Synergistic strengthening mechanism of copper matrix composite reinforced with nano-Al2O3 particles and micro-SiC whiskers

Huanran Lin; Xiuhua Guo; Kexing Song; Jiang Feng; Shaolin Li; Xiangfeng Zhang

doi:10.1515/ntrev-2021-0006

Article Open Access

Synergistic strengthening mechanism of copper matrix composite reinforced with nano-Al₂O₃ particles and micro-SiC whiskers

Huanran Lin , Xiuhua Guo , Kexing Song , Jiang Feng , Shaolin Li and Xiangfeng Zhang

Published/Copyright: March 1, 2021

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From the journal Nanotechnology Reviews Volume 10 Issue 1

Abstract

Although Cu–Al₂O₃ composites have good comprehensive performance, higher mechanical properties and arc erosion resistance are still required to meet heavy-duty applications such as electromagnetic railguns. In this work, a novel hybrid SiC_w/Cu–Al₂O₃ composite was successfully prepared by combining powder metallurgy and internal oxidation. The microstructure and mechanical behavior of the SiC_w/Cu–Al₂O₃ composite were studied. The results show that nano-Al₂O₃ particles and micro-SiC_w are introduced into the copper matrix simultaneously. Well-bonded interfaces between copper matrix and Al₂O₃ particles or SiC_w are obtained with improved mechanical and arc erosion resistance of SiC_w/Cu–Al₂O₃ composite. The ultimate tensile strength of the SiC_w/Cu–Al₂O₃ composite is 508.9 MPa, which is 7.9 and 56.1% higher than that of the Cu–Al₂O₃ composite and SiC_w/Cu composite, respectively. The strengthening mechanism calculation shows that Orowan strengthening is the main strengthening mechanism of the SiC_w/Cu–Al₂O₃ composite. Compared with Cu–Al₂O₃ composite, the hybrid SiC_w/Cu–Al₂O₃ composite has lower arc time and energy and better arc stability.

Graphical abstract

Copper matrix composites reinforced with nano-Al₂O₃ particles and micro-SiC whiskers were prepared. Nano-Al₂O₃ particles are uniformly dispersed in the copper matrix (Figure a), and there is an obvious amorphous transition layer at the interface between the copper matrix and SiC_w (Figure d). Nano-Al₂O₃ particles and micro-SiC whiskers reinforcing phase synergistically strengthen the SiC_w/Cu–Al₂O₃ composite.

Keywords: SiC whiskers; nano-Al2O3 particles; SiCw/Cu–Al2O3 composite; mechanical properties; synergistic strengthening effect

1 Introduction

Cu–Al₂O₃ composites have a wide range of applications in electrical contact due to their excellent conductivity [1] and high strength at elevated temperatures. For example, in the electromagnetic railguns system, the guide rail is seriously worn and partly melted due to the high projectile launching speed and driving current of the armature/guide rail system [2]. This kind of equipment puts forward higher requirements on mechanical properties [3], current-carrying friction and wear resistance, and arc erosion resistance of materials [4]. However, the commercial Cu–Al₂O₃ composites cannot meet the above requirements, and copper matrix materials used in the guide rail with better mechanical and electrical erosion resistance are still not developed.

Recently, hybrid copper matrix composites with two or more reinforcing phases have present better performance compared with the copper matrix composites reinforced by a single reinforcement [5]. And, the reported papers on synergistic reinforcements are mainly focused on CNTs [6]; Cr [7] and WC particles [8] strengthened the Cu–Al₂O₃ composite [9]. For example, Zhang et al. [10] reported that the ultimate tensile strength of a Cu–Al₂O₃–La composite was 309 MPa. Pan et al. [11] found that the ultimate tensile strength (345 MPa) of Cu–6.1 vol% CNTs–1.2 vol% Al₂O₃ composite was 41.1% higher than that of Cu-CNTs composite. Singh and Gautam [12] discovered that the ultimate tensile strength of Cu–0.5 vol% WC–5.0 vol% Al₂O₃-2.4 vol% Cr composite (385 MPa) was 71.9% higher than that of pure copper (224 MPa). Although the addition of particles or whiskers is beneficial to improve the mechanical properties of Cu–Al₂O₃ composites, their ultimate tensile strength are still under 400 MPa [13]. The reason for the low mechanical property is the poor interface bonding between reinforcements and copper matrix, in which the reinforced phases are introduced into the copper matrix by a common powder metallurgy process [14]. However, hybrid copper-based materials with high mechanical properties fabricated by in-situ synthesis have not yet been reported.

