Orowan Strengthening Research Articles

Effect of Nb on Microstructure and Mechanical Property of Novel Powder Metallurgy Superalloys during Long-Term Thermal Exposure.

Microstructure and mechanical properties of novel Ni-20Co-12Cr superalloys, with and without Nb addition, were systematically studied during long-term thermal exposure. With increased exposure time, the average diameter of the γ′ precipitates increased in both alloys in succession; this is more obviously observed in alloy containing 1 wt% Nb (1Nb). It is suggested that Nb increased the γ′ coarsening rate by accelerating the diffusion of Al and Nb in γ matrix. In addition, the γ′ phase fraction is increased by about 4% in 1Nb compared to the alloy without Nb (0Nb). The morphology of the γ′ phase changed from near-spherical to cuboidal shape during exposure in both alloys. Due to the increased γ/γ′ lattice misfit by Nb addition, 1Nb alloy showed an earlier tendency of shape change. Vickers hardness results revealed that the overall hardness decreased with the exposure time because the size increment of the γ′ precipitate weakened the precipitates strengthening and Orowan strengthening.

The role of MgO nanoparticles addition, and γ-irradiation on the microstructural, and tensile properties of Al-1100 alloy

Aluminum matrix composites (AMCs) are innovative engineering materials in which a tough reinforcement is included in the aluminum matrix to improve its properties. In the study, MgO (0–4 wt.%) was loaded to Al-1100. The XRD reveals that MgO has a cubic crystal structure, purity of 100 %, and the average crystallite size is 17.4 nm, from Scherer's formula. HR-TEM reflected that MgO displays nanoparticle-like morphology. The microstructural properties of AMCs manifested the intermetallic compounds’ absence, grain refinement, good MgO distribution, and the presence of few porosities. The density measurement confirmed the decrease in the experimental density with increasing MgO while the theoretical density increased. The maximum porosity found is 1.4 % which is accepted in the fabrication of AMCs. The tensile properties revealed that as the strain rate ([Formula: see text]), γ-irradiation dose, and MgO content increases, the fracture stress ([Formula: see text]) increases while the ductility (εΤ) decreases. These three parameters could control the tensile properties of AMCs reinforced with MgO as well. An improvement by 140 % in σf was achieved for AMC with 4 wt.% MgO (at [Formula: see text] = 1.2 × 10−3 s−1, 2 MGy) compared to plain Al-1100 alloy (at [Formula: see text] = 5.4 × 10−5 s−1, 0 Gy). It was suggested that the load transfer from matrix to reinforcement was efficient which directly improves the load-carrying ability of these synthesized AMCs. Several mechanisms such as Orowan strengthening, and dislocation strengthening, were suggested to interpret the tensile properties.

Precipitation behavior and mechanical properties of Al-Zn-Mg-Cu matrix nanocomposites: Effects of SiC nanoparticles addition and heat treatment

In this study, the SiC/Al-Zn-Mg-Cu nanocomposites were fabricated using high energy ball milling combined with spark plasma sintering (SPS) and hot extrusion. The microstructure and mechanical properties were investigated by utilizing X-ray diffraction (XRD), scanning electron microscopy (SEM) and high resolution transition electron microscopy (HRTEM) analysis as well as tensile tests. The results showed that the as-extruded SiC/Al-Zn-Mg-Cu nanocomposite samples demonstrated a microstructure consisting of ultrafine α-Al grains, dispersed SiC nanoparticles and nano-scaled T phases probably formed by dynamic precipitation during extrusion. After T6 heat treatment, the coarsening of α-Al grains, dissolution of T phases and consequently the precipitation of fine η′ phases occurred, leading to a simultaneous increase of the strength and ductility. With increasing the content of SiC nanoparticles from 1 vol% to 3 vol%, the yield strength (YS) and ultimate tensile strength (UTS) increased from 456 and 528 MPa to 580 and 588 MPa (27.2% and 11.4% increase), respectively while the elongation to fracture decreased slightly from 11.8% to 10.2% (13.6% decrease). Various strengthening mechanism calculation results show that Orowan strengthening was mostly contributed to the improved strength of the T6 heat treated SiC/Al-Zn-Mg-Cu nanocomposites.

