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:
“In my public statements I have earnestly urged that there rested upon government many responsibilities which affect the moral and spiritual welfare of our people. The participation of women in elections has produced a keener realization of the importance of these questions and has contributed to higher national ideals. Moreover, it is through them that our national ideals are ingrained in our children.”
—Herbert Hoover (1874–1964)
“A toothache, or a violent passion, is not necessarily diminished by our knowledge of its causes, its character, its importance or insignificance.”
—T.S. (Thomas Stearns)
“Grow your tree of falsehood from a small grain of truth.
Do not follow those who lie in contempt of reality.
Let your lie be even more logical than the truth itself,
So the weary travelers may find repose.”
—Czeslaw Milosz (b. 1911)
“A revolution is not the overturning of a cart, a reshuffling in the cards of state. It is a process, a swelling, a new growth in the race. If it is real, not simply a trauma, it is another ring in the tree of history, layer upon layer of invisible tissue composing the evidence of a circle.”
—Kate Millett (b. 1934)