Abstract: For the magnesia based castable made up with sintered magnesia，fused magnesia，and silica powder，it was found that the addition of silicon carbide powder can create fibrous needle MgO whiskers on the surface and interface of the castable. The impact of the dosage of silicon carbide fine powder and heat treatment temperature on magnesium oxide whiskers are compared and analyzed. When the temperature reached above 1 450 ℃ in the low oxygen partial pressure region， the magnesium thermal reduction reaction will cause the migration of magnesium vapor to the material surface and interface，and MgO whiskers grow after oxidation. The surface of magnesium siliceous samples with addition of 3% to 7% of 97% silicon carbide fine powder is prone to agglomeration of magnesium oxide whiskers after 3 hours of heat treatment at 1 500 ℃ . Moreover， as the dosage of silicon carbide increases，the generation and growth of whiskers are improved.

Key words: Magnesium material, Silicon carbide, Magnesium oxide whiskers, Growth mechanism