Texture evolution in two-phase Zr/Nb lamellar composites during accumulative roll bonding

https://doi.org/10.1016/j.ijplas.2014.01.008Get rights and content

Highlights

  • Novel two phase lamellar composites are fabricated via accumulative roll-bonding.

  • Earlier developed a dislocation density based hardening law for HCP is adapted to BCC.

  • Bulk texture development in the two phases is not affected by the interface.

  • Predictions of texture and deformation mechanisms for the individual phases are reported.

Abstract

We study the texture evolution and deformation mechanisms in a Zr/Nb layered composite using a combination of electron backscattered diffraction, dislocation density evolution modeling, and polycrystal plasticity simulations. Zr/Nb composites with individual layer thicknesses ranging from 1 to 4 mm one-millimeter to four-micrometers were successfully fabricated at room temperature by accumulative roll bonding. Measured texture data during rolling and stress–strain curves in compression are presented. Under severe plastic deformation, we show that the textures of each polycrystalline phase correspond to textures of severely rolled single-phase rolled Zr and Nb. A visco-plastic self-consistent (VPSC)-dislocation density based model is applied to predict the deformation textures in the individual phases. The model indicates that large-strain deformation in Zr is accommodated by prismatic, pyramidal, and anomalously basal slip, and in Nb by both {110} and {112} slip. Our findings suggest that the polycrystalline layers of four micrometers per phase are still too coarse for the bimetal interfaces to have an effect on the texture evolution.

Introduction

Multi-layered (lamellar) two-phase metals have been shown to exhibit a number of extraordinary properties, such as high strength, thermal stability, and hardness, which are not characteristics of their constituents (Anderson et al., 2003, Beyerlein et al., 2011a, Chu and Barnett, 1995, Embury and Hirth, 1994, Ham and Zhang, 2011, Mara et al., 2008, Misra and Kung, 2001, Was and Foecke, 1996). A majority of these bimetallic systems investigated recently were fabricated by near-equilibrium, thermodynamic techniques, such as solidification (Beyerlein et al., 2011a, Inoue et al., 2001), magnetron sputtering (Broussard et al., 1984, Fu et al., 2008, Ham and Zhang, 2011, Schweitz et al., 2001) and electro or chemical deposition (Huang and Spaepen, 2000, Zhai et al., 1997), that yield small volumes of material.

As a possible method for scaling up these two-phase metals to sizes suitable for structural applications, bulk severe plastic deformation (SPD) techniques such as equal channel angular pressing or extrusion (ECAE) or accumulative roll bonding (ARB) are being considered. These SPD techniques have been applied to single-phase metals, such as Cu (Li et al., 2005, Wang et al., 2003), Nb (Sandim et al., 2007, Zhu et al., 2013a, Zhu et al., 2013b), Ta (Wei et al., 2003), Ni (Zhang et al., 2011), Al (Saito et al., 1999), Ag (Beyerlein et al., 2007), Mg (Ma et al., 2009, Pérez-Prado et al., 2004), Zr (Jiang et al., 2008, Yapici et al., 2009), steel (Li et al., 2006) and Be (Beyerlein et al., 2010). The number of studies on SPD processing of two-phase metals is rising and include studies of co-deformation of Cu/Ag (Han et al., 1999, Ohsaki et al., 2007), Cu/Nb (Carpenter et al., 2012a, Demkowicz and Thilly, 2011, Lee et al., 2012, Segal et al., 1997, Thilly et al., 2001, Zheng et al., 2013), Al/Zn (Dehsorkhi et al., 2011), Cu/Ni (Liu et al., 2011), Ag/Fe (Yasuna et al., 2000), and even hard/soft systems like Cu/Cr or Ni/W (Embury and Sinclair, 2001, Sinclair et al., 1999).

Scaling up from the epitaxial growth of films to the SPD processing of bulk metals is not straightforward due to several differences in the final microstructure at several material length scales. One of the fundamental differences is that SPD causes substantial texture evolution (Beyerlein and Tóth, 2009, Jiang et al., 2008, Knezevic et al., 2013b, Yapici et al., 2009). The final textures depend on the specific SPD deformation path by which the material was processed (Beyerlein and Tóth, 2009). It is not expected that the texture resulting from the SPD technique will be similar to that from electro or chemical deposition. The plastic deformation behavior of the final material will depend on many microstructural aspects, one of them being texture evolution. Thus, understanding the mechanical properties of two-phase metals fabricated by SPD requires knowledge of their crystallographic texture.

