Some studies into wire electro-discharge machining of alumina particulate-reinforced aluminum matrix composites

Non-traditional process like wire electro-discharge machining is found to show a promise for machining metal matrix composites. However, the machining information for the difficult-to-machine particle-reinforced material is inadequate. This paper is focused on experimental investigation to examine the effect of electrical as well as non-electrical machining parameters on performance in wire electro-discharge machining of metal matrix composites (Al/Al₂O₃p). Taguchi orthogonal array was used to study the effect of combination of reinforcement, current, pulse on-time, off-time, servo reference voltage, maximum feed speed, wire speed, flushing pressure and wire tension on cutting speed, surface finish, and kerf width. Reinforcement percentage, current, and on-time was found to have significant effect on cutting rate, surface finish, and kerf width. The optimum machining parameter combinations were obtained for surface finish, cutting speed, and kerf width separately. Wire breakages were found to pose limitations on the cutting speed in machining of these materials. Wire shifting was found to deteriorate the machined surfaces.     

Effect of Cl on microstructure and mechanical properties of in situ Ti/TiB MMCs produced by a blended elemental powder metallurgy method

A modified blended elemental powder metallurgy (MBEPM) method has been developed for the production of low-cost Ti alloys and in situ Ti/TiB MMCs for automobile components such as connecting rods and inlet and exhaust valves. The MBEPM method uses Ti sponge fines as raw material, which contain a substantial amount of Cl. The Cl refines the microstructure of the as-sintered Ti–6Al–4V alloys, with a reduced prior β-grain size and a reduced α-lath size and aspect ratio. However, the grain refining effect of Cl is much less pronounced in as-sintered Ti–6Al–4V–10%TiB MMCs. The Cl is present in the as-sintered microstructure in three forms: (1) shells consisting of fine NaCl particles in macropores; (2) cuboidal NaCl precipitates in the alloy matrix; and (3) Cl and Na segregated to prior β-grain boundaries. Increasing the Cl content increases the tensile ductility of both Ti–6Al–4V alloys and Ti–6Al–4V–10%TiB MMCs, but has little effect on strength.     

铝基复合摩擦材料摩擦磨损性能研究

以S iC颗粒增强的铝基复合材料(S iCp)与GCr15钢配副为对象,与现用的蠕墨铸铁(Compacted graph ite iron)制动盘材料进行对比,应用销-盘式高速摩擦磨损模拟试验,研究摩擦磨损条件对摩擦学特性的影响规律。     

Ceramic particles reinforced copper matrix composites manufactured by advanced powder metallurgy:preparation,performance, and mechanisms

Copper matrix composites doped with ceramic particles are known to effectively enhance the mechanical properties, thermal expansion behavior and high-temperature stability of copper while maintaining high thermal and electrical conductivity. This greatly expands the applications of copper as a functional material in thermal and conductive components, including electronic packaging materials and heat sinks, brushes, integrated circuit lead frames. So far, endeavors have been focusing on how to ch...     

Friction and wear properties of short carbon fiber reinforced aluminum matrix composites

The friction and wear properties of short carbon fibers (SCFs) reinforced aluminum matrix composite were studied. The influences of the fiber volume fraction, load applied, rotating speed, and wear mechanism were discussed. The results indicated that SCFs/Al composite had better tribological properties than Al alloy. The friction coefficient and wear mass loss decreased with the fiber volume fraction increased, but increased as the load and rotating speed increased, respectively. SCF reduced direct contact between the matrix and counterpart and improved the wear resistance of SCFs/Al composite greatly. The wear displayed a linear evolution in all the range of load. Surfaces before and after wear tests were characterized using scanning electron microscopy (SEM) and energy-dispersive analysis of X-ray (EDAX) spectroscopy.     

Properties of powder produced by a high-speed method

A high-speed method of powder production is analyzed. X-ray, chemical, and granulometric analysis indicates that the particle size of the powder obtained depends on the grinding conditions. The properties of the powder are basically the same as those of the initial sample.

