Electropulsing Aging Treatment of Cu–Ni–Si Sheet for Microforming

Abstract

Electropulsing aging treatment (EAT) can achieve a significant increase in the strength and conductivity of a Cu–Ni–Si alloy in a short time while maintaining a lower temperature. Compared with aging treatment in a conventional heating furnace at 450 °C for 120 min, EAT can reach or even exceed the same strength and conductivity in only 5 min. The mechanical and electrical properties of samples treated with 630 and 680 A mm−2 current density are prominently improved. After 45 min of treatment with 680 A mm−2 current density, the tensile strength exceeds 600 MPa, and the conductivity reaches 33.45% International Annealed Copper Standard. The main precipitates of the EAT sample is the δ‐Ni2Si nanoscale strengthening phase, and there is also the β‐Ni3Si phase in the copper matrix. The strengthening mechanism is the localized Joule heating generated by the electropulsing and the kinetic energy conversion caused by drift electrons, which increases the migration rate of solute atoms Si and Ni and reduces the energy barrier required in the precipitation process, thereby accelerating the formation of precipitates. EAT has the potential to become a new process for the preparation of high‐strength and high‐conductivity copper alloys.

Mechanism of Electropulsing Treatment Technology for Flow Stress of Metal Material: A Review

“…As depicted in Figure 9A, Bao and colleagues [115] hypothesized that during Electro-Assisted Micro-Compression (EAMC), the current initiates the α→β→α phase transition in Ti-6Al-4V alloys, where the "hot spot" effect of localized Joule heating serves as the primary driver for the nucleation of new β-phase. Zhu et al [116] suggested that when vacancies migrate and accumulate in areas such as dislocations and grain boundaries, they turn into nucleation sites for precipitates. The kinetic energy exchange between drifting electrons and solute atoms (Ni and Si) enhances the diffusivity of the solute atoms and lowers the energy barrier that the solute atoms have to overcome during the precipitation process, thereby speeding up the formation of precipitates (Figure 9B).…”

On the mechanical properties and damping behaviour of thermally aged unmodified and Ni modified Cu-Zn-Al shape memory alloys

“…This has been reported to be due to the modification of the sharp and elongated tips of the Cu-Zn-Al alloys, which results in the reduction of the stress concentration within the grain tip vicinity. The impact this has is to mitigate the potential tri-axial stress state created by the sharp grain tips, which facilitate brittle fracture [25,26]. The improved fracture toughness with ageing temperature may be rationalized to be on account of the precipitates which act as crack arresters/crack branching facilitators that serve to slow the crack propagation rate, thereby resulting in improved fracture toughness [27].…”

Achieving Excellent Properties of Cu-Ni-Si Copper Alloy by Cold Rolling and Electropulsing Aging

“…Additionally, Cu-Ni-Si alloys owe the excellent aging efficiency to the pipe diffusion along dislocation, which is brought by cold rolling. 21 Pipe diffusion through dislocation can increase the nucleation rate at the beginning of aging. 29,30 The alloy aged by electropulsing was cold rolled with a thickness reduction of 99.3%, and high-density dislocations were observed in the TEM microstructure.…”

“…20 At present, many works focus on the assistance effect of electropulsing in furnace treatment. Although Zhu has reported that Cu-Ni-Si alloys were treated by electropulsing directly to improve the properties, the tensile strength and electrical conductivity are < 610 MPa and 33.5% IACS, respectively, 21 having a gap compared with the properties of commercial C7025. In addition, treating the alloy takes a long time, 45 min.…”