Microstructures and mechanical properties of Al 2519 matrix composites reinforced with Ti-coated SiC particles

Ti-coated SiC_p particles were developed by vacuum evaporation with Ti to improve the interfacial bonding of SiC_p/Al composites. Ti-coated SiC particles and uncoated SiC particles reinforced Al 2519 matrix composites were prepared by hot pressing, hot extrusion and heat treatment. The influence of Ti coating on microstructure and mechanical properties of the composites was analyzed by scanning electron microscopy (SEM) and energy dispersive spectroscopy (EDS). The results show that the densely deposited Ti coating reacts with SiC particles to form TiC and Ti₅Si₃ phases at the interface. Ti-coated SiC particle reinforced composite exhibits uniformity and compactness compared to the composite reinforced with uncoated SiC particles. The microstructure, relative density and mechanical properties of the composite are significantly improved. When the volume fraction is 15%, the hardness, fracture strain and tensile strength of the SiC_p reinforced Al 2519 composite after Ti plating are optimized, which are HB 138.5, 4.02% and 455 MPa, respectively.     

Influence of addition of Grp/Al2O3p with SiCp on wear properties of aluminum alloy 6061-T6 hybrid composites via friction stir processing

Aluminum alloy base surface hybrid composites were fabricated by incorporating with mixture of (SiC+Gr) and (SiC+Al₂O₃) particles of 20 μm in average size on an aluminum alloy 6061-T6 plate using friction stir processing (FSP). Microstructures of both the surface hybrid composites revealed that SiC, Gr and Al₂O₃are uniformly dispersed in the nugget zone (NZ). It was observed that the addition of Gr particles rather than Al₂O₃ particles with SiC particles, decreases the microhardness but immensely increases the dry sliding wear resistance of aluminum alloy 6061-T6 surface hybrid composite. The observed microhardness and wear properties are correlated with microstructures and worn micrographs.     

真空压力浸渗制备SiCp/AZ91复合材料的显微组织、力学性能和磨损行为

采用真空压力浸透法制备SiC_p/AZ91复合材料,研究其显微组织、力学性能和耐磨性。结果表明,SiC颗粒均匀分布于金属基体中,并与基体界面结合良好。Mg₁₇Al₁₂相在SiC颗粒附近优先析出,SiC与AZ91基体的热膨胀系数失配导致高密度位错的产生,加速基体的时效析出。与AZ91合金相比,SiC颗粒的加入提高了复合材料的硬度和抗压强度,这主要是由于载荷传递强化和晶粒细化强化机制。此外,由于SiC具有优异的耐磨性,在磨损过程中形成稳定的支撑面保护基体。     

Abrasive Wear of In Situ AlB2/Al-4Cu Composite Material Produced by Squeeze Casting Method

The wear behavior of a weight fraction of particles with up to 30 wt.% in situ AlB₂ flakes reinforced in Al-4Cu matrix alloy composites and fabricated by a squeeze casting method was investigated in a pin-on-disk abrasion test instrument against different SiC abrasives at room conditions. Wear tests were performed under the load of 10 N against SiC abrasive papers of 80, 100, and 120 mesh grits. The effects of sliding speed, AlB₂ flake content, and abrasive grit sizes on the abrasive wear properties of the matrix alloy and composites have been evaluated. The main wear mechanisms were identified using an optical microscope. The results showed that in situ AlB₂ flake reinforcement improved the abrasion resistance against all the abrasives used, and the abrasive wear resistance decreased with an increase in the sliding speed and the abrasive grit size. The wear resistances of the composites were considerably bigger than those of the matrix alloy and increased with increases in in situ AlB₂ flake contents.     

