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:
“We have been told over and over about the importance of bonding to our children. Rarely do we hear about the skill of letting go, or, as one parent said, “that we raise our children to leave us.” Early childhood, as our kids gain skills and eagerly want some distance from us, is a time to build a kind of adult-child balance which permits both of us room.”
—Joan Sheingold Ditzion (20th century)
“The moment Germany rises as a great power, France gains a new importance as a cultural power.”
—Friedrich Nietzsche (1844–1900)
“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)