Particle Removal Mechanism of High Volume Fraction SiCp/Al Composites by Single Diamond Grit Tool

Particle removal mechanism was presented during machining particle SiC/Al composites with diamond grinding tool. The relevant removal modes and their mechanisms were discussed considering the impact and squeezing effect of diamond grit on the SiC particle. The experimental results show that the aluminum matrix has larger plastic deformation, so the aluminum mixed with the surplus SiC particles is cut from the surface. The SiC particles can be removed in multiple ways, such as broken/fractured, micro cracks, shearing and pulled out, etc. More particles removed by shearing, and less particles removed by fractured during material removal progress can produce a better machined surface.

超声振动辅助车削SiCp/Al切屑形成机理及表面粗糙度研究

目的研究切屑形成机理对加工过程的影响。方法超声振动辅助车削技术通过刀具振动的拟间歇切削特征控制切屑尺寸和切屑形态,从而提高了加工表面质量。针对SiCp/Al复合材料的切屑形成机理,探究常规车削和超声振动辅助车削的切屑形成过程。研究了颗粒分布对第一变形区变形阶段的影响,以及不同加工方式下切削参数对切屑形态的影响。最后,描述了切屑自由表面和刀-屑接触界面的颗粒损伤形式,以直观地描述常规车削与超声振动辅助车削SiCp/Al复合材料加工中切屑的形成过程。结果通过测试加工后工件表面形貌发现超声振动辅助车削的切屑更加连续、切屑尺寸较小的加工表面粗糙度更小,常规车削的表面粗糙度为0.805μm,超声振动辅助车削的表面粗糙度为0.404μm,超声振动辅助车削比常规车削的表面粗糙度降低了49.8%。结论与常规车削相比,超声振动辅助车削有利于减小切屑厚度。超声振动辅助车削得到的切屑更加连续,避免了切屑碎裂,促进了切屑的顺利排出。通过对切屑形态进行研究,选择最优切削参数可以有效提高工件表面质量。

60%SiCp/2009铝基复合材料表面等离子体电解氧化膜的生长和表征

在硅酸盐溶液中采用等离子体电解氧化技术在60%SiCP(体积分数)/2009铝基复合材料表面制备陶瓷膜。研究氧化膜的显微组织、成分、润湿性及其耐腐蚀性能,探讨SiC颗粒表面火花放电的产生机理。结果表明,来自硅酸盐溶液的不溶性化合物(SiO_(2))使SiC颗粒表面产生火花放电,Al-Si-O化合物中的缺陷为SiC颗粒表面放电电流的传导提供优先路径。1200s时铝基复合材料表面形成5.5μm厚的均匀膜层,膜层的表面自由能在40s时达到最大值37.10 m J/cm^(2),并在1200 s时下降到25.95 m J/cm^(2)。此外,等离子体电解氧化处理可以显著提高复合材料的耐蚀性。

Microstructure and mechanical properties of SiC-particle-strengthening tri-metal Al/Cu/Ni composite produced by accumulative roll bonding process

In this study, a multilayer Al/Ni/Cu composite reinforced with Si C particles was produced using an accumulative roll bonding(ARB) process with different cycles. The microstructure and mechanical properties of this composite were investigated using optical and scanning microscopy and hardness and tensile testing. The results show that by increasing the applied strain, the Al/Ni/Cu multilayer composite converted from layer features to near a particle-strengthening characteristic. After the fifth ARB cycle, a composite with a uniform distribution of reinforcements(Cu, Ni, and SiC) was fabricated. The tensile strength of the composite increased from the initial sandwich structure to the first ARB cycle and then decreased from the first to the third ARB cycle. Upon reaching five ARB cycles, the tensile strength of the composite increased again. The variation in the elongation of the composite exhibited a tendency similar to that of its tensile strength. It is observed that with increasing strain, the microhardness values of the Al, Cu, and Ni layers increased, and that the dominant fracture mechanisms of Al and Cu were dimple formation and ductile fracture. In contrast, brittle fracture in specific plains was the main characteristic of Ni fractures.

