Modern materials

Metallurgy &Metallurgy &
Materials ScienceMaterials Science
Dr.S.Jose
Dept of Mechanical Engg.,
TKM College of Engineering, Kollam
drsjose@gmail.com

2
 Ferrous Materials
 Non – ferrous alloys
 Composite Materials
 Metal matrix composites
 Smart Materials.
 Nano materials
 Bio materials
 Bioplastics.
Module IV

A composite can be defined as a multiphase
material that is artificially made with chemically
dissimilar constituent phases which are separated by a
distinct interface.
Many composite materials consist of only two
phases.
The properties of composites are dependent on the
Composite Materials

The matrix phase, which is present in larger amounts, is
continuous and surrounds the other one called as dispersed
phase or reinforcing phase.
The matrix phase may be metal, polymer or ceramic.
When some ductility is desirable, metals and polymers
are used, to which the reinforcing particles or fibres
incorporate fracture toughness.
The matrix phase binds the reinforcement together and
Composite Materials

Particle Reinforced Composites
Fibre-Reinforced Composites
Metal Matrix Composites
Ceramic Matrix Composites
Carbon-Carbon Composites
Laminated Composites
Composite Materials

The matrix is reinforced by hard particles of three
dimensional shapes.
Here the matrix and dispersed particles share the load.
Typical examples are cemented carbides, tungsten
reinforced copper, concrete, cermets etc.
For effective reinforcement, the particles should be small
and evenly distributed throughout the matrix.
Particle Reinforced Composites

When the dispersed phase is in the form of fibres, the most
important type of composite is obtained.
 The matrix phase is usually metal, ceramic or plastic
materials.
This type of composites has unique combination of
properties like high stiffness, high strength and fracture
toughness.
Fibre Reinforced Composites

Glass fibre reinforced polymer (GFRP) composites are
popularly known as fibre glass.
This is a composite consisting of continuous or discontinuous
glass fibres embedded in a polymer matrix.
It is having high strength, stiffness and rigidity, but is not
suitable for structural applications at higher temperatures.
Fibre glass is used for automotive bodies, storage

Carbon fibre reinforced polymer (CFRP) composites are
among the advanced composite materials used for aircraft and
aerospace applications.
Carbon fibres used for this purpose are having diameters
between 4 to 10 microns.
These fibres exhibit a diversity of physical and mechanical
properties.

A ductile metal is used as the matrix material.
Alloys of aluminium, copper, titanium and magnesium are
used as matrix materials.
Reinforcement materials are silicon carbide, aluminium
oxide, boron carbide, graphite etc. in the form of fibers,
whiskers or particles.
The reinforcement may improve specific strength, abrasion
Metal Matrix Composites

Particulates, fibres or whiskers of one ceramic material is
embedded into a matrix of another ceramic material
Fracture toughness of these composites are significantly
higher than that of ceramics.
Silicon carbide whisker reinforced alumina are used as
cutting tool inserts for machining hard metal alloys.
Ceramic Matrix Composites

Carbon fibre reinforced carbon matrix composite is an
advanced engineering material.
This material is having high tensile strength, which is
retained even at temperature above 2000C.
In addition, higher creep resistance and fracture toughness
also are the features of these materials.
Due to the complexity of processing techniques used, the
Carbon Carbon Composites

Laminated composite is composed of thin sheets or layers
that have a high strength direction oriented along the direction
of fibres.
The layers are stacked and cemented together to form a
laminated composite. Eg. plywood
Laminated composite is one among the structural
composites, the properties of which are dependent on the
constituent materials as well as on the geometrical design of
Laminated Composites

Homogenous distribution of the reinforcement phase is the
key challenge.
The primary processes can be grouped under two broad
categories.
Liquid state processes like stir casting, squeeze casting
and spray casting
Solid state processes include powder blending (powder
Fabrication of
Metal Matrix Composites

Stir casting is done by introducing fibres of particles into
molten or partially solidified metal/alloy followed by casting in
moulds.
The main advantages are the simplicity, flexibility and cost
efficiency.
The stir casting process begins with preparation of a melt of
the selected metallic matrix material followed by cooling it to a
semi solid state.
Stir Casting

The slurry is again heated to convert the matrix phase to
liquid state.
During the process the melt is agitated (stirred) vigourously
to obtain uniform dispersion of the reinforcement phase.
The resultant melt is immediately used for die casting,
permanent mould casting or sand casting.
Stir Casting

