Wear and friction of Al–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composites at various sliding speeds

The present study addresses the dry wear behavior of Al₂O₃ 6061 Aluminum particulate composite under different sliding speeds and applied load using pin-on-disk tribometer at room temperature. Three grades of the submicron particle composites containing 10, 20, and 30 vol.% Al₂O₃ were tested. The results illustrate that higher load and higher concentration of Al₂O₃ particles lead to higher wear rates. For 10 and 20% Al₂O₃ concentrations, the wear rate decreases with increasing sliding speed, while it increases for 30% Al₂O₃. The surface morphologies of the worn composites indicate that at lower sliding speeds abrasion is dominant, while at higher sliding speeds delamination and adhesion increases. Results also indicate that the friction coefficient between the composite and the mating steel surface decreases with increasing sliding speed to a steady state.     

Microstructural, mechanical and wear behavior of A390/graphite and A390/Al2O3 surface composites fabricated using FSP

In the present investigation, A390/graphite and A390/Al₂O₃ surface composite (SC) layers were fabricated using friction stir processing (FSP). The effect of tool rotational and traverse speeds on the microstructural, mechanical and wear characteristics of the surface layers was studied. The results revealed that increasing the tool rotational speed increases the hardness of the composite layers. The traverse speed has less significant influence on the hardness of the composite layer than the tool rotational speed. The A390/Al₂O₃ surface composites exhibited higher hardness than the A390/graphite surface composites. The surface composites exhibited better wear resistance than the matrix alloy. The A390/Al₂O₃ surface composites exhibited lower wear rates than the A390/graphite surface composites. Increasing the tool rotational reduces the wear rate of both A390/Al₂O₃ and A390/graphite surface composites.     

(Mg2B2O5w+ND)/ZK60镁基复合材料的摩擦磨损性能研究

在湿球磨条件下以600 r/min高能球磨混粉,并将球磨后的粉末经过热压烧结-热挤压成型制备(Mg2B2O5w+ND)/ZK60镁基复合材料。研究了(Mg2B2O5w+ND)/ZK60镁基复合材料在不同载荷和转速下的干摩擦磨损性能。结果表明:干摩擦条件下,材料的摩擦系数随着滑动距离的增加会经历跑和阶段和稳定阶段;材料的质量磨损率随着转速的增大而降低,随着载荷的增大而增大,且基体镁合金的质量磨损率始终低于复合材料。随着摩擦载荷和转速的增加,材料的摩擦系数减小,然后逐渐趋于平稳。混杂增强的镁基复合材料相比基体合金具有更低的摩擦系数。     

An experimental study on the bearing strength behavior of Al2O3 particle filled glass fiber reinforced epoxy composites pinned joints

An experimental study has been carried out to investigate the bearing strength behavior of pinned joints of glass fiber reinforced composite filled with different proportions of Al₂O₃ particles, as a function of filler loading and joint geometry. The weight fractions of the filler in the matrix were 7.5, 10, and 15%. Single-hole pin-loaded specimens of each composite material were tested in tension. The results show that the bearing strength of glass fiber reinforced epoxy composites pinned joints is associated with the filler content and geometric parameters. The increase of the Al₂O₃ particle loading in the matrix improved the bearing strength of the composites. The highest bearing strengths were obtained for composite specimens with 10 wt.% Al₂O₃ particle content. Further increases in the Al₂O₃ particle content in the matrix resulted in a decrease of the bearing strength, but remains above that of the unfilled glass reinforced epoxy composites.     

