Co-continuous development of Al 2 O 3 matrix and Silicon fibre

The reaction model is divided into 5 steps; according to the time the sample is submitted to heat treatment.

• In the first stage there are only 2 phases present silica fibre and pure Al.
  
  
• Al starts reaction with silica according to the equation 3SiO₂+ 4Al = 2Al₂O₃ + 3Si by a solid-state diffusion mechanism, and a thin layer of Al₂O₃ is formed at the fiber's surface, while some silicon is released to the Al matrix direction.
  
• At the second stage, the thin alumina layer cracks, as a result of the high tensile stresses induced by the transformation of 3 moles of silica in 2 moles of alumina. Liquid Al-Si starts infiltrating the cracks or channels in the alumina and the reaction is accelerated by the liquid dynamic.
  
  
• In stage 3, the thin alumina layer grows and transforms into a co-continuous layer of alumina and Al-Si liquid alloy as the channels create two complex three-dimensional networks.
  
  
• Stages 4 and 5 show the growing of co-continuous Al- Al₂O₃ until the fiber is fully transformed and the reaction stops.