Effect of Deformation, Annealing and Doping with Zr on Nb Filaments Nanocrystalline Structure in High-Strength In Situ Cu-Nb Composites

Abstract

The structure and properties of in situ Cu-Nb composites have been studied by the methods of TEM and SEM, X-ray analysis and mechanical testing. The evolution of Nb filaments structure at drawing and the effect of annealing and doping with Zr on the composites structure and texture have been investigated. Sharp fibre texture with <110>Nb develops in the ribbon-shaped Nb filaments, while the Cu matrix possesses a two-component fibre texture, <111>Cu and <100>Cu, appreciably affected by annealing. Annealing results in softening due to Nb filaments coagulation. In Zr doped composites two types of ZrO2 particles are observed, dispersed and coarse ones. The former result in the dispersion strengthening, while the latter may cause embrittlement.

Specific Features of Interfaces in Cu-Nb Nanocomposites

“…4e). They are markedly elongated along the drawing axis coinciding with <110> Nb and <111> Cu directions, which is a typical fiber texture for these composites [12][13][14][15], but between these directions there is always an angle of about 2-5° (Fig. 4f).…”

“…1c, d). It was observed in numerous studies [3][4][5][6][10][11][12][13][14][15][16][17] and is attributed to the multiple slip systems in the BCC Nb, dislocation interaction in different slip systems and to the impact of the FCC Cu matrix. The Nb filaments thicknesses in this sample are widely scattered from 20 to 120 nm.…”

“…The Cu grains are coarse, the sizes of 200-300 nm, they have polyhedral shape and low dislocation density. It is well known that in such composites Cu matrix undergoes dynamic recrystallization at multiple cold drawing [13,14,17,19], which results in the structure observed. The same specific features of the structure are observed in the rectangular Sample 2, which has a higher true strain.…”

“…It has been well-established by now that the determining role in the attainment of anomalous properties of nanomaterials is played by their internal interfaces [7]. In a number of studies it is demonstrated, that in the in situ Cu-Nb composites interfaces are semi-coherent and partly amorphous [8][9][10][11], whereas the impact of texture on their strengthening and deformation mechanisms is revealed in [12][13][14][15]. According to [16], the structure and properties of Cu-Nb multi-core nanocomposites, fabricated at the Bochvar Institute of Inorganic Materials, are stable at room temperature for several years and do not degrade at heating up to 200 о С, whereas at annealing higher than 500 о С considerable decrease of mechanical strength due to coagulation of Nb ribbons was found.…”

Peculiarities of Structure and Texture of High-Strength Cu-Nb Composites

“…Because of the great interest in the Cu-Nb wires, with their unique combination of high strength and good electrical conductivity, the authors of the present paper (and their coauthors) for many years studied the Cu-Nb composites of various types fabricated at Bochvar High-Technological Institute of Inorganic Materials [14,15,[33][34][35][36][37][38], and the most interesting results of these studies, together with the available data of other authors, are discussed below.…”