Low-temperature partial transient liquid phase diffusion bonding of Al/Mg2Si metal matrix composite to AZ91D using Al-based interlayer

Partial transient liquid phase diffusion bonding of an aluminium metal matrix composite (Al/Mg2Si) to magnesium alloy (AZ91D) was performed using two heating rates. The influence of different heating rates on the microstructure, microhardness and shear strength has been studied. With a decrease in heating rate from 20 to 2 °C/min, the Mg content in the bond line decreased and the microstructure was altered. The composition and microstructure of the joined areas were examined by X-ray diffraction (XRD) and scanning electron microscopy equipped with energy dispersive X-ray spectroscopy (EDS). It was found that a heating rate of 2 °C/min resulted in an increasing in the shear strength of the joints. The kinetics of the bonding process accelerated due to the increase of solute diffusivity through grain boundaries of the metal matrix composite. Results suggest that Mg and Si contained in the interlayer favours the partial disruption of oxide films, facilitating the bonding process

The Development of Advanced Materials - High Performance Properties of Composite for Automotive and Aerospace Applications

Magnesium metal matrix composite (MMC) is an excellent candidate for moving engine components and airframes due to its low density. Magnesium's lightweight and natural affinity for wetting to ceramic particle reinforcements such as silicon carbide (SiC) make it one of the best choices as a matrix metal. However, magnesium alone without reinforcement is not suitable for mechanical applications due to its low wear resistance performance. The magnesium matrix composites used in this study were produced by powder metallurgy technique. The wear resistance of SiC/AZ91 composite reinforced with 0, 5, 10, 15 and 20 wt.% SiC were studied. Pin-n-disk dry sliding wear tests were carried out to study the volumetric wear, wear rate and wear mechanisms. The magnesium matrix composites were used as pins while the counter face consisted of mild steel disks. Worn surfaces of pins and the wear debris were investigated by using Scanning Electron Microscopy (SEM) and Energy Dispersive X-Ray Analysis (EDX). The wear resistance performance of magnesium matrix composites was found to improve with increasing volume fraction of SiC. Volumetric wear was found to increase with sliding distance and the wear rate was greatly reduced after the wear-in phenomenon. For AZ91 Mg-SiCp/ steel dry sliding wear system, 2D-wt.% SiC/AZ91 magnesium composite was found to have the best wear resistant performance. During the wear-in period, abrasion was predominant during the wear-in stage. In the corrosion study, corrosion behavior of Mgbased metal matrix composites SiC particulate reinforced AZ91 (SiC/AZ91) with reinforcement weight fraction of 5, 10, 15 and 20 wt.% as well as the monolithic AZ91 alloy was studied. The galvanic effect of SiC reinforcement on the matrix alloy was also investigated. The studies were carried out under temperature of 30° ± 1°C and pH 7 in aerated 0.1 M NaCI solution. The materials were studied by using electrochemical corrosion test, weight-loss measurement of corrosion rate, elemental analysis, X-ray diffraction and microscopic examination. The corrosion rates of the composites increased with the increase of SiC weight fraction. The significance of galvanic effect of SiC on the matrix alloy was proven where intersection of superimposed Tafel curves between sintered SiC and monolithic AZ91 occurred at higher corrosion current density (i...,) and lower corrosion potential (E...,). The corrosion was found localized at low SiC weight fraction, and gradually change to general corrosion. The corrosion rates of the composites were at least three times higher than the monolithic AZ91, due to galvanic effect of SiC on the matrix alloy and detachment of SiC particles from the materials

Influence of milling time on growth morphology and mechanical properties of aluminum-silicon-carbide composites

Achieving improved mechanical properties of aluminum (Al) in the composite structures by mixing ceramics is ever-demanding for sundry applications. We synthesize aluminum-silicon-carbide composites via ball milling of aluminum which is reinforced with 5% of the silicon carbide (SiC) powders having particles size of 20 µm. Microstructures of powdered composite is characterized via XRD, EDX, and FESEM measurements. These mixtures are grinded at the speed of 200 rpm in a planetary ball mill for 0, 40, 80, and 120 minutes using zirconium balls as milling media. The ratio of the ball to powder is selected to be 10:1. At room temperature and pressure of 10 ton the mixed powders are die-pressed in a cylindrical stainless steel mold having internal diameter of 12.7 mm. The impact of milling time on the growth morphology (microstructures) and mechanical properties of the prepared Al–SiC (5 wt %) composite are scrutinized. The method mechanical alloying (MA) is comprised of milling, cold pressing, and sintering. The increase in milling time is demonstrated to enhance the hardness of the composites. Furthermore, the highest hardness and superior strength is achieved for 80 minutes of milling. Both the hardness and strength of such composites are decreased beyond this milling time. The excellent features of the results suggest that Al–SiC (5 wt%) composite with the present composition may be potential to fortify the structural network in terms of strength and stiffnes

Wettability enhancement of SiCp in cast A356/SiCp composite using semisolid process

