In this study, the MgO-coated graphene nanoplatelets (GNP)-reinforced aluminum matrix AlSi10Mg composites are fabricated by mechanical alloying and a 3D printing process. The interfacial structure of GNPs–Al has been investigated using high-resolution transmission electron microscopy, and their strengthening mechanism has been analyzed. A weak amorphous Al2O3 was found at the GNP–Al interface area in the composites made with uncoated GNPs. The structure of amorphous Al2O3 becomes distorted when load transfer is initiated, causing the detachment of GNPs from the matrix. This results in quick failure at the interface between uncoated GNPs and aluminum, restricting its overall strength. Once GNPs are coated with MgO, an Al/C mixing zone forms at the contact area, resulting in increased interface strength. The MgO coating on the GNP serves as a protective barrier, preventing the creation of a weaker amorphous Al2O3 layer at the interface and facilitating direct interaction between the GNP and Al matrix. The stress–strain curve demonstrates a 27.5% enhancement in tensile strength in the MgO-coated GNP–Al composite compared to the composite with uncoated GNPs. The strength is increased while maintaining toughness through load transmission of GNPs, bridging, and enhancing dislocation storage capacity by the Mg-rich phase. This study offers a new reference for strengthening 3D-printed aluminum alloys using GNPs.
I. INTRODUCTION
Aluminum (Al) and its alloys are widely employed in diverse industries such as transportation, aircraft, energy, and power.1,2 The growing recognition of Al is due to its beneficial features, including its relatively low density, high specific strength, great heat conduction, strong electrical conductivity, and anti-corrosion properties.3 Aluminum-based lightweight metals possess qualities that make them particularly appealing for innovative engineering applications that demand robustness and durability.4 The AlSi10Mg alloy stands out among the many types of aluminum alloys due to its extensive application in additive manufacturing. The AlSi10Mg produced via laser powder bed fusion (LPBF) demonstrates ∼25% improvement in tensile strength compared to alloys cast using traditional methods.5–7 Hence, the AlSi10Mg alloy exhibits considerable promise for use in the automotive and aerospace domains.8,9 Nevertheless, its comparatively lower strength in comparison to titanium, iron, and nickel-based alloys hinders its extensive utilization in industrial settings.10
In order to alleviate this problem, researchers have been investigating the integration of supplementary phase elements as reinforcements in AlSi10Mg components. This strategy seeks to augment the durability of these metallic components, unleashing their whole capacity for extensive industrial utilization.11–14 Graphene nanoplatelets (GNPs) or graphene nanosheets (GNSs), which are made up of multilayer graphene, have exceptional mechanical capabilities and a 2D geometric feature. As a result, they have great promise for enhancing the strength of materials.15–18 Nevertheless, the untapped capacity for enhancing the strength of GNPs has not been ultimately used, and the resulting composites have exhibited limited ductility. This is mostly attributed to the aggregation of GNPs and the poor bonding between aluminum and GNPs. More precisely, the clusters of GNPs might serve as regions where stress accumulates, leading to the formation of cracks when the material is subjected to external forces. This ultimately results in the composites failing prematurely. Furthermore, the inadequate capacity of GNPs to moisten Al surfaces results in a weak bond at the interface, hence diminishing the load transfer efficiency of GNPs.19
Efficient load transmission is often acknowledged to require strong cohesion between the reinforcement and matrix interfaces.20 Nevertheless, the interface between Al and GNP is characterized by a lack of coherence and exhibits a weak form of bonding at the interface.21 The transition from van der Waals force bonding to chemical covalent bonding through interfacial reactions has been extensively studied as a method to enhance the interfacial bonding between GNP and Al substrates.22–24 While the interfacial reaction allows for the creation of Al–GNP bonding and greatly enhances the efficiency of load transmission, it poses challenges in terms of precise control.25,26 Furthermore, the interfacial interaction results in the destruction and consumption of GNPs. In order to improve the strength of the link between interfaces, several ways of modifying the interface have been suggested. The development of interfacial carbides (such as Al4C3 and TiC) by specific interfacial reactions can enhance the bonding at the interface and improve the load transfer capacity of GNPs. This is due to the anchoring effect of carbides and the formation of strong chemical bonds at the interface.27–30 Furthermore, the application of nanoparticles to modify the surface of GNPs can enhance the connection between the matrix and GNPs, as well as improve the dispersion of GNPs.31 The modification nanoparticles on the surface of GNPs serve a dual purpose: they prevent the GNPs from clustering together by acting as a spacer, and they connect the GNPs with the matrix by acting as a bridge. Pre-coating GNPs with metals such as Cu and Ni is said to enhance interfacial wettability by facilitating the creation of an interfacial intermetallic phase or binary solid solution.32 However, the adhesion between a pure metal coating (such as Cu) and GNPs may still be weak due to the insufficient capacity of the two materials to spread and make contact with each other. The effectiveness of Ni coating in enhancing the bonding between the matrix and GNPs is higher than Cu coating. This is attributed to the superior wettability and greater contact at the interface with graphene.33