Microstructural, mechanical, and wear properties characterization and strengthening mechanisms of Al7075/SiCnp composites processed through ultrasonic cavitation assisted stir-casting

Abstract In this investigation, Al7075 matrix composites reinforced with nano-SiC particles were manufactured using an ultrasonic cavitation assisted stir casting approach. The microstructural characterization by SEM confirms the presence of nano-SiC particles with all the composites, particle size, and with reasonably homogeneous particle dispersion. Characterization by EDS and XRD confirm no trace of oxide formations, and secondary phase or impurities formations with the composites. Optical microscopic examinations shown matrix phase grain refinement due to the presence of nano-SiC particles as-well-as the aggressive ultrasonic cavitation effect. The mechanical properties of the composites have been substantially improved with an increased amount of nano-SiC particles. The manufactured composites demonstrated an outstanding yield strength of 284 MPa with the only 2.0 wt% reinforcement of nano-SiC particles which is 94.52% improvement compared with the yield strength of the ultrasonically treated Al7075 matrix alloy. The strength of Al7075/SiCnp composites has been estimated by various models of strengthening mechanisms. The strengthening contribution due to thermal mismatch is more dominant followed by Orowan strengthening, Hall-Petch mechanism, and load transferring effect for Al7075/SiCnp composites. The strengthening contributions of CTE difference, dislocations interactions between matrix-reinforcement particles, grain-refinement, and load transfer mechanism increased monotonically for the increased percentage of SiCnp content with the composite. The wear resistance of the composites was found as superior to the matrix alloy and was continuously decreased rapidly up to 750 m of sliding distance while it was protracted up to 2250 m. The composite with 2.0% nano-SiC particles reinforcement has shown approximately 79.8% improvement in wear resistance compared with the matrix alloy.

Synergistic effects of hybrid (SiC+TiC) nanoparticles and dynamic precipitates in the design of a high-strength magnesium matrix nanocomposite

Novel nanocomposites based on an AZ91 magnesium alloy matrix reinforced with a hybrid mixture of SiC and TiC nanoparticles with different nanoparticle contents (0.5% and 1%, by mass fraction) were fabricated by semi-solid stirring followed by ultrasonic vibration. Microstructural analysis indicated that the hybrid nanoparticles were uniformly distributed in the nanocomposite. The morphology of the Mg17Al12-based eutectic phase changed from plate-like, in the as-cast AZ91 alloy, to lamellar in the as-cast nanocomposites. The tensile strength and micro-hardness of the nanocomposites were improved by increasing the fraction of nanoparticles in the composite. Following extrusion, the matrix grains in the nanocomposite were significantly refined. The extent of the grain refinement increased at higher mass fractions of the nanoparticle. This refinement was not only due to dynamic recrystallization, but also the synergistic pinning effects arising from both the externally added nanoparticles as well as dynamically precipitated Mg17Al12 particles. The nanoparticle additions led to increases in yield strength (YS), ultimate tensile strength (UTS) and elongation to failure (EL). The increase in YS was mostly attributed to the effects of grain refinement, with additional contributions from the influence of Orowan strengthening and thermal expansion effects. The values of both the work hardening rate (θ) and strain hardening exponent (n) increased with increasing fraction of nanoparticles. The high θ value in stage III was attributed to both grain refinement and weakening of the basal plane texture, while the high n value was mainly related to the increase in resistance to dislocation movement caused by pinning effects of the nanoparticles.

Simultaneously improving strength and ductility of hybrid Al–Si matrix composite with polyphasic and multi-scale ceramic particles

Hybrid aluminum matrix composites have received widespread attention because of their superior performance to single-phase reinforced aluminum matrix composites. In situ VB2–AlN–Al4C3–VSi2/Al ribbons with polyphasic and multi-scale reinforcement particles were prepared by powder metallurgy method and controlled by melt-spinning and then verified the reinforcement efficacy in Al–12Si alloy. It was found that the addition of VB2–AlN–Al4C3–VSi2/Al ribbons not only refined the grain of α-Al, but also optimized the morphology of eutectic silicon for Al–12Si matrix composite. Thereafter, the mechanical properties of the VB2–AlN–Al4C3–VSi2/Al–12Si composite, including the tensile strength, ductility and hardness were increased by 36.2%, 82.2% and 33.4%, respectively, with the addition of VB2–AlN–Al4C3–VSi2/Al ribbons. The excellent mechanical properties can be attributed to the micron-sized VSi2 particles, nano-sized AlN, VB2, and Al4C3 as well as the well-bonded particle/matrix interface. In addition, multiple strengthening mechanisms have also made outstanding contributions to the improvement of the mechanical properties, including (1) Orowan strengthening; (2) Coefficient of thermal expansion (CTE) mismatch strengthening; (3) the Hall-Petch effect caused by grain refinement. The present experimental results provide an insight into the understanding of polyphasic and multi-scale reinforcement particles, and extend the effort for the development of Al–Si composite.

