The plastic deformation of single crystals of an aluminium-silver alloy

Abstract

Tensile tests have been carried out at a variety of temperatures between 77°k and 373°k on Single crystals of an aluminium −20 wt % silver alloy. The crystals were aged either at room temperature, or at 160°c, within the cold-hardening range. Single crystals of this material are very ductile. Stress-strain curves have been obtained and the change of flow stress with temperature, during deformation, has been measured and compared with the change of elastic modulus over the same temperature range. Observations have been made with the optical microscope of the appearance of slip lines on polished surfaces of' the specimens. The stress-strain curves are approximately linear showing a rate of work hardening about the same as that of pure aluminium in stage II of the stress-strain curve. The temperature dependence of the flow stress is small, varying less than does the elastic modulus over the temperature range investigated. The temperature dependence of the flow stress is compared with new measurements of the same quantity in pure aluminium single crystals. The crystals deform by a {111} slip mechanism but cross slip is profuse at all stages of the deformation and at all temperatures. This is attributed to the very high flow stress of these single crystals which is two orders of magnitude greater than that shown by pure aluminium.