Currently, SiC_w has become a potential reinforcement phase in copper-based materials, which has the advantages of low density [15], high strength [16], corrosion resistance [17], and high-temperature stability [18]. The object of this work is to develop a novel SiC_w/Cu–Al₂O₃ composite with well-bonded interfaces between copper matrix and reinforcements. And, the preparation procedure combined powder metallurgy and internal oxidation, and the nano-Al₂O₃ particles and micro-SiC_w were introduced into the copper matrix simultaneously. The well-bonded interfaces between copper matrix and Al₂O₃ particles or SiC_w are obtained with improved mechanical and arc erosion resistance. The strengthening mechanisms of the SiC_w/Cu–Al₂O₃ composite were calculated and discussed. The fabrication procedures and experimental results can provide a reference for the design and preparation of high-performance copper matrix composites.

2 Experiment

2.1 Materials and methods

The raw materials used in the preparation of composites are Cu–0.2 wt% Al alloy powders (99.6% purity, the median particle size of 40 µm, Hunan Huabang Powder Material Co., Ltd), Cu₂O powders (provide oxygen for internal oxidation, 99.8% purity, the median particle size of 1 µm, Shanghai Xiangtian Nano Materials Co., Ltd), and SiC whiskers (98% purity, 5–10 µm length and 0.5 µm diameter).

The experimental procedures were as follows: first, mixing of powders was performed. Cu–0.2 wt% Al alloy powder, Cu₂O powder, and SiC_w were mixed in appropriate proportions. The powders were blended by a QQM/B light ball mill for 16 h at 35 rpm and a ball-to-powder ratio of 5:1. Note that to realize the complete internal oxidation of Al to produce Al₂O₃ in the subsequent internal oxidation process, the mass ratio of Cu₂O powder to Cu₂O powder is calculated to be 1.1:1 [19] (M(Cu–0.2 wt% Al):M(Cu₂O) = 56.8:1). Second, cold isostatic pressing was performed. The mixed powders were pressed into cylindrical samples (Φ50 × 40 mm) in LDJ200/600-300 cold isostatic press at a pressure of 210 MPa and held for 10 min. Third, sintering was performed. The obtained cylindrical samples were sintered in a tube furnace protected by argon at 950℃ for 3 h. (Nano-Al₂O₃ particles were formed in the chemical reaction of internal oxidation, and the specific process has been reported in ref. [20]). Finally, the sintered samples were put into a ZT-200-22Y vacuum sintering furnace under a hydrogen–argon atmosphere and kept at 900℃ for 2 h for reduction. To further improve the relative density of the copper matrix composites, the sintered samples were put into a YA32-315 four-column hydraulic press for hot extrusion, the extrusion ratio was 10:1, and bars with a diameter of 15 mm were obtained. For comparison, the Cu–Al₂O₃ composite, the SiC_w/Cu composite, and the pure copper were prepared under the same conditions. The specific composition is listed in Table 1.

Table 1

Composition of copper matrix composites (vol%)

Materials	Cu	Al₂O₃	SiC_w
Cu	100	—	—
SiC_w/Cu	95.3	—	4.7
Cu–Al₂O₃	99.1	0.9	—
SiC_w/Cu–Al₂O₃	94.4	0.9	4.7

2.2 Material characterization

The microstructures of composites were observed by inverted metallurgical microscopy (DMi8C, Leica Microsystems Inc). The transmission electron microscopy (TEM) samples were polished by a precision polishing system (GATAN691, USA), and the interface between the matrix and reinforcing phase was characterized by high-resolution transmission electron microscopy (HR-TEM; JEM-2100, JEOL, Japan). The grain size of the copper matrix composites was analyzed by field-emission scanning electron microscopy (FE-SEM; JSM-7800F, JEOL, Japan).

