抄録
Tensile behaviors of aluminum thin wires have been studied over a diameter range of 5 to 200 μmφ. Critical resolved shear stress (C.R.S.S.) increases linearly against the inverse square root of specimen diameter. By in-situ deformation of thin wires in an ultra-high voltage electron microscope, it has been revealed that many dislocations pile up against the specimen surface before yielding. At the yield point, many dislocations abruptly escape out from the specimen surface, and no more dislocation pile-up is observed at the same positions. On the basis of these data, it is concluded that the size effect on C.R.S.S. is attributed to the blocking of mobile dislocations at the surface due to the surface film before the yielding. It is also concluded that the surface promotes the deformation because of continuous escape of dislocations through the slip bands after the yielding and no debris layer exists in the surface layer under the stressing.
