12 Questions
What is the minimum percentage of chromium required in steel to make it stainless?
18 %
What is the characteristic of titanium that makes it suitable for high-speed aircraft?
High strength at high temperatures
What type of diagram shows the critical heat treating temperatures?
Phase diagram
What does the 'O' in aluminum alloy designation 6061-O indicate?
No hardening or tempering treatment
Through which material will magnetic lines of force pass most readily?
Iron
What is Alclad?
Aluminum alloy surface layers and a pure aluminum core
What method is usually used to harden aluminum alloys used in aircraft construction?
Heat treatment
What does the first digit in the AISI and SAE designation for steel represent?
Percentage of alloying element
What type of aluminum is identified by the code number 1100?
99 percent commercially pure aluminum
What is the major alloying element in the copper alloy called brass?
Zinc
What is the purpose of normalising in heat treating?
To relieve stresses
What is the advantage of using clad aluminum alloys in aircraft construction?
They are less subject to corrosion than uncoated aluminum alloys
Study Notes
Steel Applications
- Low carbon steel is typically used in structural and sheet applications.
Aluminum Index System
- In the four-digit aluminum index system, the first digit indicates the major alloying element.
- The aluminum alloy designation "6061-O" indicates that the metal has received no hardening or tempering treatment.
Heat Treatment
- Reheating a heat-treated metal can significantly alter its properties in the reheated area.
- Tempering requires the work piece to be reheated and quenched.
- Normalising is a process of heat treating that can be applied to both aluminum alloys and iron-base metals.
Metal Properties
- Titanium is used in high-speed aircraft due to its high strength at high temperatures.
- Magnetic lines of force pass most readily through iron.
- Carburizing and nitriding affect the metal's surface by adding hardness.
- Annealing of aluminum removes stresses caused by forming.
Steel Composition
- The minimum percentage of chromium in steel to render it stainless is 10.5%.
- The AISI and SAE use a four-digit designation for steel, where the first digit represents the alloying element.
- The second digit represents the percentage of carbon in the alloy in hundredths of a percent.
Aluminum Alloys
- Alclad is a metal consisting of aluminum alloy surface layers and a pure aluminum core.
- 99 percent commercially pure aluminum is identified by the aluminum code number 1100.
- Clad aluminum alloys are used in aircraft because they are less subject to corrosion than uncoated aluminum alloys.
Other Metals
- Brass is a copper alloy containing zinc.
- Rechargeable batteries usually contain nickel and cadmium alloy.
Aerospace Applications
- Chrome molybdenum alloy steel is generally used in the construction of aircraft engine firewalls.
- Titanium is used in high-speed aircraft due to its high strength at high temperatures.
Thermal Processes
- Stress relieving temperatures are usually low to moderate.
- Annealing of steel during and after welding is a process that reduces the hardness of the steel.
Test your knowledge of metallurgy with these multiple choice questions, covering topics such as steel applications, aluminum indexing, and heat treatment.
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