Lecture 1- Lecture 3

Question 1

material science

Answer 1

study of structure property and processing relationship

Question 2

structure

Answer 2

the way materials organize themselves. Arrangement of atoms in different way.

Think Graphite vs Diamond. Di(single vs polycrystal). Diamond has zinc blend structure, FCC while graphineis a layer structure with covalent bonds in plane and VanWals between planes

Note structure dictates properties.

Question 3

property

Answer 3

the way materials respond to the surroundings, environment, external stimulus included mechanical, electrical, magnetic, thermal, optical, chemical etc

Question 4

processing

Answer 4

the way to “fabricate” materials including the application of heat (heat treatment), mechanical force (hot work, cold work), ect. to affect their micro structure therefore same properties.

Question 5

Give a classification of materials based on (solid phase)

Answer 5

1) homogeneoity of properties, 2) chemical make up (bond nature), 3)Whether they have long range ordering

Question 6

Categorize materials based on homogeneoity of properties:

Answer 6

monolithic (uniform), composite (different phases not monolithic), hierarchical (most common in bio, cells tissues, bone),

Question 7

characterize material based on chemical make up (bond nauture)

Answer 7

metals= combination of metallic elements, “sea of electrons” –> metallic bond, good electrical/ thermal conducting –> strong deformable”

ceramics= compound between metallic and non metallic element oxides, nitrides, carbides, “ionic bonding”, good insulators!

Polymers= based on H.C or non metallic element, chain like structures, covalent bond, Van Walls make them flexible and easy to deform

Glasses= lack of long range ordering; are in non-equlibrium strength, brittle mechanically.

semiconductor- special type, mostly covalent bonding, in between conductors and insulators, extremely sensitive to contaminates

liquid crystal= shares properties of both liquid and crystals, more strain stronger it gets

porous and cellular= not completely compact with low density; important for energy absorbing applications elastic –> collapse of pores –> densification

Question 8

Characterize material based on long range ordering or not

Answer 8

crystalline metals- structured

quasicrystal - inbetween

non crystallline- not structured

Question 9

define crystal structure=

Answer 9

lattice structure (mathematical term) + basis (can be atom, atom cluster, group atoms

Question 10

lattice

Answer 10

highly periodic arrays of points in 3D space

Question 11

Bravais Lattice

Answer 11

14 types –> organized into 7 crystal systems

`1). orientation and arrangement: appears exactly the same for the lattice point

2). All points in the lattice can be reached with a Translational vector, R=n2a1+n2a2+n3a, where a1,a2,a3 are non coplanar vectors and n1,n2,n3 are integers

Question 12

Primitive cell....
Corner=?
face=?
edge center=?
center=1?

Answer 12

1 lattice point/cell

corner =1/8
face= 1/2
edge center= 1/4
center=1

I=body Center
F= face center
c= base center

Question 13

platisicity

Answer 13

motion of dislocation not necessarily from existing dislocations, FCC easiest for dislocations

Question 14

BCC structure

Answer 14

nearest neighbor= coordination number = 8; close packing direction = <1 1 1>, relationship between cube edge length and atomic radius

Question 15

Bcc

Answer 15

chromium, alpha iron, molybedum, tantalum, tungsten, (all high tempertaure)

Question 16

FCC

Answer 16

aluminium, copper, gold lead, nickel, platinium, silver

Question 17

HCP

Answer 17

cadium, colbalt, zinc, tantulum, (least deformable)

Question 18

point defect

Answer 18

O-D- interstitial or vacancies. Important in diffusion

Question 19

line defect dislocation

Answer 19

1Ddislocations

Question 20

interface defects

Answer 20

2D surface, ang surface defects

Question 21

volume defect

Answer 21

3D voids in the structure “negative crystals”

Question 22

name some mechanical testing methods

Answer 22

tensile, compression, bending, torsion, impact, fatigue, hardness testing

Question 23

ASTM

Answer 23

american standard for testing materials

Question 24

tensile testing

Answer 24

yhoungs modules, poissons ration, yield strength, ultimate tensile strength, dustility, Strain at failure/ area reduction

Question 25

rotating bend fatigue and charpy impact test

Answer 25

bending sample and rotating it

Question 26

youngs modulus

Answer 26

depends on material, but is independent of the cross sectional area and length of the bear. Youngs modulus is a material property!