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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
What problems does residual stress contribute?
Loss of dimensional accuracy limits maximum dimensions in process failure/cracking reduced mechanical performance
26
Why is the structure-property relationship difficult to understand?
need new physics and scaling laws for predictability and long-term reliability and sustainability from computer modeling
27
How do AM material properties compare to commercial properties?
Commercial properties are better.
28
What are different types of differences in microstructures?
voids weld pools grain sizes textures impurities compositional inhomogeneity phases
29
What are the typical properties of metals?
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
What are characteristics of Al alloys?
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
What are application areas for Al?
aerospace automotive construction packaging electrical transmission lines
32
Are high-strength Al alloys easy to print?
high-strength Al alloys are one of the most difficult to print
33
What are the characteristics of Ni superalloys?
outstanding high temp strength and creep properties high temp resistance to oxidation not lightweight $7/lb
34
What are the applications of Ni superalloys?
high temp in aerospace, automotive, power generation biotechnology
35
What are difficulties to printing Ni superalloys?
difficult to control precipitates and single crystals
36
What are the characteristic properties of Cu alloys?
high ductility good thermal and electrical conductivity ultrahigh vacuum compatibility good corrosion resistance medium strength poor high temp properties $4/lb
37
What are the applications of Cu alloys?
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
What type of Cu alloy is the most difficult to print?
pure Cu
39
What are the characteristic properties of Fe alloys?
high strength high ductility high corrosion resistance good fatigue properties good medium temperature properties cheap vacuum compatibility biocompatibility
40
What are the application areas of Fe alloys?
Construction (buildings, bridges) Transportation (vehicles, ships, rails, trains) Oil gas pipelines Weapons Consumables Nuclear and chemical plants
41
Why are steels not p3D printed more?
different compositions no added value by printing
42
What are the characteristic properties of Ti alloys?
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
What are applications of Ti alloys?
aerospace medical implants other appliances
44
What are the four material science issues?
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
What is ductility?
the ability of a material to be plastically deformed without fracture
46
What is yield strength?
the point at which material begins to deform plastically
47
What is ultimate tensile strength?
the maximum stress that a material can withstand before breaking
48
What is elastic deformation?
temporary deformation of a material's shape that is self-reversing
49
What is plastic deformation?
permanent distortion when stresses exceed yield strength
50
What is fracture strength?
The stress at which a material breaks or fails
51
What is hardness?
the ability of a material to resist deformation
52
What is creep?
time dependent deformation at elevated temperature or constant stress
53
Why do we prefer alloys over pure elements?
properties tend to be better than their constitutional components
54
What are two characteristics about Ti alloys?
lucrative many material science issues to be solved

MAT SCI 298 (11 decks)

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