Extrusion textures in Al, 6061 alloy and 6061/SiCp nanocomposites

The 6061 alloy matrix composites reinforced with 10 wt.% and 15 wt.% of SiC nanoparticles with an average diameter of ~ 500 nm were hot extruded in strip shape from ball milled powders. The microstructures and textures of the hot extruded nanocomposites have been investigated by means of three dimensional orientation distribution functions and electron backscatter diffraction (EBSD) techniques. Pure Al and 6061 alloy extruded strips from atomised powders have been produced for comparison purposes. The results show that the non-deformable SiC particulates have a strong influence on the formation of extrusion textures in the matrix. Pure Al and 6061 alloy develop a typical β fibre texture after extrusion in strip shape. For 6061/SiC_p nanocomposites, the intensities of major texture components decrease with increasing amount of SiC particles. The total intensities of Brass, Dillamore and S components have decreased by 19% for 6061/10 wt.% SiC_p and 40% for 6061/15 wt.% SiC_p composites when compared with the 6061 alloy. EBSD analysis on local grain orientations shows limited Al grain rotations in SiC rich zones and decreased texture intensities.     

Effect of SiC particle size on the physical and mechanical properties of extruded Al matrix nanocomposites

In this work, the effect of SiC particle size and its amount on both physical and mechanical properties of Al matrix composite were investigated. SiC of particle size 70 nm, 10 μm and 40 μm, and Al powder of particle size 60 μm were used. Composites of Al with 5 and 10 wt.% SiC were fabricated by powder metallurgy technique followed by hot extrusion. Phase composition and microstructure were characterized. Relative density, thermal conductivity, hardness and compression strength were studied. The results showed that the X-ray diffraction (XRD) analysis indicated that the dominant components were Al and SiC. Densification and thermal conductivity of the composites decreased with increasing the amount of SiC and increased with increasing SiC particle size. Scanning electron microscope (SEM) studies showed that the distribution of the reinforced particle was uniform. Increasing the amount of SiC leads to higher hardness and consequently improves the compressive strength of Al–SiC composite. Moreover, as the SiC particle size decreases, hardness and compressive strength increase. The use of fine SiC particles has a similar effect on both hardness and compressive strength.     

Investigation of microstructure,hardness and wear properties of Al–4.5 wt.% Cu–TiC nanocomposites produced by mechanical milling

The present work deals with studies on the manufacturing and investigation of mechanical and wear behavior of aluminum alloy matrix composites (AAMCs), produced using powder metallurgy technique of ball milled mixing in a high energy attritor and using a blend–press–sinter methodology. Matrix of pre-mechanical alloyed Al–4.5 wt.% Cu was used to which different fractions of nano and micron size TiC reinforcing particles (ranging from 0 to 10 wt.%) were added. The powders were mixed using a planetary ball mill. Consolidation was conducted by uniaxial pressing at 650 MPa. Sintering procedure was done at 400 °C for 90 min. The results indicated that as TiC particle size is reduced to nanometre scale and the TiC content is increased up to optimum levels, the hardness and wear resistance of the composite increase significantly, whereas relative density, grain size and distribution homogeneity decrease. Using micron size reinforcing particulates from 5% to 10 wt.%, results in a significant hardness reduction of the composite from 174 to 98 HVN. Microstructural characterization of the as-pressed samples revealed reasonably uniform distribution of TiC reinforcing particulates and presence of minimal porosity. The wear test disclosed that the wear resistance of all specimens increases with the addition of nano and micron size TiC particles (up to 5 wt.%). Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some delamination wear mechanism.     

Microstructure and mechanical properties of in situ TiC and Nd2O3 particles reinforced Ti–4.5 wt.%Si alloy composites

(TiC + Nd₂O₃)/Ti–4.5 wt.%Si composites were in situ synthesized by a non-consumable arc-melting technology. The phases in the composites were identified by X-ray diffraction. Microstructures of the composites were observed by optical microscope and scanning electron microscope. The composite contains four phases: TiC, Nd₂O₃, Ti₅Si₃ and Ti. The TiC and Nd₂O₃ particles with dendritic and near-equiaxed shapes are well distributed in Ti–4.5 wt.%Si alloy matrix, and the fine Nd₂O₃ particles exist in the network Ti + Ti₅Si₃ eutectic cells and Ti matrix of the composites. The hardness and compressive strength of the composites are markedly higher than that of Ti–4.5 wt.%Si alloy. When the TiC content is fixed as 10 wt.% in the composites, the hardness is enhanced as the Nd₂O₃ content increases from 8 wt.% to 13 wt.%, but the compressive strength peaks at the Nd₂O₃ content of 8 wt.%.     

