Flashcards in Objective 07: Aluminum Deck (30)
What is the density of Aluminum?
How does the weight of Aluminum compare to magnesium and iron?
It is much lighter than iron and heavier than magnesium
What are the properties of Aluminum?
2. Relatively low tensile strength
3. Very malleable
4. Very ductile
5. Very good heat and electrical condutivity
Is Aluminum easily derived?
Redish brown ore of a complex mixture of minerals containing mostly aluminum hydroxides
Caustic leaching process which produces alumina from bauxite
Final refining step after Bayer process
What are the steps of the Hall-Herout Process?
1. Alumina from Bayer Process is fed to an electrolytic cell in the presence of the mineral cryolite
2. An electric current fuses these minerals together to form molten aluminum
3. The molten aluminum settles and is tapped off from the bottom of the bed
Aluminum combined with other metals such as copper, silicon, manganese, zinc, nickel, magnesium, chromium, and lithium with a remarkable range of attributes
What are some applications of Aluminum Alloys?
1. Aircraft and spacecraft construction
2. Automobile parts
3. Industrial plant equipment
4. Military hardware
5. Domestic implements
How is Aluminum Alloy with Copper made?
1. Aluminum is heated above 550ºC
2. The crucible is saturated with copper to form a solution that is 5% copper by weight
Precipitation Hardening of Aluminum Copper
Process by which Aluminum is quenched by cold water so that the copper does not have time to precipitate into copper crystals and instead forms an intermetallic compound (CuAl2)
What is the benefit of Precipitation Hardening to make Aluminum Copper Alloy?
It produces an alloy that is 5-6 times stronger than pure aluminum
How does Precipitation Hardening improve strength in Aluminum Copper Alloy?
The CuAl2 (Copper Aluminide) micro-particles are extremely hard and interfere with the surrounding aluminum atoms by preventing easy slippage of their atomic-plane structures, resulting in hard, strong alloy
What are the benefits of Aluminum-Lithium Alloys and Aluminum Metal Matrix Composites (MCC)?
1. Very high strengths
2. Heat resistant
What are some applications of Aluminum-Lithium Alloys and Aluminum MMC?
They are used to manufacture machine parts, e.g. diesel engine pistons ahd high load-bearing components for the aerospace industry
How are MMCs made?
Solidifying molten alloys that have been reinforced with boron or ceramic fibers
What is a unique property of Aluminum?
It is the only metal known that increases in tensile strength as temperature decreases
What is an application of Aluminum's unique property?
Large plate-fin aluminum-alloy heat exchangers with multiple interal flow paths that display incomparable heat exchange efficiency in cryogenic process plants
How are aluminum and aluminum alloy conductors applied in the electrical field?
1. Large electric transmission lines
2. Switchgear equipment
3. Motor Control Centre Main Bus Bar Connectors
What are the benefits of Aluminum Conductors?
1. Don't need additional surface protection because they develop a thin, passivating, corrosion-resistant oxide surface layer which protects the underlying base metal from further corrosion
2. High electrical conductivity
What kind of conductor do most high-voltage transmission systems use?
Strand-twisted aluminum alloy conductor cable
What kind of alloy are modern conductor cables made from?
Aluminum Conductor Steel Reinforced (ACSR)
Aluminum conductor made with a solid or stranded steel core surrounded by aluminum stranded wire
Where are ACSR used?
River crossings and other long-span installations
What is an advantage of ACSR?
High tensile strength
What are disadvantages of ACSR?
1. Greater diameter is required to carry a given electrical load
2. Inner steel core is prone to corrosion
3. Comparatively costly
Aluminum Conductor Composite Core (ACCC)
ACSR conductor that use a continuous carbon fibre-polymer resin composite instead of the steel inner core