining (4 to 12 passes), the σ

_{0.2}and UTS values increase slowly, leading to gradual strengthening.

_{0.2}and UTS are 445 MPa and 465 MPa after 12 ECAP passes, respectively. The strengthening by deformation to strain levels of 12 leads to a degradation in the plasticity. Total elongation decreases from 60% in the initial state to 11% after 12 passes of ECAP. The severe plastic deformation of the Cu–Cr–Zr alloy shortens the hardening stage. In contrast to the initial state, the necking in the ECAP processed samples takes place at relatively small tensile strain levels, leading to rapid fracture during the tensile tests. As a result, the UTS and σ

_{0.2}values are very close to each other in the Cu–0.1Cr–0.06Zr alloy subjected to the ECAP processing.

## 4. Discussion

_{HAB}fraction, while F

_{UFG}does not increase remarkably at early stage of deformation (Figure 3). The number of the deformation microbands rapidly increases during ECAP to a strain level of two. Then, the new ultrafine grains readily develop along the microbands and the initial grain boundaries, as well as at their intersections, accelerating an increase in F

_{UFG}. The deformation microbands and the new (sub)boundaries lead to the appearance of new triple junctions formed by low-angle and/or high-angle boundaries. The number of high-angle boundaries in the triple junctions and the distribution of the triple junction fractions are controlled by continuous dynamic recrystallization and grain refinement.

_{J0}= 0.8 exp(−0.25 ε).

_{J3}= 0.54/(1 + exp(−0.56 ε − 2.4)).

_{J0}= −0.30 + 1.2 F

_{LAB}

_{J3}= 0.08 exp(3.23 F

_{HAB})

_{HAB}, F

_{UFG}, and F

_{J3}is represented in Figure 7. The rapid growth of the high-angle boundaries fraction is associated with the appearance of deformation bands. The ultrafine-grain formation requires the high-angle misorientations for all of the boundaries surrounding the crystallite. Therefore, the formation of ultrafine-grains is delayed at the early deformation stage until the density of high-angle boundaries attains a sufficiently large value. In contrast, the J3 fraction clearly correlates with the ultrafine-grain fraction, and can be expressed by a linear function passing through the origin:

_{J3}= 0.76 F

_{UFG}

_{J3}= 1 − exp(−k ε

^{n}).

_{DRX})) vs. ε in logarithmic scale should represent a straight line. The change in the J3 fraction for the Сu–0.1Cr–0.05Zr and Cu–0.3Cr–0.5Zr alloys in solution-treated and aged conditions are presented in Figure 8a,b.

## 5. Conclusions

- The ECAP processing was accompanied by a significant decrease in the grain size, from 120 μm in the initial condition to 0.5 μm after a total strain of 12. The grain size rapidly decreased during the first four ECAP passes, and then remained almost unchanged during further ECAP.
- The formation of the ultrafine-grained structure resulted from the deformation of band evolution and an increase in the misorienations of strain-induced subboundaries during ECAP processing. An increase in total strain led to an increase in both the high-angle boundary fraction and the ultrafine-grain fraction. The grain refinement can be discussed in the terms of continuous dynamic recrystallization.
- The ECAP deformation was accompanied by gradual strengthening. The yield strength increased from 60 MPa in the initial state to 445 MPa after 12 ECAP passes. Correspondingly, total elongation decreased from 60% to 9%.
- The fraction of boundary triple junctions consisting of only low-angle boundaries gradually decreased through an exponential law function of total strain during severe plastic deformation. The fraction of boundary triple junctions, with one high-angle boundary and two low-angle boundaries was about 0.1–0.15, and did not change remarkably with straining. The fraction of boundary triple junctions with two high-angle boundaries and one low-angle boundary increased to a peak after four to six strain levels, followed by a small decrease at large strain levels. The fraction of boundary triple junctions that consisted of only high-angle boundaries increased by a sigmoid law function with deformation.
- The fractions of the low-angle boundary triple junctions and the high-angle boundary triple junctions can be related to the low-angle boundary fraction and the ultrafine-grain fraction, respectively, through linear functions. The strain dependence of the high-angle boundary triple junctions can be expressed by a modified Johnson–Mehl–Avrami–Kolmogorov equation, F
_{J3}= 1 − exp(−k ε^{n}), with a strain exponent of n = 1.49 and k = 0.03.