Investigation of microstructure and mechanical properties of aluminum hybrid nano-composites with the additions of solid lubricant

In this experimental study, the tribological behavior of Al 2024–5 wt.% SiC–X wt.% graphite (X = 5 and 10) hybrid nano-composites was produced using powder metallurgy (P/M) technique. All specimens were prepared by mechanical milling of Al 2024 and SiC–Gr nano-composite powders, followed by a blend–press–sinter methodology. Pin on disc type apparatus has been used for determining the wear loss. The sintered samples have been characterized by XRD. Wear mechanisms are discussed based on scanning electron microscopy observations of worn surface and wear debris morphology. The hardness and wear resistance of the hybrid nano-composites were increased considerably by increasing the reinforcement content. The nano-composite with 5 wt.% SiC and 10 wt.% Gr showed the greatest improvement in tribological performance. Primary wear mechanisms for hybrid nano-composites were determined to be formation of lubricating layer on the surface of samples. The overall results revealed that hybrid aluminium nano-composites can be considered as an outstanding material where high strength and wear-resistant components are of major importance, particularly structural applications in the aerospace, automotive and military industries.     

Nanocrystalline matrix TiC–Al3Ti and TiC–Al3Ti–Al composites produced by reactive hot-pressing of milled powders

Mechanically alloyed nanocrystalline TiC powder was short-term milled with 40 vol.% of Al powder. The powders mixture was consolidated at 1200 °C under the pressure of 4.8 GPa for 15 s and at 1000 °C under the pressure of 7.7 GPa for 180 s. The bulk materials were characterised by X-ray diffraction, light and scanning electron microscopy, energy dispersive spectroscopy, hardness, density and open porosity measurements. During the consolidation a reaction between TiC and Al occurred, yielding an Al₃Ti intermetallic. The microstructure of the produced composites consists of TiC areas surrounded by lamellae-like regions of Al₃Ti intermetallic (after consolidation at 1200 °C) or Al₃Ti and Al (after consolidation at 1000 °C). The mean crystallite size of TiC is 38 nm. The hardness of the TiC–Al₃Ti and TiC–Al₃Ti–Al composites is 13.28 GPa (1354 HV1) and 10.22 GPa (1041 HV1) respectively. The produced composites possess relatively high hardness and low density. The results obtained confirmed satisfactory quality of the consolidation with keeping a nanocrystalline structure of TiC.     

Microstructure and mechanical properties of an Al–TiC metal matrix composite obtained by reactive synthesis

A metal matrix composite has been obtained by a novel synthesis route, reacting Al₃Ti and graphite at 1000 °C for about 1 min after ball-milling and compaction. The resulting composite is made of an aluminium matrix reinforced by nanometer sized TiC particles (average diameter 70 nm). The average TiC/Al ratio is 34.6 wt.% (22.3 vol.%). The microstructure consists of an intimate mixture of two domains, an unreinforced domain made of the Al solid solution with a low TiC reinforcement content, and a reinforced domain. This composite exhibits uncommon mechanical properties with regard to previous micrometer sized Al–TiC composites and to its high reinforcement volume fraction, with a Young’s modulus of ∼110 GPa, an ultimate tensile strength of about 500 MPa and a maximum elongation of 6%.     

Effect of 10Ce-TZP/Al2O3 nanocomposite particle amount and sintering temperature on the microstructure and mechanical properties of Al/(10Ce-TZP/Al2O3) nanocomposites

A zirconia/alumina nanocomposite stabilized with cerium oxide (Ce-TZP/Al₂O₃ nanocomposite) can be a good substitute as reinforcement in metal matrix composites. In the present study, the effect of the amount of 10Ce-TZP/Al₂O₃ particles on the microstructure and properties of Al/(10Ce-TZP/Al₂O₃) nanocomposites was investigated. For this purpose, aluminum powders with average size of 30 μm were ball-milled with 10Ce-TZP/Al₂O₃ nanocomposite powders (synthesized by aqueous combustion) in varying amounts of 1, 3, 5, 7, and 10 wt.%. Cylindrical-shape samples were prepared by pressing the powders at 600 MPa for 60 min while heating at 400–450 °C. The specimens were then characterized by scanning and transmission electron microscopy (SEM and TEM) in addition to different physical and mechanical testing methods in order to establish the optimal processing conditions. The highest compression strength was obtained in the composite with 7 wt.% (10Ce-TZP/Al₂O₃) sintered at 450 °C.     