While it is widely recognized that modifying the surface of graphene is a crucial technique for enhancing the wettability of the interface, as it generates a transitional layer that serves as a bridge for load transfer between the matrix and reinforcement, certain studies have discovered that the Al–GNP interface can exhibit greater strength even in the absence of a transitional or carbide layer. Zhang et al.34 utilized friction stir processing (FSP) to fabricate a carbon nanotube (CNT)-reinforced Al matrix composite. The strength of the composites was increased twice by leveraging the direct interaction between CNTs and Al at the interface. The findings indicate that the presence of a transition layer is unnecessary if significant plastic deformation takes place during the manufacturing stage of the composite. Significant plastic deformation may effectively resolve the wetting issue between C and Al, thereby preventing the detrimental effects and reduction of GNPs caused by interfacial reactions during sintering at elevated temperatures.35 Therefore, the fabrication of high-performance Al matrix composites using microplastic deformation is a highly effective approach. Nevertheless, the extensive equipment prerequisites and exorbitant expenses associated with microplastic deformation hinder its widespread implementation in the industrial sector. MgO nanoparticles are desirable reinforcements due to their exceptional thermal and mechanical qualities, as well as their outstanding chemical stability. Previous research has shown that MgO has a partially coherent relationship with the Al matrix, which explains the strong bonding between MgO and Al at the interface. In addition, other studies indicate that MgO particles can be firmly attached to the graphene surface through carbon–oxygen bonds. Consequently, MgO is believed to form a robust interfacial bond with both Al and GNPs. Therefore, in this study, a new strengthening method was employed: coating GNPs with MgO. GNPs were initially coated with MgO using a chemical co-precipitation method. The coated GNPs, referred to as MAGCs, were subsequently added to the AlSi10Mg alloy via mechanical alloying. Finally, the composite samples were fabricated using LPBF (Laser Powder Bed Fusion). Subsequently, the microstructures, mechanical properties, and interfacial characteristics of the composite were analyzed, and the strengthening mechanism was evaluated.
II. MATERIALS AND METHODS
The primary materials utilized in this investigation were aluminum alloy, AlSi10Mg powder (15–53 µm), and GNPs (5–10 nm in thickness, 1–10 µm in lateral size). Based on our prior research, it was found that MMCs containing 1.0 wt. % GNPs exhibit superior mechanical properties and even distribution.36,37 Therefore, the concentration of GNPs was maintained at 1.0 wt. %, producing two distinct kinds of Al–GNP composites. One type of sample was prepared with 1.0 wt. % uncoated GNPs and AlSi10Mg powder (referred to as AGC), while the other kind of sample was prepared with MgO-coated 1.0 wt. % GNP-reinforced AlSi10Mg powder (referred to as MAGC). The GNPs were coated with MgO by a chemical co-precipitation process. The composite powder was created by subjecting 1% GNPs to sonication in an ethanol solution for a duration of 2 h, ensuring a uniform suspension. The suspension was supplemented with aluminum alloy powder and subjected to magnetic stirring for a duration of one hour, resulting in the formation of a slurry mixture. The mixture underwent vacuum drying at a temperature of 70 °C for a period of 12 h. Finally, the powder mixture underwent ball milling for 4 h in an argon atmosphere, forming composite powders. The ratio of balls to powder and the rotational speed were consistently maintained at 10:1 and 250 rpm, respectively. The MAGC powder mixture was developed using an identical process. The composite samples were produced using Laser Powder Bed Fusion (LPBF), a 3D printing technology, with powder-bed equipment (BLT-S200) in a high-purity argon atmosphere. A laser output of 365 W was employed in the experiment. The parameters used for the 3D printing process consisted of a laser spot size (D) of 100 µm, a layer thickness (t) of 30 µm, a hatch spacing (h) of 100 µm, and a hatch style rotation of 90°. A dog-bone-shaped 3D printed sample with dimensions of Φ6 × 170 mm2 was finally obtained. All composite samples underwent T6 heat treatment. The T6 treatment conditions consisted of thermal treatment at 400 °C for 3 h and 150 °C for 24 h. The schematic diagram of the composite fabrication and the SEM micrograph of the constituent powders are depicted in Fig. 1. Transmission electron microscopy (TEM) (JEM-2100) and an energy dispersive spectrometer (EDS) were used to examine the morphology of the GNPs and the interfacial structure of the Al–GNP interface. The microstructure and fracture morphology of the composites were examined by the utilization of a FESEM (ZEISS) and an energy dispersive spectrometer (EDS). The materials were subjected to a tensile test at ambient temperature using a universal testing machine (Instron 5985). The specimens were subjected to three tests conducted at a strain rate of 5 × 10−4 s−1. The interfacial strengthening mechanism of the composites was investigated by high-resolution transmission electron microscopy (HRTEM), fast Fourier transform (FFT), IFFT, and geometrical phase analysis (GPA).
