Strengthening defect size

Volume defects consist of inclusions or precipitates of a second phase material or voids. Voids can be formed by vacancy clusters or from the nucleation of bubbles from dissolved gases or from components with high vapor pressures. Such defects can range in size from microscopic to gross. Bear in mind that not all such defects are unwanted. Many are purposely introduced into the final solid to tailor certain electrical, optical, and magnetic properties, or to serve as strengthening mechanisms. These topics are discussed in later chapters. 

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