Microstructure evolution and texture tailoring of reduced graphene oxide reinforced Zn scaffold

Zinc (Zn) possesses desirable degradability and favorable biocompatibility, thus being recognized as a promising bone implant material. Nevertheless, the insufficient mechanical performance limits its further clinical application. In this study, reduced graphene oxide (RGO) was used as reinforcement in Zn scaffold fabricated via laser additive manufacturing. Results showed that the homogeneously dispersed RGO simultaneously enhanced the strength and ductility of Zn scaffold. On one hand, the enhanced strength was ascribed to (i) the grain refinement caused by the pinning effect of RGO, (ii) the efficient load shift due to the huge specific surface area of RGO and the favorable interface bonding between RGO and Zn matrix, and (iii) the Orowan strengthening by the homogeneously distributed RGO. On the other hand, the improved ductility was owing to the RGO-induced random orientation of grain with texture index reducing from 20.5 to 7.3, which activated more slip systems and provided more space to accommodate dislocation. Furthermore, the cell test confirmed that RGO promoted cell growth and differentiation. This study demonstrated the great potential of RGO in tailoring the mechanical performance and cell behavior of Zn scaffold for bone repair.

Precipitation strengthening of nano-scale TiC in a duplex low-density steel under near-rapid solidification

Precipitation strengthening of nano-scale TiC is a promising method to improve mechanical properties of Fe–16Mn–9Al–0.8C (wt.%) low-density steel. This work attempted to introduce nano-scale TiC precipitates by adding 1 wt.% Ti element. The experimental results show that these precipitates with the total fraction of about 2 vol.% were formed and no coarse precipitates were observed despite the high Ti addition. It was interesting that the polygonal and needle-shaped TiC precipitates were observed in γ-austenite and δ-ferrite, respectively. Ti addition also decreased the volume fraction of γ-austenite significantly. Correspondingly, the yield strength was increased, but the elongation was significantly decreased due to the significant decrease of γ-austenite. Comparing with the Ti-free steel, the formation of TiC precipitates was the main reason for the increase in yield strength of Ti-bearing steel, and TiC precipitates also led to a higher strain hardening index at the first deformation stage. TiC precipitates promoted the Orowan strengthening, resulting in a higher strain hardening capability than Ti-free steel reinforced by shearable κ-carbide.

Investigation on the elevated-temperature mechanical properties of TiB2/Al-4.5%Cu composites

Mechanical performance of TiB2/Al-4.5%Cu composites at elevated-temperature were evaluated by means of tensile behaviors and fracture mechanisms. Results indicated that the composite reinforced by nano-sized TiB2 particles exhibited excellent mechanical ability during deformation at elevated temperatures, the optimum addition level for dispersion, refinement and modification was 5wt.% TiB2/Al-4.5%Cu at 473K, i.e., yield strength is 358MPa and elongation is 4 %. The enhanced resistance of the composite was mainly attributed to Orowan strengthening and load transfer enhancement, additionally, interface debonding increasingly affects the damage and fracture of the composites.

Microstructures, mechanical properties, and grease-lubricated sliding wear behavior of Cu-15Ni-8Sn-0.8Nb alloy with high strength and toughness

Alloys used as bearings in aircraft landing gear are required to reduce friction and wear as well as improve the load-carrying capability due to the increased aircraft weights. Cu-15Ni-8Sn-0.8Nb alloy is well known for possessing good mechanical and wear properties that satisfy such requirements. In this study, the microstructure, mechanical properties, and grease-lubricated sliding wear behavior of Cu-15Ni-8Sn-0.8Nb alloy with 0.8 wt% Nb are investigated. The nanoscale NbNi3 and NbNi2Sn compounds can strengthen the alloy through the Orowan strengthening mechanism. A Stribeck-like curve is plotted to illustrate the relationship among friction coefficient, normal load, and sliding velocity and to analyze the grease-lubricated mechanism. The wear rate increases with normal load and decreases with sliding velocity, except at 2.58 m/s. A wear mechanism map has been developed to exhibit the dominant wear mechanisms under various friction conditions. When the normal load is 700 N and the sliding velocity is 2.58 m/s, a chemical reaction between the lubricating grease and friction pairs occurs, resulting in the failure of lubricating grease and an increase in wear.

