Types and applications of materials Flashcards
Metal alloys are grouped into two classes, which are … and …
Ferrous alloys, and non ferrous alloys
Alloys in which iron is the principle consituent (steels and cast irons).
Ferrous alloys
… are produced in larger quantities than any other metal alloy.
Ferrous alloys
What are the advantages of ferrous alloys?
- Offer a wide range of mechanical and physical properties.
- Economical production techniques.
- Abundant quantities within the earth’s crust.
… are metal alloys that are not iron based.
Non-ferrous alloys
… are iron–carbon alloys that may contain appreciable concentrations of other alloying elements.
Steels
The mechanical properties of steel are sensitive to the content of carbon, which is normally less than …
1.0 wt%.
Some of the more common steels are classified
according to carbon concentration into … , … , …
low-carbon medium-carbon, and
high-carbon types
Subclasses exist within each group of steels according to the …
concentration of other alloying elements.
What type of steel is produced in the greatest quantities?
low-carbon
How much carbon do low-carbon steels have?
less than about 0.25 wt% C
… are relatively soft and weak but have outstanding ductility and toughness; in addition, they are machinable, weldable, and, of all steels, are
the least expensive to produce.
low-carbon steels
What are typical applications of low carbon steels?
automobile body components, structural shapes, and sheets that are used in pipelines,buildings, bridges, and tin cans.
For low-carbon steels what is the yield strength? tensile strengths? and ductility ?
Yield strength: 275 MPa
Tensile strengths: between 415 and 550 MPa
Ductility: 25% EL
Another group of low-carbon alloys are the high-strength, low-alloy (HSLA) steels. What other alloying elements do they contain and in what concentrations? Compare their strength in relation to plain low-carbon steels.
copper, vanadium,nickel, and molybdenum in combined concentrations as high as 10 wt%, and
they possess higher strengths than the plain low-carbon steels.
high-strength, low-alloy (HSLA) steels may be strengthened by …
heat treatment,
What are other properties of high-strength, low-alloy steels?
ductile, formable, and machinable.
HSLA steels are more resistant to … than
the plain carbon steels,
corrosion
Medium-carbon steels have carbon concentrations between about… .
These alloys may be … to improve their mechanical properties.
0.25 and 0.60 wt%,
heat-treated
Heat-treated medium-carbon steels are stronger than the low-carbon steels, but at a sacrifice of …
ductility and toughness
Additions of … improve the capacity of medium-carbon alloys to be heat-treated, giving rise to a variety of strength–ductility combinations.
chromium, nickel, and molybdenum
Applications of which type of carbon steel include railway wheels and tracks, gears, crankshafts, and other machine parts and high-strength structural components calling for a combination of high strength, wear resistance, and toughness.
Medium-carbon
The high-carbon steels, normally having carbon contents between …, are the … , … , and yet least … of the carbon steels.
0.60 and 1.4 wt%
hardest, strongest, ductile
What type of carbon steel is wear resistant and capable of holding a sharp cutting edge.
high-carbon
high-carbon alloys contain alloying elements …
which when combine with carbon form very hard and wear-resistant carbide compounds.
chromium, vanadium, tungsten, and molybdenum.
… steels are used as cutting tools and dies for forming and shaping materials, as well as in knives, razors, hacksaw blades, springs, and high strength
wire.
High-carbon
… are highly resistant to corrosion especially the ambient atmosphere.
The stainless steels
The predominant alloying element for stainless steel is …; a concentration of at least … is required. Corrosion
resistance may also be enhanced by … and … additions.
chromium, 11 wt% Cr
nickel, molybdenum
… are frequently used at elevated temperatures and in severe environments because they resist oxidation and maintain their mechanical integrity under such conditions; the upper temperature limit in oxidizing
atmospheres is about 1000°C.
stainless steels
Applications of … include gas turbines, high-temperature steam boilers, heat-treating
furnaces, aircraft, missiles, and nuclear power-generating units.
stainless steels
Cast irons are ferrous alloys with more than … wt% C
more commonly …wt% C
2.1,
3 - 4.5
What are properties of cast irons?
Low melting temperature, relatively easy to cast. Generally brittle, thus casting is the most convenient fabrication method.
… iron is a type of cast iron, it is
- graphite flakes
- weak & brittle in tension
- stronger in compression
- excellent vibrational dampening
- wear resistant
Gray iron
What is this type of cast iron? -add Mg and/or Ce (cerium) - graphite as nodules not flakes - matrix often pearlite - stronger but less ductile
Ductile iron
what type of cast iron?
- Low silicon
- < 1 wt% Si
- very hard and brittle
White iron
what type of cast iron?
- heat treat white iron at 800-900ºC
- graphite in rosettes
- reasonably strong and ductile
Malleable iron
What type of cast iron?
- relatively high thermal conductivity
- good resistance to thermal shock
- lower oxidation at elevated temperatures
Compacted graphite iron
What are limitations of ferrous alloys?
high densities, low electrical conductivity, poor corrosion resistance.
… are characterized by a relatively low density (2.7 g/cm3 as compared to 7.9 g/cm3 for steel), high electrical and thermal conductivities, and a resistance to corrosion in some common environments, including the ambient atmosphere.
Aluminium and alloys
Aluminum has an FCC crystal structure, its … is retained even at very low temperatures.
ductility
What is a limitation of Aluminium?
low melting temperature (660°C)
The mechanical … of aluminum may be enhanced by cold work and by alloying; however, both processes tend to decrease resistance to corrosion.
strength
Principal alloying elements with Aluminium include …
copper, magnesium, silicon, manganese, and
zinc.
Applications of ceramics include …
die blanks, cutting tools, sensors
What are refractories?
Materials to be used at high temperatures