Cooling Curve for Binary Alloys Forming Solid Solutions

Introduction

• Topic: Cooling curve of binary alloy forming solid solutions
• Example: Metal A (melting point: 1000°C) and Metal B (melting point: 700°C)
• Binary Alloy: Composed of metals A and B, forming a solid solution AB

Plotting the Cooling Curve

• Axes:
  • X-axis: Time
  • Y-axis: Temperature (°C)
  • Temperature ranges: 200°C, 400°C, 600°C, 800°C, 1000°C, 1200°C, 1400°C
• Dotted lines:
  • Horizontal line at 1000°C: Melting point of Metal A
  • Horizontal line at 700°C: Melting point of Metal B

Phases in Cooling

• Above Melting Points: Both metals A and B in liquid phase
• Perfect Solubility: 100% solubility in liquid state

Cooling Process

• Point A: 100% liquid material
• Point B: Starting point of solidification, where tiny particles (nuclei) begin to form (at higher melting point, Metal A)
• Point C: End point of solidification (at melting point of Metal B)
• Region A to B: 100% liquid (A + B)
• Region B to C: Liquid + solid (A + B)
• Region C to D: 100% solid (A + B)
  • Solid structure rearrangement from C to D

Gibbs Phase Rule

• Equation: P + F = C + 1
  • P: Number of phases
  • F: Degrees of freedom
  • C: Number of components
• Application:
  • Region A to B: P=1 (liquid), F=2 (temperature and composition change without phase change)
  • Region B to C: P=2 (liquid + solid), F=1 (single variable, temperature drop)
  • Region C to D: P=1 (solid), F=2 (temperature and composition change without phase change)

Summary

• Microstructure: Changes from nuclei formation to complete solidification
• Relevance: Understanding solid solution formation and phase changes in binary alloys
• Implications: Varying solubility affects graphical representations and cooling curves

Conclusion

• Subscription: If you found this useful, subscribe to Modi Mechanical Engineering Tutorials
• Thanks: Thank you for watching and keep following our content!