2.3 Performance tests

To evaluate the tensile strength of the composites, the samples were processed into rod-shaped tensile samples with a diameter of 5 mm and a gauge length of 25 mm. The tensile tests were performed by a tensile testing machine (AUTOGRAPH AG-I 250KN, Japan) by stretching along the extrusion direction with a tensile strain rate of 0.5 mm/min. Tensile fractures were analyzed by scanning electron microscopy (SEM; JSM-IT100, JEOL, Japan).

Electrical contact tests were carried out by an electrical contact tester (JF04C, Kunming Institute of Precious Metals, China) shown in Figure 1. As-extruded samples were processed into electrical contact samples with a diameter of 3.8 mm and a length of 10 mm. Each contact pair was tested for 5,000 operation times under resistance load, with a voltage of 24 V DC, a current of 15 A, an average contact force of 50 cN, and an electrode spacing of 2 mm. Data on arc energy and arcing duration were automatically recorded by the JF04C test system. The arc erosion morphologies of the cathode and anode contacts were observed by SEM (JSM-IT100, JEOL, Japan).

Figure 1

Schematic of JF04C electrical contact test apparatus.

3 Experimental results and discussion

3.1 The microstructure of the SiC_w/Cu–Al₂O₃ composite

The metallographic structures of pure copper, the Cu–Al₂O₃ composite, and the SiC_w/Cu–Al₂O₃ composite are presented in Figure 2. Comparing Figure 2a with Figure 2b shows that the grain size of the Cu–Al₂O₃ composite is smaller than that of pure copper, which indicates that Al₂O₃ particles are formed in the process of internal oxidation and can inhibit grain growth. Figure 2b and c show that compared with the Cu–Al₂O₃ composite, the grain size of the SiC_w/Cu–Al₂O₃ composite has no obvious decrease, which indicates that the addition of SiC_w has a certain influence on the grain size change but has little effect. Figure 2d shows that the SiC whiskers are arranged in an orderly manner and distributed along the extrusion direction without large-area agglomeration.

Figure 2

Microstructure of pure copper and its composites: (a) pure copper, (b) Cu–Al₂O₃, (c) cross-sectional microstructure of SiC_w/Cu–Al₂O₃, and (d) longitudinal-section microstructure of SiC_w/Cu–Al₂O₃.

Figure 3 shows the high-resolution transmission electron microscopy (HR-TEM) images of the SiC_w/Cu–Al₂O₃ composite. Figure 3a shows that γ-Al₂O₃ particles with a particle size of 3–8 nm are uniformly dispersed in the copper matrix, with an average particle spacing of 50 nm. Fine nano-Al₂O₃ particles are more conducive to pinning dislocations, hindering dislocation movement and grain boundary slip and thus improving the strength of composites [21]. Figure 3b is an Inverse Fast Fourier Transform (IFFT) image of the area in the yellow dotted box in Figure 3a. The interface between γ-Al₂O₃ and the copper matrix is flat, and there are no physical gaps at the interface and no compounds produced by adverse reactions. The HR-TEM image of the interface between SiC_w and the copper matrix in Figure 3d shows that there is an obvious amorphous transition layer at the interface between the copper matrix and SiC_w. This is because Si atoms in SiC diffuse into the copper matrix, leaving only a layer of carbon at the interface between the copper matrix and SiC_w [22]. This can also be proven by the existence of an amorphous diffuse scattering halo in the FFT diagram in the lower-left corner of Figure 3d. Meanwhile, the SAD pattern in the upper right corner Figure 3d shows the SiC diffraction spots, proving that the whiskers used are β-SiC. Compared with α-SiC, β-SiC has better hardness, tensile strength, elastic modulus, and high-temperature resistance, which is more conducive to improve the tensile strength of composites [23]. It is generally believed that the rough or bamboo-like surface of whiskers can increase the friction between whiskers and the matrix, thus improving the interfacial bonding strength [24]. Excessive interfacial strength leads to the fracture of whiskers and copper matrix composites during stretching, which limits the contribution of the whisker pull-out effect to the toughness of copper matrix composites [25]. The amorphous ribbon transition layer formed at the interface between the copper matrix and SiC_w can reduce the interfacial bonding strength, reduce the shear stress that needs to be overcome when whiskers are pulled out, facilitate whisker pulling out, and play an obvious role in improving the tensile strength and toughness of the composite [26].