     

Effect of powder thixoforging process on microstructural and mechanical properties of recycled 520 aluminum alloy

In this paper, reusing Al alloy chips via novel recycling process of powder thixoforging (PTF) is presented. PTF is a direct machining chips conversion method with partial melting into high quality final products with improved mechanical properties compared to parent alloy. 520.0 Al alloy powders from milling chips were produced via mechanical alloying (MA). The PTF product exhibited remarkable combination of mechanical properties of 168 HV hardness, compression yield strength (CYS) of 515 MPa, ultimate compression strength (UCS) of 1121MPa, and substantial fracture plastic strain of 45 %. Additionally, the PTF product showed relative weight reduction of 55.7 %. As a consequence, the microstructure refinement and modification during PTF have significant effects on dramatic improvement of mechanical properties, leading to considerable combination of superior strength and ductility.     

Deformation and mechanical properties of components produced by plastic shaping

The deformation and mechanical properties of components obtained by cold stamping may be analyzed by determining the scalar hardness field over the volume of the plastically deformed material. This permits the prediction of the components’ performance.     

Influence of matrix precursors on the microstructure and mechanical properties of C/C composites

The microstructure and properties of uni-directional pitch-based carbon-carbon composites are explained in terms of the chemical composition of pitch precursors. Pitches are characterized by standard procedures (elemental analysis, softening point and solubility tests), extrography which is a simple and rapid silica gel adsorption chromatographic technique, Fourier transform infra-red and gas chromatography of the toluene-soluble fraction. Pitch pyrolysis behaviour is monitored by hot-stage microscopy. The main microstructural features of uni-directional composites from pitches and commercial PAN-based carbon fibres are determined by light microscopy and scanning electron microscopy.     

镁基复合材料磨损性能研究进展

介绍近年来有关颗粒、短纤维(或晶须)和纤维增强镁基复合材料干滑动摩擦磨损的研究现状,分析了正载荷、滑动速度、滑动距离和增强相种类、大小、形状、取向、体积分数等因素对镁基复合材料磨损性能的影响.     

Application of ANN in the prediction of the pore concentration of aluminum metal foams manufactured by powder metallurgy methods

In this work, the effect of fabrication parameters on the pore concentration of aluminum metal foam, manufactured by the powder metallurgy process, has been studied. The artificial neural network (ANN) technique has been used to predict pore concentration as a function of some key fabrication parameters. Aluminum metal foam specimens were fabricated from a mixture of aluminum powders (mean particle size 60 μm) and NaCl at 10, 20, 30, 40(wt)% content under a pressure of 200, 250, and 300 MPa. All specimens were then sintered at 630°C for 2.5 h in argon atmosphere. For pore formation (foaming), sintered specimens were immersed into 70°C hot running water. Finally, the pore concentration of specimens was recorded to analyze the effect of fabrication parameters (namely, NaCl ratio, NaCl particle size, and compacting pressure) on the foaming behavior of compacted specimens. It has been recorded that the above-mentioned fabrication parameters are effective on pore concentration profile while pore diameters remain unchanged. In the ANN training module, NaCl content (wt)%, NaCl particle size (μm), and compacting pressure (MPA) were employed as inputs, while pore concentration % (volume) of compacts related to fabrication parameters was employed as output. The ANN program was successfully used to predict the pore concentration % (volume) of compacts related to fabrication parameters.     

Effect of fabrication parameters on the pore concentration of the aluminum metal foam, manufactured by powder metallurgy process

In this paper, the effect of fabrication parameters on the pore concentration of aluminum metal foam manufactured by powder metallurgy process is studied. Aluminum metal foam specimens were fabricated from the mixture of aluminum powders (mean particle size 60 μm) and NaCl at 10,20,30,40(wt) % content under 200, 250, 300, MPa Pressures. All specimens were then sintered at 630°C for 2.5 hours in an argon atmosphere. For pore formation (foaming), sintered specimens were immersed into 70°C hot running water. Finally the pore concentration of specimens was recorded to analyze the effect of fabrication parameters (namely NaCl ratio, NaCl particle size and compacting pressure) on the foaming behavior of compacted specimens. As a result of the study, it has been recorded that the above mentioned fabrication parameters are effective on pore concentration profile while pore diameters remained unchanged.     

