Characterization of ZrC reinforced AA6061 alloy composites produced using stir casting process

In the present study, effect of ZrC vol.% on mechanical properties of AA6061 metal matrix composites (MMCs) produced via stir casting technique was investigated. The vol.% of ZrC particles was varied as 5,10 and 15. The composites were characterized for its microstructure and mechanical properties and their relationships were obtained. The scanning electron microscope (SEM) images revealed uniform distribution and good bonding between the AA6061 alloy and the ZrC particles. The mechanical properties of the AA6061 alloy was found to significantly improve with the addition of ZrC particles from 5 to 15 vol.%, the hardness increased from 32 to 68 HV, yield strength increased from 50 to 86 MPa and the ultimate tensile strength increased from 118 to 165 MPa. However, the % of elongation of the composite samples decreased with 15 vol.% addition of ZrC particles. Sliding wear behaviour of the composites was investigated using a pin-on-disc wear tester at a load of 9.8 N and addition of ZrC particles was significantly found to reduce the wear rate of AA6061 alloy.

     

Fretting wear of Al-Si alloy matrix composites

Ball-against-disk type fretting wear tests for Al-Si alloy matrix composites in contact with bearing steel were conducted in wet air to investigate the effects of relative slip amplitude on friction and wear of the composites. In the larger range of relative slip amplitude, the Al-Si alloy-impregnated graphite composite (ALGR-MMC) shows lower friction coefficients than those of alumina short fiber-reinforced composite (ASFR-MMC) and hollow silica particle-reinforced composite (HSPR-MMC). Although the wear rate of the ALGR-MMC is higher than that of the ASFR-MMC and HSPR-MMC, the composite hardly causes damage to the mating material due to adhesion of compacted films of graphite powder and Al-Si alloy wear particles.     

Assessment of the machinability of Ti-6Al-4V alloy using the wear map approach

The high strength to density ratio of titanium alloys coupled with excellent corrosion resistance even at elevated temperatures make them ideal for aerospace applications. Moreover, the biocompatibility of titanium also enables its widespread use in the biomedical and food processing industries. However, the difficulty in machining titanium and its alloys along with the high cost of its extraction from ore form presents a major economic constraint. In the context of machining economics, the wear map approach is very useful in identifying the most suitable machining parameters over a feedrate–cutting velocity plane. To date, wear maps have only been prepared for the machining of ferrous alloys. In this article, a review of the machinability of Ti-6Al-4V alloy is presented with emphasis on comparing the wear performance of various tool materials. In addition, a new wear map for Ti-6Al-4V alloy is presented based on unified turning tests using H13A grade carbide inserts. This wear map can be used as a guide in the selection of cutting variables that ensure the least tool wear rates. This article contrasts the occurrence of a safety zone in the case of machining steels to that of an avoidance zone for Ti-6Al-4V alloy.     

Laser hole cutting into Ti-6Al-4V alloy and thermal stress analysis

Laser hole cutting into Ti-6Al-4V alloy is carried out. Temperature and stress fields during the cutting process are predicted using the finite element code. Temporal variation of surface temperature in the region close to the kerf edge is monitored by a thermocouple and compared with the predictions. The residual stress formed in the cutting region is obtained from the XRD technique and compared with the predictions. The morphological changes around the kerf surfaces are examined incorporating optical and scanning electron microscopes. It is found that von Mises stress attains slightly higher values at the top circumference as compared to that corresponding to the bottom circumference of the hole cut. The prediction of temperature variation agrees well with the thermocouple data. The residual stress predicted also agrees with the results of the XRD technique.     

