Effect of individual and hybrid additions of Al2O3 NP and CNTs on the mechanical strengthening of aluminum-bronze alloy
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Aluminum bronze metallic composite (ABMCs) alloys were fabricated via the powder metallurgy technique. The present work has been incorporated an individual as well as hybrid additions of Al2O3 nanoparticles and multiwall carbon nanotubes (CNTs) into ABMCs. Microstructural characteristics and mechanical properties and sliding wear behavior plus some of the physical properties such as density, electrical conductivity, and thermal conductivity of the composite alloys have been studied. Microstructure features were discovered by utilizing FE-SEM and XRD measurements. The addition of 2 wt% of CNTs was caused more uniform distributed refined grains, but the adding of 2 wt% Al2O3 was formed an agglomeration upon the active grain boundaries. Moreover, the yield stress and ultimate tensile strength of AB/Al2O3/CNTs hybrid composite alloy were improved up to ≈ 84% and ≈ 52%, respectively with respect to the plain monolithic alloy. Also, the hybrid addition enhanced both hardness and wear resistance by ≈ 12% and ≈ 189%, respectively. This enhancement may be attributed to the physical synergistic reinforcement of the hybrid addition and improvement of the internal microstructure as well as the Zener pinning effect which restricted the growth of the grains. Additionally, the addition of 2 wt% CNTs enhanced the electrical and thermal conductivity up to \(\approx\) 5.3% and \(\approx\) 22.8, respectively. Because the CNTs creating new conductive paths in the Aluminum bronze alloy.
KeywordsPowder metallurgy Aluminum bronze alloy Hardness Electrical conductivity Wear rate
Aluminum bronze (AB) alloys are deemed as essential materials for the various industrial scopes. These alloys have high mechanical strength, remarkable thermal behavior, good corrosion and wear resistance, as well as less expensive [1, 2]. Currently, AB alloys and their composites are utilized for several parts of automobile manufacturing and military instruments plus operating effectively in high power electronic circuits . Indeed, AB alloys have limited ductility, as well as low reliability, which has restricted their use in the different applications of many technological fields. Moreover, they have a dangerous defect, where their grains coarsening with aging especially at elevated temperatures, so their internal microstructural is unstable . Consequently, the main challenge is how to develop aluminum bronze alloys without loss of their excellent mechanical characteristics and optimum electrical conductivity. It is worth to note that the fusion of Nano-sized particles (NP) is supporting the copper alloys features and increment their mechanical properties without a drop of the else physical properties . Recently, a new approach of research emerged in the field of copper matrix composites (CMCs) after the production of the carbon nanotubes (CNTs) . where the CNTs molecules possess an extraordinary chemical structure where their carbon atoms bonded together by sp2 planner hybridization configuration. Obviously, these bonds have responsible to grant CNTs particles the excellent tensile strength, stellar thermal and electrical conductivity besides its special physical properties [7, 8]. Though, many issues still remain such as the inhomogeneous distribution of CNTs during the mixing process. Also, the little wettability behavior between CNTs and CMCs has a negative effect on thermal stability and reduces their wear resistance . For solving the current issues, Kwon et al. succeeded to incorporate the CNTs with the help of SiC NP which acts as a blending factor with Aluminum powder to obtain uniform distribution [10, 11]. Du et al.  notified that the addition of Al2O3 NP with MMCs/CNTs is increased the interfacial coherence force between CNTs and MMCs due to improving the adhesion force and augmented the wettability behavior. Cui et al. [13, 14] reported the merging of 2 wt% SiC and 11.7 wt% nickel-coated graphite within a bronze alloy enhanced the tribological results due to the strengthening effects of their ingredient. The new strategy has been used to build a hybrid synthesis of TiC and graphite powder to reinforce the CMCs by utilizing the high-power microwave sintering . Koppad et al. announced the thermal and electrical conductivities are decreased after adding the MWCNTs into the Cu matrix . Unfortunately, there are little works that discussed the influence of the individual and hybrid additions of CNTs and Al2O3 NP on the physical characteristics and their strengthening behavior for the aluminum bronze composites. Consequently, a methodical work has been performed to synthesizes the aluminum bronze alloy (Cu-11 wt% Al) via the powder metallurgy technique. Moreover, the aluminum bronze matrix was reinforced by incorporating an individual and hybrid additive of nano-sized Al2O3 particles and Multi-wall carbon nanotubes (CNTs). Additionally, the equipped specimens have been researched to reveal their internal microstructure by field emission scanning electronic microscope (FE-SEM) and X-ray diffraction patterns (XRD). Also, the different physical properties such as hardness, stress–strain behavior, wear characteristics, and electrical conductivity have been examined at room temperature.
2 Experimental work
2.1 The elementary materials
The morphological characteristic of materials is utilized to prepared the composite alloys
Source of materials
Alpha Chemika, Co.
Alpha Chemika, Co.
Sigma Aldrich, Co.
D0 ≈ 25
Nanotech Egypt Co.
L ≈ 35 μm
2.2 Powder metallurgy fabrication of monolithic and composite alloy
2.2.1 Blending, compacting and sintering processes
Chemical composition and concentration (weight%) of studied composite alloys and their abbreviations
Cu-11.0 wt% Al
Cu-11.0 Al-2.0 wt% Al2O3
Cu-11.0 Al-2.0 wt% CNTs
Cu-11.0 Al-1.0 Al2O3-1.0 wt% CNTs
2.3 Microstructural characterization and measurements
3 Results and discussion
3.1 Microstructure and phases characteristics
3.2 Mechanical characteristics
3.2.1 Hardness and density
3.2.2 Tensile stress–strain characteristics
3.3 The sliding wear characteristics
3.4 Electrical and thermal conductivity
The microstructure examination of composite alloys confirmed the presence of α-Cu, Al, and Cu3Al phases were created during the sintering process. The addition of CNTs enhances the distribution and refinement of the grains, otherwise adding of Al2O3 NP agglomerates along the coarse grain boundaries.
The hybrid addition of Al2O3 and CNTs has a great positive effect on microstructure texture and other properties of hybrid alloy.
The density and hardness of AB/CNTs composite alloy has slightly decreased than monolithic AB alloy and other composite alloys due.
The tensile parameters (YS, and UTS) and wear rate of the hybrid composite alloy is improved due to the synergistic reinforcement of CNTs and Al2O3 nanoparticles.
The individual addition of CNTs has exhibited the highest electrical and thermal conductivity comparing to the other composite alloys.
Compliance with ethical standards
Conflict of interest
The authors declare that they have no conflict of interest.
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