METALLIC GLASS

Material Science

INTRODUCTION

• With the advent of material science and so many new engineering material are discovered having major application in industries.

• This are classified as metals and alloys,cermics,glasses,glass ceramics,composites and semiconductor.

• Our presentation is on one of such material which is METALLIC GLASS.

INTRODUCTION

• The material which has the properties of both metals and glasses is known as metallic glass or metglass.

• They have high strength,good magnetic properties and better corrosion resistance.

• METALLIC GLASS = AMORPHOUS METAL

METALLIC GLASSES

• It shares the property of both metals and alloys.

• Metallic glasses are metal alloy that are amorphous.That is they don’t have long range atomic order.

• The major advantages of such glasses are that they are generelly homogeneous in composition,offer strong and superior corrosion resistance.

BASIC CONCEPT

ΔT = 1,000,000 °C / s

CLASSIFICATION

• METAL-METALLOID GLASS (Fe,Co, Ni ) and(B , Si, S, P )• METAL – METAL GLASS

Nickel - Niobium(Ni-Nb)Magnesium-Zinc (Mg-Zn)Copper-Zirconium (Cu- Zr)Hafnium-Vanadium(Hf-V)

PREPARATION

• To have peculiar property, metallic glasses are to be made by cooling a molten metal rapidly at rate of 2*1060 c/s.

• During the proccess of solidification,atoms do not have enough time or enegy to rearrange for crystal nucleation.Thus,li reaching the glass tranition temperature Tg solidifies as metallic glass.Again,upon heating metallic glasses shows a reversible glass-liquid transition at Tg

TECNIQUES OF PREPARATION

• Various rapid cooling tecniques such as spraying,spinning and laser deposition are used for the production of metallic glasses.

GLASS TRANSITION TEMPERATURE(TG)

• Metallic glass is prepared by cooling a metallic liquid having disordered structure.[ RATE OF COOLING IS 2 X 106 O C ]

• The temperature at which the transition from liquid to solid is known as glass transition temperature.Tg = 20O C TO 300O C

PREPERATIONMELT SPINNING

• Melt spinner contains refractory tube , copper disc, induction heater.

• Mixture of alloy has taken in refractory tube and is heated to very high temperature by using induction furnace.

• The molten alloy is ejected through fine nozzle at the bottom of refractory tube.

• Molten alloy is suddenly cooled while that is interact with the wheel and that is solidified.

MELT SPINNING

PROPERTIES• High strenth but lighter in weight.• They are ductile ,malleable,brittle and opaque.Hardness is very

high.• The toughness is very high i.e. the fracture resistance is very high.• High elasticity.• High Corrosion resistance.• They are soft magnetic materials.As a result,easy to

magnetisation and demagnetisation are possible.• Narrow hytresis loop thus low hytresis energy losses.• They have high electrical resistivity which leads to a low eddy

current loss.

• Non-crystalline, amorphous structure

No dislocations

No grain boundaries

• High elastic limit

• High strength

PROPERTIES

• Structural Properties• Mechanical Properties• Electrical Properties• Magnetic Properties• Chemical Properties

STRUCTURAL PROPERTIES

• There is no grain boundaries and dislocations.• They have TCP [ Tetrahedral closely packed

structure ]

Grain boundary

MECHANICAL PROPERTIES

• They have high corrosion resistance.• They are very strong.• They have high workability.• They are highly ductile.

ELECTRICAL PROPERTIES

• They have high electrical resistivity 100 μΩ - cm .

• Temperature coefficient is zero or negative.• Eddy current loss is very small.

MAGNETIC PROPERTIES

• They have soft and hard magnetic propeties.• They exhibit high saturation magnetisation.

[ the amount of magnetic field that a magnet can produce is known as saturation magnetisation ] Strong magnets have higher saturation.

• The core loss is very less.• They have narrow hysteresis loop.

CHEMICAL PROPERTIES

• They are highly reactive and stable.• They can act as a catalyst.• They have no crystalline defects.

APPLICATION• Metallic glasses are used as transformer core material in high

powertransformers.• Due to its high electrical resistivity and nearly zero

temperature coeficient of resistance,these materils are uset in making cryothermometers,magnetoresistance sensor and computer memory.

• As the magnetic property of metalic glass are not affected by irradiation they are used in making container for nuclear waste disposal.

• These materials are used in preparation of magnets for fusion reactors and magnets for leviated trains etc.

• Metallic glasses can also be used for making watch cases to replace Ni and other metals which can cause allergic reactions.

APPLICATION(Conti…)

• Used in cutting and in surgical instrument.• Infuture ,it will be used in electronic field can

yield stronger,lighter,and more esaily moulded castings for personal electronics products.

• They are used in tap recoders as heads ,in the manufacture of springs and standard resistances.

APPLICATIONS

• They are used as reinforcing elements.• They are used to construct fly wheels.

• They are used to make razor blades and different kinds of springs.

• They are used in core of highpower transformers.

• They are used in tape recorder heads.

• The metglass wires and ribbons are ideal for generating harmonics.

• They are used in producing high magnetic field for magnetic levitation effect.

• They are used to make standardresistance,computer memories and magnetic resistance sensors.

• They are useful for preparing container for nuclear waste disposal, magnets for fusion reactors.

They are used in marine cables, chemical filters, and inner surfaces of the reactor vessel

• They are ideal for making surgical instruments and implantation materials.