Most studies of texture evolution of metals in SPD have largely focused on single-phase metals. Crystal plasticity models typically chosen for calculating texture evolution in these cases are mean-field homogenization schemes, such as the Taylor (Fast et al., 2008, Kalidindi et al., 1992, Kalidindi et al., 2006, Kalidindi et al., 2009, Knezevic et al., 2008, Knezevic et al., 2009, Knezevic and Kalidindi, 2007, Shaffer et al., 2010, Taylor, 1938, Wu et al., 2007) model or self-consistent modeling (Lebensohn and Tomé, 1993, Lebensohn et al., 2007), since they are capable of treating very large-strain deformation. Crystal plastic finite element models (CPFE) have also been used for moderate strain deformation (Kalidindi et al., 1992, Knezevic et al., 2010, Roters et al., 2010) with the advantage that, unlike the aforementioned schemes, grain–grain interactions can be captured.

In two-phase composites, the presence of another phase or the bi-phase interface can potentially affect texture evolution. While not extensively investigated, these effects have been studied in two-phase cubic systems, such as Cu/Nb (Beyerlein et al., 2013, Lee et al., 2012) and Cu/Ag (Beyerlein et al., 2011a). The Cu/Nb works collectively reveal the importance of individual layer thickness, h, on texture evolution (Carpenter et al., 2012a). Large layer thicknesses led to rolling textures that displayed no signs of interface effects, whereas small layer thicknesses, comprised of a single grain across the thickness, produced unusual deformation textures. Texture evolution in the former case was successfully simulated by crystal plasticity finite element method (Hansen et al., 2013). Recently, using the same technique, the phenomenon of shear banding in Cu/Nb and Cu/Ag laminates was studied (Jia et al., 2013). As an example of unusual textures, in a study of an ultra-fine Cu/Ag laminate, it was found that Ag promoted profuse twinning in Cu, which would have been uncommon if Cu were rolled alone (Beyerlein et al., 2011a). Studies on texture evolution in the SPD of composite material systems containing low symmetry metals, such as hcp/bcc or hcp/fcc interfaces are even more limited.

Here we fabricate a novel hcp Zr/bcc Nb layered composite and study texture evolution that develops in large strain roll bonding. We show that these composites can be successfully fabricated with controlled individual layer spacing, h, down to h = 4 μm. Achieving this fine scale required strains of ∼4. The resulting texture was similar to the rolling textures, found in literature, in the corresponding monolithic materials after large strains. As a means of confirming this result, we calculated the rolling textures of the individual phases using a visco-plastic self-consistent polycrystal plasticity code that integrates a hardening law based on dislocation densities (Beyerlein and Tomé, 2008). Doing so required adapting a dislocation density based hardening law for Nb. At large strains, the predicted textures agreed well with the measured deformation textures for each phase in the composite. Thus, from the experimental and simulation results, we conclude that the interface did not affect bulk texture development in the micron-scale Zr/Nb composite fabricated by ARB. The model indicated that Zr deformed by a combination of prismatic 〈a〉 slip, pyramidal 〈c + a〉 slip, and anomalously basal 〈a〉 slip. This result arises in spite of large strain development, fine lamellar layer thickness (4 μm), and close proximity of the interfaces to the grain boundaries.

Section snippets

Materials and experiments

This section describes the starting microstructure of Zr and Nb, the ARB fabrication process and measured texture evolution as a function of rolling passes in the Zr/Nb layered composites to a final mean layer thickness of ∼4 μm.

Single-crystal to polycrystal modeling

In the measurements, we have found no apparent Zr/Nb interface effects on texture evolution of the Zr and Nb phases. As another means of understanding the texture evolution observed here and the corresponding plastic deformation mechanisms, texture has been simulated in each phase individually to test how this independent prediction compares with the measurements.

