This microstructure gives poor mechanical properties because of the platelike shape, brittleness and poor bonding of the silicon particles in the aluminum matrix.
Specimen 3 has been improved by a key elemental addition.
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When the silicon content of the aluminum is raised to 12% as
shown at left at 50X (same HF etchant) an excessive amount of coarse
eutectic silicon forms. |
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At left the same specimen is shown at 200X. This microstructure gives poor mechanical properties because of the platelike shape, brittleness and poor bonding of the silicon particles in the aluminum matrix. Specimen 3 has been improved by a key elemental addition. |