Q: What are the main differences between brass and bronze?
Brasses, and there are very many brasses in the specification books, are essentially alloys of copper with zinc. There are usually some other elements added to provide specific characteristics.
Bronzes, and again there are many different bronzes, are alloys of copper and tin, once again other elements may be added to provide particular characteristics. Just to make life complicated there are the “aluminium bronzes” which contain no tin but are alloys of copper and aluminium.
Q: I want to replace a small GRP component with something stronger. It must be lightweight to minimize inertial forces.
The best alternative to a polymer or composite in this application is a magnesium alloy forging, such as ASTM, AZ80A.
This has a density of 1.8 g/cc. To develop maximum strength, AZ80A
Should be heat treated to the “T5” – artificially aged condition.
Q: I have heard that magnesium alloys can catch fire on machining.
Magnesium and its alloys can be machined at extremely high speeds using greater depth of cut and higher rates of feed than can be used in machining other structural materials.
The possibility of chips or turnings catching fire must be considered.
Factors that increase the probability of chip ignition are:
• Extremely fine feeds
• Dull tools
• Improper tool design
• Improper machining techniques.
Even under the most adverse conditions, fires are very unlikely at cutting speeds below 3.5 m/s.
Q: Are magnesium alloys corrosion-resistant?
Corrosion resistance of a magnesium alloy part depends on environmental conditions and on the chemical composition, thermal and mechanical history and surface condition of the part.
In some environments, contact with parts made from dissimilar metals can lead to severe damage of the magnesium part due to galvanic corrosion.
Magnesium alloys, when properly made and applied, are corrosion resistant and are used successfully in a wide variety of applications.
The corrosion that is encountered usually is a result of improper design or application.
Q: What is alloy ASTM AG40A and what is it used for?
This is a pressure die cast zinc alloy. The chemical analysis is available. The mechanical properties are available.
It is primarily used in the automotive industry for both under bonnet and decorative functions.
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