Microstructure characterization,mechanical properties,compressibility and sintering behavior of Al-B4C nanocomposite powders

In the present work, Al-xB₄C nanocomposite (x = 0, 1, 2, 3, 4 and 5 in wt%, having the average B₄C size of 50 nm) were prepared using a high-energy ball mill. The milling times up to 16 h were applied. Then, the microstructural evolutions, mechanical properties, compressibility and sintering behavior of nanocomposites were investigated. The changes in powders morphology and microstructure during the milling process were characterized by laser diffraction particle size analyzer (LDA), SEM, XRD, EDS and TEM techniques. Compressibility and sintering behavior of milled powders compacted under different pressures (100–900 MPa) and at different sintering temperatures (500, 550 and 600 °C) were also studied. The pressing behavior of the nanocomposites was analyzed using linear compaction equations developed by Heckel, Panelli-Filho and Ge. The results showed the significant effects of B₄C amounts and sintering temperatures on the compressibility and sintering behavior of nanocomposites. The increase in the B₄C amount led to a decrease in both the compressibility rate and the sinterability of specimens. The maximum compression strength of 265 MPa and Vickers hardness of 165 VHN were obtained for Al-5 wt.% B₄C nanocomposite milled for 16 h followed by sintering at 600 °C.     

Effects of diamond nanoparticles reinforcement into lead-free Sn–3.0Ag–0.5Cu solder pastes on microstructure and mechanical properties after reflow soldering process

This paper presents the effects of diamond nanoparticles reinforcement on lead-free SAC 305 solder paste after the reflow soldering process. Different diamond nanoparticles amounts (0.5, 1.5, and 2.5 wt.%) were mechanically mixed with SAC 305 to produce a new form of nanocomposite solder paste. The characteristics of the nanocomposite solder, such as melting point, morphology and thickness of the intermetallic compound (IMC), agglomeration of diamond nanoparticles, and hardness, were investigated. The experimental results revealed that the addition of diamond nanoparticles slightly decreases the melting point but significantly reduces the IMC thickness. The morphologies of the nano-reinforced solder paste showed the agglomeration of nanoparticles on the surface of the solder paste with increasing diamond nanoparticles percentage. The addition of 0.5 wt.% diamond nanoparticles was well embedded in the solder matrix after the reflow soldering process. The hardness of the nano-reinforced solder paste was evaluated via nanoindentation technique. The addition of 0.5 wt.% diamond nanoparticles improved the hardness of SAC 305 by 77.5%. Increasing the nanoparticles amount by 1.5 and 2.5 wt.% in SAC 305 enhanced the hardness of SAC 305–0.5 wt.% by 6.3% and 17.8%, respectively.     

Synthesis and microstructural characterization of Al–Ni3Al composites fabricated by press-sintering and shock-compaction

Aluminum matrix composites reinforced with nanocrystalline Ni3Al intermetallic particles, were synthesized using powder metallurgy techniques. Nanocrystalline Ni3Al was obtained by mechanical alloying of Ni75–Al25 stoichiometric mixture from elemental powders after 900 ks of milling with a 5 nm grain size average. Mixture powders of aluminum with 0.007, 0.02 and 0.04 volume fractions of Ni3Al intermetallic particles were compacted using two different compaction methods, the cold isostatic press and sintered at 873 K and the shock-compaction technique. Microstructure of shock-compacted composites showed fine particles of a few microns and also coarse particles less than 100 μm homogeneously distributed on the matrix, also the presence of micro-cracks and low porosity. However the nanoscale features of intermetallic was retained. On the other hand, the press and sintered composites showed good densification. The densities of the composites were about 90% and 94% of the theoretical density for the shock-compacted and press-sintered process, respectively. Finally, the results of hardness measurements showed that the nanocrystalline Ni3Al reinforcement improves the hardness of Al matrix for all conditions. The highest hardness was obtained for the Al–4 vol.%Ni3Al shock-compacted composite.     

Effect of electroceramic particles on damping behaviour of aluminium hybrid composites produced by ultrasonic cavitation and mechanical stirring

In this study, electroceramics PBN and PLZT along with SiC were included in Al–3.96 wt.% Mg (A514.0) master alloy. Ultrasonic cavitation (UST) and mechanical stirring (MS) were employed to improve wettability and dispersion during casting. Two composite systems were produced: PBN system (5 wt.% PBN + 1 wt.% SiC and 15 wt.% PBN + 1 wt.% SiC) and the PLZT system (follows the same designation). The influence of fabrication method on the microstructures, particle distribution and wettability as well as electroceramic impact on dynamo-mechanical properties of prepared composites were investigated. Optical microscope (OM) and scanning electron microscope (SEM) results indicate that the processing technique was effective as it promoted wettability and homogeneous dispersion of particles throughout the Al matrix. Dynamic mechanical analysis (DMA) study of the composites demonstrated that the addition of the functional particles to the Al alloy matrix improved damping capacity (Tan δ) at 200 °C. The composites exhibited an increase in Tan δ of 24.3 ± 0.3% and 91.4 ± 0.2% for 5 and 15 wt.% PBN + 1 wt.% SiC and an increase of 19.7 ± 0.5% and 42.5 ± 0.3% for 5 and 15 wt.% PLZT + 1 wt.% SiC, respectively, when compared to the aluminium alloy matrix.     

