UNIT-IIIMetal Matrix Composites

04/21/23 1

Lecture-4

Characteristics of MMCs, Various types of Metal matrix

composites,

Effect of reinforcements on properties

Volume fraction – Rule of mixtures,

Liquid state processing- stir casting, squeeze casting

infiltration,

solid state processing - Powder metallurgy, diffusion bonding,

In situ processes, applications of MMCs

Metal Matrix Composites

Polymer Matrix Composites

Syllabus

Processing of polymer matrix composites

Hand lay-up, Spray lay-up processes,

Compression molding-

SMC Reinforced reaction injection molding,

Resin transfer molding,

Pultrusion, Filament winding,

Applications of polymer matrix composites

Solid state processing-Diffusion bonding

Introduction

Solid state fabrication of Metal Matrix Composites

Metal Matrix Composites are formed as a result of bonding matrix

metal and dispersed phase due to mutual diffusion occurring

between them in solid states at elevated temperature and under

pressure.

There are two principal groups of solid state fabrication of Metal

Matrix Composites:

Diffusion bonding

Powder Metallurgy

Diffusion Bonding

Diffusion bonding is a common solid-state processing technique

for joining similar or dissimilar metals.

Inter diffusion of atoms between clean metallic surfaces, in

contact at an elevated temperature, leads to bonding.

The principal advantages of this technique are the ability to

process a wide variety of metal matrices and control of fiber

orientation and volume fraction.

Variants of diffusion bonding are roll bonding and wire/fiber

winding:

Roll Bonding is a process of combined Rolling (hot or cold)

strips of two different metals (e.g. steel and aluminum alloy)

resulted in formation of a laminated composite material with a

metallurgical bonding between the two layers.

Wire/fiber Winding is a process of combined winding

continuous ceramic fibers and metallic wires followed by

pressing at elevated temperature.

Roll Bonding

Roll Bonding

Roll bonding is a common technique used to produce a laminated composite consisting of different metals in layered form. Such composites are called sheet laminated metal matrix composites

Dis advantages

Long processing times,

High processing temperatures and pressures

Expensive process

complexity of shapes is limited

Polymer Matrix Composites

Syllabus

Processing of polymer matrix composites

Hand lay-up, Spray lay-up processes,

Compression molding-

SMC Reinforced reaction injection molding,

Resin transfer molding,

Pultrusion, Filament winding,

Applications of polymer matrix composites

Solid state processing-Powder metallurgy

Sintering

Sintering fabrication of MMC is a solid state process,

Powder of a matrix metal is mixed with a powder of dispersed

phase in form of particles or short fibers for subsequent

compacting and sintering in solid state

Sintering is the method involving consolidation of powder grains

by heating the “green” compact part to a high temperature

below the melting point, when the material of the separate

particles diffuse to the neighboring powder particles.

Solid-State Processes Powder Processing

When sintering is combined with a deformation operation, the fabrication

methods are called:

Hot Pressing Fabrication of Metal Matrix Composites

Hot Isostatic Pressing Fabrication of Metal Matrix Composites

Hot Powder Extrusion Fabrication of Metal Matrix Composites

Hot Pressing Fabrication of MMC

Hot Isostatic Pressing Fabrication of MMC

Sintering under a pressure applied from multiple directions

through a liquid or gaseous medium surrounding the

compacted part and at elevated temperature.

Hot Powder Extrusion Fabrication of MMC

Hot Powder Extrusion Fabrication of Metal Matrix Composites – sintering

under a pressure applied by an extruder at elevated temperature.

Hot Extrusion