Schematic diagram of the composite fabrication process and powder microstructure.
Schematic diagram of the composite fabrication process and powder microstructure.
III. RESULTS AND DISCUSSION
A. Microstructural analysis of the GNP–Al interface
The impact of the Mg element on the microstructure of GNP–Al composites is examined by comparing TEM images of AGCs and MAGCs, where typical folded GNPs are highlighted as shown in Fig. 2. The AGCs are represented in Figs. 2(a) and 2(c), and the MAGCs in Figs. 2(b) and 2(d). In the AGCs where uncoated GNPs are added, a distinct black phase was seen separating the GNPs from the Al matrix, as indicated by the green arrow in Fig. 2(a). When using MgO-coated GNPs, the black phase between the GNPs and the Al matrix went away, and a gray–white phase was detected near the GNPs, as indicated by the red arrow in Fig. 2(b). Figures 2(c) and 2(d) display the microstructures of tiny uncoated and coated GNPs in AGCs and MAGCs. The uncoated GNPs in Fig. 2(c) are in close proximity to the aluminum matrix in an encapsulated form. At this stage, the GNPs do not show the lamellar or folded structure that was shown in the GNPs in Fig. 1. In addition, the MgO-coated GNPs made direct contact with the Al matrix without any obstructions, as shown in Fig. 2(d). The microscopic structure of the GNPs remains similar to the original GNP powder observed in Fig. 1, with a flaky or folded form. When coated with MgO, unimpeded direct contact is established between GNPs and the Al matrix, resulting in less structural damage to the GNPs. Previous investigations have shown that the brittle rod-like aluminum carbide (Al4C3) is commonly found in GNP-reinforced Al-composites, resulting from the Al–C contact reaction.26 Structural defects in GNPs are more likely to trigger the Al–C interface reaction, leading to an increase in Al4C3 and the depletion of GNPs. Studies have demonstrated that the transiently elevated temperatures produced during manufacturing are effective in preventing the generation of Al4C3 and that Mg elements can also impede the Al–C reaction. Because of the high temperature generated during 3D printing and the presence of magnesium in the aluminum alloy AlSi10Mg, Al4C3 is not detected surrounding the GNPs in AGCs and MAGCs.
TEM photograph showing the interface state of the composite: (a) and (c) uncoated GNP–Al composite (AGCs) and (b) and (d) MgO-coated GNP–Al composite (MAGCs).
TEM photograph showing the interface state of the composite: (a) and (c) uncoated GNP–Al composite (AGCs) and (b) and (d) MgO-coated GNP–Al composite (MAGCs).
High-resolution transmission electron microscopy (HRTEM) is used to describe the GNP–Al interface, and element distribution is measured by EDS in order to study the interfacial structure in both materials. The findings that correspond to Figs. 2(a) and 2(b) are displayed in Figs. 3(a) and 3(b), respectively. A high-brightness zone can be seen in the AGCs of Fig. 3(a) between the GNPs and the Al matrix, suggesting a significant level of atomic concentration between the GNPs and Al. Furthermore, there is a substantial quantity of O-rich phase between the GNPs and Al, according to the elemental analysis of EDS. Figure 3(i) shows the HRTEM image of the region (i) in Fig. 3(a). Figure 3(i) shows a sandwich-like interface made of three materials. Fast Fourier transform (FFT) analysis was performed at points (ii), (iii), and (iv) in Fig. 3(i) to examine this interfacial material and its organization in the interface; the findings are shown in Figs. 3(ii)–3(iv) correspondingly. Region (iii) displays amorphous phase diffraction, whereas regions (ii) and (iv) display Al matrix and GNPs, respectively, with regular atomic structures. This is in accordance with what Liu et al. found.38 Hence, amorphous Al2O3 may be recognized as the O-rich phase that was seen between the GNPs and the Al matrix. Previous research indicates that the amorphous Al2O3 has worse mechanical characteristics, which weaken the GNP–Al interface’s strength and cause the composite components to break earlier than expected.25,39 Thus, the existence of amorphous Al2O3 at the interface region of the produced AGCs in the current investigation could have a significant impact on the mechanical properties of the composite that we will examine in the subsequent paragraphs.