Aging Behavior of High Volume Fraction SiC Particles Reinforced 2024Al Composite

2024 Al matrix composite reinforced by SiC particles with 45% volume fraction and 1 um diameter was successfully fabricated by squeeze-exhaust casting method. The aging behavior of SiCp/2024AI composite at four temperatures was investigated and compared to 2024 alloy. It was found that the addition of high volume fraction SiC particles does not alter the aging sequence, but it significantly accelerates the kinetics of precipitation in the composite matrices. Therefore, the aging peak of the composite appears earlier than that of 2024AI alloy. This is attributed to the decrease in the activation energy for the precipitate formation and the increase in the precipitate growth rate due to the high density dislocations in the composite with high volume fraction particles. The high density dislocations, as preferential nucleation sites for precipitates, bring about the tiny and dense precipitates in the composite.

Effect of second-phase particle size and presence of vibration on AZ91/SiC surface composite layer produced by FSP

An improved method of friction stir processing(FSP)was introduced for the processing of AZ91 magnesium alloy specimens.This novel process was called“friction stir vibration processing(FSVP)”.FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles.The effect of reinforcing SiC particles with different sizes(30 and 300 nm)on different characteristics of the composite surface was studied.The results indicated that the microstructure was refined and mechanical properties such as hardness,ductility,and strength were enhanced as FSVP was applied.Furthermore,it was concluded that the effect of reinforcing particles with a size of 30 nm on the microstructure and mechanical properties of the surface composite was more obvious than that of particles with a size of 300 nm.It was also found that mechanical properties and microstructure of FSV-processed specimens were improved as vibration frequency increased.The hardness value in the stir zone was about 157 MPa for the FSV-processed specimen at a vibration frequency of 50 Hz,while this value was around 116 MPa for the FSV-processed specimen at a vibration frequency of 25 Hz.

Effect of SiC particle addition on microstructure of Mg_2Si/Al composite

In the present study, by adding SiC particles into AI-Si-Mg melt, Mg2Si and SiC particles hybrid reinforced AI matrix composites were fabricated through the Mg2Si in situ synthesis in melt combined with the SiC ex situ stir casting. The as-cast microstructure containing primary Mg2Si and SiC particles that distribute homogenously in AI matrix was successfully achieved. The effects of SiC particle addition on the microstructure of Mg2Si/AI composites were investigated by using scanning electron microscopy （SEM） and XRD. The results show that, with increasing the fraction of the SiC particles from 5wt.% to 10wt.%, the morphologies of the primary Mg2Si particulates in the prepared samples remain polygonal, but the size of the primary phase decreases slightly. However, when the SiC particle addition reaches 15wt.%, the morphologies of the primary Mg2Si particulates change partially from polygonal to quadrangular with a decrease in size from 50 pm to 30 μm. The size of primary AI dendrites decreases with increasing fraction of the SiC particles from 0wt.% to 15wt.%. The morphology of the eutectic Mg2Si phase changes from a fiber-form to a short fiber-form and/or a dot-like shape with increasing fraction of the SiC particles. Furthermore, no significant change in dendrite arm spacing （DAS） was observed in the presence of SiC particles.

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 SiCp composites. The effect of nano SiCp content in Ti64 alloy/SiCp 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% SiCp composite specimens and resulted in no beneficial effect on the strength and hardness. The compressive strength and hardness of Ti64 alloy/5% nano SiCp MMCs showed higher values. Hence, 5% SiCp can be considered to be the optimal replacement content for the composite.

