Metals

Question 1

what is malachite?

Answer 1

copper carbonate hydroxide

Question 2

metals form giant regular [] where a sea of delocalised [] move freely

Answer 2

lattice
electrons

Question 3

A metallic bond can be explained as

Answer 3

The attraction between the negative sea of electrons to the positive metal lattice

Question 4

A metallic bond is [], therefore metals have [] boiling points

Answer 4

strong
high

Question 5

A mixture of metals is called a

Answer 5

alloy

Question 6

FCC stands for

Answer 6

Face centred cubic

Question 7

HCP stands for

Answer 7

hexagonal close packed

Question 8

BCC stands for

Answer 8

body centred cubic

Question 9

in HCP, the atoms are layered in which kind of pattern?

Answer 9

ABA

Question 10

in FCC, the atoms are layered in which kind of pattern?
What is the result of this?

Answer 10

CBA
all holes are filled

Question 11

What are the types of imperfections in crystal structures?

Answer 11

substitutional atoms
intersticial atoms
vacancies
dislocation

Question 12

What is a substitutional atom?

Answer 12

when different size foreign material is introduced

Question 13

What is an intersticial atom?

Answer 13

an atom that is squeezed into uniform structure, causing local stresses

Question 14

What is a vacancy?

Answer 14

a missing atom which causes a stress field in the missing reigon

Question 15

What is a grain boundary?

Answer 15

it is the interface between adjacent crystalline reigons that have different orientation

Question 16

what is intergranular fracture?

Answer 16

facture that may occur between grains

Question 17

What is a dislocation?

Answer 17

Extra line of atoms in a structure, makes for easier plastic deformation

Question 18

In plastic deformation, how does a dislocation move in a lattice structure?

Answer 18

the row of dislocations will be pushed along by a force
it will slip under the plane of atoms and move through the structure

Question 19

Under low [] dislocations move along the direction of []

Answer 19

shear
force

Question 20

What are the properties of alloys determined by?

Answer 20

composition of microstructure
distribution of phases
processing
size+shape of grain

Question 21

Steel is an alloy of mainly which materials?

Answer 21

iron
carbon(<2%)
silicon, phosphorous, sulphur, O2 (<1%)

Question 22

Grain boundaries are barriers to

Answer 22

dislocation motion

Question 23

The more [] sites, the more [].

Answer 23

nucleation sites
the more boundaries

(nucleation is the initial process of forming a crystal from a solution btw)

Question 24

Reduced grain size =

Answer 24

higher yield stress

Question 25

solute atoms have an associated []

Answer 25

strain field

Question 26

the associated strain field of atoms interacts with the strain field of nearby [] and inhibits []

Answer 26

dislocations motion

Question 27

Plastic deformation increases the number and density of

Answer 27

dislocations

Question 28

dislocations also increase in density in []. dislocations moving on intersecting slip planes [] and []

Answer 28

plastic flow pile up and tangle

Question 29

precipitation strengthening requires a fine distribution of of [] phase particles

Answer 29

2nd

Question 30

the 2nd phase particles used in precipitation strengthening have their very own [] that interacts with dislocations by [] and [] them

Answer 30

strain fields pinning and locking them

Question 31

What is a phase diagram?

Answer 31

a diagram that depicts the relationships between different phases of a substance under varying conditions of temperature and composition

Question 32

What will the phase diagram axes represent?

Answer 32

y axis - temperature x axis - composition % e.g wt% of C in a steel alloy

Question 33

What does a tie line represent?

Answer 33

a horizontal line that connects two phases in equilibrium at a specific temperature and composition

Question 34

What does the lever rule tell us?

Answer 34

determines the fraction of each phase present based on the ratio of lengths of the tie line when you bisect it with a point and want to know the ratio of phases present.

Question 35

What is a eutectic point in a phase diagram?

Answer 35

specific composition and temperature at which a binary mixture undergoes a eutectic reaction.

Question 36

what is a eutectic reaction?

Answer 36

The liquid phase transforms into two different solid phases at the same time