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Flashcards in metals Deck (24):
1

name the 4 different crystalline defects

Point defects
line defects
planar defects
volume defects

2

name the type of point defects

substitution
vacancy
atom out of place (self interstitial)
interstitial impurity

3

name the type of line defects

edge, screw and mixed dislocation

4

name the type of planar defects

stacking fault, grain boundaries and twin boundaries

5

name the volume defects

precipitates
inclusions
voids

6

what is a phase

a physically distinct homogenous region of an assembly atoms defined by a set of thermodynamic parameters like density

7

phase transformation

rearrangement of atoms of molecules to a new configuration of lower free energy

8

out of ferromagnetic and paramagnetic which on retains its magnetism when the magnetic field is removed

ferromagnetic

9

unlimited solubility is

1 solid phase regardless of the amount of solute of solvent

10

limited solubility

describes the extent to which one phase can tolerate the addition of a new solute

11

what is solid solution strengthening

the addition of atoms (a solute) from one element to a phase (solvent) giving rise to a solid solution

causes distortions In the lattice which leads to localised stress fields that interact with dislocations strengthening it

12

effects of solid solution strengthening

increases: hardness, strength, creep resistance and resistivity
decreases ductility

13

what is the solidus

defines a temp below which is 100% solid for a given composition

14

whats the formuls for % of a phase

opposite lever arm/ full length *100

15

what are nucleations

the first step of either a new thermodynamic phase or a new structure via self assembly

16

when does non equilibrium cooling occur

when something cools too quick for atoms to diffuse produces segregation

17

describe the process of solidification, starting at 52% Ni

Ni atoms diffuse away from solid
remaining liquid becomes enriched in carbon
Process continues to solidus is reached

18

do atoms diffuse quicker in a solid or liquid?

liquid

19

explain micro segregation and how its reduced

-occurs over short distances
-cools too quick for atoms to diffuse (so the solids are high in Ni)
-reduced by homogenisation heat treatment

20

whats macro segregation and how is it reduced

occurs over large distances
- reduced during processing- rolling

21

when does precipitation strengthening occur and whats the effects

-occurs in a system of limited solubility
-occurs when solubility of one material is exceeded by the addition of too much of a given alloy element
-gives rise to an interface boundary
-which interferes with the movement of dislocations>> strengthening it

22

explain the steps in precipitation strengthening

1- solution treatment: heat to temp above solvus temp
2-quench- to RT
3-Age- hold at a temp range between RT and solvus temp
after a long enough time precipitation of equilibrium theta phase

23

eutectic phases- fast cooling has what effect

-less time for diffusion
-results in small intermellor spacing
-more boundaries
-higher strength

24

the 4 classes of alloys in a eutectoid system

1- solid solution alloys
2-alloys that exceed solubility limit
3-eutectoid alloys
4-off eutectoid alloys