Role of particle stimulated nucleation in recrystallization of hot extruded Al 6061/SiC_p composites

Studies on texture and microstructure evolution in hot extruded Al 6061 aluminium alloy reinforced with uncoated and nickel coated SiC p were carried out by electron backscattered diffraction technique.Textures of both the alloy and its composite with nickel coated SiC p do exhibit strong β fiber with its axis parallel to the direction of extrusion.In addition to the dominant cube texture（001） 100,fully recrystallized grains with partially equiaxed structure have been observed in the alloy reinforced with uncoated SiC p.The recrystallization texture of this composite can be attributed to the particle stimulated nucleation（PSN） due to the presence of SiC p with size less than 5 μm.Under these conditions,the low value of Zener-Hollomon,Z（～1012s-1） confirms that PSN is one of the dominant mechanisms for recrystallization and is governed by formation of deformation zone rather than stored energy.

Microscopic impacts of ultrasonic vibration on interfacial strength of SiCp/Al composites

SiCp/Al composites are used in aerospace and deep-space exploration equipment because of their extremely high strength and thrust-to-weight ratios;however,the differences in the properties of the reinforcement and matrix materials in this type of composites have restricted their applications.The ultrahigh-frequency vibration characteristics of ultrasonic vibration processing technology can effectively solve the above bottlenecks,but the effect of high-frequency vibration on the interfacial properties of SiCp/Al composites is still unclear.The effects of ultrasonic vibration on the interface strength of composites were analyzed from a microscale perspective by means of single particle push-out Molecular Dynamics(MD)simulations and tests under different conditions.The results show that the interface strength is negatively correlated with particle size but positively correlated with ultrasonic amplitude,with a maximum increase of about 51%relative to no ultrasound.Brittle-plastic transition was observed on the surface of particles with high interface strength,and lateral microcracks due to stress concentration were present on the surface of particles with low interface strength.Higher strains and grain refinement were obtained for larger amplitudes,and stacking faults and tangle dislocations appeared on the side of the interface layer close to the Al matrix.The results provide potential insights to improve the micromechanical and mechanical properties of SiCp/Al composites,enhance the longevity of the materials,and realize the sustainable use of resources by expanding the efficient,precise,and clean machining of such materials.

Tensile behavior of SiC_p/2124Al composites with various SiC particle sizes at room temperature

The tensile properties of 2124Al alloy composites reinforced with various sizes of SiC particles were investigated at room temperature. The size of SiC p was changed from 0.2 μm to 48.0 μm with an identical volume fraction of 20%. The results show that the relative density of the composite decreased with increase of the SiC p size from 3.0 μm to 48.0 μm, whereas 0.2 μm SiC p reinforced composite has the lowest relative density. The pore density, interparticle spacing, SiC particle cracking, SiC p/Al interfacial debonding, the distribution of SiC particles, in the composites are considered as factors to determine the failure behavior of the composites. [

Incorporation of nano/micron-SiC particles in Ni-based composite coatings towards enhanced mechanical and anti-corrosion properties

Ni-based composite coatings incorporated with nano/micron SiC particles were fabricated via electrochemical co-deposition in Watts bath,followed by the evaluation of their mechanical and anti-corrosion properties.The micrographic observations suggest that the SiC particles with various sizes can be well incorporated to the Ni substrate.X-ray diffraction(XRD)patterns indicate that SiC particles with smaller sizes could weaken the preferential growth of Ni along(200)facet.In addition,it is found that the incorporated SiC particles with medium micron sizes(8 and 1.5μm)could significantly enhance the micro-hardness of the Ni composite coatings.Nevertheless,electrochemical measurements demonstrate that micron-sized SiC particles would weaken the corrosion resistance of Ni composite coatings ascribed to the structure defects induced.In contrast,the combined incorporation of nanosized(50 nm)SiC particles with medium micron(1.5μm)ones is capable of promoting the compactness of the composite coatings,which is beneficial to the long-term corrosion resistance with negligible micro-hardness loss.

Effect of SiC particles on microstructure and mechanical property of friction stir processed AA6061-T4

Friction stir processing of AA6061-T4 alloy with SiC particles was successfully carried out.SiC particles were uniformly dispersed into an AA6061-T4 matrix.Also SiC particles promoted the grain refinement of the AA6061-T4 matrix by FSP.The mean grain size of the stir zone (SZ) with the SiC particles was obviously smaller than that of the stir zone without the SiC particles.The microhardness of the SZ with the SiC particles reached about HV80 due to the grain refinement and the distribution of the SiC particles.