Al–GNP interface state: (a) elemental distribution of GNPs in AGCs, (i) HRTEM image of region (i) in (a), (ii)–(iv) FFT and IFFT results of the corresponding region stated in (i), (b) elemental distribution of GNPs in MAGCs, (v) and (vi) SAED image and EDS results of region (v) in (b), (vii) HRTEM image of region (vii) in (b).
Al–GNP interface state: (a) elemental distribution of GNPs in AGCs, (i) HRTEM image of region (i) in (a), (ii)–(iv) FFT and IFFT results of the corresponding region stated in (i), (b) elemental distribution of GNPs in MAGCs, (v) and (vi) SAED image and EDS results of region (v) in (b), (vii) HRTEM image of region (vii) in (b).
The elemental mapping of GNPs in MAGC is depicted in Fig. 3(b). Due to the thinness of the GNPs, the C element concentration in Fig. 3(b) is not readily apparent. Consequently, the GNPs in the region indicated as (v) in Fig. 3(b) undergo SAED calibration, and the outcomes are displayed in Fig. 3(v). The findings from the point scan indicate that the C elements exhibit a higher concentration in the region denoted as (v), as shown in Fig. 3(vi). Hence, the twisted phases shown in Fig. 3(b) can be classified as GNP. The elemental mapping using EDS indicates no consistent increase in O elements between the GNP and the Al matrix. Nevertheless, the presence of Mg elements, in conjunction with O, is observed in the periphery of the GNPs, suggesting the existence of MgO at the interface of MAGCs. The presence of MgO is further confirmed by the HRTEM image of the area (vii) in Fig. 3(b). The presence of MgO coating on the GNP serves as a protective barrier, inhibiting the development of an oxygen-rich area and interfering with the production of a less robust amorphous Al2O3 layer between the GNPs and Al matrix. Therefore, the matrix and reinforcement establish a direct connection, which substantially impacts the composite's strengthening process and mechanical characteristics.
Furthermore, to assess the strength of the interface between MgO-coated GNP–Al composites (MAGCs), the interface was examined and evaluated using HRTEM and geometrical phase analysis (GPA) both prior to and following the application of a tensile load, as shown in Fig. 4. Research findings indicate that the presence of geometrically essential dislocations in the aluminum matrix around GNPs can be attributed to the significant disparity in coefficients of thermal expansion (CTE) between GNPs and aluminum.40 The dislocation density inside the aluminum matrix undergoes a reduction following T6 heat treatment, mostly attributed to the annihilation and rearrangement of dislocations that occur throughout the aging process. Prior to the tensile test, it was observed that the interface between GNP and Al exhibited a relatively flat surface, and the strain within the Al matrix at the Al–GNPs interface was found to be below 7% [Figs. 4(a-i)–4(a-iii)]. Following the tensile test, significant strains over 20% are seen at the interface between Al and GNP, suggesting a robust bonding between the GNPs and Al interface, as depicted in Figs. 4(b-i)–(b-iii).
TEM photograph showing the Al–GNP interfacial structure of MAGCs: (a) before tensile testing, (a-i)–(a-iii) the strain field of εxx, εxy, and εyy corresponding to (a), and (b) after tensile testing, (b-i)–(b-iii) the strain field of εxx, εxy, and εyy corresponding to (b).
TEM photograph showing the Al–GNP interfacial structure of MAGCs: (a) before tensile testing, (a-i)–(a-iii) the strain field of εxx, εxy, and εyy corresponding to (a), and (b) after tensile testing, (b-i)–(b-iii) the strain field of εxx, εxy, and εyy corresponding to (b).
Based on the preceding study, it has been shown that the application of an energy level of about 6 eV results in the breach of the migration barrier by Al atoms, leading to their movement toward the GNP.41 The movement of Al atoms toward the GNPs results in the creation of a deformation region between the GNPs and the aluminum matrix. This interfacial deformation subsequently leads to an augmentation in interfacial adhesion.42 The ongoing migration of aluminum atoms into the GNPs resulted in an augmentation of the irregular surface structure of the GNPs. This is supported by the observed strains in the GNPs prior to tensile testing.