Influence of SiC, Si3N4 and Al2O3 particles on the structure and properties of electrodeposited Ni

The structure and properties of electrodeposited nickel composites reinforced with inert particles like SiC, Si₃N₄ and Al₂O₃ were compared. A comparison was made with respect to structure, morphology, microhardness and tribological behaviour. The coatings were characterized with optical microscopy, Scanning electron microscopy (SEM), Energy dispersive X-ray analysis (EDX) and X-ray diffraction (XRD) technique. The cross-sectional microscopy studies revealed that the particles were uniformly distributed in all the composites. However, a difference in the surface morphology was revealed from SEM studies. The microhardness studies revealed that Si₃N₄ reinforced composite showed higher hardness compared to SiC and Al₂O₃ composite. This was attributed to the reduced crystallite size of Ni — 12 nm compared to 16 nm (SiC) and 23 nm (Al₂O₃) in the composite coating. The tribological performance of these coatings studied using a Pin-on-disk wear tester, revealed that Si₃N₄ reinforced composite exhibited better wear resistance compared to SiC and Al₂O₃ composites. However, no significant variation in the coefficient of friction was observed for all the three composites.     

Effect of Al2O3 particle size on vacuum breakdown behavior of Al2O3/Cu composite

In order to clarify the effect of Al₂O₃ particle size on the arc erosion behavior of the ceramic-reinforced Al₂O₃/Cu composite, Al₂O₃/Cu composites with different sizes of Al₂O₃ particles were prepared by powder metallurgy, the effect of Al₂O₃ particle size on the characteristics of arc motion was studied, and the mechanism of arc erosion of Al₂O₃/Cu composites was discussed as well. The results show that with decrease in the size of Al₂O₃ particles, the erosion area increases significantly and the erosion pits become shallower. The vacuum breakdown is preferred to appear in the area between Al₂O₃ particle and the copper matrix. Based on the experimental results and theoretical analysis, a particle partition arc model is proposed.     

The investigation of the effect of particle size on wear performance of AA7075/Al2O3 composites using statistical analysis and different machine learning methods

In this study, 7075 - Al₂O₃ (5 wt%) composites with a particle size of 0.3 µm, 2 µm, and 15 µm were developed by hot pressing. The dry sliding wear performance of the specimens was evaluated under loads of 5 N, 10 N, 20 N, 30 N, and at sliding speeds of 80 mm/s, 110 mm/s, 140 mm/s by reciprocating wear tests. The wear tests showed that 7075 - 5Al₂O₃ (15 µm) exhibited the best wear performance. The volume loss of 7075 - 5Al₂O₃ (15 µm) under load of 30 N for sliding speed of 140 mm/s was 37.1% lower than the unreinforced 7075 alloy. The volume loss (mm³) of composites reinforced with the particle size of 0.3 µm, 2 µm, and 15 µm was 11.62, 9.87, and 8.07, respectively, for load of 30 N and sliding speed of 140 mm/s. An increase in the applied load and sliding speed increased the wear severity by changing the wear mechanism from abrasion to delamination. The analysis of variance (ANOVA) showed that the load was the most significant parameter on the volume loss. The linear regression (LR), support vector regression (SVR), artificial neural network (ANN), and extreme learning machine (ELM) were used for the prediction of volume loss. The determination coefficient (R²) of the LR, SVR, ANN, and ELM was 0.814, 0.976, 0.935, and 0.989, respectively. The ELM model has the highest success. Thus, the ELM model has significant potential for the prediction of wear behaviour for Al matrix composites.     

Optimization of cold-sprayed AA2024/Al2O3 metal matrix composites via friction stir processing: Effect of rotation speeds

In this study, friction stir processing (FSP) was employed to modify cold-sprayed (CSed) AA2024/Al₂O₃ metal matrix composites (MMCs). Three different rotation speeds with a constant traverse speed were used for FSP. Microstructural analysis of the FSPed specimens reveals significant Al₂O₃ particle refinement and improved particle distribution over the as-sprayed deposits. After FSP, a microstructural and mechanical gradient MMC through the thickness direction was obtained. Therefore, a hybrid technique combining these two solid-state processes, i.e. CS and FSP, was proposed to produce functionally gradient deposits. The Guinier-Preston-Bagaryatskii zone was dissolved during FSP, while the amounts at different rotation speeds were approximately the same, which is possibly due to the excellent thermal conductivity of the used Cu substrate. Mechanical property tests confirm that FSP can effectively improve the tensile performance and Vickers hardness of CSed AA2024/Al₂O₃ MMCs. The properties can be further enhanced with a larger rotation speed with a maximum increase of 25.9% in ultimate tensile strength and 27.4% in elongation at 1500 rpm. Friction tests show that FSP decreases the wear resistance of CSed MMCs deposits due to the breakup of Al₂O₃ particles. The average values and fluctuations of friction coefficients at different rotation speeds vary significantly.     