Distribution of SiC particles in semisolid electromagnetic-mechanical stir-casting Al-SiC composite

The distribution of SiC particles in Al-SiC composite can greatly influence the mechanical performances of Al-SiC composite. To realize the homogeneous distribution of SiC particles in stir-casting Al-SiC composite, semisolid stir casting of Al-4.25 vol.%SiC composite was conducted using a special electromagneticmechanical stirring equipment made by our team, in which there are three uniformly-distributed blades with a horizontal tilt angle of 25 ° to mechanically raise the SiC particles by creating an upward movement of slurry under electromagnetic stirring. The microstructure of the as-cast Al-SiC composites was observed by Scanning Electron Mcroscopy(SEM). The volume fraction of SiC particles was measured by image analysis using the Quantimet 520 Image Processing and Analysis System. The tensile strength of the Al-4.25 vol.%SiC composites was measured by tensile testing. Results show that the Al-4.25 vol.%SiC composites with the homogeneous distrbutin of SiC particles can be obtained by the electromagnetic-mechanical stirring casting with the speed of 300 and 600 r·min-1 at 620 °C. The differences between the volume fraction of Si C particles at the top of ingot and that at the bottom are both ~0.04 vol.% with the stirring speed of 300 and 600 r·min-1, which are so small that the distribution of SiC particles can be seen as the homogeneous. The tensile strength of the Al matrix is enhanced by 51.2% due to the uniformly distributed SiC particles. The porosity of the composite mainly results from the solidification shrinkage of slurry and it is less than 0.04 vol.%.

Study on Preparation and Separation of SIC Whiskerand Particle from Rice Hulls

The growth mechanism of paramorphic SiC whisker (SiCw) and SiC particle (SiCp) produced from rice bulls under the catalytic actions is studied. The results indicate that the growtb mechanism of the SiCw is vapour-liquid-solid (VLS) , while the crystalline structure of the SiCw is β-SiC. Some SiCp will be formed during the production of the SiCw. Under the pilot-plant condition, the grade of SiCw is over 20%, and SiCp is over 50%. The micron-grade of SiCw and SiCp are separated successfully by flotation and other traditional mineral separation and purification technology. So the grade of the high purity SiCw is over 95 %.

THE EFFECT OF SiC PARTICLE AND WHISKER ON THE STRENGTHOF ALUMINUM ALLOY MATRIX COMPOSITES

The effects of SiC particle and whisker on the strength of aluminum alloy matrix composites have been discussed. The effects of the characteristics of discontinuons reinforcements on the strength of compsites was revealed on the basis of a review of the elastic-plastic finite element method which was applied to predict the stress-strain constituent relationship for particle and whisker reinforeed MMCs. It is snggested that the reinforcement shape or morphology, aspect ratio and distribution in the matrix should be considered in order to get more accumte numerical results. Theoretical strength analysis models predicted the trend of the strength for particle MMCs, but the theoretical results are generally lower compared with the experimental results, especially for the lower strength aluminum alloy. This is becaase strength theories did not consider the change of microstructure of reinforced matrix after particle incorpomtion. We have proposed a combined microstructure strengthening analysis, and the prediction is consistent with the eperimental results.

