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Questions and Answers
What does a higher working temperature do to dislocations?
How does cryogenic deformation impact dynamic recovery?
What effect does alloying with Mg have on dynamic recovery in Al?
What process restores pre-deformation properties in Al alloys?
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What initiates the formation of Guinier-Preston (GP) zones in Al-Cu system?
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What does the first digit in the alloy designation define?
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Which suffix letter indicates that the aluminum alloy has undergone cold working (strain hardening)?
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In the NHT family of alloys, what is a common characteristic of the compositions?
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What does the second digit in the alloy designation indicate?
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Approximately what percentage of rolled aluminum products are made from non-heat-treatable alloys?
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Why is aluminium resistant to corrosion?
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What effect does copper have on the corrosion resistance of Al-Cu alloys?
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How does anodising protect aluminium from corrosion?
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What type of alloys exhibit the most corrosion resistance?
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Why are wrought aluminium products less susceptible to localised attack?
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Which defect is characterized by large isolated voids?
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What is the phenomenon known as 'hot tearing' a result of?
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Which alloy type has the greatest resistance to hot tearing?
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What can result in the formation of bubbles that freeze as pores in casting processes?
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Where are porosity defects usually concentrated in moulds to minimize harm?
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What is the current emphasis in developing superplastic behavior in aluminium alloys?
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Why are forming strain rates very low in superplastic aluminium alloys?
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What is the main reason for the increasing ratio of cast aluminium to wrought in applications?
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Which type of casting uses recycled stock and typically has more impurities?
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What are the most common systems for cast aluminum alloys?
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Study Notes
- Cold working temperature significantly impacts resulting strength by affecting the rate of dynamic recovery processes
- Cryogenic deformation slows dynamic recovery, leading to increased strength at the expense of ductility
- Alloying, such as with Mg in Al-5%Mg, can improve strain hardening and slow down dynamic recovery compared to pure Al
- Annealing at elevated temperatures can restore pre-deformation properties of Al alloys partially or fully
- Age hardening process involves solution heat treatment, rapid quenching, and controlled decomposition to form precipitates in aluminum-copper system
- Non heat-treatable alloys do not respond to strengthening by heat treatment and include pure aluminum grades and alloys with Mn or Mg as main alloying elements
- Aluminum is resistant to corrosion due to a protective oxide film, but can undergo galvanic corrosion when in contact with electrolytes and less reactive metals
- Anodizing aluminum can further protect it from corrosion by increasing the thickness of the protective oxide film through an electrolyte bath process
- Wrought aluminum products include sheet/plate, foil, wire, and tube/rods, with complex extrusions produced from cast ingots
- Porosity in aluminum castings can result from entrapped gases, volume shrinkage, and hot tearing during solidification
- Hot tearing in castings occurs due to high stresses during solidification, more susceptible in alloys with wide freezing ranges or low eutectic fractions
- Superplastic behavior is exhibited by some aluminum systems, like 5083 SPF, but has limited applications and high cost
- Cast aluminum products are increasingly used, especially in the automotive industry, with common systems being Al-Si, Al-Si-Mg, and Al-Si-Cu
- The ratio of cast aluminum to wrought aluminum is increasing, with 70% of aluminum castings in Western Europe used in the automotive sector
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Description
Explore the relationship between cold working temperature and resulting strength in materials science. Learn how cryogenic deformation affects dynamic recovery processes and the trade-off between strength and ductility. Discover how alloying can improve strain hardening for enhanced material properties.