Parametric study of aluminium alloy fouling in marine environment using RSM technique

ABSTRACT

Fouling is known to be a prominent industrial problem which is greatly affected by parameters like temperature, time and flowrate. The aim of this work was to simulate the fouling process in AA 6061 by developing a model through Minitab 16 and evaluate the models. Box Behnken design of Response surface methodology was applied for modelling and optimization of fouling propensity in artificial sea water. A response surface model was obtained and Analysis of Variance was performed to test the significance of the model. Fouling propensity was found in terms of weight gain. An experimental rig consisting of a recirculating loop mimicking the industrial conditions of fouling was used in the study. SEM analysis shows uneven deposits on the metal surface. Sharp, irregular deposits pressed deep into the metal was observed. The finding of this work would enable us to evaluate the individual and interactive effects of the parameters.     

Drilling of hybrid Al-5%SiCp-5%B4Cp metal matrix composites

Hybrid metal matrix composites consist of at least three constituents—a metal or an alloy matrix and two reinforcements in various forms, bonded together at the atomic level in the composite. Despite their higher specific properties (properties/unit weight) of strength and stiffness, the nonhomogeneous and anisotropic nature combined with the abrasive reinforcements render their machining difficult. The work piece may get damaged and the cutting tools experience high wear rates, which may lead to an uneconomical production process or even make the process impossible. This work reports on the drilling of Al-5%SiC_p-5%B₄C_p hybrid composite with high-speed steel (HSS), not expensive PCD, or carbide drills in an attempt to explore the viability of the process. Drilling of Al-5%SiC-5%B₄C composites with HSS drills is possible with lower speed and feed combination. The cutting conditions for minimized tool wear and improved surface finish are identified. Characterization of tool wear and surface integrity are also carried out.     

Vibrational power-flow analysis of a MIMO system using the transmission matrix approach

The transmission matrix approach is employed in this paper for the vibrational power-flow analysis of a multiple-input/multiple-output (MIMO) system. The substructures in each subsystem are modelled as a group of general MIMO transmission elements, which are described in terms of discrete or distributed properties. The global transmission matrix of the system is formed by assembling the transmission matrices together. Using the proposed approach, the output variables of any subsystem can be expressed in terms of the input state variables of that subsystem. Hence, the proposed approach is very systematic in analysing the dynamic behaviour of a complex system with a group of elements. In the numerical example, the power flow of a multi-mount system is modelled analytically. The transmission of vibratory power flow from the vibrating rigid body into a simply supported plate through elastic mounts is studied in detail. The effects on the power flows of various factors, such as the plate thickness, loading type, mounting locations, and mass and damping properties of the mounts, are addressed.     

On wire breakage and microstructure in WEDC of SiCp/6061 aluminum metal matrix composites

Unconventional machining like wire electric discharge machining/cutting (WEDM/WEDC) seems to be a better choice for machining/cutting the metal matrix composites (MMCs) because it offers easy control and has the capability of machining intricate complex shapes. But wire breakage in the WEDM/WEDC process decreases the machining accuracy and the quality of the machined surface. This paper describes the effect of four input process parameters (i.e., servo voltage, pulse-on time, pulse-off time, and wire feed rate) on wire breakage frequency and the microstructure of the cut surface during WEDC of SiC_p/6061 Al MMC. An optimum range of input parameters has been bracketed as the outcome of this work for determining the effects of input process parameters on the average cutting speed, material removal rate, and surface roughness during WEDC of SiC_p/6061 Al MMC. This range of input parameters can also be used for carrying out further research to develop the models for WEDC of SiC_p/6061 Al MMC and to optimize the WEDC parameters for smooth cutting.     

