Define Eutectic, Eutectoid, and Peritectic Reactions. Provide Corresponding Reaction Equations and Schematic Drawings.

Eutectic, eutectoid, and peritectic reactions are types of phase transformations that occur in alloy systems, significantly influencing material properties.

Eutectic Reaction

A eutectic reaction occurs when a liquid phase transforms into two solid phases upon cooling. This happens at a specific composition and temperature, known as the eutectic point.

Reaction Equation:
L → α + β

Here, L represents the liquid phase, and α and β are the two solid phases that form from the liquid.

Schematic Drawing:

   Liquid  
      |    
      |-----
     /      
    /        
   α     β  

Eutectoid Reaction

The eutectoid reaction is similar to the eutectic reaction but occurs in the solid state. A solid phase transforms into two different solid phases upon cooling.

Reaction Equation:
α → β + γ

In this case, α is the original solid phase, while β and γ are the new solid phases that form.

Schematic Drawing:

   α   
   | 
   |------
  /         
 β           γ

Peritectic Reaction

A peritectic reaction occurs when a solid phase and a liquid phase react to form a new solid phase. This typically occurs at a different temperature and composition than eutectic reactions.

Reaction Equation:
L + α → β

In this equation, L is the liquid phase, α is the solid phase, and β is the new solid phase formed as a result of the reaction.

Schematic Drawing:

   Liquid   
      |  
      |----
     /      
    /       
   α       β 

In summary, these reactions illustrate different mechanisms of phase changes in materials, each with distinct implications for the properties of the resulting phases.