微纳SiC_P粒度和浓度对化学镀Ni-P-SiC_(P)复合镀层组织与性能影响

以微纳SiC为第二相微粒,在42CrMo钢表面制备Ni-P-SiC_(P)复合镀层,研究了微纳SiC_(P)的粒度(5μm和0.5μm)和浓度对化学镀Ni-P-SiC_(P)复合镀层沉积速率、表面形貌、成分、显微硬度和耐蚀性的影响,并结合Ni-P-SiC_(P)复合镀层截面形貌和成分分布,探讨了Ni-P-SiC_(P)复合镀层的沉积机理。结果表明:SiC_(P)的添加抑制了化学沉积反应,导致Ni-P-SiC_(P)复合镀层的沉积速率下降,但0.5μm的SiC_(P)对沉积反应的抑制作用较弱,形成的NiP-SiC_(P)-0.5复合镀层表面的胞状物尺寸更均匀、平整、致密,随SiC_(P)浓度的增加,Ni-P-SiC_(P)复合镀层的沉积速率下降,复合镀层表面的Ni∶P增加;当SiC_(P)浓度7 g/L时,复合镀层表面的SiC_(P)发生堆积或团聚。当SiC_(P)浓度为5 g/L时,Ni-P-SiC_(P)-0.5复合镀层的显微硬度最大,约753 HV,耐蚀性也最优,自腐蚀电位为-0.363 V。浸润处理后的SiC微粒表面带负电,吸附大量的Ni~(2+),向基底表面运动,与Ni、P均匀的共沉积到基底表面,共沉积的SiC_(P)在复合镀层中具有弥散强化和惰性物理屏障的作用,使Ni-P-SiC_(P)复合镀层具有更高的硬度和更优的耐蚀性。

Effect of SiC Particle Size on Properties of SiC Porous Ceramics

We used different SiC particle size as raw materials and via reaction bonding technique to prepare porous SiC membrane supports.The phase composition,microstructure,bending strength,open porosity,and pore size distribution were investigated as a function of SiC particle size and firing temperature.It is found that the reduction of SiC particle size not only dramatically enhances the bending strength of porous SiC membrane supports,but also slightly reduces the firing temperature duo to smaller SiC particle with higher specific surface area and higher reaction activity.Besides,the open porosity and pore size distribution are dependent on the firing temperature,but insensitive to the SiC particle size due to the pore related characters mainly controlled by the binder.The bending strength increases with the increasing of the firing temperature and with the decreasing of SiC particle size.When the firing temperature was 1500℃and SiC average particle size was 447.75μm,the optimal performance were achieved,the bending strength was 15.18 MPa,the open porosity was 36.02%,the pore size distributed at 3.09-112.47μm,and the mean pore size was 14.16μm.

Influence of stirring speed on SiC particles distribution in A356 liquid

A straight-blade mechanical stirrer was designed to stir A356-3.5vol%SiCp liquid in a cylindrical crucible with the capability of systematically investigating the influence of rotating speed of stirrer on the distribution of SiC particles in A356 liquid. The experimental results show that the vertical distribution of SiC particles in A356 liquid can be uniform when the rotating speed of stirrer is 200 rpm, but the radial distribution of SiC particles in A356 liquid is always nonhomogeneous regardless of the rotating speed of stirrer. The radial centdfugalization ratio of SiC particles in A356 liquid between the center and the periphery of crucible increases with the rotating speed of stirrer. The results were explained in the light of SiC particles motion subject to a combination of stirring and centrifugal effect.

Removal of SiC particles from solar grade silicon melts by imposition of high frequency magnetic field

Non-metallic particles and metallic impurities present in the feedstock affect the electrical and mechanical properties of high quality silicon which is used in critical applications such as photovoltaic solar cells and electronic devices. SiC particles strongly deteriorate the mechanical properties of photovoltaic cells and cause shunting problem. Therefore, these particles should be removed from silicon before solar cells are fabricated from this material. Separation of non-metallic particles from liquid metals by imposing an electromagnetic field was identified as an enhanced technology to produce ultra pure metals. Application of this method for removal of SiC particles from metallurgical grade silicon （MG-Si） was presented. Numerical methods based on a combination of classical models for inclusion removal and computational fluid dynamics （CFD） were developed to calculate the particle concentration and separation efficiency from the melt. In order to check efficiency of the method, several experiments were done using an induction furnace. The experimental results show that this method can be effectively applied to purifying silicon melts from the non-metallic inclusions. The results are in a good agreement with the predictions made by the model.