Figure 3

TEM images of the SiC_w/Cu–Al₂O₃ composite: (a) HR-TEM image of nano-Al₂O₃ particles, (b) IFFT image of the boxed area in (a), (c) TEM cross-sectional image of SiC_w, and (d) HR-TEM image of the boxed area in (c).

3.2 Mechanical properties and fracture morphology of the SiC_w/Cu–Al₂O₃ composite

Figure 4 shows the engineering tensile stress–strain curves of pure copper and its composites. In summary, compared with pure copper, the strength of the SiC_w/Cu composite is not greatly improved by adding a single reinforcing phase of SiC_w, but the tensile strength of the SiC_w/Cu–Al₂O₃ composite is greatly improved. The addition of the reinforcing phase inevitably led to a decrease in the ductility of the composites [27]. The ultimate tensile strength of pure copper is 228.4 MPa, and the elongation is 50.4%. The ultimate tensile strength of the Cu–Al₂O₃ composite is 471.5 MPa, and the elongation is 15.4%. The elongation of the Cu–Al₂O₃ composite decreased due to uncoordinated deformation between hard Al₂O₃ particles and the copper matrix, with good plasticity during deformation, which indicated that the tensile strength of the composites increased at the expense of elongation [28]. The ultimate tensile strength of the SiC_w/Cu composite is 246.5 MPa, which is not greatly improved compared with that of pure copper, and its elongation is poor, which may be caused by SiC_w agglomeration. The ultimate tensile strength of the SiC_w/Cu–Al₂O₃ composite is 508.9 MPa, and the elongation is 8.5%. Compared with that of the Cu–Al₂O₃ and SiC_w/Cu composites, the tensile strength of the SiC_w/Cu–Al₂O₃ composite is increased by 7.9 and 51.6%, respectively. The further improvement in tensile strength indicates that the effect of the hybrid reinforcement of SiC_w and nano-Al₂O₃ particles is better than that of the composite reinforced by SiC_w or nano-Al₂O₃ particles alone. Hybrid reinforcement can improve the spatial configuration of each reinforcing phase, which is beneficial to fully exploiting the advantages of SiC_w and nano-Al₂O₃ particles and then improve the strength of copper matrix composites [29].

Figure 4

Engineering tensile stress–strain curves of pure copper and composites.

Figure 5 shows the tensile fracture morphology of pure copper and copper matrix composites. The pure copper sample has obvious plastic deformation before fracture, the fracture surface is mainly composed of large and deep dimples and torn edges, and the fracture surface is characterized by a typical micropore aggregation fracture surface, as shown in Figure 5a. Compared with the fracture morphology of pure copper, the dimples of the Cu–Al₂O₃ composite become smaller and shallower, which worsens the plasticity of the composite (Figure 5b). Figure 5c shows the fracture morphology of the SiC_w/Cu composite, and there is a large amount of agglomerated SiC_w at the fracture. Agglomerated SiC_w cannot effectively contact the copper matrix, which reduces the interfacial bonding strength and makes it easier to fall off under the action of an external force, resulting in the lower strength of the SiC_w/Cu composite [30]. The fracture morphology of the SiC_w/Cu–Al₂O₃ composite (Figure 5d) shows that the axial direction of SiC_w is the same as the tensile direction, which hinders grain boundary slip, and there are “SiC_w bridges” and SiC_w pulling out at the crack. The bridging effect of SiC_w can hinder crack propagation and promote crack deflection. Nano-Al₂O₃ particles can inhibit grain growth and promote crack deflection, which is conducive to improve the strength of composites, and dispersed nano-Al₂O₃ particles are beneficial to improve the plasticity of materials [31].

$Figure 5 Tensile fracture morphology of copper matrix composites: (a) Pure copper, (b) Cu–Al2O3, (c) SiCw/Cu, and (d) SiCw/Cu–Al2O3.$

Figure 5

Tensile fracture morphology of copper matrix composites: (a) Pure copper, (b) Cu–Al₂O₃, (c) SiC_w/Cu, and (d) SiC_w/Cu–Al₂O₃.

