K. M. Sree Manu

Liquid Metal Infiltration Processing of Metallic Composites: A Critical Review

Metal matrix composites (MMC) are one of the advanced materials widely used for aerospace, automotive, defense, and general engineering applications. MMC can be tailored to have superior properties such as enhanced high-temperature performance, high specific strength and stiffness, increased wear resistance, better thermal and mechanical fatigue, and creep resistance than those of unreinforced alloys. To fabricate such composites with ideal properties, the processing technique has to ensure high volume fraction of reinforcement incorporation, uniform distribution of the reinforcement, and acceptable adhesion between the matrix and the reinforcing phase without unwanted interfacial reactions which degrades the mechanical properties. A number of processing techniques such as stir casting/vortex method, powder metallurgy, infiltration, casting etc. have been developed to synthesize MMC employing a variety of alloy and the reinforcement’s combinations. Among these, infiltration process is widely used for making MMC with high volume fraction of reinforcements and offers many more advantages compared to other conventional manufacturing processes. The present paper critically reviews the various infiltration techniques used for making the MMC, their process parameters, characteristics, and selected studies carried out worldwide and by authors on the development of metal ceramic composites by squeeze infiltration process.

Squeeze Infiltration Processing of Functionally Graded Aluminum–SiC Metal Ceramic Composites

The objective of the present work is on fabrication of functionally graded SiC/Al composite by direct squeeze infiltration of 6061 aluminum alloy using graded SiC porous preform prepared by inorganic porogen technique. Graded SiC preform is synthesized by varying the concentration of inorganic salt mixture and using Al as the binder. The microstructure analysis indicates the graded distribution of SiC particle and the melt has infiltrated completely throughout the preform to form functionally graded materials. The influence of preform and mold temperature, liquid metal superheat, squeeze pressure, and its rate of application plays major role on solidification microstructures and properties of the composites. The macro porous graded SiC preforms and the composites were characterized using SEM, optical microscopy, and XRD. The major interfacial reaction product is MgAl2O4 spinel which helps in formation of good interface bonding.

Synthesis of Porous SiC Preform and Squeeze Infiltration Processing of Aluminium-SiC Metal Ceramic Composites

Metal-Ceramic Composites with high volume fraction of reinforcement find wide applications in the area of tribology and high temperature resistant components like piston, brake pads, heat shields etc. Most of these components can be made by infiltration processing of porous ceramic preforms. The present investigation is to synthesize porous ceramic preform based on SiC particles using inorganic salt as a pore forming agent and Squeeze infiltration is applied to fabricate the Al-SiC metal-ceramic composites. The direct squeeze infiltration of 6061 aluminum alloy on SiC preform is successfully carried out with the controlled process parameters of initial preform temperature, liquid metal superheat, squeeze pressure and its rate of application, and die temperature. The preform and composites are characterized using XRD, optical microscopy, electron microscopy, and hardness and compression strength. Porous ceramic preform with more than 50% porosity has been fabricated by sodium chloride as pore former. The infiltrated composite have shown uniform and complete infiltration of Aluminium alloy in between SiC particles and posses very high hardness of 147 BHN in as cast condition compared to 57 BHN for the 6061 Al alloy.

Development of Al 319-Micro Silica Metallic Composite by Squeeze Infiltration Technique

The objective of present investigation is to synthesize porous micro silica based ceramic preform with varying composition of particles using burn out technique and processing of Al-Micro silica metal-ceramic composites by squeeze infiltration method. Direct squeeze infiltration of 319 aluminum alloy on micro silica preform is successfully carried out with the controlled process parameters of initial preform temperature, liquid metal superheat, squeeze pressure and its rate of application, and die temperature. The preform and composites are characterized using optical microscopy, electron microscopy, hardness and compression strength testing. Porous ceramic preform with more than 70% porosity has been fabricated by PEG as pore former. The infiltrated composite have shown uniform and complete infiltration of aluminum alloy in between micro silica particles.

Selectively Reinforced Aluminum Metallic Hybrid Composites by Liquid Metal Squeeze Infiltration Process

AbstractPresent study aims to fabricate selectively reinforced aluminum hybrid composites using varying combinations of porous ceramic preforms containing discontinuous dispersoids of silicon carbide, aluminosilicate fiber, and carbon followed by direct squeeze infiltration processing of molten aluminum into the preforms. Porous preforms are successfully fabricated by the burn out of polyethylene glycol, and aluminum is used as the binder for the sintered body. Selectively reinforced hybrid aluminum composite has been successfully processed using liquid metal squeeze infiltration of porous preforms by controlled process parameters like preform preheating temperature, liquid metal temperature, squeeze pressure, and die temperature.

Processing of Porous Ceramics Using Aluminium Derived Binders and Sacrificial Porogen Leaching Method

Porous ceramics was successfully fabricated by a sacrificial porogen leaching method using in-situ synthesised aluminium based binders by reaction bonding at low sintering temperatures of 600-1000°C. Porous ceramics with porosity in the range of 27 to 65% were obtained by leaching technique. Interconnected bimodal pores were produced by both stacking of starting particles and leach out of salt. During sintering, the aluminium binder experienced metal to ceramic transformations and act as good binder.

Fabrication and Characterization of a Hybrid Functionally Graded Metal-matrix Composite Using the Technique of Squeeze Infiltration

In this research paper, the results of a recent study that focussed on preparing hybrid and graded cylindrical preforms by stacking alumina-silicate fibre, SiC particles and the pore forming agent in different layers along with aluminium powder as the binding agent and the resultant mixture sintered at a high temperature is presented and discussed. The stacked preforms were compacted and sintered above the melting temperature of aluminium. Decomposition of the fugitive pore former was done using the leaching technique. Direct squeeze infiltration of aluminium alloy 319 on a graded hybrid preform was successfully carried out using controlled process parameters spanning initial preform temperature, liquid metal superheat, squeeze pressure and its rate of application, and die temperature. The liquid metal did fully infiltrate through the ceramic preform to form a functionally graded composite. The resultant composites were characterized using the techniques of scanning electron microscopy, optical microscopy, x-ray diffraction and measurement of density. The extrinsic influence of infiltration pressure, preform temperature and mold temperature on microstructural development and hardness of the engineered composites is briefly highlighted.

Use of Squeeze Infiltration Processing for Fabricating Micro Silica Reinforced Aluminum Alloy-based Metal Matrix Composite

A number of processing techniques have been developed and tried for the primary purpose of synthesizing metal-matrix composites (MMCs) using a variety of alloy and reinforcement combinations. In particular, the technique of infiltration processing has been preferred and used for making composites based on metal matrices and reinforced with a high volume fraction of the reinforcing phase. In this paper, the results of a study on using fine particle size microspheres as the reinforcement for an aluminium alloy metal matrix is presented and discussed. Polyethylene glycol was used as the pore former along with aluminium powder as the binding agent. The resultant mixture was sintered at a high temperature. The preforms were compacted and subsequently sintered at a temperature above the melting temperature of aluminium. Decomposition of the fugitive pore former was done using the burnout technique. Key aspects pertinent to characterizing the fabricated preforms and composite using the technique of light optical microscopy, thermo gravimetric analysis (TGA) and hardness measurement is briefly presented.