Microdeformation of Solids

A technique is described for observing and measuring the deformation of solids on a very small scale. A very fine stylus (approx 1000 Å in diameter) is pressed against the surface of a metal crystal with a load which can be as small as 10−4 g, and the deformation observed simultaneously by performing the experiment in a scanning electron microscope. Measurements were made on crystals of gold, copper, and aluminium. The behavior under these conditions of microdeformation was unusual in that no penetration occured until a critical load was reached. This critical load was frequently very high and corresponded to a shear strength which approached the theoretical shear strength of metals. Microfriction experiments could also be performed by allowing the stylus to slide over the crystal and the nature of the surface deformation could be examined during the sliding process.