Alumina ceramic manufacturers say what is the temperature resistance and toughness of alumina ceramics in heat treatment
Alumina ceramic manufacturers say that alumina ceramic wear-resistant pipe, as a typical alumina ceramic part, has good comprehensive properties, such as sufficient strength, excellent plasticity and low hardness, which is one of the reasons why it is widely used . Like most other metals, the tensile strength, yield strength, and hardness of alumina ceramic parts increase with decreasing temperature, while plasticity decreases with decreasing temperature.
According to alumina ceramic manufacturers, the tensile strength increases rapidly in the range of 15-80, but when the temperature is further reduced, the change is slow, and the yield strength increases uniformly. More importantly, as the temperature of alumina ceramic parts decreases, the impact toughness decreases slowly, and there is no ductile-brittle transition temperature.
Alumina ceramic manufacturers say that usually the microstructure of alumina ceramics is equiaxed grains, which is a polycrystalline structure composed of ionic bonds or covalent bonds, so the fracture toughness is low. Under the action of external load, the stress will cause tiny cracks on the ceramic surface, and the cracks will expand rapidly, resulting in brittle fracture. Therefore, in the process of cutting alumina ceramics, chipping often occurs, that is, small cracks appear on the surface of the ceramic.
Alumina ceramic manufacturers say that the reason for the collapse of alumina ceramics is that the separation of the cut part of the material from the machined surface is caused by tensile damage, not the result of normal cutting. Cracks caused by crushing and cutting deformation generally crack down along the surface of the workpiece. At this time, due to the cutting tensile stress, the cut and bonded workpiece substrates will peel off together, resulting in crushing. It should be noted that the greater the tensile stress, the more serious the collapse phenomenon, which may lead to the waste of the entire workpiece.
Alumina ceramic manufacturers say that transparency is a key performance of alumina ceramics, which is not only related to the basic chemical composition of the material, but also depends on the microstructure of the material. Therefore, the transparency of alumina ceramics depends on the porosity, grain size, grain boundary structure and surface finish of the ceramic.
Alumina ceramic manufacturers say that the preparation process of alumina is essentially a densification process that completely eliminates microscopic pores during sintering. The size, number and type of pores in a material will have a dramatic effect on its transparency. In addition to porosity, pore size also has a great influence on the transmittance of alumina ceramics. When the aperture is larger than the incident light wave, the transmittance is low.
According to alumina ceramic manufacturers , the particle size of alumina polycrystalline also has a great influence on the transmittance. When the wavelength of the incident light is equal to the particle size, the scattering effect of light is large and the transmittance is low. In view of this, in order to improve the light transmittance of alumina ceramics, the grain size should be controlled outside the wavelength range of the incident light.
It is well known that grain boundaries are one of the important factors that destroy the optical uniformity of alumina ceramics, causing light scattering and reducing the transmittance of the material. Moreover, the greater the difference in material composition and refractive index, the lower the transmittance of the entire alumina ceramic.
Alumina ceramic manufacturers said that in addition, the transmittance of alumina ceramics is also affected by surface roughness, which is not only related to the fineness of raw materials, but also related to the processing finish of the ceramic surface. The surface roughness of untreated alumina ceramics after sintering is relatively large, so the light incident on the surface will be diffusely reflected, resulting in light loss.