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:
“Never before has a generation of parents faced such awesome competition with the mass media for their children’s attention. While parents tout the virtues of premarital virginity, drug-free living, nonviolent resolution of social conflict, or character over physical appearance, their values are daily challenged by television soaps, rock music lyrics, tabloid headlines, and movie scenes extolling the importance of physical appearance and conformity.”
—Marianne E. Neifert (20th century)
“Any novel of importance has a purpose. If only the “purpose” be large enough, and not at outs with the passional inspiration.”
—D.H. (David Herbert)
“Have We not made the earth as a cradle and the mountains as pegs? And We created you in pairs, and We appointed your sleep for a rest; and We appointed night for a garment, and We appointed day for a livelihood. And We have built above you seven strong ones, and We appointed a blazing lamp and have sent down out of the rain-clouds water cascading that We may bring forth thereby grain and plants, and gardens luxuriant.”
—Qur’An. “The Tiding,” 78:6-16, trans. by Arthur J. Arberry (1955)
“Although its growth may seem to have been slow, it is to be remembered that it is not a shrub, or plant, to shoot up in the summer and wither in the frosts. The Red Cross is a part of us—it has come to stay—and like the sturdy oak, its spreading branches shall yet encompass and shelter the relief of the nation.”
—Clara Barton (1821–1912)