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Engineering LibreTexts

20: Diffusion

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    • 20.1: Fick's First Law of Diffusion
      The fact that a concentration difference causes diffusion should be familiar to everyone, particularly in the case of liquids and gases. Consider adding a drop of ink to a bowl of water. The ink will diffuse through the water until the concentration is the same everywhere. There is no force causing the ink particles to diffuse through the water. It is in fact a statistical result of the random motion of the particles.
    • 20.2: Fick's Second Law of Diffusion
      Fick’s second law is concerned with concentration gradient changes with time.
    • 20.3: Applications of Diffusion
      Carburisation is the process by which carbon is diffused into the surface of steel in order to increase its hardness. The carbon forms carbide precipitates (particularly if the steel contains carbide forming elements such as manganese or molybdenum) which pin dislocations and prevent slip, thus making the material harder. However, the increased carbon content reduces the toughness of the material.
    • 20.4: Interdiffusion
    • 20.5: Microstructural Effects
    • 20.6: Temperature Effects