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Silicon carbide particles reinforced aluminum matrix composites are widely used in national defense and related high-end technology fields due to their excellent mechanical properties. To explore the milling mechanism and tool wear mechanism of low-volume SiCp/Al composites in high velocity milling, the milling experiments for 20% volume SiCp/Al2009 composites were performed using a polycrystalline diamond (PCD) tools. A three-dimensional milling model of SiCp/Al composite was established considering the random distribution of SiC particles, the influence of milling parameters on surface quality was comprehensively analyzed and its cutting mechanism was described, and the wear forms and mechanism of PCD tools were revealed during milling of SiCp/Al composites. The result showed that the cutting depth is the main factor affecting the machined surface quality, followed by the spindle speed, and the feed rate has the smallest effect on it. It was observed that when spindle speed (n) was 17,000 r/min, the feed rate (f) was 8 mm/min, the depth of cut (ap) was 0.04 mm, the surface roughness value was the smallest, Ra was 0.056 μm. The surface morphology was mainly manifested as pits, cracks, burrs, and so on, subsurface defects included particle breakage, peeling, and matrix cracks, and the tool wear forms included chipping, flaking, and bond wear.

As a classic in-situreaction, the Al-TiO2reaction is expected to prepare aluminum matrix composites with high thermal stability. In this study, it was found that the preparation method of ensuring sufficient reaction using higher temperatures in previous studies was not conducive to acquiring optimized high-temperature strength. With the increase of hot-pressing temperature and the extension of holding time, the in-situreaction became more thorough, but the strength of the composites first increased and then decreased. Coarsening of the microstructure at high temperatures would lead to degradation of strength and controlling the in-situreaction process by the hot-pressing parameters could optimize the mechanical properties of the composites. Strengthening mechanisms at room and high temperatures were studied, and it was found that the load-transfer and Orowan strengthening mechanisms are the main strengthening effects at room temperature, while the pinning effect of fine particles became more crucial at elevated temperatures. As a result, the coarsening of the reinforcing phases was more detrimental to the high-temperature strength. Therefore, an insufficient in-situreaction led to more excellent mechanical properties, and the composite hot-pressed at 605°C and held for 2 h exhibited the highest strength, which was 367 MPa at room temperature and 170 MPa at 350°C.

A 3D representative volume element (RVE) model was developed to analyze the effective thermal expansion coefficient (CTE) of carbon nanotube reinforced aluminum (CNT/Al) composites. The influences of geometric configuration, orientation and volume fraction of CNTs on CTE of the CNT/Al composites were investigated. The results show that the orientation of CNTs significantly influences the stress and strain distributions around CNTs, and when CNTs are parallel to the load direction, the constraint effect of CNTs on the matrix is the largest. Furthermore, the configuration of CNTs also plays an important role in reducing thermal expansion behavior of CNT/Al composites, and the bundled configuration exhibit the lowest CTE. In particular, with the increase of the number of CNTs in each bundle, the CTE decreases and then tends to be unchanged. When the volume fraction of CNTs is 5%, and the number of CNTs in each bundle is 25, the CTE of the composite reaches 5.12 × 10−6/°C, which is 76% lower than the CTE of the matrix. A linear decrease of the CTE of CNT/Al composites is observed as the CNT volume fraction increases. Overall, this work establishes a comprehensive understanding of factors affecting the CTE, and the obtained findings could provide a good theoretical basis for designing low CTE CNT/Al composites.

In this paper, the finite element cutting simulation model with irregular distribution of multiple particles is established, the stress and strain distribution of SiC particles in the process of machining, as well as the material removal mechanism are analyzed. The effects of cutting velocity and feed per tooth on the surface quality of the material are also analyzed. The effect of feed per tooth on subsurface damage is revealed. The results show that in the micro-milling of SiCp/Al2024 composites, the particle removal form is mainly crushing and extraction. The surface defects of the workpiece mainly include pits, scratches, cracks, and extrusion damage. When the cutting velocity increases, the surface defects gradually change to crack, which can improve the surface quality of the workpiece. Increasing the feed per tooth will increase the surface defects of the workpiece and lead to poor surface quality. When the feed per tooth increased from 0.428 µm to 0.714 µm, the subsurface damage thickness increased from 35.2 µm to 47.3 µm.