The effect of Mg add on morphology and mechanical properties of Al–xMg/10Al2O3 nanocomposite produced by mechanical alloying

Effect of Mg content on microstructure and mechanical properties of Al–xMg/10 wt.%Al₂O₃ (x = 0, 5, 10 and 15 wt.%) powder mixtures during milling was investigated. The results show that for the binary Al–Mg matrix, the predominant phase was an Al–Mg solid solution. With the increment of Mg to 15 wt.% the crystallite sizes of 20 h milled powders diminish from 44 to 26 nm and lattice strains increased from 0.22% to 0.32% caused by Mg atomic penetration into the substitution sites of the Al lattice. With up to 15 wt.% Mg (for 20 h milled composites) microhardness increases from 120 to 230 HV caused by the increment of the Mg concentration and dislocation density as well as the decrease of the crystallite size.     

Analysis of the compaction behavior of Al–SiC nanocomposites using linear and non-linear compaction equations

The compressibility behavior of Al–SiC nanocomposite powders was examined and the density-pressure data were analyzed by linear and non-linear compaction equations. SiC particles with an average size of 50 nm were mixed with gas-atomized aluminum powder (40 μm average size) at different volume fractions (up to 20 vol%) and compacted in a rigid die at various pressures. In order to highlight the effect of reinforcement particle size, the compressibility of micrometric SiC particles of two sizes (1 and 40 μm) was also examined. Analysis of the compressibility data indicated hindering effect of the hard ceramic particles on the plastic deformability of soft aluminum matrix, particularly at high volume fractions. More pronounced effect on the yield pressure was obtained for the nanometric particles compared with the micrometric ones. Nevertheless, better particles rearrangement was taken place when the ultrafine SiC particles were utilized. In light of the experimental and theoretical analysis, the densification mechanism of aluminum matrix composites and the effect of reinforcement particle size and volume fraction are discussed.     

Tribological behavior of Ni3Al matrix self-lubricating composites containing WS2, Ag and hBN tested from room temperature to 800 °C

Ni₃Al matrix self-lubricating composites (NMSC) containing varied amounts of WS₂, Ag and hBN (WAh) with weight ratio of 1:1:1 were fabricated by in situ technique using spark plasma sintering. The friction and wear properties of NMSC against the commercial Si₃N₄ ceramic ball at the load of 10 N and sliding speed of 0.234 m/s for 80 min from room temperature to 800 °C were investigated. The results showed that the tribological properties of NMSC strongly depended on the addition content of WAh. Moreover, NMSC with 15 wt.% WAh and 5 wt.% TiC exhibited the relatively lower friction coefficients and the less wear rates from RT to 800 °C. The excellent tribological behavior of NMSC with 15 wt.% WAh and 5 wt.% TiC was attributed to the synergetic action of composite lubricants of WAh and reinforced phase of TiC.     

Effect of cup and ball types on alumina–tungsten carbide nanocomposite powder synthesized by mechanical alloying

Alumina-based nanocomposite powders with tungsten carbides particulates were synthesized by ball milling WO₃, Al and graphite powders. X-ray Diffraction (XRD) was used to characterize the milled and annealed powders. Microstructures of milled powders were studied by Transmission Electron Microscopy (TEM). Results showed that Al₂O₃–W₂C composite formed after 5 h of milling with major amount of un-reacted W in stainless steel cup. The remained W was decreased to minor amount by increasing carbon content up to 10 wt.%. When milled with ZrO₂ cup and balls, Al₂O₃–W₂C composite was completely synthesized after 20 h of milling with the major impurity of ZrO₂. In the case of stainless steel cup and balls with 10 wt.% carbon, Fe impurity after 5 h of milling (maximum 0.09 wt.%) was removed from the powder by leaching in 3HCl·HNO₃ solution. The mean grain size of the powder milled for 5 h was less than 60 nm. The powder preserved its nanocrystalline nature after annealing at 800 °C.     

