The role of metals in refractory materials
发布时间：
2022-05-27 17:41
The role of metals in refractory materials:
Plastic phase forming: The crystal lattice of the metal will slip under the action of stress, and it has plastic characteristics. It is introduced into the refractory material. Compared with the hard inorganic material particles, it will exert plastic forming characteristics during the forming process, so that in the same The density of the green body prepared under the molding pressure is higher than that of the sample without metal added.
Promotion of sintering: The sintering effect of metals on refractory materials can be attributed to two factors:
First, the plastic phase forming formed by the introduction of metal can increase the density of the green body, shorten the distance between particles, and reduce the energy required for diffusion and mass transfer during the firing process;
Second, the melting point of the metal is generally lower than that of the refractory material, and it can generate a liquid phase at a lower temperature. The capillary force formed by the liquid phase and its own viscous flow accelerate the migration rate of atoms and the shrinkage of the green body, which promotes The densification process of sintering.
Improved toughness: Metals can improve the toughness of composites through mechanisms such as crack bridging, crack deflection, and crack barrier, where crack bridging is the most effective toughening mechanism, that is, when the crack propagates to the interface of the metal material and the matrix material, Due to the ductility of the metal particles, the crack makes it stretched by force, which will exert a bridging stress on the upper and lower surfaces of the crack. On the one hand, it can prevent the crack from opening and reduce the strength factor of the crack tip. The opening of the crack leads to plastic deformation, which consumes the energy of the crack tip and plays a toughening role.
Oxidation resistance: Carbon composite refractories have excellent thermal shock resistance and slag resistance due to the existence of carbon, but they have the defect of easy oxidation. Once carbon is oxidized, its advantages will be lost. In order to give full play to the advantages of carbon composite refractories, the oxidation resistance is often improved by adding appropriate additives. Due to its active properties, metals are easy to react with O2 and CO, etc., and have been used as antioxidants in refractory materials. Al, Si, Mg and corresponding alloys are commonly used as antioxidants.
In-situ reaction to generate non-oxides: metals are introduced into refractory materials, and during the firing process, they are used to react with raw material components or surrounding gases to generate non-metal reinforced and toughened phases, which can improve the normal temperature and high temperature performance and resistance of the matrix. Thermal shock and other effects. At present, this technology has received extensive attention.
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