Question

 • It is a eutectic system.

 • The melting point of pure aluminum is 6600C

 • The melting point of silicon is 1410 0C 

• The eutectic temperature is 5800C

 • Aluminum is insoluble in silicon 

• The eutectic composition is 85% Al + 15% Si 

• The Al-rich phase (α) is a solid solution of Si in Al and the maximum solubility of Si in α is 3% at the eutectic temperature

 • At 500°C the solubility of Si in α has fallen to 0% and remains at that level until room temperature 

Use your diagram to estimate the proportion of pure silicon in the eutectic alloy just below the eutectic temperature and sketch the possible microstructure.