Equilibrium Diagrams Having Intermediate Phases or Compounds

The fractions of total a, (both eutectic and primary), and also of total /S, W, are determined by use of the lever rule and a tie line that extends entirely across the a + p phase field. Again, for an alloy having composition C4, 

Lever rule expression for computation of total /3-phase mass P + Q + R  

Analogous transformations and microstructures result for alloys having compositions to the right of the eutectic (i.e., between 61.9 and 97.8 wt% Sn). However, below the eutectic temperature, the microstructure will consist of the eutectic and primary p microconstituents because, upon cooling from the liquid, we pass through the p + liquid phase field. 

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Equilibrium Diagrams Having Intermediate Phases or Compounds 325... 

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