Polycrystalline material metallic ceramics

After recrystallization is complete, the strain-free grains will continue to grow if the metal specimen is left at the elevated temperature (Figures 7.21d to 7.21/) this phenomenon is called grain growth. Grain growth does not need to be preceded by recovery and recrystallization it may occur in all polycrystalline materials, metals and ceramics alike. 

Superplasticity is macroscopically defined as the ability of a polycrystalline material to exhibit large elongations at elevated temperatures and relatively low stresses. It is commonly found in a wide range of materials from metals to ceramics (bioceramics or high-temperature superconductors, among others) when the grain size is small enough a few micrometres for metals and less than a micron in ceramics. 

Today, from an engineering point of view, the name superplasticity is ascribed to a polycrystalline material pulled out to very high tensile elongations prior to failure with necking-free strain. This phenomenon is usually found in many metals, alloys, intermetallics, composites and ceramics (recently in high-temperature superconductor ceramics) when the grain size is small enough, less than 10 pm for metals and less than 1 pm for ceramics. 

With the development of cermets (ceramic-metallic composites materials) and glassy ceramics, the borderlines between ceramics and metals and ceramics and glasses have become somewhat blurred. Modern ceramics include both materials and products, which range from single crystals and dense polycrystalline materials by way of glass-bonded composites to foams and glassy substances. 

Today, QXRD methods are used for organic and inorganic compounds, macromolecules, polymers, drugs, zeolites, cements, catalysts, metals, ceramics, atmospheric aerosols (airborne particulates), fly ash, and minerals. The physical states of the materials can be powders, thin films, polycrystalline, and bulk materials. 

Conversion of glass to a polycrystalline ceramic is accompanied by increased strength (two to four times), increased fracture toughness (two to four times), increased electrical resistivity (10 times), increased deformation temperature (200-400°C), increased abrasion resistance, and increased thermal shock resistance. All these factors contribute to many applications for glass ceramics dinnerware, cooking utensils, stove tops, radomes, hermetic seals to metals, building materials, and so on. 

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