Evolution of microstructure and mechanical properties influenced by nanosized precipitates during rolling deformation

In this research work, the 6111Al reinforced by rare earth element Er was subjected to severe plastic deformation with different rolling reduction ranging from 50%, 70%–90% respectively. Continuous deepening of the dynamic recrystallization occurred during the increment on rolling deformation and the average size of α-Al grains decreased to 7.9 μm eventually. The nanosized Al3Er particles were characterized by the combined function of inhibiting and promoting the DRX at the same time during the rolling process. And the competitive relationship between the driving force and the restraining force has been studied via systematic calculation here. A noticeable enhancement on 6111Al–Er alloy has been obtained with YS, UTS and elongation increasing to 359 MPa, 380 MPa and 27.4% respectively when the rolling deformation reached to 90%, which was attributed to the synergistic strengthening effect induced by the fine grain strengthening and the Orowan strengthening mechanisms. The evolution of microstructure was characterized by the equipments including Electron backscattered diffraction (EBSD), Scanning electron microscope (SEM) and High resolution transmission electron microscope (HRTEM).

Influence of heat treatment on microstructure evolution and mechanical properties of TiB2/Al 2024 composites fabricated by directed energy deposition

The influence of heat treatment on microstructure evolution and mechanical properties of TiB2/Al 2024 composites fabricated by laser-powder directed energy deposition (DED) were investigated. The results showed that the addition of TiB2 resulted in a significant grains refinement with random orientation. Compared with DED-Al 2024, a lot of network-like θ-Al2Cu phases was generated in the as-deposited TiB2/Al 2024 composite, leading to low plasticity. After 10h solution treatment, the θ phase disappeared, the thermally stable block T-Al20Cu2Mn3 phase was formed and the ultimate tensile strength (UTS) and elongation improved due to solution strengthening. During the aging process, Cu element was precipitated and semi-coherent θ’ phase was generated, improving the effect of Orowan strengthening. The composite material reached the maximum UTS of 453.65 MPa after 10h aging. The yield strength (YS) enhanced with the increase of aging time. After 15h aging, the YS and microhardness reached the maximum of 245.73 MPa and 133.50HV, respectively. This research provides a theoretical basis for the repair and manufacture of Al 2024 alloy and composite parts.

Effects of stress state, strain rate, and temperature on fracture behavior of in situ TiB2/2024 Al composite

To gain insights into the relationship between the fracture behavior and the unique microstructure of the in situ TiB2/2024 Al composite, systematic experiments were conducted over wide ranges of temperature (298–673 K), strain rate (0.001–4000/s), and stress triaxiality (−0.82–1.03). The results showed that the strengthening mechanism of the composite was related to Orowan strengthening and coefficient of thermal expansion (CTE) mismatch strengthening. Owing to the smaller particle size and sturdy interfacial bonding, the tensile strength of the in situ nano/submicron TiB2/2024 composite was higher than that of the ex situ composite and the in situ micron composite. Through a morphologic study by scanning electron microscopy (SEM), the microstructural deformation and crack propagation path were found to be largely dependent on the stress state, strain rate, and temperature. The melted matrix precipitated in the dynamic tensile fracture surface can hinder the crack propagation and is considered the determining factor that improves the ductility at room temperature. Furthermore, a 3D fracture locus in the space of the fracture strain, stress triaxiality, and the Lode angle parameter was formed. Finally, a new fracture criterion that considers the Lode angle parameter, the stress triaxiality cutoff value, and the coupling effect of strain rate and temperature was developed. The developed criterion exhibited a robust and accurate capability to describe the fracture behavior of the in situ TiB2/2024 Al composite.

Effect of Heat Treatment on Wear Behavior of A357/Cenosphere Composites

The present paper is based on the effect of heat treatment on the wear behavior of A357/cenosphere composites. The aluminum metal matrix composites were fabricated by the squeeze casting method. Both base alloy and composites are heat treated. The hardness of the matrix alloy and composites, both in as cast and heat-treated conditions, is measured by Vickers microhardness tester. The mechanical properties of the Al alloy/cenosphere composites got enhanced due to dispersion hardening, grain boundary strengthening and Orowan strengthening. The abrasive wear behavior was carried out on the composites using pin-on-disk wear tester with various operating parameters. The wear test results showed that the matrix alloy suffered higher wear rate than that of composites both in untreated and heat-treated conditions, depending on load.

