Objective 07: Aluminum Flashcards Preview

2A2-4: Metallurgy > Objective 07: Aluminum > Flashcards

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What is the density of Aluminum?

2699 kg/m3


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?

1. Lightweight
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


Bayer Process

Caustic leaching process which produces alumina from bauxite


Hall-Heroult Process

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 Alloy

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
3. Durable
4. Lightweight


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?

Cold Boxes


Cold Boxes

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
3. Lightweight


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-magnesium-silicon alloy


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


What are the benefits of ACCC?

1. 75% lighter than steel
2. Comparable tensile strength for a given wire diameter
3. Completely unaffected by corrsion