Plastic Deformation of a Single Crystal Slip System When the applied force increases, it may break the bonds of Preferred planes for dislocation another to produce areflanisent shift s to slide he atoms to produce a fract Preferred crystallographic directions brittle materials the first mechanism requires lower forces. but for ductile metals the second one occurs more planes directions (lip systems) highest packing density. a Plastic slip occurs most easily in densely packed planes Distance between atoms shorter than that are widely spaced apart and along directions of closest erage,distance perpendicular to The specific combination of plane and direction is called a nes can slip more easily. BCC and which determines the ease with which a crystal can be s Each lattice structure ha ecific number of slip propagate =FCC and BCC are more deformed ductile than hcp Superplasticity of Nanoscaled Copper Cleavage e-0% taade Some minerals split along flat surfaces when struck hard-this is called mineral cleavage. A mineral cleavage is the way it breaks mInerals tend to break where the bonds holding the aWhen they break, a series of surfaces parallel to 51o0N these bonds may form; the surfaces are called cleavage planes Other minerals break unevenly along rough or mA few minerals have both cleavage and fracture Mineral Cleavage and Crystal Form Mineral cleavage This is the tendency of minerals to break along smooth cLeavage in one direction cLeavage in two directions at right angle CLeavage in three directions at right angles cLeavage in four directions Some minerals lack cleavage( like quartz) Cleavage is related to the atomic structure of the mineral4 Plastic Deformation of a Single Crystal When the applied force increases, it may break the bonds of the atoms to produce a fracture, or cause the atoms to slide over one another to produce a permanent shift. For brittle materials the first mechanism requires lower forces, but for ductile metals the second one occurs more easily. Plastic slip occurs most easily in densely packed planes that are widely spaced apart and along directions of closest packing. The specific combination of plane and direction is called a slip system. Each lattice structure has a specific number of slip systems which determines the ease with which a crystal can be deformed. Slip System Preferred planes for dislocation movement (slip planes) Preferred crystallographic directions (slip directions) Slip planes + directions (slip systems) ‡highest packing density. Distance between atoms shorter than average; distance perpendicular to plane longer than average. Far apart planes can slip more easily. BCC and FCC have more slip systems compared to HCP: more ways for dislocation to propagate Þ FCC and BCC are more ductile than HCP. Superplasticity of Nanoscaled Copper Cleavage Some minerals split along flat surfaces when struck hard ¾ this is called mineral cleavage. A mineral cleavage is the way it breaks. Minerals tend to break where the bonds holding the atoms together in the crystal are the weakest. When they break, a series of surfaces parallel to these bonds may form; the surfaces are called cleavage planes. Other minerals break unevenly along rough or curved surfaces ¾ this is called fracture A few minerals have both cleavage and fracture Mineral Cleavage This is the tendency of minerals to break along smooth planes. Cleavage in one direction Cleavage in two directions at right angles Cleavage in three directions at right angles Cleavage in three directions not at right angles Cleavage in four directions Some minerals lack cleavage ( like quartz) Cleavage is related to the atomic structure of the mineral Mineral Cleavage and Crystal Form