Importance of Grain Growth
Most materials exhibit the Hall–Petch effect at room-temperature and so display a higher yield stress when the grain size is reduced. At high temperatures the opposite is true since the open, disordered nature of grain boundaries means that vacancies can diffuse more rapidly down boundaries leading to more rapid Coble creep. Since boundaries are regions of high energy they make excellent sites for the nucleation of precipitates and other second-phases e.g. Mg–Si–Cu phases in some aluminium alloys or martensite platlets in steel. Depending on the second phase in question this may have positive or negative effects.
Read more about this topic: Grain Growth
Famous quotes containing the words importance of, importance, grain and/or growth:
“One’s condition on marijuana is always existential. One can feel the importance of each moment and how it is changing one. One feels one’s being, one becomes aware of the enormous apparatus of nothingness—the hum of a hi-fi set, the emptiness of a pointless interruption, one becomes aware of the war between each of us, how the nothingness in each of us seeks to attack the being of others, how our being in turn is attacked by the nothingness in others.”
—Norman Mailer (b. 1923)
“The importance to the writer of first writing must be out of all proportion of the actual value of what is written.”
—Elizabeth Bowen (1899–1973)
“As polishing expresses the vein in marble, and grain in wood, so music brings out what of heroic lurks anywhere. The hero is the sole patron of music.”
—Henry David Thoreau (1817–1862)
“The reality is that zero defects in products plus zero pollution plus zero risk on the job is equivalent to maximum growth of government plus zero economic growth plus runaway inflation.”
—Dixie Lee Ray (b. 1924)