Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Dr. Alagiriswamy A A, (M.Sc, PhD, PDF)Asst. Professor (Sr. Grade),

Dept. of Physics & Nanotechnology, SRM-University,

Kattankulathur campus, Chennai

Mar. 18/2014

UNIT III

Lecture 2

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Shape memory alloys (SMAs)

Metallic glasses or amorphous metals

examples, features, preparation, applications

Composites

Features, examples, products

Advanced ceramics

Examples Categories, preparation (processing techniques) properties features, examples

Outline

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Stents as SMAs

Before I proceed

Ability to bend, stay bent, and regain its shapeUses internal atomic arrangement to recognize their shapesAustentite (high temperature cubic phase) & Martensite (low temperature deformed or twinned phase)

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Metallic Glass: A Revolution of Metallurgy

• Metallic glass = Amorphous metal– Metals (have long range order, ductility, malleability, lusture)– Glasses (lack of long range order – short range order, no

crystallinity features )– It's called metallic glass, and it shines like a mirror, but when

you drop a piece of it to the floor, it doesn't break. In fact, it bounces--wildly--thanks to its unusual atomic structure

– can it be called as a liquid metal – Conventional metals crystallize when cooled from a liquid to a

solid. But metallic glass cools to an amorphous (glassy) structure, making it much stronger, lighter, and springier than other metals--and virtually corrosion-proof

– low hysteresis (may be a soft magnetic)

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

X-ray spectrum of ………..

(a) crystalline material and (b) amorphous material

,,, 114186710137720 SiBCOFeBSiFeB21734741843840 , SiBMONiFeBMONiFe

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

(a) Mechanical properties

Unique features of MG………..

(b) Magnetic properties

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

More interesting features of MG ……

• Imagine a razor blade that stays super sharp

for a year.

• A golf club so springy it can drive a ball farther

than a titanium club.

• An artificial hip implant that is stronger and

more flexible than current implants.

• A cell phone case that is almost indestructible

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Fabrication of MG …

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Advanced Ceramic Materials

• Non-metallic elements, need not be inorganic

• Hard and brittle, toughness,

• Chemically inert, having high melting points

• Electrically/thermally considered to be insulators

Ceramic materials

Traditional ceramics (bricks, porcelain)

Advanced ceramics (SiC, Si3N4, Al2O3)

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

A few applications of Adv. Cer…..

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Comparison metals v ceramics

Ceramics Metals

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Processing of advanced ceramics

• Material preparation– Milling/sizing to form desired particle size

• Forming or casting– Pressing into a die – to form a shaped product

• Thermal treatment– Drying: to remove water from the plastic and the

process is carried out in the range 200 to 3000C.– Sintering: small particles of a material bonded

together - solid-state diffusion. During this process ceramic porous product is made into a dense coherent product.

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Composites

A composite is basically a material that contains both a

reinforcing material to provide strength and stiffness and a

matrix material to surround and hold the reinforcement

together.

• Natural composites:– Wood (cellulose/lignin)– Bone (apatite/collagen)– Nacre ( Mother of pearl)

(Aragonite/protein) – Granite (quartz, feldspars…)

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

• Engineered materials – (reinforcing phase, matrix phase)– Orthotropic :- depends on the direction of

the external load applied– Difficult to explain the mechanical

properties– Shock/impact creates failure at

micro/macro level– Fiber reinforced, glass reinforced, carbon

reinforced composites

features

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

What are the advantage of composites ?

• Light weight

• High strength & stiffness

• Reinforcement fibres can be arranged to follow the direction of principle loads and stresses

• Good fatigue resistance

• Very low coefficient of thermal expansion

• Good environmental and corrosion resistance

• The ability to manufacture complex shapes by moulding results in cost-effective production

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Applications as

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Applications as

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Dr. Alagiriswamy A A, Asst. Professor, Dept. of Physics, SRM-U, Chennai

Thanks for the kind attention