Effect of welding processes on tensile properties of AA6061 aluminium alloy joints

The present investigation is aimed at to study the effect of welding processes such as GTAW, GMAW and FSW on mechanical properties of AA6061 aluminium alloy. The preferred welding processes of these alloys are frequently gas tungsten arc welding (GTAW) and gas metal arc welding (GMAW) due to their comparatively easier applicability and better economy. In this alloy, the weld fusion zones typically exhibit coarse columnar grains because of the prevailing thermal conditions during weld metal solidification. This often causes inferior weld mechanical properties and poor resistance to hot cracking. Friction stir welding (FSW) is a solid phase welding technique developed primarily for welding metals and alloys that heretofore had been difficult to weld using more traditional fusion techniques. Rolled plates of 6 mm thickness have been used as the base material for preparing single pass butt welded joints. The filler metal used for joining the plates is AA4043 (Al-5Si (wt%)) grade aluminium alloy. In the present work, tensile properties, micro hardness, microstructure and fracture surface morphology of the GMAW, GTAW and FSW joints have been evaluated, and the results are compared. From this investigation, it is found that FSW joints of AA6061 aluminium alloy showed superior mechanical properties compared with GTAW and GMAW joints, and this is mainly due to the formation of very fine, equiaxed microstructure in the weld zone.     

On the surface and tribological characteristics of burnished cylindrical Al-6061

Surface treatment is an important aspect of all manufacturing processes to impart specific physical, mechanical and tribological properties. Burnishing process is a post-machining operation in which the surface irregularities of the workpiece are compressed by the application of a ball or roller. In the present study, simple and inexpensive burnishing tools, with interchangeable adapter for ball and roller were designed and fabricated. Ball burnishing processes were carried out on aluminium 6061 under different parameters and different burnishing orientations to investigate the role of burnishing speed, burnishing force and burnishing tool dimension on the surface qualities and tribological properties. The results showed that burnishing speed of 330 rpm and burnishing force of 160 N produce optimum results. Meanwhile, a decrease in the burnishing ball diameter leads to a considerable improvement in the surface roughness up to 75%. On the other hand, parallel burnishing orientation exhibits lower friction coefficient compared to cross-burnishing orientation. Furthermore, ball burnishing process is capable of improving friction coefficient by 48% reduction and weight loss by 60-80% reduction of burnished surface of aluminium 6061. These findings are further supplemented by the surface features as seen in SEM photomicrographs.     

铝复合材料钻削加工性能实验研究

通过4种不同增强相的铝复合材料和3种对比材料的钻削试验，得出了钻头进给量、增强相种类及体积含量、刀具材料、钻头修磨情况对钻削扭矩和轴向力的影响规律，分析实验结果认为，除晶须、微粉级磨料(20．30μm)颗粒增强铝复合材料外，超细级磨料(≤0．5μm)颗粒增强铝复合材料完全可以用高速钢钻头加工。     

Ion microprobe studies of reactions in squeeze-cast aluminium alloy matrix composites

An ion microprobe with high lateral resolution has been used to study the chemical reactions at the fibre/matrix interface of metal–matrix composites. During the squeeze-casting process, the Al–Si–Mg matrix reacts with the preform made of Saffil fibres (96% Al₂O₃, 4% SiO₂). The reaction occurs mainly between the silica binder and Mg from the matrix according to SiO₂ + 2Mg = 2MgO + Si. A continuous layer of MgO was formed around the fibres, even on surfaces that were not covered by the silica binder. Possible reasons are discussed for the formation of MgO in areas where binder coating was missing. In such areas, Mg reduces SiO₂ that is contained in the fibre. However, the fibres (A1₂O₃) are not attacked by Mg. In the isolated case of fibres that were completely uncoated, no reaction products were observed at the interface. The presence of silica binder seems to be an essential requirement for this reaction to occur. When squeeze-casting is performed with sufficiently high melt temperature, Al from the matrix also reduces silica.     