3.3 Analysis of strengthening mechanism of the SiC_w/Cu–Al₂O₃ composite

There are many strengthening mechanisms in composites, such as grain refinement (GR) [32], Orowan strengthening (OS) [33], load transfer (LT) [34], and thermal mismatch (TM) [35]. Due to the different thermal expansion coefficients of the reinforcing phase and copper matrix, thermal mismatch strengthening occurs in the cooling process of the composite material, but the samples will play a considerable role in thermal mismatch strengthening only during rapid cooling [36]. As the cooling process of this test is furnace cooling or slow cooling, the contribution of thermal mismatch strengthening to the strength of materials is temporarily ignored. Therefore, the strength contribution of the SiC_w/Cu–Al₂O₃ composite mainly comes from grain refinement, Orowan strengthening, and load transfer strengthening.

3.3.1 Orowan strengthening

Research shows that long whiskers with large aspect ratios cannot be effectively surrounded by dislocation loops [37]. Therefore, the contribution of Orowan strengthening to the strength of the SiC_w/Cu–Al₂O₃ composite mainly comes from dispersed nano-Al₂O₃ particles. Dislocation lines cannot cut through hard Al₂O₃ particles directly, but bend gradually under the action of external stress until the dislocation lines at both ends meet to form a closed dislocation loop, and the remaining dislocation lines continue to move forward under the action of external force. The Orowan strengthening equation is as follows [38]:

(1) σ OS = 0.4 G b π 1 − ν 1 L ln D b

where G is the shear modulus (42.1 GPa for Cu [39]), v is the Poisson’s ratio (0.326 for Cu [39]), b is the Burger’s vector (0.256 nm for Cu [39]), L is the particle spacing, and D is the average particle size. According to the calculation, the contribution of the Orowan strengthening mechanism to the strength of the SiC_w/Cu–Al₂O₃ composite is 145.2 MPa. Equation (1) shows that the smaller the distance between particles is the greater the critical shear stress required for dislocation motion. Dislocation loops around particles also hinder the movement of dislocation sources and other dislocations, and further strengthen the copper matrix.

3.3.2 Grain refinement

Figure 2b and c show that the addition of SiC_w and nano-Al₂O₃ particles can obviously refine the grains. Theoretically, SiC_w also hinders the movement of grain boundaries, but in this experiment, the addition of silicon carbide whiskers has little effect on grain size, and nano-Al₂O₃ particles play a major role in grain refinement. To further determine the influence of nano-Al₂O₃ particles and SiC_w on grain size, EBSD analysis was carried out, as shown in Figure 6. The movement of nano-Al₂O₃ particles on the grain boundary of the copper matrix produces Zener resistance, inhibits grain growth, and produces Hall-patch fine grain strengthening, according to the following equation [38]:

(2) σ GR = k ( d c − 1 / 2 − d m − 1 / 2 )

where k is a constant (Cu = 0.07 MPa × m ^0.5 [40]), d _c is the grain size of the SiC_w/Cu–Al₂O₃ composite (d _c = 1.43 μm), and d _m is the average size of pure Cu. The σ _GR value provided by nano-Al₂O₃ particles was calculated to be 35.6 MPa.

Figure 6

EBSD map (IPF) and grain size distributions of copper matrix composites: (a and b) pure Cu, (c and d) Cu–Al₂O_3, and (e and f) SiC_w/Cu–Al₂O₃.

3.3.3 Load transfer

When the load is fully applied and the whiskers arranged along the tensile direction are evenly distributed in the copper matrix, load transfer strengthening can be effectively realized [41]. Whiskers or short fibers are pulled out and broken during stretching. When the length is less than a certain critical length will be drawn out. When the length of SiC_w is less than a certain critical length l _c, the whiskers or short fibers will be pulled out; otherwise, it will break. The critical length can be obtained according to the equilibrium condition of force [42]:

(3) l c = σ SiC w 2 τ y D SiC w ; τ y ≈ σ my 2

where σ SiC w is the tensile strength (20.8 GPa) of SiC_w, D SiC w is the diameter of SiC_w (0.5 µm), τ _y is the matrix shear stress, and σ _my is the yield strength of the Cu matrix (200.1 MPa). According to the calculation, the critical length is 52 μm, which is far greater than the actual length of whiskers; so, SiC_w fails in the form of pulling out during the drawing process, which can be verified from Figure 5d. The strength increase provided by the load transfer strengthening of silicon carbide whiskers can be calculated by the following equation:

