Researchers at Sharif University of
Technology, Iran have proposed a model which explains the relationship between
grain size, grain internal stresses and its yield strength.
"A controversial phenomenon in nanocrystalline materials is that as grain size reduces to less than 100 nanometers, the material's strength drops surprisingly," said A. Shafiei, researcher in material science. "To explain this so-called Inverse Hall-Petch Relation, multiple models have been already proposed."
"However, for larger grains, the yield strength is expected to increase with decreasing their size. Therefore the diagram of size versus yield strength is subjected to a maximum, typically around 100 nanometers," he said about his research Published in the journal of Materials Engineering and Performance (2008).
"Scientists' researches show that decrease of grain size to less than 100 nanometers, gives rise to internal stresses which contribute to smaller yield strengths."
"The presented theory in this research which relates grain size, yield strength and internal stresses is in good agreement with experimental results," he told the news website of Iranian Nanotechnology Initiative.
... Payvand News - 09/22/08 ... --