The effects of SiCp treatment and magnesium addition on microstructural and mechanical properties of Al356/20 wt% SiCp semisolid composites were investigated. The results showed that cleaning and oxidizing of SiCp and addition of 1 wt% Mg resulted in improving wettability, incorporation, and uniform distribution of SiCp in A356 matrix. Consequently, the ultimate tensile strength (UTS) value increased by 19% and 32% when the SiC was treated and also when Mg was added, respectively, compared to as-received SiCp. In addition, hardness value increased from 69.7 HV in as-received SiCp to 94.8 HV after SiCp treatment and addition of Mg

HYGROTHERMAL RESPONSE OF PLANT FIBRE REINFORCED COMPOSITES

ABSTRACT The effect of soaking time and temperature response for coconut and raffia fibre reinforced composite on their mechanical properties have been studied. Tensile and compression test for treated and untreated were performed using a universal testing machine (Monsanto Tensometer). The conditioned samples in each case show better tensile and compressive strength compared to the untreated samples. Raffia fibre reinforced polyester showed a better mechanical and moisture absorption properties at various operating temperature in the study

The effect of Sol-Gel technique on the aluminium-SiCp composite

Due to the low reactivity between the silicon carbide particulate (SiCp) and Aluminium (Al) interface bonding strength, SiCp is treated by applying a coating on its surface. The objective of this paper is to study the effect applying ceramic sol coating, which is silica sol via sol gel technique onto SiCp. The various concentrations applied are 2 wt%, 4 wt% and 10wt% of silica sol. Aluminium metal matrix composite (Al-MMC) reinforced with 10% and 20% volume fraction of SiCp produced by powder metallurgy technique with sintering temperature of 550°C was studied. The surface morphology of Al-MMC is observed using SEM to examine the particle distribution, porosity and flow pattern. While the degradation of SiCp due to interfacial reaction between the particulate and Al matrix is examined by x-ray diffraction (XRD). SiCp degradation is evaluated by the ratio of the SiC to the silicon (Si) XRD peak. From microstructure analysis, the specimens coated with 2 wt% and 4 wt% silica sol coating showed the best result which has uniform reinforcement distribution, lower porosity and better flow pattern. For XRD analysis, the best coating was obtained by 4 wt% silica sol concentration that has greater reaction between Al and SiC

The use of scanning acoustic microscope for flaw detection in metallic materials

The main objective of this paper is to understand the principles and theories behind the operation of the equipment, and its architecture. The advantages and limitations of the scanning a coustic microscope are also investigated by imaging a set of samples. The principle of operation of a scanning acoustic microscope is producing magnified acoustic images of the surface or interior of a solid by passing high-frequency focused acoustic pulses through the material and displaying the received signal in the image form as shades of grey. The significant advantage to be gained in using scanning acoustic microscope for producing images are the ability of acoustic waves to penetrate opaque material and the distinctive origin of contrast in the mechanical properties of the specimen. Three sets of samples are observed under the scanning acoustic microscope and they are Vickers hardness indention samples, quenched samples and porosity samples. It is found that results obtained for the samples are subjected to the overall ability of the equipment used. The operating frequency was one of the most significant limiting factors in this work, as the resolution obtained was not as high as would be favourable. However, satisfactory images with distinctive contrast were still achieved. One of the advantages of using scanning acoustic microscope, which is the sub-surface imaging ability, is also revealed. Finally, the operating software of the equipment is also an important aspect that should be given proper consideration

Microstructure and mechanical properties of aluminum-silicon carbide composite fabricated by powder metallurgy

The aluminum powder is mixed with silicon carbide powder with parameters of 0, 0.7, 1.3 and 2 hours milling time. The ball mill type planetary PM 400 with stainless steel jar and zirconium balls with ball to powder ratio 10:1and rotation speed 200 rpm. The silicon carbide reinforcement 10% and the rest aluminum, then the milled powders compacted to samples in stainless steel mold. The maximum hardness at 1.3 hour milling time after this value the hardness starts to drop. With increasing the milling time were observed improvement of the dispersion of silicon carbide in aluminum matrix

A fuzzy application on a development planning model for a container terminal

Conventional container terminal development planning methodology lacks the human modes of reasoning that uses approximate, imprecise, linguistic, and subjective values. Fuzzy methods could be applied to the current method to improve such shortcoming. This study applies fuzzy methods to a container terminal development planning model which has been improved by incorporating container handling system selection (chs) and determination of terminal other area (toa) to the current container park area (cpa), freight station area (cfs), berth-day requirement (bdr), and ship cost at terminal (sct). Membership functions have been derived for all the planning variables and planning process flowcharts showing fuzzy operations and defuzzification stages have been drawn. A simulated planning exercise has been performed on chs and cpa and the results obtained indicate that the application has been successful. The potential of coupling the method with an expert system has also been highlighted

Vehicle equipment selection model for preliminary design using fuzzy multi-criteria decision making method

Equipments selection process is one of the key planning and design activities of marine, land and air vehicles. Equipments are often selected from a set of possible alternatives. More than one decision makers are usually involved and selection of one particular choice is made against a set of strategic selection criteria. Approximate mode of decisionmaking is normally employed and hence selection criteria are subjectively specified. This paper presents the fuzzy approach to the subjective representation of design data and the multi-criteria decision making method to the treatment of subjective criteria rating and ranking of equipment to serve as collective decision making too