To model texture evolution in each phase, we use the visco-plastic self-consistent scheme (VPSC) for the polycrystal model. This

Results of rolling texture simulations

Using the above model, we carried out simulations of rolling to high strains sufficient to achieve texture saturation for each phase. Since our measurements indicate that the interface did not affect bulk texture evolution, we consider separate homogeneous effective media i.e. one for Zr and another for Nb. Fig. 6 shows the predicted deformation textures for both phases. It appears that the model captures the main texture features consistent with experimental observation (see Fig. 3).

For a

Discussion

In this work, we explored texture developments in an hcp Zr/bcc Nb composite during ARB processing. The finest composite we made had 4 μm Zr and Nb layers and microstructural characterization found them to be polycrystalline in-plane and through-thickness. In these conditions, we successfully predict texture evolution and deformation modes in both phases using VPSC. Much recent experimental work suggests that even finer composites may exhibit unusual microstructural evolution and properties. For

Conclusions

In this work, we demonstrated that it is possible to fabricate a Zr/Nb composite via the accumulative roll bonding technique. With large strains (∼4), the individual layer thickness was refined to approximately 4 μm. We show that the deformation textures in Zr and Nb are consistent with those typically found when Zr and Nb are rolled alone. The measurements show the characteristic spread of the basal pole along the transverse direction and its concentration 30–50° from the normal direction in

Acknowledgments

MK and MA were supported by the University of New Hampshire faculty startup funds. IJB was supported by a Los Alamos National Laboratory LDRD program 20140348ER. TMP and NAM wish to acknowledge support by the UC Lab Fees Research Program # UCD-12-0045.15. TN was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

References (109)

  • M.J. Demkowicz et al.

    Structure, shear resistance and interaction with point defects of interfaces in Cu–Nb nanocomposites synthesized by severe plastic deformation

    Acta Mater.

    (2011)
  • J.D. Embury et al.

    On dislocation storage and the mechanical response of fine scale microstructures

    Acta Metall. Mater.

    (1994)
  • J.D. Embury et al.

    The mechanical properties of fine-scale two-phase materials

    Mater. Sci. Eng. A

    (2001)
  • T. Fast et al.

    Application of microstructure sensitive design to structural components produced from hexagonal polycrystalline metals

    Comput. Mater. Sci.

    (2008)
  • E.G. Fu et al.

    Mechanical properties of sputtered Cu/V and Al/Nb multilayer films

    Mater. Sci. Eng. A

    (2008)
  • B. Ham et al.

    High strength Mg/Nb nanolayer composites

    Mater. Sci. Eng. A

    (2011)
  • K. Han et al.

    The fabrication, properties and microstructure of Cu–Ag and Cu–Nb composite conductors

    Mater. Sci. Eng. A

    (1999)
  • W.Z. Han et al.

    Deformation and failure of shocked bulk Cu–Nb nanolaminates

    Acta Mater.

    (2014)
  • B.L. Hansen et al.

    Modeling the texture evolution of Cu/Nb layered composites during rolling

    Int. J. Plast.

    (2013)
  • H. Huang et al.

    Tensile testing of free-standing Cu, Ag and Al thin films and Ag/Cu multilayers

    Acta Mater.

    (2000)
  • P.J. Jackson

    Dislocation modelling of shear in f.c.c. crystals

    Prog. Mater Sci.

    (1985)
  • N. Jia et al.

    Simulation of shear banding in heterophase co-deformation: example of plane strain compressed Cu–Ag and Cu–Nb metal matrix composites

    Acta Mater.

    (2013)
  • H. Jiang et al.

    Cold rolling evolution in high purity niobium using a tapered wedge specimen

    Phys. C

    (2006)
  • L. Jiang et al.

    Texture, microstructure and mechanical properties of equiaxed ultrafine-grained Zr fabricated by accumulative roll bonding

    Acta Mater.

    (2008)
  • S.R. Kalidindi et al.

    Crystallographic texture evolution in bulk deformation processing of Fcc metals

    J. Mech. Phys. Solids

    (1992)
  • S.R. Kalidindi et al.

