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MAT SCI 298 > Lecture 2 - Materials Science Issues > Flashcards

Lecture 2 - Materials Science Issues Flashcards

1
Q

What is an alloy?

A

a mixture of one metal with another or multiple elements

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2
Q

What are the most common metals?

A

lithium, beryllium, sodium, magnesium, aluminum, copper, iron, nickel, titanium

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3
Q

What percentage of the periodic table is metals?

A

~80%

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4
Q

Which alloys are the most popular?

A

FCC metallic alloys

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5
Q

Which alloys have poor ductility?

A

HCP metallic alloys due to asymmetry

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6
Q

How many elements are typically in multicomponent metallic alloys?

A

3-6

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7
Q

What three types of alloys are in FCC metallic alloys?

A

Cu-alloys, Al-alloys, Ni superalloys

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8
Q

What are metallic composites?

A

reinforced by nonmetallic elements like carbon, oxides

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9
Q

What do Cu-alloys consist of?

A

Cu-Zn (brass)
Cu-Sn (bronze)
Cu-Ni
Cu-Be
~400 other types

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10
Q

Why are most materials (>5500 alloys) not printable?

A

low/poor weldability
brittle (cracking)
low absorptivity/high thermal conductivity

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11
Q

What do Al-alloys consist of?

A

1xxx through 7xxx series

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12
Q

What does low absorptivity and high thermal conductivity mean?

A

materials cannot hold onto energy well enough to melt into desired shape

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13
Q

What do Ni superalloys consist of?

A

inconel, hastelloy

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14
Q

What do HCP metallic alloys consist of?

A

Ti-alloys (Ti-6Al-4V and variations) and Mg-alloys (biodegradable)

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15
Q

What do BCC metallic alloys consist of?

A

Fe-based alloys: carbon steel, alloy steel, stainless steel, tool steel

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16
Q

What are multicomponent metallic alloys?

A

high entropy alloys

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17
Q

What are the five types of metals and alloys?

A

FCC, HCP, BCC, multicomponent, and composite

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18
Q

Which metal powder is the cheapest?

A

Steel

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19
Q

Which materials are currently mostly printable?

A

Steel, Nickel, Titanium, Cobalt, non silicone aluminum, non-pure copper

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20
Q

What material properties are evaluated?

A

strength, ductility, creep, corrosion/oxidation resistance, dynamic/impact, thermal and electrical conductivity, biocompatibility*

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21
Q

Why does processing lead to unique microstructures/compositions?

A

recoil pressure causes evaporation of metal
impurities/pores
melting/remelting of previous layers

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22
Q

How do AM materials differ from commercial alloys?

A

different compositions
impurities
residual stresses
porosities
microstructural features
surface roughness
accident failure parts

23
Q

What does oxidation during AM lead to?

A

degraded mechanical and functional properties

24
Q

What problems does surface roughness create?

A

affects build and leads to machine crashing if comparable to resolution

25
Q

What problems does residual stress contribute?

A

Loss of dimensional accuracy
limits maximum dimensions
in process failure/cracking
reduced mechanical performance

26
Q

Why is the structure-property relationship difficult to understand?

A

need new physics and scaling laws for predictability and long-term reliability and sustainability from computer modeling

27
Q

How do AM material properties compare to commercial properties?

A

Commercial properties are better.

28
Q

What are different types of differences in microstructures?

A

voids
weld pools
grain sizes
textures
impurities
compositional inhomogeneity
phases

29
Q

What are the typical properties of metals?

A

elastic (damping)
mechanical strength (yield strength, ultimate tensile strength, fracture strength, hardness)
ductility and fracture toughness
creep and fatigue
electrical and thermal conductivities
corrosion resistance
biocompatibility

30
Q

What are characteristics of Al alloys?

A

light weight (2.7 g/cc)
good ductility
medium strength
good machinability and castability
general corrosion resistance
poor weldability
poor high temperature properties (bp - 2470C)
~$1/lb

31
Q

What are application areas for Al?

A

aerospace
automotive
construction
packaging
electrical transmission lines

32
Q

Are high-strength Al alloys easy to print?

A

high-strength Al alloys are one of the most difficult to print

33
Q

What are the characteristics of Ni superalloys?

A

outstanding high temp strength and creep properties
high temp resistance to oxidation
not lightweight
$7/lb

34
Q

What are the applications of Ni superalloys?

A

high temp in aerospace, automotive, power generation
biotechnology

35
Q

What are difficulties to printing Ni superalloys?

A

difficult to control precipitates and single crystals

36
Q

What are the characteristic properties of Cu alloys?

A

high ductility
good thermal and electrical
conductivity
ultrahigh vacuum compatibility
good corrosion resistance
medium strength
poor high temp properties
$4/lb

37
Q

What are the applications of Cu alloys?

A

Electrical applications (power transmission and generation, building
wiring, telecommunication, and electrical and electronic products).
Thermal transferring systems (heat exchangers)
Marine applications - good corrosion resistance in seawater (seawater piping).
Architectures
Catalysts

38
Q

What type of Cu alloy is the most difficult to print?

A

pure Cu

39
Q

What are the characteristic properties of Fe alloys?

A

high strength
high ductility
high corrosion
resistance
good fatigue properties
good medium temperature properties
cheap
vacuum compatibility
biocompatibility

40
Q

What are the application areas of Fe alloys?

A

Construction (buildings, bridges)
Transportation (vehicles, ships, rails, trains)
Oil gas pipelines
Weapons
Consumables
Nuclear and chemical plants

41
Q

Why are steels not p3D printed more?

A

different compositions
no added value by printing

42
Q

What are the characteristic properties of Ti alloys?

A

low elastic modulus
light weight (4.5 g/cc)
high strength
poor ductility
high corrosion resistance
good medium
temperature properties
biocompatibility
expensive
tough to process

43
Q

What are applications of Ti alloys?

A

aerospace
medical implants
other appliances

44
Q

What are the four material science issues?

A
  1. printability
  2. different compositions compared to commercial
  3. structure-property relationship is not well understood
  4. properties of AM materials are not good enough
45
Q

What is ductility?

A

the ability of a material to be plastically deformed without fracture

46
Q

What is yield strength?

A

the point at which material begins to deform plastically

47
Q

What is ultimate tensile strength?

A

the maximum stress that a material can withstand before breaking

48
Q

What is elastic deformation?

A

temporary deformation of a material’s shape that is self-reversing

49
Q

What is plastic deformation?

A

permanent distortion when stresses exceed yield strength

50
Q

What is fracture strength?

A

The stress at which a material breaks or fails

51
Q

What is hardness?

A

the ability of a material to resist deformation

52
Q

What is creep?

A

time dependent deformation at elevated temperature or constant stress

53
Q

Why do we prefer alloys over pure elements?

A

properties tend to be better than their constitutional components

54
Q

What are two characteristics about Ti alloys?

A

lucrative
many material science issues to be solved

MAT SCI 298 (11 decks)

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