(4) σ LT = σ SiC w l 2 l c − σ my f SiC w

where f SiC w is the volume of the reinforcing phase (4.7 vol%). According to equation (4), the contribution of load transfer enhancement to strength is 61.1 MPa. There is a positive correlation between the strength of the composites and the volume fraction of the reinforcing phase; that is, with increasing volume fraction, the strength of the composites increases gradually, but if the volume fraction of the reinforcing phase is too high, the strength of the composites will decrease.

3.3.4 Synergistic strengthening

The total contribution of various strengthening mechanisms in the Cu–Al₂O₃ composite is 370.9 MPa, which is 68.8 MPa less than the actual tensile yield strength (439.7 MPa). The total contribution of various strengthening mechanisms in the SiC_w/Cu–Al₂O₃ composite is 442 MPa, which is 33.9 MPa less than the actual tensile yield strength (475.9 MPa). Therefore, it can be inferred that the addition of SiC_w reduces the difference between the calculated and experimental values of single-reinforced composite (Cu–Al₂O₃) and double-reinforced composite (SiC_w/Cu–Al₂O₃), and nano-Al₂O₃ particles play a positive role in enhancing the load transfer of SiC_w. Liu et al. [43] studied the strengthening mechanism when SiC_w and nanoparticles were added alone or in combination and found that the combination of SiC_w and nanoparticles can change the microstructure of materials, and thus the mechanical properties of composites. Particle-whisker hybrid-reinforced copper matrix composites exert the advantages of each reinforced phase, and at the same time, each component synergistically strengthens copper matrix composites [37]. As seen in Figure 5c, agglomerated SiC_w can be seen in the fracture morphology of the SiC_w/Cu composite, but there is no large area of agglomerated SiC_w in the fracture morphology of the SiC_w/Cu–Al₂O₃ composite in Figure 5d. The synergistic effect is that nano-Al₂O₃ particles can adjust the spatial distribution of SiC_w in the copper matrix and reduce the agglomeration of SiC_w. With the addition of SiC_w, the distribution of nano-Al₂O₃ particles is more uniform, and the spatial configuration is better, as shown in Figure 7. The contact area between dispersed SiC_w and the copper matrix increases, which is beneficial for improving the interfacial bonding strength and reducing the shedding phenomenon caused by the agglomeration of SiC_w during stretching. Nano-Al₂O₃ particles further restrict the shedding and pulling-off of SiC_w and further improve the tensile strength of the SiC_w/Cu–Al₂O₃ composite. The above results show that SiC_w and nano-Al₂O₃ particles have synergistic effects on strengthening copper matrix composites. The difference between the calculated value and the experimental value can be regarded as the contribution value of thermal mismatch and synergistic strengthening mechanism to the strength of the SiC_w/Cu–Al₂O₃ composite, and the contribution ratio to the strength is 7.1%.

Figure 7

Schematic diagram of the particle and whisker hybrid-reinforced SiC_w/Cu–Al₂O₃ composite.

3.4 Arc erosion resistance of the SiC_w/Cu–Al₂O₃ composite

The distributions of arc duration and arc energy data of Cu–Al₂O₃ composite and SiC_w/Cu–Al₂O₃ composite are shown in Figure 8a and b. Arc duration and arc energy have the same fluctuation tendency. The electrical contact test of the Cu–Al₂O₃ composite cannot be continued after 1,500 operations due to the serious oxidation of the contact surface. The SiC_w/Cu–Al₂O₃ composite has good arc stability in the first 2,700 operation times, and the arc duration and arc energy increase sharply in the later stage, but 5,000 operations have been successfully completed. Comparing the arc duration and arc energy of the first 1,500 operation times, it is found that the average arc duration and arc energy of the SiC_w/Cu–Al₂O₃ composite are lower than that of the Cu–Al₂O₃ composite, and the SiC_w/Cu–Al₂O₃ composite has a better arc stability. Therefore, the addition of SiC_w has a more significant effect on reducing the arc duration and energy of the Cu–Al₂O₃ composite.

