Turning Machinability of SiC Particle Reinforced Aluminum Alloy Composites

An overview of the effect of stirrer design on the mechanical properties of Aluminium Alloy Matrix Composites fabricated by stir casting

Analyses of metallurgical behavior of Al–SiCp composites after ballistic impacts

The fracture mechanisms of composites which contain coarse second phase (30 µmSiC) have been studied by acoustic emissions measurement. The fracture mechanism for these composites is different from that for composites containing small particles. In the latter case, it is well known that the void nucleation during fracture occurs at interface between matrix and reinforcement. The experimental data and the current model for fracture were compared, and fracture strain has been estimated using a modified particle fracture model based on the Evensen void growth model. Acoustic emissions were detected from fractured particle, although there are some differences in AE responses caused by difference in heat treatment. Void nucleation occurs by particle fracture in all of the materials. A modified equation for the fracture strain has been proposed and this equation provides a good quantitative agreement with experimental data.

Silicon carbide particle–reinforced aluminum matrix (SiCp/Al) composites were milled at a high speed by adopting polycrystalline diamond (PCD) tools, which the diamond grain sizes were 5, 10, 25, and 32 μm. The machined materials were SiCp/Al composites which the volume fraction was 45% and grain size of SiC particles was 5 μm. The tool wear resistance and wear morphology of polycrystalline diamond cutters were investigated. And it centered on the effects of diamond grain sizes on the cutting forces as well as the machined surface roughness. The obtained results indicated the difference of corresponding tool wear resistance between larger SiC particles and smaller SiC particles during high-speed milling SiCp/Al composites with higher volume fraction. When the grain size and volume fraction of SiC granules are 5 μm and 45%, the tool wear resistances of four diamond grain sizes were all far higher than those of tools in machining composites with higher volume fraction (56%) and larger 60-μm SiC particles. And the PCD tools of larger diamond grain size acted on better wear resistance. Both the corresponding cutting forces and surface roughness were also smaller. As cutting distance increased, the variation law of cutting forces had a good correspondence with the tool wear of PCD cutters of different diamond grain sizes. The machined surface roughness had a decreasing trend in general, but the fluctuation range was tiny. The main wear morphology was flank wear and slight wear groove marks. And there was no chipping of cutting edge and coarse wear groove marks. A large amount of the machined materials was adhered on flake face in the cutting process, but built-up edge was not formed.

Silicon carbide particle reinforced aluminium alloy composites have been studied. One of the most important problems with metal matrix composites is low interfacial bonding strength between reinforcement and matrix, which results in poor mechanical properties. This work studied the coating method with the aim of improving interfacial bonding between SiC particles and Al alloy. Titanium coated SiC plates and particles were prepared by plasma enhanced chemical vapour deposition (PECVD) using the reactant system TiCl4–H2. Continuous and adherent films on the SiC plates and particles were obtained by PEC VD treatment for 2 min. Treatment by PECVD for periods greater than 2 min resulted in crack formation and agglomeration of particles. Chlorine content in the films was reduced by using laser CVD as compared with PECVD.

Tool wear and surface roughness of Al 2O 3 particle-reinforced aluminium alloy composites

Mirror surface machining for large area flattening in the display field has a problem such as a tool wear and a increase in machining time due to large area machining. It should be studied to decrease machining time and tool wear. In this paper, multi-tool machining method using a PCD tool and a SCD tool was applied in order to decrease machining time and tool wear. Machining characteristics (cutting force, machined surface and surface roughness) of PCD tool and SCD tool were evaluated in order to apply PCD tool to flattening machining. Based on basic experiments, the PCD/SCD multi-tool method and the SCD single-tool method were compared through surface roughness and machining time for appllying large area mold machining.

Flexural strength, elastic modulus, and hardness were used to characterize the mechanical properties of ZrB 2 –SiC composites that contained varying SiC particle sizes. Dense ZrB 2 –SiC composites consisting of 70 vol% ZrB 2 and 30 vol% α‐SiC were produced via hot pressing. This series of composites had maximum SiC particle sizes that ranged from 4.4 to 18 μm. The mechanical properties scaled with the maximum SiC particle size, not with ZrB 2 grain size. Flexural strength decreased as the maximum size of SiC particles increased from 1150 MPa at 4.4 μm to 245 MPa at 18 μm with an abrupt decrease in strength at ~11.5 μm. Elastic modulus remained constant at ~530 GPa for compositions containing SiC particles smaller than 11.5 μm, but exhibited a decrease with larger SiC particle sizes. Vickers and Knoop hardness were 21.4 and 17.2 GPa, respectively, for ceramics with SiC particle sizes <11.5 μm, but hardness decreased for larger SiC particle sizes. The decreases in strength, elastic modulus, and hardness with SiC particles larger than 11.5 μm were coincident with stress‐induced microcracking in the composites.

The available temperature range of the self-healing induced by high temperature oxidation of SiC can be controlled by the particle size of the contained SiC particles. In this study, three types of alumina–SiC composites were prepared. The SiC particle sizes of the composites were 270, ∼30 nm, and less than 10 nm. The self-healing abilities were estimated by the strength recovery behavior at several temperatures. The use of nanometer-sized dispersed SiC particles as healing agent decreases the activation energy of the SiC oxidation obtained from the differential thermal analysis with several heating rates. This implies that smaller SiC particles can give rise to the oxidation at lower temperature. Moreover, the lowest temperature at which the cracked strength was completely recovered for 10 h was strongly affected by the SiC particle size. As the SiC particle size varied from 270 to ∼30 nm, the lowest temperature varied from 1300 to 950 °C. However, alumina composite containing SiC particles whose particle size is less than 10 nm cannot recover completely the cracked strength under every condition, because the space between crack walls cannot be filled with the formed oxide due to the small volume of SiC on the crack walls. Therefore, it was found that there is an optimal SiC particle size for endowing self-healing ability.