Spray processing and wear characteristics of Al-Cu-Al2O3-Pb based composites

The spray deposition process has been employed in synthesis of Al-4.5Cu-10Al₂O₃ and Al-4.5Cu-10Al₂O₃-10Pb based composites. The microstructure and wear characteristics of composites were investigated. The rapid solidification inherent in spray deposition processing resulted in a uniform dispersion of Al₂O₃ and Pb particles co-existing in the matrix of the- primary α-phase. The grain size of the Al-4.5Cu-10Al₂O₃-Pb composite was observed to be higher than that of the Al-4.5Cu-10Al₂O₃ composite in various sections of the spray deposit. The wear rate of composite materials decreased with addition of Pb phase. This behavior is discussed in the light of the microstructural modification induced by spray deposition and the morphology of debris particles on the wear track surfaces. The wear characteristics of the composites are compared with that of the liquid immiscible Al-4.5Cu-10Pb alloy.     

Relationship between thermal and sliding wear behavior of Al6061/Al<Subscript>2</Subscript>O<Subscript>3</Subscript> metal matrix composites

Al6061 alloy and Al6061/Al₂O₃ metal matrix composites (MMCs) were fabricated by stir casting. The MMCs were prepared by addition of 5, 10 and 15 wt% Al₂O₃ particulates and the size of particulates was taken as 16 μm. The effect of Al₂O₃ particulate content, thermal properties and stir casting parameters on the dry sliding wear resistance of MMCs were investigated under 50–350 N loads. The dry sliding wear tests were performed to investigate the wear behavior of MMCs against a steel counterface (DIN 5401) in a block-on-ring apparatus. The wear tests were carried out in an incremental manner, i.e., 300 m per increment and 3,000 m in total. It was observed that, the increase in Al₂O₃ vol% decreased both thermal conductivity and friction coefficient and hence increased the transition load and transition temperature for mild to severe wear during dry sliding wear test.     

Effects of particulate reinforcement and heat treatment on the hardness and wear properties of AA 2024-MoSi2 nanocomposites

In this study, nanocomposites of AA 2024 aluminum alloy matrix reinforced with different volume fractions of nanometric MoSi₂ intermetallic particles ranging from 0 to 5%, were produced using mechanical alloying technique. For comparison, samples without reinforcing particles and mechanical alloying and a sample with micrometric MoSi₂ particles were also synthesized. The prepared composite powders were consolidated by cold and hot pressing and then heat treated to solution and aged condition (T6). The effects of MoSi₂ particle size, volume fraction and also heat treatment on the hardness and wear properties of the composites were investigated using Brinell hardness and pin-on-disc wear tests. The results indicated that although T6 heat treatment increases the hardness of all samples compared to as hot-pressed (HP) condition, the age-hardenability (aging induced hardness improvement) decreases after mechanical alloying and with increasing MoSi₂ volume fraction due to the high dislocation density produced during mechanical alloying. With increasing the volume fraction of nano-sized MoSi₂ particles up to 3–4%, the hardness of the composites continuously increases and then declines most probably due to the particle agglomeration. The wear sliding test disclosed that the wear resistance of all specimens in T6 condition is higher than that of HP condition and increases with increasing MoSi₂ content. Scanning electron microscopic observation of the worn surfaces was conducted and the dominant wear mechanism was recognized as abrasive wear accompanied by some adhesive wear mechanism.     