Figure 8

Fluctuation distribution curves of arc duration (a) and arc energy (b).

Figure 9 shows the surface morphologies of anode and cathode contact materials after arc erosion. Compared with the erosion morphologies of the SiC/Cu–Al₂O₃ composite, the erosion area of the Cu–Al₂O₃ composite is larger. It is found that a large number of molten droplets adhere to the contact surface, which seriously damages the connectivity of the circuit and leads to the failure of the Cu–Al₂O₃ contact pairs. The electrical contact experiment shows that the arc erosion resistance of the Cu–Al₂O₃ composite is far less than that of the SiC_w/Cu–Al₂O₃ composite.

Figure 9

Erosion morphologies of anode and cathode for the Cu–Al₂O₃ composite (a and b) and the SiC_w/Cu–Al₂O₃ composite (c and d).

4 Conclusions

Nano-Al₂O₃ particles and SiC_w can adjust the spatial distribution of each other in the copper matrix, which is more conducive to fully exploiting the advantages of each reinforcing phase. The introduction of high-strength SiC_w can bridge the copper matrix, promote crack deflection, and further improve the tensile strength of copper matrix composites.
Nano-Al₂O₃ particles and micro-SiC_w reinforcements synergistically strengthened the SiC_w/Cu–Al₂O₃ composite. Orowan strengthening is the main strengthening mechanism in the SiC_w/Cu–Al₂O₃ composite, accounting for 30.5%.
The addition of SiC whiskers can improve the arc erosion resistance of the Cu–Al₂O₃ composite. Compared with the Cu–Al₂O₃ composite, the average arc duration and arc energy of the SiC_w/Cu–Al₂O₃ composite were lower, and the arc stability was better.

Funding information: This work was supported by the project of the National Natural Science Foundation of China (51605146, U1502274), Henan Provincial Key Young Teachers Training Program for Higher Education Institutions (2018GGJS045), China Postdoctoral Science Foundation (2020T130172, 2020M682288), Henan Province “Innovative Science and Technology Team” Program (182101510003), and the Key Scientific Research Projects of Higher Education Institutions in Henan Province (21A430014).
Author contributions: All authors have accepted responsibility for the entire content of this manuscript and approved its submission.
Conflict of interest: The authors state no conflict of interest.

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Received: 2021-01-22

Accepted: 2021-02-05

Published Online: 2021-03-01

This work is licensed under the Creative Commons Attribution 4.0 International License.

Articles in the same Issue

https://doi.org/10.1515/ntrev-2021-0006

Keywords for this article

SiC whiskers; nano-Al2O3 particles; SiCw/Cu–Al2O3 composite; mechanical properties; synergistic strengthening effect

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BY 4.0

Synergistic strengthening mechanism of copper matrix composite reinforced with nano-Al2O3 particles and micro-SiC whiskers

Article

Abstract

Graphical abstract

1 Introduction

2 Experiment

2.1 Materials and methods

2.2 Material characterization

2.3 Performance tests

3 Experimental results and discussion

3.1 The microstructure of the SiCw/Cu–Al2O3 composite

3.2 Mechanical properties and fracture morphology of the SiCw/Cu–Al2O3 composite

3.3 Analysis of strengthening mechanism of the SiCw/Cu–Al2O3 composite

3.3.1 Orowan strengthening

3.3.2 Grain refinement

3.3.3 Load transfer

3.3.4 Synergistic strengthening

3.4 Arc erosion resistance of the SiCw/Cu–Al2O3 composite

4 Conclusions

References

Articles in the same Issue

Articles in the same Issue

Articles in the same Issue

Synergistic strengthening mechanism of copper matrix composite reinforced with nano-Al₂O₃ particles and micro-SiC whiskers

3.1 The microstructure of the SiC_w/Cu–Al₂O₃ composite

3.2 Mechanical properties and fracture morphology of the SiC_w/Cu–Al₂O₃ composite

3.3 Analysis of strengthening mechanism of the SiC_w/Cu–Al₂O₃ composite

3.4 Arc erosion resistance of the SiC_w/Cu–Al₂O₃ composite