## Acknowledgments

## Author Contributions

## Conflicts of Interest

## References

- Tang, N.Y.; Taplin, D.M.R.; Dunlop, G.L. Precipitation and aging in high-conductivity Cu–Cr alloys with additions of zirconium and magnesium. Mater. Sci. Technol.
**1985**, 1, 270–275. [Google Scholar] [CrossRef] - Correia, J.B.; Davies, H.A.; Sellars, C.M. Strengthening in rapidly solidified age hardened Cu–Cr and Cu–Cr–Zr alloys. Acta Mater.
**1997**, 45, 177–190. [Google Scholar] [CrossRef] - Fujii, T.; Nakazawa, H.; Kato, M.; Dahmen, U. Crystallography and morphology of nanosized Cr particles in a Cu–0.2% Cr alloy. Acta Mater.
**2000**, 48, 1033–1045. [Google Scholar] [CrossRef] - Batra, I.S.; Dey, G.K.; Kulkarni, U.D.; Banerjee, S. Microstructure and properties of a Cu–Cr–Zr alloy. J. Nucl. Mater.
**2001**, 299, 91–100. [Google Scholar] [CrossRef] - Chibihi, A.; Sauvage, X.; Blavette, D. Atomic scale investigation of Cr precipitation in copper. Acta Mater.
**2012**, 60, 4575–4585. [Google Scholar] [CrossRef] - Shangina, D.V.; Bochvar, N.R.; Morozova, A.I.; Belyakov, A.N.; Kaibyshev, R.O.; Dobatkin, S.V. Effect of chromium and zirconium content on structure, strength and electrical conductivity of Cu–Cr–Zr alloys after high pressure torsion. Mater. Lett.
**2017**, 199, 46–49. [Google Scholar] [CrossRef] - Shangina, D.; Maksimenkova, Y.; Bochvar, N.; Serebryany, V.; Raab, G.; Vinogradov, A.; Skrotzki, W.; Dobatkin, S. Influence of alloying with hafnium on the microstructure, texture, and properties of Cu–Cr alloy after equal channel angular pressing. J. Mater. Sci.
**2016**, 51, 5493–5501. [Google Scholar] [CrossRef] - Murashkin, M.Y.; Sabirov, I.; Sauvage, X.; Valiev, R.Z. Nanostructured Al and Cu alloys with superior strength and electrical conductivity. J. Mater. Sci.
**2016**, 51, 33–49. [Google Scholar] [CrossRef] - Zhou, H.T.; Zhong, J.W.; Zhou, X.; Zhao, Z.K.; Li, Q.B. Microstructure and properties of Cu–1.0 Cr–0.2 Zr–0.03 Fe alloy. Mater. Sci. Eng. A
**2008**, 498, 225–230. [Google Scholar] [CrossRef] - Lu, L.; Shen, Y.; Chen, X.; Qian, L.; Lu, K. Ultrahigh strength and high electrical conductivity in copper. Science
**2004**, 304, 422–426. [Google Scholar] [CrossRef] [PubMed] - Peng, L.; Xie, H.; Huang, G.; Xu, G.; Yin, X.; Feng, X.; Yang, Z. The phase transformation and strengthening of a Cu–0.71 wt% Cr alloy. J. Alloys Compd.
**2017**, 708, 1096–1102. [Google Scholar] [CrossRef] - Topuz, A.I. Enabling microstructural changes of FCC/BCC alloys in 2D dislocation dynamics. Mater. Sci. Eng. A
**2015**, 627, 381–390. [Google Scholar] [CrossRef] - Ghosh, G.; Miyake, J.; Fine, M.E. The systems-based design of high-strength, high-conductivity alloys. JOM
**1997**, 49, 56–60. [Google Scholar] [CrossRef] - Li, J. Petch relation and grain boundary sources. Trans. Metall. Soc. AIME
**1963**, 277, 239–247. [Google Scholar] - Kato, M. Hall-Petch Relationship and Dislocation Model for Deformation of Ultrafine-Grained and Nanocrystalline Metals. Mater. Trans.
