mG-2 Flashcards

1
Q

Which materials are crystalline?

A

metals, many ceramics, some polymers

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2
Q

When are materials typically noncrystalline?

A

complex structures, rapid cooling

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3
Q

What does amorphous mean?

A

noncrystalline

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4
Q

Do most engineering applications use single or polycrystals?

A

polycrystals

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5
Q

What is the term for properties that vary with direction?

A

anisotropic

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6
Q

Are single crystals anisotropic or isotropic?

A

anisotropic

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7
Q

If the grains of a polycrystal are randomly oriented is it anisotropic or isotropic?

A

isotropic

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8
Q

If the grains of a polycrystal are textured is it anisotropic or isotropic?

A

anisotropic

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9
Q

What is polymorphism?

A

two or more distinct crystal structures for the same material

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10
Q

Describe how to find crystallographic directions

A
  1. find x,y,z change in positions
  2. clear fractions
  3. write as numbers without commas in brackets []
  4. express negative numbers with a bar over the number
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11
Q

equation for linear density

A

LD = number of atoms / unit length of direction vector

number of atoms refers to radius

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12
Q

What is the algorithm for finding crystallographic planes?

A
  1. Read off intercepts of plane with axes (if no intercept use infinity)
  2. Take reciprocals of intercepts
  3. Reduce to smallest integer values
  4. Enclose in parentheses, no
    commas i.e., (hkl)
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13
Q

What is the name of the indices used for crystallographic planes?

A

Miller indices

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14
Q

equation for planar density

A

PD = number of atoms centered on the plane / area of the plane
(number of atoms refers to radius)

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15
Q

x-ray diffraction give us what information?

A

crystal structure and interplanar spacing determinations

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16
Q

What is solidification?

A

molten material cooling, crystals forming and growing unitl they meet. The result is a grain structure

17
Q

What is the equation for the equilibrium number of vacancies in a material?

A
Nv/N=e^(-Q/kT)
Nv: number of defects per unit volume
N: number of potential defect sites per unit volume
Q: activation energy
k: boltzman constant
T: temperature

N=pNa/A
p: density
Na: Avogadro’s number 6.022
10^23
A: atomic weight (g/mol)

18
Q

What are the conditions for a substitutional solid solution?

A
  1. difference in radius less than 15%
  2. Proximity in periodic table (similar electronegatives)
  3. Same crystal structure for pure metals
  4. Higher valency
19
Q

What is the burger’s vector?

A

measure of lattice distortion

20
Q

What are the types of point defects in solids?

A

vacancy, interstitial, substitutional

21
Q

What are the types of 1D or line defects in solids?

A

edge and screw dislocations

22
Q

What are types of 2D or area defects in solids?

A

grain boundaries, stacking faults

23
Q

What measurement can you see with optical microscopy at 2000x magnification?

A

about 1 micron

24
Q

Can you see unit cell edge lengths with optical microscopy?

A

no

25
Q

What is diffusion?

A

Introducing a foreign atom into a host material

26
Q

What are the two mechanisms of diffusion?

A
  1. vacancy/substitutional

2. interstitial

27
Q

What is Fick’s first law?

A

Steady state diffusion:
J=M/(At)
J=-D*dC/dx

28
Q

What is Fick’s second law?

A

Non steady state diffusion:

Cx-C0/(Cs-C0) = 1 - erf(x/(2sqrt(Dt))

29
Q

What does diffusion equation reduce to if everything is constant except for time and temperature?

A

D1t1=D2t2

30
Q

What is the modulus of steel?

A

200 GPa or 29 Msi

31
Q

What is the yield stress of steel?

A

250 MPa or 36 Ksi

32
Q

How many atoms (n) for SC?

A

1

33
Q

How many atoms (n) for BCC?

A

2

34
Q

How many atoms (n) for FCC?

A

4

35
Q

SC side length?

A

2r

36
Q

BCC side length?

A

4r/sqrt(3)

37
Q

FCC side length?

A

2sqrt(2)r