In order to conduct a more comprehensive examination of the interfacial structure and strengthening process at the interface between MgO-coated GNP and Al, an IFFT analysis was carried out. Figure 5 displays the HRTEM results of the chosen interface area and the IFFT results of MAGCs before and after the tensile test. At the interface area of the MAGCs, a significant Al–C mixed zone is found. Figure 5(a) displays an HRTEM image that exhibits a flat and uncracked interface region composed of Al and C. The IFFT picture exhibits a distinct lattice distortion zone between the GNP and Al prior to the tensile test. The distortion zone is comprised of a combination of Al and C atoms that are organized in an inconsistent manner. Following the tensile test, the interface between GNP and Al exhibits deformation and cracking, as shown in Fig. 5(b). Nevertheless, lattice-distorted areas consisting of mixed Al and C atoms are evident in the GNP–Al, displaying similarities to the regions identified prior to tensile testing. Previous research findings indicate that the introduction of a limited quantity of flaws and deformations on the surface of GNPs can result in a fivefold increase in the adhesion between GNP and Al.43 It is evident that the application of MgO coating disrupts the production of oxygen and demonstrates a robust adhesive force at the contact. The observed robust adhesive force at the interface between MgO-coated GNP and Al can be attributed to the presence of the Al–C mixed zone and the non-uniform morphology of the GNPs. Research has shown that when the distance between Al atoms and C atoms is smaller than the combined radii of both atoms, the electron cloud that overlaps can result in the creation of chemical bonds between the Al and C atoms.44 Therefore, it is quite probable that a substantial quantity of Al–C bonds are present in the interface area, resulting in a significantly greater strength of the GNP–Al contact than previously documented. Typically, the formation of Al–C compounds (Al4C3) occurs at the interface area and persists until the carbon supply is fully depleted.45 The transient elevated temperatures resulting from the Laser Powder Bed Fusion (LPBF) technique are adequate to impede the synthesis of Al4C3.46 Laser bed fusion induces the formation of a densely interconnected Al–C mixed zone at the interface between the MGO-coated GNPs and the Al matrix, as shown in Fig. 5. This process prevents the depletion of GNPs by Al4C3 and facilitates robust interfacial bonding.
TEM micrograph of GNP–Al interfacial structure of MAGCs: GNPs–Al interface and corresponding IFFT results (a) before tensile test and (b) after tensile test. [(a) Smooth interface, (b) cracked interface, and (i) and (iii) mixed zone].
TEM micrograph of GNP–Al interfacial structure of MAGCs: GNPs–Al interface and corresponding IFFT results (a) before tensile test and (b) after tensile test. [(a) Smooth interface, (b) cracked interface, and (i) and (iii) mixed zone].
B. Tensile strength analysis
The stress–strain curve (s–s curve) for AGCs and MAGCs, as well as the tensile fracture surfaces of both materials, are depicted in Fig. 6. The MAGCs have a greater ultimate tensile strength (UTS) compared to the AGCs. In comparison to the weakly interface bonded AGCs, the average value of UTS exhibits a notable increase of about 27.8%, rising from 348 to 445 MPa. Typically, the enhancement in strength frequently accompanies a reduction in plasticity.41 GNPs are often found at grain boundaries in Al–GNP composites, and the primary factor leading to plasticity deterioration during strength augmentation is stress concentration at these grain boundaries. Nevertheless, in this study, the improvement of UTS did not result in a rapid reduction in plasticity.
(a) Stress–strain (s–s) curves of AGCs and MAGCs, (b) tensile fracture surface of AGCs, and (c) and (d) tensile fracture surface of MAGCs.
(a) Stress–strain (s–s) curves of AGCs and MAGCs, (b) tensile fracture surface of AGCs, and (c) and (d) tensile fracture surface of MAGCs.
Figures 6(b)–6(d) depict the tensile fracture surfaces of AGCs and MAGCs, respectively. Figure 6(b) illustrates the pull-out of GNPs from the Al matrix on the fracture surface. Load transfer disrupts the weaker structure of amorphous Al2O3, resulting in the separation of GNPs from the matrix and the quick failure of the GNP–Al interface. Upon the application of MgO coating to the GNPs, the occurrence of GNP bridging and fracture becomes evident on the fracture surface, as depicted in Figs. 6(c) and 6(d). This observation suggests a seamless transmission of load between the Al matrix and the GNP reinforcement. The presence of MgO coating on the GNP serves as a protective barrier, impeding the development of a less robust amorphous Al2O3 layer between the GNP and the Al matrix. This, in turn, facilitates a direct interface between the matrix and reinforcement.
