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:
“More than ten million women march to work every morning side by side with the men. Steadily the importance of women is gaining not only in the routine tasks of industry but in executive responsibility. I include also the woman who stays at home as the guardian of the welfare of the family. She is a partner in the job and wages. Women constitute a part of our industrial achievement.”
—Herbert Hoover (1874–1964)
“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)
“There was not a grain of poetry in the whole composition of Lord Fawn, and poetry was what her very soul craved;Mpoetry, together with houses, champagne, jewels, and admiration.”
—Anthony Trollope (1815–1882)
“The wind of change is blowing through the continent. Whether we like it or not, this growth of national consciousness is a political fact.”
—Harold MacMillan (1894–1986)