Wear of ceramic particle-reinforced metal-matrix composites

Pin-on-disc dry sliding tests were carried out to study the wear mechanisms in a range of metal-matrix composites. 6061-aluminium alloys reinforced with 10 and 20 vol% SiC and Al₂O₃ particles were used as pin materials, and a mild steel disc was used as a counterface. A transition from mild wear to severe wear was found for the present composites; the wear rate increased by a factor of 10². The effects of the ceramic particles on the transition load and wear with varying normal pressure were thoroughly investigated. Three wear mechanisms were identified: abrasion in the running-in period, oxidation during steady wear at low load levels, and adhesion at high loads. A higher particle volume fraction raised the transition load but increased the wear rate in the abrasion and adhesion regimes. Increase of particle size was more effective than increase of volume fraction to prolong the transition from mild wear to adhesive wear. The reasons for different wear mechanisms were determined by analyses of the worn surfaces and wear debris.     

Characterization of microstructure and properties of Al–Al<Subscript>3</Subscript>Zr–Al<Subscript>2</Subscript>O<Subscript>3</Subscript> composite

Aluminium-based metal matrix composite strengthened by in situ Al₂O₃ and Al₃Zr particles were synthesized by powder metallurgy route. Phase analysis by X-ray diffraction and scanning electron microscopy revealed that the reaction between Al and ZrO₂ produced Al₂O₃ and Al₃Zr phases in the sintered composites. The hardness of the composite is a strong function of sintering temperature as well as the volume fraction of reinforcements. The dry sliding wear test results clearly indicated that increasing the volume fraction of zirconia particles in the composite improved the wear resistance. Microcutting, ploughing, delamination and oxidation were the main mechanisms of wear.     

Tribological investigation of Zamak alloys reinforced with alumina (Al2O3) and fly ash

ABSTRACT

In this study, zinc aluminum alloy (Zamak) (ZA-27) composites reinforced by different weight fractions of fly ash, alumina (Al₂O₃), or both particles were produced using compo-casting technique. The composites were subjected to hardness and wear tests. The hardness of the composites increases with increase of the weight fractions of reinforcements. In wear test, the composites were examined under dry sliding conditions using pin on disc apparatus. The wear results revealed that the wear resistance increases with increase of the weight fractions of reinforcements. However, the effect of fly ash particles on the wear resistance of the produced composites is more statistically significant than the effect of Al₂O₃ particles. The morphology of the composites was examined using scanning electron microscopy (SEM) after the test. The SEM images revealed the existence of adhesion and delamination wear mechanism.     

Microstructure and characterization of Ni-Co/Al2O3 composite coatings by pulse reversal electrodeposit

Ni-Co/Al₂O₃ composite coatings were obtained by pulse reversal electrodeposit (PRC) and direct current electrodeposit (DC). The microstructure of the coatings was characterized by means of SEM, XRD and TEM. Hardness, wear resistance and macro residual stress of coatings were also investigated. The results showed that the microstructure and performance of the coatings were significantly affected by the electrodeposit methods and the Al₂O₃ particles content. The PRC composite coatings exhibited compact surface, high hardness and excellent wear resistance. The macro residual stress of PRC composite coatings was lower than that of DC ones. With the increasing of Al₂O₃ particles content, the hardness and wear resistance of the composite coatings increased.     

Experimental investigation on tribological behaviours of PA6, PA6-reinforced Al<Subscript>2</Subscript><Emphasis Type="Italic">O</Emphasis><Subscript>3</Subscript> and PA6-reinforced graphite polymer composites

This article reports on the preparation, characterization and experimental investigation of polyamide 6 (PA6) reinforced with alumina oxide (Al₂O₃) and graphite composites. The test specimens were prepared in an injection-moulding machine by varying the weight proportions of Al₂O₃ and graphite particles blended with PA6. The tribological properties of the composites were observed by using pin-on-disc wear test rig under dry sliding conditions. The worn surfaces of the composites were examined using scanning electron microscope. The addition of Al₂O₃ and graphite significantly enhanced the tribological properties of PA6. The PA6 containing 30 wt% Al₂O₃ and 20 wt% graphite revealed the best tribological behaviours due to the stronger interfacial bonding characteristics with improved wear resistance. Further, the thermal stability of Al₂O₃ and graphite particles was studied through thermogravimetric analysis test. It was also found that further addition of Al₂O₃ and graphite in PA6 had no significant improvement in wear resistance, the co-efficient of friction and heat generation.     