Wear Performance of A356 Matrix Composites Reinforced with Different Types of Reinforcing Particles

To improve the wear resistance of Al-Si alloys, different types of reinforcing particles such as SiC, TiC, ZrO₂, and B₄C were used to produce matrix composites by friction stir processing (FSP). First, microstructural properties of different locations of stir zone (SZ) in the FSPed specimens such as advancing side, retreating side, shoulder-affected area, and pin-affected area were investigated. The results demonstrate that Si particles size is not the same in different SZ subdomains. SEM investigation was performed in order to investigate the particles distribution in different areas of the SZ as well as bonding quality between particles and metal matrix. Hardness and wear tests were carried out to determine mechanical and wear properties of the composites. The pin-on-disk wear tests were performed at room temperature, with the normal applied loads of 5, 10, and 20 N and sliding speed of 1 and 2 m/s. All fabricated composites show higher resistance in wear than A356 alloy. Wear test results show, by increasing the normal load and sliding velocity, the wear loss weight of all composites increased gradually.     

Effects of Ti-addition on the characteristics of wear resistant Al-Si-Fe base alloys processed via rapid solidification

Rapidly solidified Al-Si-Fe base alloys were prepared by gas atomization, hot pressing and extrusion. To optimize wear resistance and mechanical properties, Al-20 wt.%Si-5 wt.%Fe base alloys containing 1–3 wt.%Ti were newly designed and characterized in detail. The additions of Ti (especially, ~2 wt.%Ti) effectively increased the wear resistance and mechanical properties such as tensile strength and hardness; however, the addition of 3 wt.%Ti was not desirable because of the precipitation of the primary Ti₇Al₅Si₁₂ phase in the as-quenched state. Based on TEM analyses, the improved properties in the Al-Si-Fe alloys containing Ti were found to be due to the formation of the (Al, Si)₃Ti phase finely dispersed in the matrix. ASCM16CE is the gas atomized and consolidated composite including 3 wt.% of SiC particles (reference alloy).     

Coating of TiB2 dispersed Ti50Ni50 superelastic alloy layer onto Ti-6Al-4V alloy by spark and resistance sintering

The spark and resistance sintering (SRS) of a mixture of Ti, Ni, and TiB₂ powders was carried out to form a TiB₂ dispersed TiNi alloy layer onto a Ti-6Al-4V alloy substrate. The strength and delamination resistance of the surface layer were evaluated by three-point bending tests. The results showed that the bending strength of the specimen with the TiNi alloy surface layer without TiB₂ particles sintered at 1273 K was low because the crack initiation occurred at an early stage of loading in a thick interface layer containing brittle Ti-Ti₂Ni eutectic. By decreasing the sintering temperature to 1200 K, the bending strength increased and the crack initiation occurred from the surface because the interface layer was thin and did not contain the brittle Ti-Ti₂Ni eutectic. For the specimens with TiB₂ dispersed TiNi surface layer that was sintered at 1273 K, the bending strength was larger than that of the specimens with TiNi surface layer because the interface layer does not contain the Ti-Ti₂Ni eutectic and compressive residual stress generated in the surface layer during cooling process after SRS suppresses the crack initiation on the surface. The coating of TiB₂ dispersed TiNi alloy onto titanium alloys by SRS provides strong interface to prevent delamination of the surface layer, strong surface due to residual compressive stress, and wear-resistant surface due to the existence of hard TiB₂ particles and superelastic deformation of TiNi matrix.     

Microstructure and wear performance of Al5083/CeO2/SiC mono and hybrid surface composites fabricated by friction stir processing

Friction stir processing (FSP) was utilized to produce surface composites by incorporating nano-sized cerium oxide (CeO₂) and silicon carbide (SiC) particles individually and in combined form into the Al5083 alloy matrix. The study signified the role of these reinforcements on microstructure and wear behavior of the resultant surface composite layers. The wear characteristics of the resultant mono and hybrid surface composite layers were investigated using a pin-on-disc wear tester at room temperature. The microstructural observations of FSPed regions and the worn out surfaces were performed by optical and scanning electron microscopy. Considerable grain refinement and uniform distribution of reinforcement particles were achieved inside the nugget zone. All the composite samples showed higher hardness and wear resistance compared to the base metal. Among the composite samples, the hybrid composite (Al5083/CeO₂/SiC) revealed the highest wear resistance and the lowest friction coefficient, whereas the Al5083/SiC composite exhibited the highest hardness, i.e., 1.5 times as hard as that of the Al5083 base metal. The enhancement in wear behavior of the hybrid composites was attributed to the solid lubrication effect provided by CeO₂ particles. The predominant wear mechanism was identified as severe adhesive in non-composite samples, which changed to abrasive wear and delamination in the presence of reinforcing particles.     

