Aluminum-silicon alloys are widely used due to high wear resistance and light weight. An alloy consisting of 40 wt% Si and 60 wt% Al is slowly cooled from 1100 ◦C to room temperature. 

 

What is the approximate composition of the first solid to appear?

 

Temperature, C 10 20 30 1500 1300 1100 900 T T T 700 659.7C L+a-Al 1.65 500 a-Al Atomic percent silicon, % 40 50 60 70 80 90 100 12.6 a-Al+Si 577 C 300 0 10 20 30 40 50 60 70 80 Weight percent silicon, % 8- 90 100 Si