“Influence of Si, Sb and Sr Additions on the Microstructure ...

Chapter 2: Literature Review
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Figure 2.3: Magnesium parts used in communication engineering [58]
Table 2.4: Limitations <strong>of</strong> magnesium alloys [12]
1. High metal cost
2. Small supply base
3. High cost <strong>of</strong> recycling
4. Replacement <strong>of</strong> SP6 cover gas (melting difficulties)
5. Low high temperature properties
6. Corrosion problem
7. Lack <strong>of</strong> joining technologies
8. Poor workability
l. The volume <strong>of</strong> magnesium shrinks after it is oxidized, <strong>and</strong> the structure <strong>of</strong>
magnesia (MgO) is loose <strong>and</strong> many small holes appear on the surface thus become
porous. So it cannot prevent the passage <strong>of</strong> oxygen <strong>and</strong> the oxidation <strong>of</strong> inner
magnesium.
2. The heat formation <strong>of</strong> magnesia is too large so that the local area
temperatures can even reach 2850°C by the heat generated in the oxidation process.
l4