Dry Sliding Wear Behavior of a Novel 6351 Al-(Al4SiC4 + SiC) Hybrid Composite

In this research study, the dry sliding wear behaviors of 6351 Al alloy and its composites with single and hybrid reinforcements (ex situ SiC and in situ Al₄SiC₄) were investigated at low sliding speed (1 ms^?1) against a hardened EN 31 disk at different loads. In general, the wear mechanism involved adhesion (coupled with subsurface cracking) and microcutting-abrasion at lower loads. With higher loads, abrasive wear involving microcutting and microplowing along with adherent oxide formation was observed. At higher loads, the abrasive wear mechanism caused rapid wear loss initially up to a certain sliding distance beyond which, by virtue of frictional heat generation and associated temperature rise, an adherent oxide layer was developed at the pin surface, which drastically reduced the wear loss. Moreover, the overall wear rates of all the composites (either single or hybrid reinforcement) were found to be lower than that of the 6351 Al alloy at all applied loads. The ex situ SiC particles were found to resist abrasive wear; while, in situ Al₄SiC₄ particles offered resistance to adhesive wear. Accordingly, the 6351 Al-(SiC + Al₄SiC₄) hybrid composite exhibited the best wear resistance among all composites.     

Production and mechanical properties of nano SiC particle reinforced Ti–6Al–4V matrix composite

Different mass fractions (0, 5%, 10%, and 15%) of the synthesized nano SiC particles reinforced Ti–6Al–4V (Ti64) alloy metal matrix composites (MMCs) were successfully fabricated by the powder metallurgy method. The effects of addition of SiC particle on the mechanical properties of the composites such as hardness and compressive strength were investigated. The optimum density (93.33%) was obtained at the compaction pressure of 6.035 MPa. Scanning electron microscopic (SEM) observations of the microstructures revealed that the wettability and the bonding force were improved in Ti64 alloy/5% nano SiC_p composites. The effect of nano SiC_p content in Ti64 alloy/SiC_p matrix composite on phase formation was investigated by X-ray diffraction. The correlation between mechanical parameter and phase formation was analyzed. The new phase of brittle interfaced reaction formed in the 10% and 15% SiC_p composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiC_p MMCs showed higher values. Hence, 5% SiC_p can be considered to be the optimal replacement content for the composite.     

Glass coating for SiCf/SiC composites for high-temperature application

This work reports on the fabrication of a self-healing, oxidation-resistant glass coating for SiC_f/SiC composites. The glass-coating material is a thermally stable boro-silicate glass with excellent wetting properties and viscosity.Some glass-coated composites were prepared by a simple and low-cost slurry technique, then treated in air for 100 h at 1200°C. Three-point bending tests were performed on the glass-coated composites after the thermal treatment, and the results were compared with the bending strength of the uncoated SiC_f/SiC before and after the same thermal treatment. The mechanical behavior of the glass-coated composite remained almost virtually unaffected after being heated at 1200°C in air for 100 h.     

二硼化钛对Al2024−TiB2非原位复合材料摩擦磨损性能的影响

用搅拌铸造法制备不同质量分数二硼化钛(TiB2)颗粒增强的铝基复合材料,并研究其摩擦磨损性能.采用销?盘式摩擦试验机对Al2024?TiB2复合材料进行干滑动磨损试验.为了研究摩擦学参数对复合材料的影响,对载荷、滑动距离和滑动速度等参数进行调整.显微组织表征结果表明,TiB2颗粒分散均匀并与基体有良好的结合.实验结果表...     