The raw and pre-smashed (PS) carbon nanotube (CNT) reinforced 6061Al composites (CNT/6061Al) with different CNT contents were respectively fabricated by powder metallurgy technology. It was found that reducing the CNT cluster size by pre-smashing processing could sharply reduce the friction coefficient, and significantly improve the density, hardness, and wear resistance of the CNT/6061Al composites. For the raw-CNT/6061Al composites, the wear rate increased approximately linear trend while the CNT content was over 1 wt.%. The plastic deformation, deep grooves, and serious delamination were presented on the wear surface. The wear process was gradually transformed from Al-copper base counterpart wear into Al-Al wear for the higher adhesion-binding energy between aluminum and copper base counterpart. While for the PS-CNT/6061Al composites, the wear rate gradually decreased as the CNT content increased from 0 to 2 wt.%. This was mainly because the generation of the thinner mechanically mixed layer (MML) and the PS-CNT prevented the direct contact between specimen and copper base counterpart, which effectively inhibited the adhesive wear. But excessive PS-CNT addition (∼3 wt.%) would weaken the bonding between CNT and 6061Al, and thus the wear resistance of the composite was reduced apparently.

The uniformly dispersed carbon nanotubes (CNTs) reinforced 6061Al composites (CNT/6061Al) with different CNT concentrations were fabricated by powder metallurgy technology. It was found that the friction coefficient as well as wear rate decreased first and then increased as the CNT concentration increasing under 15 N as well as 30 N, and the minimum wear rate was achieved at the CNT concentration of 2 wt%. Adhesive wear and abrasive wear were the dominated wear mechanisms for the 1–2 wt% CNT/6061Al composites under 15 N and 30 N, while the delamination occurred on the wear surface at 3 wt% CNT. As the applied load increased to 60 N, the wear rate of composites increased dramatically. The wear mechanism transformed from abrasive wear to severe delamination wear, accompanied by the generation of wear debris with sharp edge due to the weaker anti-shearing strain capacity of CNT/6061Al composites.

In this paper, Abaqus software was used to construct a SiCp/Al2024 composite cutting simulation model with a multi-particle random distribution model, and the particle removal mechanism and surface defect evolution under mesoscopic size were analyzed. In addition, the influence of spindle speed on particle removal and surface defect formation was studied, and the best cutting parameter combination was explored. The results show that in the milling of high volume fraction SiCp/Al2024 composites, because the cutting edge radius of the tool is much larger than the particle size, the main form of particle removal is crushing. The surface defects of the workpiece mainly include pits, cracks, scratches and sliding layers. Increasing the cutting speed will increase the surface defects of the workpiece and the surface quality will deteriorate. The feed rate has the greatest influence on the surface roughness, followed by the spindle speed, and the milling depth has the least influence. The best combination of surface roughness is 14000 r/min spindle speed, 0.072 m/min feed rate and 45 μm milling depth. At this time, the surface roughness of the workpiece is 0.578 μm.

The separation of misalignment aberrations is a crucial step in interferometric testing for the acquisition of the real surface. In this paper, a Fizeau interference system and a conical mirror with a certain angle were used to achieve the shape measurement of the inner surface of the frustum of a cone. Based on the ray-tracing method, the relationship between the adjustment errors and misalignment aberrations was established, and the misalignment aberrations could be removed by using the error separation model that accords with the least-square algorithm theory. The simulation and practical measurement results indicate that the approach proposed is valid and feasible.

B 4 C particulate-reinforced 6061Al composite was fabricated by powder metallurgy method. The as-rolled composite possesses high tensile strength which is comparable to that of the peak-aged 6061Al alloy. More importantly, the microstructures and mechanical properties are thermally stable during long-term holding at elevated temperature (400 °C). The microstructual contributions to the strength of the composite were discussed. Transmission electron microscopy (TEM) analysis indicates that the in-situ formed reinforcement Mg(Al)B 2 , as products of the interfacial reactions between B 4 C and the aluminum matrix, show not only good resistance to thermal coarsening but also strong pinning effect to the grain boundaries in the alloy matrix. [ABSTRACT FROM AUTHOR]

