Category: Science & Engineering

From an atomic perspective, plastic deformation corresponds to the breaking of bonds with original atom neighbors and then reforming bonds with new neighbors as large numbers of atoms or molecules move relative to one another; upon removal of the stress they do not return to their original positions. From an atomic perspective, diffusion is just the stepwise migration of atoms from lattice site to lattice site. In fact, the atoms in solid materials are in constant motion, rapidly changing positions. For an atom to make such a move, two conditions must be met: (1) there must be an empty adjacent […]

1. What is ductile-to-brittle transition? At low temperatures metals having b.c.c. and h.c.p. structures become brittle and fail by cleavage, even though they may be tough at or above room temperature. In fact, only those metals with an f.c.c. structure (like copper, lead, aluminium) remain unaffected by temperature in this way. In metals not having an f.c.c. structure, the motion of dislocations is assisted by the thermal agitation of the atoms. At lower temperatures the thermal agitation is less, and the dislocations cannot move as easily as they can at room temperature in response to a stress – the intrinsic […]

What are materials? Materials simply are atoms joined together in the solid state. Materials Science studies the fundamental physical and chemical basis for the controlled combination of atoms to form new compounds, phases and microstructures, as well as the characterization of the resulting structures and properties. – http://www.mse.uiuc.edu/home/introduction.html Classification of Materials + Based on atomic bonding type – 1. Ionic crystals – 2. Covalent crystals – 3. Metals – 4. Intermetallics – 5. Semiconductors – 6. Polymers – 7. Composite materials – 8. Vitreous materials – http://en.wikipedia.org/wiki/Materials_Engineering What is matter? 1. The word "matter" describes everything that has physical existence. […]