**2014**, 55, 19–24. [Google Scholar] [CrossRef] - Hansen, N. Boundary strengthening in undeformed and deformed polycrystals. Mater. Sci. Eng. A
**2005**, 409, 39–45. [Google Scholar] [CrossRef] - Borodin, E.N.; Mayer, A.E. Influence of structure of grain boundaries and size distribution of grains on the yield strength at quasistatic and dynamical loading. Mater. Res. Express
**2017**, 4, 085040. [Google Scholar] [CrossRef] - Valdés León, K.; Munoz-Morris, M.A.; Morris, D.G. Optimisation of strength and ductility of Cu–Cr–Zr by combining severe plastic deformation and precipitation. Mater. Sci. Eng. A
**2012**, 536, 181–189. [Google Scholar] [CrossRef] [Green Version] - Mishnev, R.; Shakhova, I.; Belyakov, A.; Kaibyshev, R. Deformation microstructures, strengthening mechanisms, and electrical conductivity in a Cu–Cr–Zr alloy. Mater. Sci. Eng. A
**2015**, 629, 29–40. [Google Scholar] [CrossRef] - Morozova, A.; Kaibyshev, R. Grain refinement and strengthening of a Cu–0.1 Cr–0.06 Zr alloy subjected to equal channel angular pressing. Philos. Mag.
**2017**, 97, 2053–2076. [Google Scholar] [CrossRef] - Zhilyaev, A.P.; Shakhova, I.; Morozova, A.; Belyakov, A.; Kaibyshev, R. Grain refinement kinetics and strengthening mechanisms in Cu–0.3 Cr–0.5 Zr alloy subjected to intense plastic deformation. Mater. Sci. Eng. A
**2016**, 654, 131–142. [Google Scholar] [CrossRef] - Estrin, Y.; Vinogradov, A. Extreme grain refinement by severe plastic deformation: A wealth of challenging science. Acta Mater.
**2013**, 61, 782–817. [Google Scholar] [CrossRef] - Zhilyaev, A.P.; Langdon, T.G. Using high-pressure torsion for metal processing: Fundamentals and applications. Prog. Mater. Sci.
**2008**, 53, 893–979. [Google Scholar] [CrossRef] - Shakhova, I.; Yanushkevich, Z.; Fedorova, I.; Belyakov, A.; Kaibyshev, R. Grain refinement in a Cu–Cr–Zr alloy during multidirectional forging. Mater. Sci. Eng. A
**2014**, 606, 380–389. [Google Scholar] [CrossRef] - Tikhonova, M.; Dolzhenko, P.; Kaibyshev, R.; Belyakov, A. Grain Boundary Assemblies in Dynamically-Recrystallized Austenitic Stainless Steel. Metals
**2016**, 6, 268. [Google Scholar] [CrossRef] - Takata, N.; Lee, S.H.; Tsuji, N. Ultrafine grained copper alloy sheets having both high strength and high electric conductivity. Mater. Lett.
**2009**, 63, 1757–1760. [Google Scholar] [CrossRef] - Valiev, R.Z.; Langdon, T.G. Principles of equal-channel angular pressing as a processing tool for grain refinement. Prog. Mater. Sci.
**2006**, 51, 881–981. [Google Scholar] [CrossRef] - Segal, V.M.; Reznikov, V.I.; Drobyshevskiy, A.E.; Kopylov, V.I. 1. Under an ideal condition without the frictional effect. Russ. Metall. (Metally)
**1981**, 1, 99–105. [Google Scholar] - Zhemchuzhnikova, D.; Lebyodkin, M.; Lebedkina, T.; Mogucheva, A.; Yuzbekova, D.; Kaibyshev, R. Peculiar Spatiotemporal Behavior of Unstable Plastic Flow in an AlMgMnScZr Alloy with Coarse and Ultrafine Grains. Metals
**2017**, 7, 325. [Google Scholar] [CrossRef] - Abib, K.; Azzeddine, H.; Tirsatine, K.; Baudin, T.; Helbert, A.L.; Brisset, F.; Bradai, D. Thermal stability of Cu–Cr–Zr alloy processed by equal-channel angular pressing. Mater. Charact.
**2016**, 118, 527–534. [Google Scholar] [CrossRef] - Dalla Torre, F.H.; Pereloma, E.V.; Davies, C.H.J. Strain hardening behaviour and deformation kinetics of Cu deformed by equal channel angular extrusion from 1 to 16 passes. Acta Mater.
**2006**, 54, 1135–1146. [Google Scholar] [CrossRef] - Edalati, K.; Imamura, K.; Kiss, T.; Horita, Z. Equal-channel angular pressing and high-pressure torsion of pure copper: Evolution of electrical conductivity and hardness with strain. Mater. Trans.