The SiC particle reinforced aluminum alloy has been developed for various machine parts. Aluminum welded machine parts often require welded joints composed of dissimilar alloys. In the present study, electron beam weldability of dissimilar joints was investigated on different combinations of aluminum alloys of 10 mm thickness. The main alloy is 10% SiC particle reinforced Al–Si aluminum alloy. Combination wrought alloys are Al–Si, Al–Mg, Al–Mg–Si and Al–Zn–Mg–Cu alloys. The electron beam machine is a 6 kW high voltage type. The joint groove is of square butt without filler metal. In the case of SiC reinforced alloy/Al–Si and Al–Mg, joints, weldability was poor because some weld imperfections were recognized such as arcing and other defects. In the case of SiC reinforced alloy/Al–Mg–Si, Al–Zn–Mg–Cu, the cracking sensitivity is low while some small porosity was recognized. Tensile strength became about 150 MPa such as SiC reinforced alloy. Impact values of the SiC reinforced alloy/Al–Mg–Si joint were recovered through 2160 h room temperature ageing. Micro segregation of the Si element was recognized for the SiC reinforced alloy/Al–Mg–Si joint by electron probe microanalyser analysis.

In this study, turning of the cemented carbides that their WC particle size was standardized were carried out with the PCD and the cBN tools. The WC particle diameter of cemented carbides was about 2µm and the Co contents were 10, 15, 20 and 25%, respectively. The influence of the WC particle size and Co contents was investigated. Summary of results are shown as follows: (1) In turning with the PCD tool, the more the Co contents increase, the more the tool wear increases. (2) In turning with the cBN tools, the more the Co contents of the work material increase, the more the tool wear decreases. (3) In turning of the cemented carbides contained the larger quantity of Co, the cBN tools are more effective than the PCD tool.

This paper deals with the investigation of mechanical properties by introducing micro size SiC particulates and Graphite particulates into Al-4.5%Cu alloy matrix. SiC and Graphite particle reinforced Al alloy metal matrix composites were prepared by stir casting method. Al-Cu alloy was taken as the base matrix to which SiC and Graphite particulates were used as reinforcements. 6 wt. % of SiC and Graphite particulates were added to the base matrix to fabricate Al-4.5Cu – 6 wt. % SiC and Al-4.5%Cu – 6 wt. % Graphite composites. For each composite, the reinforcement particles were pre-heated to a temperature of 600oC and then dispersed in steps of two into the vortex of molten Al-Cu alloy to improve wettability and distribution. The Micostructural study was done by using optical microscope, which revealed the uniform distribution of SiC and Graphite particles in matrix alloy. Mechanical properties like hardness, tensile and impact strength were evaluated as per ASTM standards. Hardness and tensile strength increased with addition of 6 wt. % of SiC particulates in the base matrix Al-Cu alloy compared to Al-Cu-6wt. % Graphite composites.

Effects of reinforcement particle size in MMCs on extrusion die wear

Charge accumulation phenomenon on gas–solid interface greatly restricts the development of HVDC energy transmission system. In this study, the surface charge transport behavior and flashover performance on alumina/epoxy spacer coated by SiC/epoxy composites are experimentally investigated under DC stress. SiC/epoxy composites with varied SiC particle size are fabricated and deposited on spacer surface. Nearly a charge free surface is achieved especially at smaller SiC particle size, even when metallic wires are adhered on spacer surface and connected to high voltage electrode. The DC flashover voltage increases with the decrease of SiC particle size. On the one hand, smaller SiC particle size exhibits more outstanding nonlinear conductivity characteristics, contributing to accelerating charge dissipation, whereas on the other hand, it would introduce plenty of shallow traps due to the increased interfacial regions between SiC particle and epoxy matrix, resulting in aggravating charge accumulation. A theoretical model is proposed to reveal the control mechanism of SiC/epoxy coating with different SiC particle size on flashover performance. The validity of this model can be confirmed based on the surface trap distribution, carrier mobility and our previous investigations on gas–solid interface flashover development process.

The dynamics of concentrated suspensions of non-colloidal, monodisperse particles in plane Poiseuille flows are investigated by fully three-dimensional numerical simulations for bulk volume fractions of 0.20–0.40 of neutrally-buoyant particles. The ensemble averages of the volume fraction and particle velocity profiles are consistent with previous experiments. A statistical analysis indicates that there is an intermediate region between particle layers near the wall and a plug region in the core, in which the behaviour of ensemble-averaged suspension field can be approximated by a continuum theory. In the intermediate region, the wall-normal and spanwise velocity fluctuations, angular velocity in the vorticity direction and particle shear stress are found to be linear functions of the distance from the wall. The particle normal stresses in the intermediate region are almost uniform, consistent with the concept of normal-stress-driven particle migration. The intermediate region decreases in extent and the width of the core region increases for larger bulk volume fractions. There is a remarkable similarity between the particle–phase pressure profiles scaled by the local shear rate for different bulk volume fractions. The particle pressure profiles in the intermediate region are compared with the rheological model proposed by Morris & Boulay (1999). The effective viscosity, evaluated from the ratio of the total shear stress to the fluid-phase shear stress, shows a good agreement with empirical viscosity relations in Couette-flow suspensions. In the present study, both non-local dynamics and finite-size effects of the particles are evident in the core of the channel. These effects are more pronounced at larger volume fractions.