Which of the following statements is true regarding aluminum/aluminum alloys? Al
ID: 492310 • Letter: W
Question
Which of the following statements is true regarding aluminum/aluminum alloys? Aluminum is very resistant to creep, because its ceramic (Al_2 O_3) oxide layer thermally insulates the base metal and prevents grain sliding due to its high degree of adherence to the base metal. Aluminum is extremely rare in abundance within the earth's crust. Aluminum and it alloys are extremely difficult to melt, so they are rarely used as materials for casted parts. Aluminum alloys are generally consider to be mechanically inferior compared to pure aluminum in terms of yield strength, because their microstructures contain precipitate phases that strain the lattice and therefore soften the relative to pure aluminum. Aluminum alloys are generally not viable as lightweight structural materials in humid environments because they are susceptible to corrosion by water vapor. High-strength aluminum alloys that leverage secondary phase hardening are often less resistant to corrosion compared to pure aluminum.Explanation / Answer
The following statement is true regarding Aluminium/ Aluminium alloys:
High strength aluminium alloys that leverage secondary phase hardening are often less resistant to corrosion compared to pure aluminium.
The following statements are false:
Aluminium is not very resistance to creep. It is subject to a climb-controlled dislocation mechanism at low stresses.(Harper Dorn creep)
Aluminium is quite abundant in the earth's crust. It comprises of about 8% of the earth's crust.
Aluminium and its alloys are not that difficult to melt. The melting point of Aluminium is about 600 degrees celsius. It is often used in casting processes.
Aluminium alloys have greater strength than pure Aluminium. Pure aluminium is relatively soft.
Aluminium alloys are viable as lightweight structures in humid environments as most aluminium alloys have good corrosion resistance.
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