Structural and mechanical characterization of Al-based composite reinforced with heat treated Al2O3 particles

In this study, the addition of 1.00 wt.% Al₂O₃ crystals to the metal matrix of the liquid aluminum was studied. In order to investigate the influence of heat treatment on activation of Al₂O₃ powders and mechanical properties of Al–Al₂O₃ composites, the Al₂O₃ particles were heated at 1000 °C. X-ray Diffraction (XRD) analysis used to characterize the crystal lattice of Al₂O₃ and its variation during heat treatment. The size and morphology of the Al₂O₃ grains was evaluated by Scanning Electron Microscopy (SEM). The results showed a considerable change in morphology of Al₂O₃ grains during the heat treatment. Mechanical evaluation such as hardness, compression and wear tests showed enhancement in the properties of Al–1.00 wt.% heat treated Al₂O₃ vs. Al–1.00 wt.% Al₂O₃ composite.     

The effect of nano-sized stainless steel powder addition on mechanical and physical properties of micropowder injection molded part

Micropowder injection molding (μPIM) is a new technology that has potential in the mass production of microcomponents. A bulk material of nanoparticles possesses completely different properties from those of large-sized particles. The main objective of this study is to study the effects of nano-sized powder addition on the μPIM process of powder-polymer mixtures for the fabrication of miniature parts. The binder systems consist of polyethylene glycol (PEG), polymethyl methacrylate (PMMA), and stearic acid (SA) with different powder loading blended with powders. The results indicate that increasing the nanopowder content to 30 wt.% increased the powder loading and decreased the injection and sintering temperatures. The sintered parts had densities of 96% of the theoretical value. High physical and mechanical properties of the sintered specimen were achieved with the 30 wt.% nano-sized powder sintered at 1200 °C at a heating rate of 5 °C/min under vacuum atmosphere. A significant reduction of the surface roughness of the sintered parts using the nano–microhybrid powder (S_a = 0.365 μm) was observed compared with the sintered parts with only micropowder (S_a = 1.002 μm). Using nanopowders, the hardness also increased from 182 HV to 221 HV with a linear shrinkage of approximately 9%, which is less than that of the micropowders (18%).     

Mechanical properties of nanostructured Al2024–MWCNT composite prepared by optimized mechanical milling and hot pressing methods

Nanostructured Al2024–multiwall carbon nanotubes (MWCNTs) composites were produced using optimized mechanical milling and hot pressing methods. Nanostructured Al2024 powder was first prepared through 30 h mechanical milling of the alloy powder. MWCNTs up to 3 vol.% were added to the milled Al2024 powder and milled for different times. Differential thermal analysis (DTA) and X-ray diffraction (XRD) were used to assess the structural changes and thermal behavior during mechanical milling and hot pressing. Hardness and compression tests were applied on bulk samples to evaluate their mechanical properties. Mechanical milling applied on Al2024 powders for 30 h resulted in the grain refinement to ～30 nm. DTA analysis showed an endothermic peak at ～632 °C due to Al2024 melting and an exothermic peak between 645 and 658 °C related to Al and MWCNTs reaction. Mechanical milling of nanocomposite powder for 4 h and following hot pressing at 500 °C under a pressure of 250 MPa for 0.5 h were selected as optimized conditions for bulk nanocomposite preparation. With MWCNTs addition up to 2 vol.%, relative density remained at 98%, and hardness increased to 245 HV. Compressive strength of nanocomposites found a maximum value of 810 MPa at 2 vol.% MWCNTs addition which is 78%, 34% and 12% greater than that for Al2024–O, Al2024–T6 and nanostructured Al2024, respectively.     

Microstructure and abrasive behaviors of TiC-316L composites prepared by warm compaction and microwave sintering

316L stainless steel composites with various weight fractions of TiC particles were prepared using warm compaction and microwave sintering. Abrasion resistance measurements were used to study the abrasive behaviors of TiC-316L stainless steel composites. The effects of TiC content and preparation methods on the microstructure and mechanical properties of 316L stainless steel composites have been investigated. The results showed that the sample prepared by warm compaction and microwave sintering exhibited significantly superior densification, higher hardness, and better abrasion resistance when compared with conventionally processed counterpart. TiC particles reinforcement improved the abrasion resistance of 316L stainless steel, and the abrasion resistance of the composites was considerably better than that of the 316L stainless steel. The volume loss initially decreases with increasing TiC content up to 5 wt.%, it then slightly increases as increase the TiC particles content to 10 and 15 wt.%. In this present abrasion tests, the composites using 5 wt.% TiC addition offers a high abrasion resistance.