**2012**, 53, 123–127. [Google Scholar] [CrossRef] - Raab, G.J.; Valiev, R.Z.; Lowe, T.C.; Zhu, Y.T. Continuous processing of ultrafine grained Al by ECAP-Conform. Mater. Sci. Eng. A
**2004**, 382, 30–34. [Google Scholar] [CrossRef] - Yuan, Y.; Li, Z.; Xiao, Z.; Zhao, Z. Investigations on Voids Formation in Cu–Mg Alloy during Continuous Extrusion. JOM
**2017**, 69, 1696–1700. [Google Scholar] [CrossRef] - Yuan, Y.; Li, Z.; Xiao, Z.; Zhao, Z.; Yang, Z. Microstructure evolution and properties of Cu–Cr alloy during continuous extrusion process. J. Alloys Compd.
**2017**, 703, 454–460. [Google Scholar] [CrossRef] - Zhu, C.; Ma, A.; Jiang, J.; Li, X.; Song, D.; Yang, D.; Chen, J. Effect of ECAP combined cold working on mechanical properties and electrical conductivity of Conform-produced Cu–Mg alloys. J. Alloys Compd.
**2014**, 582, 135–140. [Google Scholar] [CrossRef] - Rollett, A.; Humphreys, F.J.; Rohrer, G.S.; Hatherly, M. Recrystallization and Related Annealing Phenomena, 2nd ed.; Sleeman, D., Ed.; Elsevier: Kidlington, UK, 2012; p. 574. ISBN 0-08-044164-5. [Google Scholar]
- Sakai, T.; Belyakov, A.; Kaibyshev, R.; Miura, H.; Jonas, J.J. Dynamic and post-dynamic recrystallization under hot, cold and severe plastic deformation conditions. Prog. Mater. Sci.
**2014**, 60, 130–207. [Google Scholar] [CrossRef] - Humphreys, F.J.; Prangnell, P.B.; Bowen, J.R.; Gholinia, A.; Harris, C. Developing stable fine-grain microstructures by large strain deformation. Philos. Trans. R. Soc. Lond. A
**1999**, 357, 1663–1681. [Google Scholar] [CrossRef] - Gourdet, S.; Montheillet, F. A model of continuous dynamic recrystallization. Acta Mater.
**2003**, 51, 2685–2699. [Google Scholar] [CrossRef] - Bratov, V.; Borodin, E.N. Comparison of dislocation density based approaches for prediction of defect structure evolution in aluminium and copper processed by ECAP. Mater. Sci. Eng. A
**2015**, 631, 10–17. [Google Scholar] [CrossRef] - Chen, Z.; Chen, Y. Nanocrystalline gradient engineering: Grain evolution and grain boundary networks. Comput. Mater. Sci.
**2018**, 141, 282–292. [Google Scholar] [CrossRef] - Roberts, W. Strength of Metals and Alloys (ICSMA-7); McQueen, H.J., Bailon, J.-P., Dickson, J.I., Eds.; Pergamon Press: Oxford, UK, 1986. [Google Scholar]
- Derby, B. The dependence of grain size on stress during dynamic recrystallisation. Acta Metall.
**1991**, 39, 955–962. [Google Scholar] [CrossRef] - Belyakov, A.; Zherebtsov, S.; Salishchev, G. Three-stage relationship between flow stress and dynamic grain size in titanium in a wide temperature interval. Mater. Sci. Eng. A
**2015**, 628, 104–109. [Google Scholar] [CrossRef] - Belyakov, A.; Zherebtsov, S.; Tikhonova, M.; Salishchev, G. Kinetics of grain refinement in metallic materials during large strain deformation. Mater. Phys. Mech.
**2015**, 24, 224–231. [Google Scholar] - Shakhova, I.; Belyakov, A.; Kaibyshev, R. Kinetics of Submicrocrystalline Structure Formation in a Cu–Cr–Zr Alloy during Large Plastic Deformation. In Materials Science Forum; Trans Tech Publications: Zürich, Switzerland, 2017; Volume 879, pp. 1749–1754. [Google Scholar] [CrossRef]
- Jazaeri, H.; Humphreys, F.J. The Recrystallization of a highly deformed Al–Fe–Mn alloy. In Proceedings of the 1st International Conference on Recrystallization and Grain Growth, Aachen, Germany, 27–31 August 2001. [Google Scholar]
- Gazizov, M.; Malopheyev, S.; Kaibyshev, R. The effect of second-phase particles on grain refinement during equal-channel angular pressing in an Al–Cu–Mg–Ag alloy. J. Mater. Sci.
**2015**, 50, 990–1005. [Google Scholar] [CrossRef]