Friction and wear of P/M Al-20Si-Al2O3 composites in kerosene

The results of friction and wear of powder metallurgy (P/M) Al-20 wt% Si-3 wt% Cu-1 wt% Mg-(2.5–10) vol% Al₂O₃ particulate-reinforced composites have been compared with those of the P/M aluminium alloy matrix and A-390 cast piston aluminium alloy. It was found that Al₂O₃ reinforcement reduces wear by five to eight times when mating with cast iron in kerosene: The higher the reinforcement volume, the lower was the wear. With increased volume of reinforcement the wear mechanism of composites changed from the adhesive to the fatigue/delaminating one. The wear of the cast-iron counter sample was several times higher than that for P/M composites. Considering the life of the piston-piston ring couple, the piston composite with 10 vol% Al₂O₃ appears to be the best. The rate of clearance development for this couple is twice as low as that for the conventional piston alloys.     

Fabrication of AA6061/Al2O3p composites from elemental and alloy powders

The tensile properties and microstructures of AA6061/Al₂O_3p composites fabricated by the pressureless infiltration method under a nitrogen atmosphere were examined. Since the spontaneous infiltration of molten metal into elemental powders bed as well as alloy powders bed occurred at 700°C for 1 hour under a nitrogen atmosphere, it was possible to fabricate 6061 Al matrix composite reinforced with Al₂O_3p irrespective of the type of metal powders. Both MgAl₂O₄ and MgO were formed at interfaces between Al₂O₃ and the matrix. In addition, MgAl₂O₄ was formed at within the matrix by in situ reaction during composite fabrication. Fine AlN was formed by in situ reaction in both composites. A significant strengthening in the composites occurred due to the formation ofin situ AlN particle and addition of Al₂O₃ particles, as compared to the commercial alloy, while tensile properties in the both elemental and alloy powders composites showed similar trend.     

Processing,microstructure and properties of ultrasonically processed in situ MgO–Al2O3–MgAl2O4 dispersed magnesium alloy composites

AZ91 alloy matrix composites are synthesized by in situ reactive formation of hard MgO and Al₂O₃ particles from the addition of magnesium nitrate to the molten alloy. The evolved oxygen from decomposition of magnesium nitrate reacts with molten magnesium to form magnesium oxide and with aluminium to form aluminium oxide. Additionally, these newly formed oxides react with each other to form MgAl₂O₄ spinel. Application of ultrasonic vibrations to the melt increased the uniformity of particle distribution, avoided agglomeration, and decreased porosity in the castings. Ultrasound induced physical phenomena such as cavitation and melt streaming promoted the in situ chemical reactions. Well dispersed, reactively formed hard oxides increased the hardness, ultimate strength, and strain-hardening exponent of the composites. Presence of well-dispersed hard oxide particles and stronger interface resulting from cavitation-enhanced wetting of reactively formed particles in the AZ91 alloy matrix improved the sliding wear resistance of the composites.     

Evaluation of wear characteristics of Al3Tip/Mg composite

The dry sliding wear tests were performed for a novel developed Al₃Ti_p/Mg composite under the ambient temperatures at 25–200 °C and the loads of 25–150 N. The wear rate of the composite increased with increasing the load, but reduced with increasing the ambient temperature. The Al₃Ti_p/Mg composite had relatively lower wear rates than AZ91D alloy under the loads of less than 100 N at 25 °C. At 200 °C, the Al₃Ti_p/Mg composite presented an absolutely higher wear resistance than AZ91D alloy, and the mild-severe wear transition was delayed. These were attributed to Al₃Ti particulates and the mechanical mixing layer formed on the worn surfaces, which hindered the plastic deformation and thermal softening of the matrix. The mechanical mixing layer contained MgO, Fe–Ti–O, Al₃Ti, Mg₁₇Al₁₂ and Mg and thickened with increasing the ambient temperature. The predominant wear mechanisms of the composite were oxidation wear and delamination wear.