    Spectral calibration of crystal plasticity models

    Acta Mater.

    (2006)
  • S.R. Kalidindi et al.

    Representation of the orientation distribution function and computation of first-order elastic properties closures using discrete Fourier transforms

    Acta Mater.

    (2009)
  • G.C. Kaschner et al.

    Role of twinning in the hardening response of zirconium during temperature reloads

    Acta Mater.

    (2006)
  • M. Knezevic et al.

    Fast computation of first-order elastic–plastic closures for polycrystalline cubic–orthorhombic microstructures

    Comput. Mater. Sci.

    (2007)
  • M. Knezevic et al.

    Computationally efficient database and spectral interpolation for fully plastic Taylor-type crystal plasticity calculations of face-centered cubic polycrystals

    Int. J. Plast.

    (2008)
  • M. Knezevic et al.

    Crystal plasticity simulations using discrete Fourier transforms

    Acta Mater.

    (2009)
  • M. Knezevic et al.

    Deformation twinning in AZ31: influence on strain hardening and texture evolution

    Acta Mater.

    (2010)
  • M. Knezevic et al.

    Anisotropic stress–strain response and microstructure evolution of textured α-uranium

    Acta Mater.

    (2012)
  • M. Knezevic et al.

    A polycrystal plasticity model for predicting mechanical response and texture evolution during strain-path changes: application to beryllium

    Int. J. Plast.

    (2013)
  • M. Knezevic et al.

    Integration of self-consistent polycrystal plasticity with dislocation density based hardening laws within an implicit finite element framework: application to low-symmetry metals

    J. Mech. Phys. Solids

    (2013)
  • M. Knezevic et al.

    Modeling mechanical response and texture evolution of α-uranium as a function of strain rate and temperature using polycrystal plasticity

    Int. J. Plast.

    (2013)
  • U.F. Kocks et al.

    Physics and phenomenology of strain hardening: the FCC case

    Prog. Mater Sci.

    (2003)
  • L.P. Kubin et al.

    Analysis of softening in the FeC system from in situ and conventional experiments-I. In situ experiments

    Acta Metall.

    (1979)
  • D. Kuhlmann-Wilsdorf

    Theory of plastic deformation:-properties of low energy dislocation structures

    Mater. Sci. Eng. A

    (1989)
  • R.A. Lebensohn et al.

    A self-consistent anisotropic approach for the simulation of plastic deformation and texture development of polycrystals: application to zirconium alloys

    Acta Metall. Mater.

    (1993)
  • S.B. Lee et al.

    The heterophase interface character distribution of physical vapor-deposited and accumulative roll-bonded Cu–Nb multilayer composites

    Acta Mater.

    (2012)
  • S. Li et al.

    Texture evolution during multi-pass equal channel angular extrusion of copper: neutron diffraction characterization and polycrystal modeling

    Acta Mater.

    (2005)
  • S. Li et al.

    Effect of processing route on microstructure and texture development in equal channel angular extrusion of interstitial-free steel

    Acta Mater.

    (2006)
  • K. Linga Murty et al.

    Texture development and anisotropic deformation of zircaloys

    Prog. Nucl. Energy

    (2006)
  • Y. Liu et al.

    Mechanical properties of highly textured Cu/Ni multilayers

    Acta Mater.

    (2011)
  • A. Ma et al.

    Improving both strength and ductility of a Mg alloy through a large number of ECAP passes

    Mater. Sci. Eng. A

    (2009)
  • R. Madec et al.

    Second-order junctions and strain hardening in bcc and fcc crystals

    Scripta Mater.

    (2008)
  • J.R. Mayeur et al.

    A crystal plasticity study of heterophase interface character stability of Cu/Nb bicrystals

    Int. J. Plast.

    (2013)
  • G. Monnet et al.

    Dislocation study of prismatic slip systems and their interactions in hexagonal close packed metals: application to zirconium

    Acta Mater.

    (2004)
  • S. Nemat-Nasser et al.

    Flow stress of commercially pure niobium over a broad range of temperatures and strain rates

    Mater. Sci. Eng. A

    (2000)
  • Cited by (115)

    View all citing articles on Scopus
    View full text