Serrated chip formation mechanism analysis for machining of titanium alloy Ti-6Al-4V based on thermal property

Based on the software ABAQUS/Explicit, a finite element (FE) model for orthogonal cutting was established. The FE model was validated by comparing the cutting forces and serrated degree of chips obtained by orthogonal cutting experiments under the cutting speeds 40, 80, 120, and 160 m/min. Based on the developed FE model, the influence of thermal conductivity on the degree of chip segmentation and the adiabatic shear localization were investigated. Furthermore, the plot contours on undeformed shape of cutting simulation was used to investigate the temperature distribution, and the high temperature zone was identified, which can help enhance the understanding of the serrated chip formation. Finally, cracks located in the adjacent segments of chips were observed. The results show that with the increase in thermal conductivity, the degree of adiabatic shear decreases. It can be concluded that the poor thermal conduction performance should be primarily responsible for the formation of serrated chips during machining Ti-6Al-4V alloy. Due to the high temperature at contact surface between cutting tool and workpiece, the increasing of cutting speed facilitates the formation of serrated chips during machining.     

Preparation of PTFE composite anodic film on aluminium alloy 6061 using electrophoretic process

Abstract

A pulse current hard anodising process and an electrophoretic process were used to form a self-lubricating polytetrafluoroethylene (PTFE) composite anodic film on aluminium alloy 6061. This encompasses an initial formation of a porous alumina film on alumina alloy 6061 by anodising in sulphuric acid, and then the film pores are appropriately enlarged to form further film pores in a diluted phosphoric acid, and subsequently, PTFE particles are introduced into the pores to form a composite hard anodic film, by an electrophoretic process, in the water soluble electrophoretic PTFE emulsion. The films were then examined by scanning electron microscopy and energy dispersive X-ray analysis, and the friction coefficient and microhardness of the film are investigated.     

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。     

Experimental investigation of weld characteristics on submerged friction stir welded 6061-T6 aluminum alloy

Journal of Mechanical Science and Technology - Mechanical properties such as fatigue life, corrosion resistance, brittle fracture, hardness and dimensional stability mainly depend on the residual...     

Modeling and analysis of performances in drilling hybrid metal matrix composites using D-optimal design

The present paper deals with the modeling and analysis of machining responses such as the thrust force, surface roughness, burr height, and tool wear in the drilling of hybrid metal matrix composites using carbide, coated carbide, and polycrystalline diamond drills. Experiments are conducted on Al 356 aluminum alloy reinforced with silicon carbide of size 25 μm and mica of size 45 μm. Machining parameters such as spindle speed, feed rate, and weight percent of silicon carbide are chosen as the numerical factors; the drill material is considered as the categorical factor. An experimental plan of a four-factor (three numerical plus one categorical) D-optimal design based on the response surface methodology is employed to carry out the experimental study. The results indicated that the predicted values through the developed model are well in agreement with the experimental results. The results also indicated that the method used is effectively applied for the modeling and analysis of drilling parameters in drilling hybrid metal matrix composites.     

颗粒增强铝基复合材料铣削加工实验研究

使用K10硬质合金铣刀,在不使用冷却液的条件下,对A12024/SiCp复合材料进行铣削加工实验,研究切削参数和颗粒尺寸对表面质量、切削力、刀具磨损的影响.研究表明,随着增强颗粒尺寸的增大,表面变粗糙、切削力增大和刀具磨损加重;在不同的切削条件下,法向力均大于切向力.随着切削用量的增大,铣削力呈增大趋势,其中,吃刀量对铣削力的影响最大,切削速度的影响最小;加工表面上存在凹坑、颗粒突起和基体材料涂敷等缺陷,表面粗糙度随着颗粒尺寸增大而增大,随着切削速度的提高而减小.     

Rapid structural mapping of ternary metallic alloy systems using the combinatorial approach and cluster analysis

We are developing a procedure for the quick identification of structural phases in thin film composition spread experiments which map large fractions of compositional phase diagrams of ternary metallic alloy systems. An in-house scanning x-ray microdiffractometer is used to obtain x-ray spectra from 273 different compositions on a single composition spread library. A cluster analysis software is then used to sort the spectra into groups in order to rapidly discover the distribution of phases on the ternary diagram. The most representative pattern of each group is then compared to a database of known structures to identify known phases. Using this method, the arduous analysis and classification of hundreds of spectra is reduced to a much shorter analysis of only a few spectra.