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:
“There is, I think, no point in the philosophy of progressive education which is sounder than its emphasis upon the importance of the participation of the learner in the formation of the purposes which direct his activities in the learning process, just as there is no defect in traditional education greater than its failure to secure the active cooperation of the pupil in construction of the purposes involved in his studying.”
—John Dewey (1859–1952)
““I’m sure you’ve often wished there was an after-life.” Of course I had, I told him. Everybody has that wish at times. But that had no more importance than wishing to be rich, or to swim very fast, or to have a better-shaped mouth.”
—Albert Camus (1913–1960)
“A true politeness does not result from any hasty and artificial polishing, it is true, but grows naturally in characters of the right grain and quality, through a long fronting of men and events, and rubbing on good and bad fortune.”
—Henry David Thoreau (1817–1862)
“Corporate America will likely be motivated to support child care when it can be shown to have positive effects on that which management is concerned about—recruitment, retention and productivity. Indeed, employers relate to child care as a way to provide growth fostering environments for young managers.”
—Dana E. Friedman (20th century)