Significantly improved particle strengthening of Al–Sc alloy by high Sc composition design and rapid solidification

Sc alloying is usually carried out by adding a small amount of Sc in typical aluminum alloys to improve the mechanical properties, however, the effect of high-Sc content on the microstructure and properties of aluminum alloys is rarely concerned. To further understand the role of Sc alloying, several Al–Sc binary alloys with high-Sc content are designed and the relationship between the Sc content and mechanical properties were investigated. It is found that the mechanical properties of Al–Sc binary alloy is determined by both the Sc content and the cooling rate. The addition amount of Sc shows relatively small effect on the mechanical properties at low cooling rate, but higher at high cooling rate, because cooling rate turns the size and distribution of Al3Sc particles. Through the high Sc content alloy design and melt spinning rapid cooling technology, the densely distributed Al3Sc precipitate of about 250 nm can be located inside the α-Al grains, resulting in the intracsystalline reinforcement. The combination of high tensile strength (344 MPa) and good plasticity (5.7%) were achieved at a grain size of ~500 nm in the hypereutectic Al–Sc binary alloys ribbons. The significant strengthening could be attributed to multiple strengthening mechanisms including (1) Orowan strengthening; (2) coefficient of thermal expansion (CTE) mismatch strengthening; (3) the Hall-Petch effect caused by grain refinement; (4) solid solution strengthening. When the cooling rate is increased, the effects of thermal mismatch strengthening and Orowan mechanism are more prominent, significantly improving the strength of the Al–Sc alloy. The present experimental results provide an insight into the understanding of microstructural evolution of nanoparticles, and extend the effort for the development of hypereutectic Al–Sc alloys as a member of high-strength structural materials.

Microstructural and mechanical evolution of 6111Al reinforced by in-situ ZrB2 particles during extrusion process

In this research work, the 6111Al matrix composites reinforced by different content of in-situ ZrB2 particles were conducted to hot extrusion process to investigate the characteristics of microstructural and mechanical evolution during deformation. The results showed that coarse particle clusters were crushed to pieces and the distribution of ZrB2 particles has been modified significantly with assistance of huge extruded force. Besides, the behavior of dynamic recrystallization (DRX) was intensified by nanosized particles causing severe dislocation pile-up around them, which resulted in tinier dynamically recrystallized (DRXed) grains generated in 6111Al/ZrB2 composites. The effect of enhancement induced by extrusion process on mechanical properties of the matrix alloy reached to the peak value when the content of ZrB2 particles was 3 wt%, where the YS, UTS and elongation of 6111Al-3wt% ZrB2 composites were 345 MPa, 396 MPa and 28.2% respectively, which was attributed to the uniform distribution of reinforcing particles, the elimination of casting defects and super-tiny DRXed grains in the microstructure. The particle stimulated nucleation (PSN) mechanism and strengthening mechanisms concerning Orowan strengthening, Dislocation strengthening, Grain refinement strengthening were systematically discussed in this paper.

Effect of micro-alloying element Ti on mechanical properties of Cu–Cr alloy

The mechanical properties and microstructure of Cu–Cr and Cu–Cr–Ti alloys after aging treatment were investigated via hardness measurements, electron backscattered diffraction analysis, and transmission electron microscopy. The results show that the hardness, yield strength, and softening temperature of the Cu–Cr–Ti alloy significantly improved. The interface of the Cu matrix and Cr-rich precipitates was semi-coherent as determined by calculations, and the strengthening mechanism of the Cr precipitates was via the Orowan strengthening relation. A high dislocation density was observed in the matrix, which was because of impediment by fine Cr precipitates in the Cu–Cr–Ti alloy. The effects of dislocation strengthening, solid-solution strengthening, and precipitate strengthening were shown to remarkably enhance the yield strength.

