Effect of temperature on localization of deformation in copper single crystals subjected to tension

The paper presents the results of topographic investigations of copper single crystals deformed under conditions of high vacuum in a tension test at a temperature within the range 293 to 1073 K. On the basis of the slip traces it has been found that a rapid drop of the tensile stress originates from a strong strain localization in a critical system. The activation of the critical system takes place independently of the deformation temperature which suggests the domination of the same deformation mechanism within the whole examined temperature range. Under conditions of high flow stress at low temperature the operation of the critical system causes the unblocking of the primary and the conjugate systems. This enforces a strong dynamics of the unblocked dislocations and results in a dramatic immediate strain localization and failure of the sample (fracture of the 'knife edge' type). At high temperatures the initiation of the critical system takes place at low stresses and does not produce such drastic results. The sample does not undergo any rapid failure, and at the place of disruption following the failure it has the shape of an 'elongated funnel'.