Powder processing methods are used to fabricate particulate
or short fibre reinforced composites.
Powdered metal and discontinuous reinforcement are
blended to produce a homogeneous distribution and then
bonded through a process of compaction, degassing and
thermo-mechanical treatment.
The composite ingot is subsequently used to fabricate
structural components using secondary fabrication processes.
Powder Metallurgy

Powder Production
Mixing or Blending
Powder Degassing
Powder Compaction
Sintering
Hot Isostatic Pressing
Powder Metallurgy -steps

Almost all metals and their alloys can be
converted into powder form.
The major methods are
 Electrolytic deposition
 Chemical reaction and decomposition
 Atomisation
 Mechanical processing
A number of metals can be precipitated on
the cathode of an electrolytic cell as powder.
Powder Production

The metal powder and reinforcement phase
are mixed in a mixer along with suitable
lubricants and binders.
The addition of lubricants will help to
minimise friction between powder particles and
between particles and walls of container
The binders will provide strength to the green
compact.
Rotating containers of different types are
used as mixers. Some of the popular types are
Blending

This is carried out to remove steam and other
gases from the powder.
Generally, the powder must be degassed at a
temperature greater than the temperature
reached during processing.
Degassing is done after keeping the green
compact in a sealed can and after degassing it
is kept in the can itself for further processing.
Powder Degassing

The compaction process consolidates the
powder mix into the desired shape and
dimensions with desired level of strength for
subsequent handling.
Die compaction is the conventional method
which makes use of special mechanical or
hydraulic presses.
Generally, the powder particles are
considered to be equally sized and spherical in
shape.
Powder Compaction

The compaction process consolidates the
powder mix into desired level of strength for
subsequent handling.
Die compaction is the conventional method
which makes use of special mechanical or
hydraulic presses.
Generally, the powder particles are
considered to be equally sized and spherical in
shape.
Densities upto 90% can be easily achieved by
Powder Compaction

This is a thermal process for consolidating
powder particles into a coherent structure by
mass transport on the atomic scale.
Before sintering, the lubricant and binder are
removed from the green compact by heating it
in vacuum or in controlled atmosphere.
Sintering is done inside sintering furnaces, at
temperatures around 75% of the melting
temperature of the metals.
The high temperatures stimulate atomic
Sintering

Here the pressing and sintering are combined
to a single step.
This process is used to impart density
consolidation, which is necessary to provide
sufficient strength to the powder processed
material.
An inert gas is used as the pressure medium
and heat is applied with the help of a furnace
The pressure is applied uniformly from all
sides and this provides uniform grain structure
Hot Isostatic Pressing

The filament winding process is employed for fabrication of a
continuous fibre reinforced composite structures having an axis
of revolution.
Common examples of such structures are tubes, pipes,
cylindrical tanks, pressure vessels, rocket motor cases, etc.
Continuous fibre strands or rovings are first coated with
resin in a resin bath and then fed through rollers to squeeze out
excess resin and finally wound, under constant tension, around
Filament Winding

The outer diameter of the mandrel corresponds to the inner
diameter of the part to be fabricated. The mandrel is usually
made of steel, plastic or rubber.
The mandrel is positioned, either horizontally (for helical
winding) or vertically (for polar winding), on a carriage that
moved back and forth along the direction parallel to the
rotational axis.
In addition to the translational (axial) motion induced by the
Filament Winding

In the helical winding a constant angle φ (known as helical
angle) is maintained by controlling the rotational and axial
motions of the mandrel.
Structural components having circular cylindrical shapes like
tubes, pipes and cylinders are normally fabricated with
alternating helical angles of+φ and -φ
When the filaments are wound at an angle φ = 90, the
winding is called hoop winding. Similarly, when φ =0, it is
Filament Winding

Biomaterials
Biomaterials are used to make devices to replace a part
or a function of the human body in safe, reliably,
economically and physiologically acceptable manner.
A biomaterial is essentially a material that is used and
adapted for a medical application.
A biomaterial is any material, natural or man made, that
comprises whole or part of a living structure or biomedical
device which performs, augments, or replaces a natural

Problem Area Examples
Replacement of diseased or
damaged part
Artificial hip joint, kidney dialysis
machine
Assist in healing Sutures, bone plates, and screws
Improve function Cardiac pacemaker, intraocular lens
Correct functional
abnormality
Cardiac pacemaker
Correct cosmetic problem Augmentation mammoplasty
Aid to diagnosis Probes and catheters
Aid to treatment Catheters, drains
Uses of Biomaterials

Organ Examples
Heart Cardiac pacemaker, artificial heart valve,
total artificial heart, blood vessels
Lung Oxygenator machine
Eye Contact lens, intraocular lens
Ear Cochlear implant
Bone Bone plate, intramedullary rod
Kidney Catheters, stent, Kidney dialysis machine
Bladder Catheter and stent
Biomaterials in Organs

Biomaterials
The most common classes of materials used as
biomedical materials are polymers, metals, ceramics and
composites.
 These classes are used singly and in combination to
form most of the implantation devices available today.