As an aluminum-based reinforcement, Mg2Si particles have excellent properties such as high hardness, high melting point, and high elastic modulus compared with other reinforcements and are widely used in aerospace and automobile fields. However, there is little research on the cutting mechanism of this material. In order to explore the surface grinding mechanism of Mg2Si/Al composites, Grinding simulation of low-volume fraction Mg2Si/Al composites was carried out by ABAQUS, and the influence of different positions of matrix and particle removal on the surface quality of Mg2Si/Al composites was expounded. The plane reverse grinding test was carried out by using CBN (boron nitride) grinding wheel. The L16(43) orthogonal test and three groups of single factor tests were designed. The orthogonal results show that the linear velocity of the grinding wheel has the greatest influence on the surface roughness, and the feed rate and grinding depth are significantly smaller. The range analysis shows that the optimal grinding parameters are: vs = 35 m/s, vw = 0.75 m/min, ap = 0.015 mm. The regression equation for surface roughness was established by using MATLAB. The single factor results show that the surface quality is obviously improved by increasing the linear velocity of the grinding wheel and reducing the feed rate and grinding depth through the observation of the morphology of the processed specimen. The analysis results show that defects such as pits, protrusions, burrs, and a small amount of fish-scale-like on the machined surface are mainly caused by the linear velocity of the grinding wheel, the pulling force of the grinding wheel, and the adhesion of the debris. The defects such as particle micro-cracks, particle pull-out, and matrix cracking on the subsurface, are mainly caused by the compressive stress of the grinding wheel and the stress concentration of the particles. The research results have guiding significance for future composite material cutting research and actual cutting processing.

Carbon nanotube aluminum matrix (CNTs/AL) composites are ideal lightweight and high-strength materials due to their excellent properties. However, the research on CNTs/AL composites only stays in the simulation and preparation stages, and no grinding research has been carried out. Revealing the grinding mechanism of CNTs/AL composites has far-reaching significance for the development of high-end equipment industries such as aerospace. Taking CNTs/2009AL composites as the research object, a minimum quantity lubrication (MQL) flat grinding platform was built for comparing the surface quality and defects of dry grinding and MQL grinding. The experimental results show that grinding wheel velocity was the grinding parameter that had the greatest influence on surface roughness in dry grinding and MQL grinding. The subsurface defects of dry grinding mainly included microcracks, burrs, pits, coatings, cavities, etc., and the rebound phenomenon of agglomerated carbon nanotubes. The subsurface defects of MQL grinding were only burrs and pits. The surface coating phenomenon of dry grinding increased with the increase in grinding wheel velocity, and the surface quality was improved. MQL grinding could significantly reduce grinding heat, reduce friction, and make the machined surface smoother. In dry grinding and MQL grinding, the subsurface damage depth decreased obviously with the increase in grinding wheel velocity. When the grinding wheel velocity was 30 m/s, the minimum subsurface damage depth of dry grinding and MQL grinding was 40.091 and 26.906 μm, respectively. Mastering the grinding mechanism of grinding CNTs/AL composites and the influence of grinding parameters on surface quality provides a basis for the selection of parameters and methods in grinding in industry. MQL grinding of CNTs/AL composites reduces the formation of many surface defects and improves the surface quality of the workpiece. It is an efficient, clean, and environmentally friendly processing method.

The effects of hot extrusion on the interfacial microstructures and tensile properties of 15 vol.% SiCp/2009Al composites fabricated at different hot pressing temperatures were investigated. After hot extrusion, the relative density of the composites increased, the SiC particle distribution became more uniform, and the SiC particles tended to align along the extrusion direction. Furthermore, the interface bonding was improved after hot extrusion; however, the extrusion exerted no obvious effect on the interfacial reaction products formed during sintering process. Tensile tests indicated that the mechanical properties of the composites were improved significantly after extrusion. Fractography revealed that the fracture mechanism of the extruded composites fabricated at the hot pressing temperatures below 540°C was mainly the interfacial debonding. For the extruded composites fabricated at 560–600°C, the fracture was the matrix ductile fracture and the SiC particle fracture. When the composites were hot pressed at or above 620°C, after extrusion, the fracture mechanism of the composites was the matrix ductile fracture, the interface cracking and the SiC particle fracture. [Copyright &y& Elsevier]