Dependence of texture evolution on initial orientation in drawn single crystal copper

Abstract

The evolution of fiber texture in the drawn single crystal copper wires with initial orientations of < 100>, < 110> and < 111> parallel to axis direction has been studied via electron backscattering diffraction. During cold drawing process, grain subdivision takes place in the < 100>, < 110> and < 111> single crystals. At high strains, a mixture of < 111> and < 100> fiber textures forms, but due to uneven shear strain, the distribution of the < 111> and < 100> fiber textures is inhomogeneous along the radial direction of wires. The < 111> fiber texture component is located in the centre of wires and < 100> is near the surface. Although grain subdivision appears in the < 100>, < 110> and < 111> single crystals, the stability of the three initial orientations is different. The initial orientations of < 100> and < 111> are more stable than < 110>. < 100> is stable at low strains while < 111> becomes stable at high strains.

Introduction

Metal wire drawing technology has been widely used to manufacture fine wires [1], [2], [3]. Due to crystal reorientation, the material deformation brings about the development of texture. The deformation texture is analyzed usually using X-ray/neutron diffraction [4], [5], [6], [7], [8], [9], [10], [11], [12] and electron backscattering diffraction (EBSD) [13], [14], [15]. Furthermore, EBSD is able to reveal the distribution of texture.

In drawn FCC metals, duplex fiber textures of < 111> and < 100> parallel to axis direction are usually observed [4], [5], [6]. However, the ratio of the < 111> to < 100> fiber texture varies with reduction [9], [16], stacking fault energy of materials [17], deformation temperature [18], [19], and so on. In copper and copper alloys, Hibbard [16] has reported that the intensity of the < 100> fiber texture decreases with increasing strain. Thus, he concluded that the < 111> fiber texture is the most stable component in FCC metals. English and Chin [17] have found that, with increasing stacking fault energy of FCC metals, the amount of < 100> fiber texture firstly increases up to ~ 90% for silver, and then decreases. McHargue et al. [18] and Ahlborn et al. [19] studied the temperature dependence of the fiber textures. It has been found that the ratio of < 100> to < 111> at room temperature is less than that at low temperature (− 196 °C, − 77 °C) and high temperature (100 °C). Thus, they suggested that the < 100> fiber texture results from recrystallisation or twining. However, the study of Shin et al. [5] did not support that recrystallisation brings about more < 100>. Meanwhile, Stout et al. [20] did not find that twinning influences observably on the amount of < 100> and presumed that the strong < 100> fiber texture in silver might be from the initial samples.

As mentioned above, the evolution of fiber textures of cold drawn FCC metals has been widely studied. However, most of previous studies are based on polycrystalline samples and it is difficult to determine the initial orientation of grains. Thus, the effect of initial orientation on texture evolution has not been revealed clearly up to now. This leads to some important questions to be still ambiguous. For example, now that < 111> and < 100> are final fiber textures of drawn FCC metals, when the initial orientation of grains is already < 111> or < 100> parallel to drawn direction, how does deformation texture evolve during cold drawing process? In the present study, therefore, three single crystal coppers with the initial orientations of < 100>, < 111> or < 110> parallel to axis direction were prepared and drawn at room temperature. Then, the evolution of fiber textures of the cold drawn single crystal coppers was investigated by EBSD.