There are a large number of polymeric materials that have
been used as implants or part of implant systems.
The polymeric systems include acrylics, polyamides,
polyesters, polyethylene, polyurethane and a number of
reprocessed biological materials.
Applications include artificial heart, kidney, liver, pancreas,
bladder, bone cement, catheters, contact lenses, cornea and
eye-lens replacements, external and internal ear repairs, heart
Polymeric Biomaterials

Metals are used as biomaterial due to their excellent
electrical and thermal conductivity and mechanical properties.
Some metallic parts are used as passive substitutes for hard
tissue replacement such as:
Total hip
Knee joints
Bone plates and screws
Spinal fixation devices
Metallic Biomaterials

The first metal alloy developed specifically for use as
biomaterial is the vanadium steel which was used to
manufacture bone fracture plates and screws.
 The biocompatibility of the metallic implant is of
considerable concern because these implants can corrode in
prolonged usage.
Stainless Steels
CoCr Alloys
Metallic Biomaterials

The most important properties for a biomaterial like, non-
toxic, non-carcinogenic, non-allergic, non-inflammatory,
biocompatible and biofunctional for its lifetime in the host are
all satisfied by certain ceramic materials.
Ceramics such as alumina, zirconia, silicone nitrides, and
carbons are inert bioceramics.
Certain glass ceramics are semi-inert (bioreactive), and
calcium phosphates and calcium aluminates are resorbable
Ceramic Biomaterials

By definition, composites contain two or more distinct
constituent materials.
In biomaterials, it is important that each constituent of the
composite be biocompatible.
Moreover, the interface between constituents should not be
degraded by the biological environment.
 Some applications are: dental filling composites, reinforced
methyl methacrylate bone cement and ultra-high-molecular-
Composite Biomaterials

Bioplastics are not just one single substance, they comprise
of a whole family of materials with differing properties and
applications.
 A plastic material is defined as a bioplastic if it is either
biobased, biodegradable, or having features of both.
Bioplastics are plastics in which all carbon is derived from
renewable feedstocks including corn, potatoes, rice, tapioca,
palm fiber, wood cellulose, wheat fiber etc.
Bioplastics

The term “biobased” means that the material or product is
(partly) derived from biomass of plants like corn, sugarcane, or
cellulose. Biobased does not equal biodegradable.
Biodegradation is a chemical process during which micro-
organisms that are available in the environment convert
materials into natural substances such as water, carbon
dioxide, and compost.
Bioplastics

Smart or intelligent materials have one or more properties
that can be significantly changed in a controlled fashion by
external stimuli, such as stress, temperature, moisture, pH,
electric or magnetic fields.
A smart material should consist of a sensor (that detects an
input signal) and an actuator (that performs a responsive and
adaptive function).
In simple words, “smart material responds to a stimulus with
Smart Materials

Normal materials have limited responses, while smart
materials have appropriate responses, but response is the same
every time.
Some simple examples are
photo chromatic glass that darkens in bright light;
low melting point wax in a fire sprinkler which blocks the
nozzle until it gets hot;
Smart Materials

♦ No moving parts.
♦ High reliability.
♦ Low power requirements.
♦ Provide new capabilities that are presently not possible.
Applications
♦ Active control inceptors using smart material motion
control.
Smart Materials -Advantages

These are materials which produce a voltage when stress is
applied.
Since this effect also applies in the reverse manner, a
voltage across the sample will produce stress within the
sample.
Suitably designed structures made from these materials can
therefore be made.
Used as sensors and actuators
Piezoelectric Materials

Shape memory alloys (SMA) and shape memory polymers
are materials in which large deformation can be induced and
recovered through temperature changes or stress changes.
The large deformation results due to martensitic phase
change.
A shape memory alloy is an alloy that “remembers” its
original, cold-forged shape: returning the pre-deformed shape
by heating.
Shape memory alloys

Thank you
Contact :
drsjose@gmail.com
0091-9446812425

Modern materials

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