Investigation of mechanical and tribological properties of tribo‐layer of Ni3Al matrix composites

The sliding wear of Ni₃Al matrix composites with addition of 1.5 wt.% graphene nanoplates was studied through pin‐on‐disc wear testing. The spontaneous formation of a tribo‐layer produced during sliding wear was found to result in a deviation from Archard scaling and an unexpected high wear resistance that was not based on hardness alone. The tribo‐layer exhibited specific microstructural evolution with significant severe deformation and grain refinement after wear. In the grain refinement area, the accumulation of dislocations and an increase in misorientations were found to lead to strain hardening. For the plastic deformed area, reduction in the dislocation density inside the elongated ultrafine grains reduced strain hardening compared with the grain refinement area. It can be concluded that the deviation from Archard scaling occurred primarily as a result of the microstructural evolution of the tribo‐layer, resulting in the specific performance of mechanical and tribological properties of Ni₃Al matrix composites under cyclic sliding wear process. Copyright © 2016 John Wiley & Sons, Ltd.     

Nanostructure of interlayers in different Nicalon fibre/glass matrix composites and their effect on mechanical properties

Interlayer phenomena, revealed by high-voltage electron microscopy (HVEM) and high-resolution electron microscopy (HREM), are presented as they occur in various SiC(Nicalon) fibre-reinforced Duran glass composites (differing in the specific sol-gel supported production processes). Their dependence on the production parameters and their influence on the materials properties are discussed, taking into account the results of scanning electron microscope (SEM) in situ tensile tests. Besides graphitic carbon, textured to a variable degree and influencing the tensile behaviour, oxycarbide formation is indicated. A reactive matrix additive, such as, e.g. TiO₂, resulted in a decrease in strength and a brittle behaviour, while the addition of ZrO₂ markedly improves the mechanical properties.     

Vibration characteristics and machining performance of a novel perforated ultrasonic vibration platform in the grinding of particulate-reinforced titanium matrix composites

Ultrasonic vibration-assisted grinding (UVAG) is an advanced hybrid process for the precision machining of difficult-to-cut materials. The resonator is a critical part of the UVAG system. Its performance considerably influences the vibration amplitude and resonant frequency. In this work, a novel perforated ultrasonic vibration platform resonator was developed for UVAG. The holes were evenly arranged at the top and side surfaces of the vibration platform to improve the vibration characteristics. A modified apparent elasticity method (AEM) was proposed to reveal the influence of holes on the vibration mode. The performance of the vibration platform was evaluated by the vibration tests and UVAG experiments of particulate-reinforced titanium matrix composites. Results indicate that the reasonable distribution of holes helps improve the resonant frequency and vibration mode. The modified AEM, the finite element method, and the vibration tests show a high degree of consistency for developing the perforated ultrasonic vibration platform with a maximum frequency error of 3%. The employment of ultrasonic vibration reduces the grinding force by 36% at most, thereby decreasing the machined surface defects, such as voids, cracks, and burnout.     

Friction of composites based on titanium carbide produced by the process combustion method

The method of SHS force compaction is used to produce composites that include TiC + 50 vol % inert. Copper, iron, nichrome, and steel G13 served as the inert. It is noted that the lattice parameter, the TiC grain size, and the mass ratio Ti/C in TiC grains are practically independent of the inert composition. It is shown that some of the composites possess high mechanical properties. The friction of the composites that contain Ni-Cr is characterized by a friction coefficient of up to 0.5 and a high wear owing to their strong adhesion to the counterbody. The materials whose compositions are TiC + (Cu, Fe) and TiC + (Cu, G13) are effective under a pressure of about 100 MPa and can serve as a basis for developing tribological materials.     

氧化铝增强铝基复合材料液态成型中的界面反应

分析了陶瓷纤维或颗粒增强铝基复合材料中出现的主要界面反应产物即MgAl2O4的形成规律、形成条件及对材料的作用,并提出了抑制该反应的途径及方法。