Property improvement of stainless-steel-base surface composites fabricated by high-energy electron-beam irradiation

This is a study on the fabrication of surface composites of SiC, TiC particulates, and AISI 304 substrate by high voltage electron beam irradiation. Using CaF₂ powders as flux, two kinds of surface composites were fabricated for a comparative analysis of the microstructural modification and mechanical properties. Through the employed process, the powders and substrate surface were melted and surface composite layers were successfully formed in both cases. In the specimen fabricated with SiC powders, a volume fraction of Cr₂₃C₆ particles (−22 vol.%) were homogeneously distributed along solidification cell boundaries. The large amount of Cr₂₃C₆ particles in combination with solid solution hardening of Si in the matrix resulted in the improved hardness and wear resistance of the surface composite layer, that are 2 to 3 times those of the substrate. In the specimen fabricated with SiC and Ti+SiC powders, TiC and Cr₂₃C₆ particles were precipitated without precipitation of SiC.     

Characteristics and wear behavior of cenosphere dispersed titanium matrix composite developed by powder metallurgy route

The cenosphere dispersed Ti matrix composite was fabricated by powder metallurgy route, and its wear and corrosion behaviors were investigated. The results show that the microstructure of the fabricated composite consists of dispersion of hollow cenosphere particles in α-Ti matrix. The average pore diameter varies from 50 to 150 μm. The presence of porosities is attributed to the damage of cenosphere particles due to the application of load during compaction as well as to the hollow nature of cenospheres. A detailed X-ray diffraction profile of the composites shows the presence of Al₂O₃, SiO₂, TiO₂ and α-Ti. The average microhardness of the composite (matrix) varies from HV 1100 to HV 1800 as compared with HV 240 of the as-received substrate. Wear studies show a significant enhancement in wear resistance against hardened steel ball and WC ball compared with that of commercially available Ti–6Al–4V alloy. The wear mechanism was established and presented in detail. The corrosion behavior of the composites in 3.56% NaCl (mass fraction) solution shows that corrosion potential (φ_corr) shifts towards nobler direction with improvement in pitting corrosion resistance. However, corrosion rate of the cenosphere dispersed Ti matrix composite increases compared with that of the commercially available Ti–6Al–4V alloy.     

Aluminum-silicon carbide coatings by plasma spraying

An aluminum base composite (Al-SiC) powder has been developed for producing plasma sprayed coatings on Al and other metallic substrates. The composite powders were prepared by mechanical alloying of 6061 Al alloy with SiC particles. The concentration of SiC was varied between 20 and 75 vol%, and the size of the reinforcement was varied from 8 to 37 μm in the Al-50 vol% SiC composites. The 44 to 140 μm composite powders were sprayed using an axial feed plasma torch. Adhesion strength of the coatings to their substrates were found to decrease with increasing SiC content and with decreasing SiC particle sizes. The increase in the SiC content and decrease in particle size improved the erosive wear resistance of the coatings. The abrasive wear resistance was found to improve with the increase in SiC particle size and with the SiC content in the composite coatings.     

Reciprocating wear behavior of 7075Al/SiC in comparison with 6061Al/Al2O3 composites

In the present study, the reciprocating wear behavior of 7075Al/SiC composites and 6061Al/Al₂O₃ composites that are prepared through liquid metallurgy route is analyzed to find out the effects of weight percentage of reinforcement and load at the fixed number of strokes on a reciprocating wear testing machine. The Metal Matrix Composite (MMC) pins are prepared with different weight percentages (10, 15 and 20%) of SiC and Al₂O₃ particles with size of 36 μm. Hardness of these composites increases with increase in wt.% of reinforcement. However, the impact strength decreases with increase in reinforcement content. The experimental result shows that the volume loss of MMC specimens is less than that of the matrix alloy. However, the volume loss is greater in 6061Al/Al₂O₃ composites when compared to 7075Al/SiC composites. The temperature rise near the contact surface of the MMC specimens increases with increase in wt.% of reinforcement and applied load. The coefficient of friction decreases with increase in load in both cases.     