Effect of extrusion speed on mixed grain microstructure and tensile properties of a Mg-2.9Zn-1.1Ca-0.5Mn nanocomposite reinforced by a low mass fraction of TiCp

In this work, a novel TiC nanoparticle (0.5 wt %) reinforced Mg-2.9Zn-1.1Ca-0.5Mn nanocomposite, with a mixed grain microstructure exhibiting high strength and targeted for biocompatible/structural applications was successfully prepared by ultrasonic assisted semi-solid stirring and extrusion at ultra-slow speeds of 1, 0.1 and 0.01 mm/s. The experimental results revealed that the morphology of the eutectic Ca2Mg6Zn3 phase in the as-cast nanocomposite changed from plate-like to lamellar as a low mass fraction of TiCp was added. Both dynamically recrystallized grains and precipitates were gradually refined with decreasing extrusion speed. The finest recrystallized grains (∼0.46 μm), with a high volume fraction (∼4.3%) of fine precipitates, appeared after extrusion at 0.01 mm/s. The refined grain structure was not only due to dynamic recrystallization, but also the synergistic pinning effects from nano-TiCp as well as precipitated MgZn2 and α-Mn particles. The superior ultimate tensile strength (∼410.3 MPa), yield strength (∼384.5 MPa) and elongation to failure (∼4%) were obtained in the nanocomposite extruded at the slowest speed (0.01 mm/s) and had the potential to serve as a candidate material in orthopaedic applications. The improved strength was mainly related to grain refinement, thermal expansion effects and Orowan strengthening. Grain refinement, in particular, contributed to the largest strengthening increment. High tensile toughness of ∼66.6 KJ mm−3 was achieved for the nanocomposite extruded at a speed of 1 mm/s. Further, it exhibited a high strain hardening rate, θ, at stage IV. The fracture surface exhibited abundant dimples and consistent with high ductility. Remnant coarse Ca2Mg6Zn3 particles acted as crack initiators under high applied stress in tension, leading to structural failure.

Preparation and properties of Nano-HfO2 reinforced NiAl intermetallics fabricated with powder metallurgy

A new approach for in-situ synthesis of nano-HfO2 reinforced NiAl intermetallics was proposed for the preparation of a new NiAl-based composite material that is expected to function at 1200 °C. The phase composition, microstructure and mechanical properties of NiAl-HfO2 composites prepared by hot pressing sintering with Ni, Al, Hf and O2 as starting materials were studied. The composites with NiAl as the matrix and nearly spherical or capsule-shaped HfO2 with an average size of 80.19 nm as the dispersion strengthening phase were designed and prepared. The results indicated that the addition of HfO2 significantly increased the high-temperature strength and slightly improved the room-temperature plasticity of the NiAl matrix due to the design of the appropriate content, size and distribution of HfO2. The NiAl-9HfO2 (in wt.%) exhibited the most excellent mechanical properties with the compressive yield strength of 351.1 MPa at 1200 °C as well as the compressive yield strength of 1316.8 MPa and ultimate compression deformation of 25.8% at room temperature. The strengthening and toughening mechanisms of HfO2 on NiAl matrix were discussed in details, and the Orowan strengthening mechanism was emphasized.

Relationship and mechanism between double cold rolling-aging process, microstructure and properties of Cu–Ni–Si alloy prepared by two-phase zone continuous casting

Developing Cu–Ni–Si alloy with high strength and high electrical conductivity is a key issue in the electrical conductor industries. The C70250 copper alloy was prepared by two-phase zone continuous casting (TZCC) technology first, and then carried out by double cold rolling-aging process. The relationship between different double cold rolling-aging processes, microstructure, mechanical properties and electrical conductivity of the alloy was studied in detail, the mechanism was revealed. The results show that the C70250 copper alloy strip fabricated by TZCC technology can be subjected to large deformation double cold rolling-aging treatment. When the alloy is primary cold rolled by 97.5% reduction rate, primary aged at 400 °C for 30 min, second cold rolled by 60% reduction rate, second aged at 400 °C for 45 min, the tensile strength and electrical conductivity of the alloy can reach 879 MPa and 48.9% IACS respectively, owning excellent comprehensive properties. The Ni2Si phases inside C70250 copper alloy after primary aging effectively pin dislocations during the secondary cold rolling process, which forms high density dislocation entanglement, promotes the further precipitation of Ni2Si phase during the process of secondary aging, and finally produces a large number of fine, dispersed, multi-scale mixed and evenly distributed Ni2Si phases, the increase of alloy strength is mainly ascribed to dislocation and Orowan strengthening effect. Solute atoms inside the C70250 copper alloy get adequately precipitated after large deformation double cold rolling-aging treatment, the recrystallization is delayed, and the fibrous microstructure along the rolling direction is produced, the scattering effect of transverse grain boundaries and solute atoms on electrons is significantly reduced, which is helpful to improve the electrical conductivity of the C70250 copper alloy.