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MSE 2034 > Test 2 > Flashcards

Test 2 Flashcards

1
Q

What allows a metal to plastically deform?

A

the movement of dislocations

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2
Q

What are the two types of dislocations?

A

edge and screw

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3
Q

What does a burger’s vector tell you about slip?

A

The slip direction (should know for FCC)

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4
Q

What does a slip system consist of?

A

a plane and a direction

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5
Q

What is the FCC slip system?

A

(111)+[110]

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6
Q

What is the equation for resolved shear stress and what do the terms mean?

A

resolved shear stress = applied stresscos(phi)cos(lamda)
Phi is the angle between the tensile axis and the normal to the slip plane.
Lamda is the angle between the tensile axis and the slip direction.

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7
Q

What equation do you use to find angles for phi and lamda in the resolved shear stress equation?

A

for vectors: a=[a1,a2,a3] and b=[b1,b2,b3]

theta=inversecos[{a1b1+a2b2+a3*b3)/(sqrt[(a1^2+a2^2+a3^2)(b1^2+b2^2+b3^2)])]

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8
Q

What is twinning?

A

A means of plastic deformation in which a shear force produces atomic displacement such that atoms on one side of the plane (the twin boundary) are located in mirror-image positions to atoms on the other side of the plane.

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9
Q

What are the mechanisms for strengthening metals?

A
  1. Cold Working/Strain Hardening
  2. Grain Size Reduction
  3. Precipitation Hardening
  4. Solid Solution Strengthening
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10
Q

How does Grain Size Reduction strengthen a metal?

A

When a dislocation passes into a different grain it must change directions. The smaller the grains, the more often it has to change directions, making it more difficult for it to move.

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11
Q

How does Solid Solution Strengthening work?

A

A host material is alloyed with impurity atoms that go into either substitutional or interstitial positions. This causes lattice strain and consequently dislocation movement restriction.

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12
Q

How does Strain Hardening/Cold Working work?

A

As dislocation density increases dislocation movement becomes more restricted.

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13
Q

How does Precipitation Hardening work?

A

Heat treatments are used to cause a formation of extremely small uniformly dispersed particles of a second phase within the original phase matrix. The precipitate acts as pinning points. Inverse relationship between yield strength and spacing between precipitates.

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14
Q

What is the Hall-Petch equation?

A

yield strength=sigma0+k/sqrt(d)
sigma0 and k are material constants
d is the average grain diameter

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15
Q

What is annealing?

A

Heat treatment that causes a material to revert to precold-worked states

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16
Q

What are the phases of annealing? Explain them.

A

Recovery - reduce dislocation density
Recrystallization - formation of a new set of grains with very few dislocations
Grain Growth - strain-free gains continue to grow. Grain growth causes a decrease in total boundary area which reduces total energy

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17
Q

What are the two types of fracture? Explain them

A

Ductile - deformation occurs before fracture (necking)

Brittle - little to no deformation occurs before fracture (clean break)

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18
Q

What is sigmam in terms of fracture mechanics?

A 
maximum stress at tip of elliptical shaped crack. 
sigmam=2*sigma0*sqrt(a/psubt)
sigma0: applied tensile stres
a: Length of a surface crack
psubt: crack tip radius
19
Q

What is the equation for Plain strain fracture toughness?

A

Kic=Ysigmasqrt(pi*a)
unless specified: Y=1
simga: applied stress
a: Length of surface crack

20
Q

What is the equation for design (or critical) stress?

A

sigmac=Kic/(Ysqrt(pia))
unless specified: Y=1
Kic: plain strain fracture toughness
a: length of surface crack

21
Q

What type of metals typically experience DBTT?

A

BCC

22
Q

Explain DBTT

A

Ductile to Brittle Transition with decreasing temperature

23
Q

What is impact energy?

A

work done to fracture a test specimen

24
Q

What are the components of an SN curve?

A

S: stress on y-axis
N: cycles to failure on x-axis
curves that don’t level off do not have a fatigue limit and will eventually fail due to fatigue

25
Q

How to improve impact of fatigue?

A

Put compression on surface

26
Q

What is the relationship between creep strain and temperature or stress?

A

If T<0.4Tm then creep strain is essentially negligible. If stress or temperature go up instantaneous deformation go up and time to rupture shortens. Slope of steady state creep rate increases.

27
Q

epsilon dot represents what? What does the equation without T represent?

A

Steady state creep rate. Steady state creep rate at constant temperature.

28
Q

What are the 4 things you should find from a phase diagram?

A
  1. # of phases & what they are
  2. composition
  3. amounts
  4. picture/pie chart
29
Q

What are the -ites in order from strongest to weakest?

A
  1. martensite
  2. tempered martensite
  3. cementite
  4. bainite
  5. fine pearlite
  6. course pearlite
  7. spherodite
  8. ferrite

pearlite is ferrite + cementite

30
Q

What are the two types of metals?

A

ferrous and non-ferrous

31
Q

Are steel and cast iron ferrous or non-ferrous?

A

ferrous

32
Q

What are the differences between steel and cast iron?

A

cast iron has more carbon (3-4.5 wt% C). Steel has <1.4 wt% C. Also, cast iron has graphite.

33
Q

What distinguishes different types of cast iron?

A

shape of graphite

34
Q

List all the non-ferrous metals along with their qualities

A 
Al - low density, cheap, manufacturable
Mg - really light, ignites easily
Ti- light, strong, expensive, hard to machine
Cu - excellent conductivity
Refractories - good at high temperatures
Noble metals - do not oxidize (rust)
35
Q

What are all of the processing techniques?

A 
Forging
Casting
     a. Sand
     b. Investment
Rolling (Hot/Cold)
Extrusion
Drawing
Power Processing
Welding

Should know what these looked like

36
Q

What are the different types of annealing procedures?

A
  1. Normalizing
  2. Spherodizing
  3. Full Anneal
  4. Stress Relief
37
Q

What is hardenabililty?

A

how easily a sample forms martensite

38
Q

What is the test for hardenability?

A

Jominy End Quench Test

39
Q

What is 1020?

A

low carbon steel

40
Q

What is 4190?

A

tool steel

41
Q

What is >10 wt% Cr?

A

stainless steel

42
Q

What is 4310?

A

HSLA

43
Q

What is the wt% C of 1020 steel?

A

0.2

MSE 2034 (4 decks)

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