Structure Amorphization and Mechanical Properties of Nanolaminates of the Copper–Niobium System During High-Pressure Torsion

Extended Shear Deformation of the Immiscible Cu–Nb Alloy Resulting in Nanostructuring and Oxygen Ingress with Enhancement in Mechanical Properties

“…Detailed work by P. Bellon and group highlights the strain-dependent modes of microstructural evolution categorized by low strain (<100), where interfacial instabilities dominate, while at high strain (>100) where the atomic mixing can be seen. , Additionally, they propose the effective temperature model to explain the observation of high solute superstation tendencies under the high-strain regime. , However, another factor that can influence the experimental observations in these processes is the interaction of the deforming material with the ambient environment, which consists of reactive gases such as oxygen. In the past, metastable supersaturated phases and amorphous structures have been reported to form in several alloys (Nb–B, Cu–Ta, Cu–Nb, and Cu–Ag) on extended deformation by mechanical alloying. − In two examples, the grain boundary excess of oxygen in nanocrystalline (NC) Al was shown to inhibit the grain boundary migration, while the Zenner pinning effect of oxide nanoparticles was shown to stabilize the NC structure in the Fe–Mg ball-milled alloy . Both these reports demonstrate the strong influence of oxygen on microstructural evolution and stabilization; however, the stabilization of defect-driven metastability such as amorphization due to the presence of oxygen has not been demonstrated.…”

“…In the past, metastable supersaturated phases and amorphous structures have been reported to form in several alloys (Nb–B, Cu–Ta, Cu–Nb, and Cu–Ag) on extended deformation by mechanical alloying. 9 − 13 In two examples, the grain boundary excess of oxygen in nanocrystalline (NC) Al was shown to inhibit the grain boundary migration, 14 while the Zenner pinning effect of oxide nanoparticles was shown to stabilize the NC structure in the Fe–Mg ball-milled alloy. 15 Both these reports demonstrate the strong influence of oxygen on microstructural evolution and stabilization; however, the stabilization of defect-driven metastability such as amorphization due to the presence of oxygen has not been demonstrated.…”

“…The Cu–Nb alloys and composites have been widely studied due to their combination of high-mechanical strength and electrical conductivity. ,− The Cu–Nb phase diagram shows a negligibly low mutual solubility in the solid state; however, extended plastic deformation techniques such as equal channel angular extrusion or high-pressure torsion (HPT) have been employed to extend the region of the solid solution, resulting in a higher strength than pure Cu or Cu-based miscible alloys. , In many cases, complete solubility is not achieved; however, the fine-scale distribution of immiscible phases results in a large improvement in the mechanical properties. , The nanofibers of Nb in Cu–Nb wires increased the ultimate tensile strength of Cu from 345 to 2230 MPa . In addition to strength, Kapoor et al showed that the resistance to grain growth at elevated temperatures increases as a function of Nb concentration in Cu–Nb alloys .…”

Amorphous-Nanocrystalline Composites Prepared by High-Pressure Torsion

“…(2) the use of Bridgman chamber for deformation processing of nanocrystalline Cu-Nb laminates prepared by multiple pack rolling (MPR) [31]. AA, due to the presence of a homogeneous structure and the absence of defects (dislocations and grain boundaries), demonstrate a higher level of mechanical properties that exceeds the level of properties achieved in the crystalline alloys.…”

“…(2) the use of Bridgman chamber for deformation processing of nanocrystalline Cu-Nb laminates prepared by multiple pack rolling (MPR) [31].…”