**Figure 1.**Typical deformation microstructures developed in a Cu–0.1Cr–0.06Zr alloy subjected to equal channel angular pressing (ECAP) at a temperature of 673 K to total strains of 1 (

**a**); 2 (

**b**); 4 (

**c**); 8 (

**d**); and 12 (

**e**). The inverse pole figures are shown for the pressing direction (PD) in (

**f**). The white and black lines indicate the low-angle (θ < 15°) and high-angle (θ ≥ 15°) boundaries, respectively.

**Figure 2.**Grain size and boundary misorientation distributions for a Cu–0.1Cr–0.06Zr alloy processed by ECAP at 673 K to total strains (ε) of two to 12.

**Figure 3.**The strain (ε) effect on the mean grain size (D), the dislocation density (ρ), the fraction of high-angle boundaries (F

_{HAB}), and the fraction of ultrafine grain (F

_{UFG}) in a Cu–0.1Cr–0.06Zr alloy subjected to ECAP at 673 K.

**Figure 4.**Stress-strain curves and the strain effect on the yield strength, (σ

_{0.2}), the ultimate tensile strength (UTS), and total elongation (δ) of a Cu–0.1Cr–0.06Zr alloy subjected to ECAP at 673 K.

**Figure 5.**The strain effect on the fraction of triple junctions with zero, one, two, or three adjacent high-angle boundaries, denoted as F

_{J0}, F

_{J1}, F

_{J2}, and F

_{J3}, respectively, for a Cu–0.1Cr–0.06Zr (0.1Cr, circle [20]), Cu–0.3Cr–0.5Zr (0.3Cr, triangles [21,24]), Cu–0.8Cr–0.05Zr (0.8Cr, square [19]) alloys after solution treatment (ST) or aging (AT) subjected to ECAP or multidirectional forging (MDF) at 673 K.

**Figure 6.**The relationship between the low-angle (F

_{LAB}) and high-angle (F

_{HAB}) boundary fractions and the fractions of triple junctions with zero (F

_{J0}) and three (F

_{J3}) adjacent high-angle boundaries in the Cu–0.1Cr–0.06Zr (0.1Cr, circle [20]), Cu–0.3Cr–0.5Zr (0.3Cr, triangles [21,24]), Cu–0.8Cr–0.05Zr (0.8Cr, square [19]) alloys after solution treatment (ST) or aging (AT) subjected to ECAP or multidirectional forging (MDF) at 673 K.

**Figure 7.**Relationships between the ultrafine-grain fraction (F

_{UFG}), the high-angle boundary fraction (F

_{HAB}), and the fraction of the triple junctions of high-angle boundaries (F

_{J3}) in the Cu–0.1Cr–0.06Zr (0.1Cr, circle [20]), Cu–0.3Cr–0.5Zr (0.3Cr, triangles [21,24]), Cu–0.8Cr–0.05Zr (0.8Cr, square [19]) alloys after solution treatment (ST) or aging (AT) subjected to ECAP or multidirectional forging (MDF) at 673 K.

**Figure 8.**The strain effect on the grain refinement in a Cu–0.1Cr–0.06Zr (circle [20]) and Cu–0.3Cr–0.5Zr (triangle [21]) alloys during ECAP at 673 K; recrystallization kinetics for solution-treated (

**a**) and aged (

**b**) samples, and the strain effect on the ultrafine-grain fraction in solution-treated (

**c**) and aged (

**d**) samples.

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## Share and Cite

**MDPI and ACS Style**

Morozova, A.; Borodin, E.; Bratov, V.; Zherebtsov, S.; Belyakov, A.; Kaibyshev, R.
Grain Refinement Kinetics in a Low Alloyed Cu–Cr–Zr Alloy Subjected to Large Strain Deformation. *Materials* **2017**, *10*, 1394.
https://doi.org/10.3390/ma10121394

**AMA Style**

Morozova A, Borodin E, Bratov V, Zherebtsov S, Belyakov A, Kaibyshev R.
Grain Refinement Kinetics in a Low Alloyed Cu–Cr–Zr Alloy Subjected to Large Strain Deformation. *Materials*. 2017; 10(12):1394.
https://doi.org/10.3390/ma10121394

**Chicago/Turabian Style**

Morozova, Anna, Elijah Borodin, Vladimir Bratov, Sergey Zherebtsov, Andrey Belyakov, and Rustam Kaibyshev.
2017. "Grain Refinement Kinetics in a Low Alloyed Cu–Cr–Zr Alloy Subjected to Large Strain Deformation" *Materials* 10, no. 12: 1394.
https://doi.org/10.3390/ma10121394