Wear resistance and thermal stability enhancement of PDC sintered with Ti-coated diamond and cBN

Ti-coated diamond with different particle sizes and proper amounts of cubic boron nitride (cBN) was used to fabricate polycrystalline diamond composite (PDC) with improved wear resistance and thermal stability under high temperature and high pressure (5.5–6.5GPa, 1500–1650 °C). The ratio of Ti-coated diamond powder, cBN powder and normal diamond powder was W_30–50: W_4–8: W_0–1 = 70: 15: 15. Cobalt (Co) was used as a binder, and cemented tungsten carbide was used as a substrate to sinter a new high-performance PDC. Ti and TiC on the surface of Ti-coated diamond reacted with cBN under high temperature and high pressure to generate new ceramic phases such as TiB₂, TiN and TiN_0.3, which have high hardness and good wear resistance. Compared with the conventional PDC, the impact toughness and wear resistance of PDC with Ti-coated diamond and cBN addition were enhanced by 19% and 28%, respectively. The ceramic phase acts as a protective barrier, which enhances the initial graphitization and oxidizing temperature to 942–950 °C, which were 162–170 °C higher than the conventional PDC. The new ceramic barrier wrapped around the surface of the diamond and Co after the formation of the D-D (diamond-diamond) bonding will give priority to the oxidation reaction of Co and diamond with oxygen, which prohibits cobalt-catalytic graphitization of diamond, meeting the needs of PDC thermal stability and wear resistance in the field of drilling.     

Fatigue properties of Al–Si casting alloy with cold sprayed Al/SiC coating

Abstract

The fatigue properties of Al–Si alloy cold sprayed Al and Al–SiC composite coatings have been studied. The specimens coated with composites reinforced with a large volume (25%) of fine SiC particles exhibited improved adhesion strength at the interface due to crater formation, and cyclic fatigue lives at room temperature more than three times those of uncoated specimens. In high temperature low cycle fatigue tests at 250°C, the pure Al coatings showed longer fatigue lives than the Al–SiC composite coatings, which is attributed to an increment in ductility at the surface retarding fatigue crack initiation.     

颗粒增强铝合金叠层复合材料的制备与强度和耐磨性

介绍了ＳｉＣ颗粒增强ＡｌＣｕ合金叠层复合材料的制备方法，研究了叠层复合材料的抗弯强度和增强层的耐磨性与ＳｉＣ颗粒含量的关系。结果表明，ＳｉＣ颗粒体积分数为２０％时该材料的抗弯强度最大，磨损量最小；ＳｉＣ颗粒与基体结合强度及层间宏观应力影响材料的强度性能     

Selective Laser Melting of in-situ TiC/Ti5Si3 composites with novel reinforcement architecture and elevated performance

A novel Selective Laser Melting (SLM) process was applied to prepare bulk-form TiC/Ti₅Si₃ in-situ composites starting from Ti/SiC powder system. The influence of the applied laser energy density on densification, microstructure, and mechanical performance of SLM-processed composite parts was studied. It showed that the uniformly dispersed TiC reinforcing phase having a unique network distribution and a submicron-scale dendritic morphology was formed as a laser energy density of 0.4 kJ/m was properly settled. The 96.9% dense SLM-processed TiC/Ti₅Si₃ composites had a high microhardness of 980.3HV_0.2, showing more than a 3-fold increase upon that of the unreinforced Ti part. The dry sliding wear tests revealed that the TiC/Ti₅Si₃ composites possessed a considerably low friction coefficient of 0.2 and a reduced wear rate of 1.42 × 10^− 4 mm³/Nm. The scanning electron microscope (SEM) characterization of the worn surface morphology indicated that the high wear resistance was due to the formation of adherent and strain-hardened tribolayer. The densification rate, microhardness, and wear performance generally decreased at a higher laser energy density of 0.8 kJ/m, due to the formation of thermal cracks and the significant coarsening of TiC dendritic reinforcing phase.