Moreover, establishing the Al–C mixing zone leads to an augmentation in the bonding between the GNP and the Al matrix. Consequently, the GNPs exhibit a delayed detachment from the Al matrix instead of persisting in their reinforcement by bridging until they ultimately fracture.47,48 The presence of coordinated deformation ability in the composites during load transfer can be attributed to the creation of Al–C mixed zones resulting from powder bed fusion, as evidenced by the bridging of the GNPs. These variables greatly enhance the strength of the composites while preventing a rapid decline in plasticity.
Figure 7 depicts the schematic diagram illustrating the strengthening mechanism in the MgO-coated GNPs–Al composites (MAGCs). The raw GNP granules include small quantities of O2, and there is an inevitable tiny layer of Al2O3 on the surface of the raw Al powders. Hence, the composites have an amorphous layer of Al2O3 around the GNPs, effectively isolating the GNPs from the Al matrix [Fig. 3(a)]. The MgO layer facilitates direct interaction between the GNP and Al by inhibiting the formation of Al2O3 [Fig. 3(b)]. With the effect of laser powder bed fusion, a mixed zone of Al–C atoms is formed at the interface of MgO-coated GNPs and the Al matrix, which enhances the bonding of the GNPs with the Al matrix (Fig. 5). A comparative analysis of the mechanical properties exhibited by GNPs on the fracture surfaces of AGCs and MAGCs shows that the interface between GNPs and Al, which is directly connected, demonstrates a superior rate of strengthening (in the case of MAGCs). Under the influence of external forces, the delicate amorphous Al2O3 material poses an obstruction to the transfer of load between the GNP and the Al matrix. Consequently, this results in rapid deterioration of the interfacial structure as the GNPs detach from the aluminum matrix. In contrast, the MAGCs coated with MgO exhibit a robust load transmission mechanism. The GNPs covered with MgO demonstrate fracture and bridging phenomena at the fracture surface, indicating robust interfacial bonding. According to Chen et al.,49 the effectiveness of carbon material pullout in strengthening is comparatively lower than that of fracture due to the constraints imposed by the strength of interfacial bonding. This is consistent with the findings presented in this study.
Schematic diagram of the interface strengthening mechanism of MgO-coated GNP–Al composites (MAGCs).
Schematic diagram of the interface strengthening mechanism of MgO-coated GNP–Al composites (MAGCs).
IV. CONCLUSIONS
This study aimed to evaluate the impact of MgO-coated GNPs on the enhancement of interface strength in a 3D-printed Al–GNP composite. A thorough examination was conducted to assess the strengthening mechanism of the Al–GNP composite and to enhance the interfacial structure. Several conclusions can be inferred.
The formation of a brittle amorphous Al2O3 layer between the GNP and the Al matrix, resulting from the interference of O2 and the initial oxide layer, has a negative impact on the reinforcing strength of the GNPs.
The interfacial binding strength between GNPs and Al was diminished by the presence of an amorphous Al2O3 layer. Consequently, the weak interfacial bonding resulted in the fast detachment of GNPs from the Al matrix, demonstrating the phenomenon of GNP pull-out.
By decorating the GNPs with MgO, the amorphous Al2O3 formation was restricted, creating a direct bond between Al and GNP.
The presence of MgO coating on the GNP serves as a protective barrier, inhibiting the development of an oxygen-rich area and interfering with the production of a less robust amorphous Al2O3 layer between the GNP and Al matrix. Therefore, the matrix and reinforcement establish a direct connection, which has a substantial impact on the composite's strengthening process and mechanical characteristics.
AUTHOR DECLARATIONS
Conflict of Interest
The authors have no conflicts to disclose.
Author Contribution
Dewan Muhammad Nuruzzaman: Conceptualization (equal); Investigation (equal); Writing – original draft (equal). AKM Asif Iqbal: Funding acquisition (equal); Project administration (equal); Supervision (equal); Writing – review & editing (equal). Md. Nurul Islam: Resources (equal); Validation (equal); Writing – review & editing (equal). A. K. M. Parvez Iqbal: Methodology (equal); Writing – original draft (equal).
DATA AVAILABILITY
The data that support the findings of this study are available from the corresponding author upon reasonable request.