IMEC 2009 Study of fracture evolution in copper sheets by in situ tensile test and EBSD analysis S. Ifergane • Z. Barkay • O. Beeri • N. Eliaz Received: 12 January 2010 / Accepted: 4 May 2010 / Published online: 18 May 2010 Ó Springer Science+Business Media, LLC 2010 Abstract Microstructural changes during plastic defor- mation and fracture evolution play an important role in the understanding of fracture mechanisms. However, most publications have focused on the initial stages of defor- mation where the latter is uniform. The current study was focused on the last stages of fracture, the necking, and crack propagation. Tensile specimens were examined by in situ scanning electron microscope equipped with a tensile module and electron backscatter diffraction. It was dem- onstrated that the fracture evolution consists of scanty diffuse necking followed by pronounced localized necking, in which the deformation band spread through the width of the specimen in two combined mechanisms—shearing and dimpling. The microstructural changes inside the defor- mation band adjacent to crack edge were compared to those in the uniform deformation zone. In the deformed areas, the grains became elongated and preferentially orientated in the loading direction. The relative frequency of twin boundaries at 60° was reduced in the deformed areas compared to non-deformed areas, while the misorientations at low angles of 3°–15°, which imply on a dislocation pileups subgrained structure, were increased to greater extent at the crack edge. Inside the deformation band, the amount of deformation was increased compared to the uniformly deformed region with grain fragments as a result of the complexity of stresses, although similar deformation mechanisms were identified. Introduction The final stage of fracture is a complicated event associated with a change from uniform deformation to a local insta- bility state. Many models, such as tensile flow instability (necking) and wrinkling, have been suggested to describe the final stages of fracture. One common application of such models is to predict the limits of mechanical forming [1]. In uniaxial tension, the Conside `re criterion [2] asso- ciates the inception of necking with the maximal applied load. Other theories [3] relate the geometry or material defects to initiation of strain localization. For specimens with a rectangular cross-section, there are two types of tensile flow instability [4]. The first type is diffuse necking, so called because its extent is much greater than the sheet thickness. Diffuse necking may terminate in fracture, although it is often followed by a second instability pro- cess, called localized necking, where the neck is a narrow band with a width about equal to the sheet thickness, inclined at an angle to the specimen axis. Localized necking is associated with plane-strain deformation [4]; both the strain and strain rate are increased considerably within the deformation band [5]. In the last decade, great interest has evolved in mea- suring the mechanical properties and studying the defor- mation and failure processes in micro- and nano- specimens, for example those made of pure copper [6–14]. Unfortunately, the study of the mechanical behavior of thicker specimens, including sheets (thickness between S. Ifergane Á O. Beeri Nuclear Research Center Negev, P.O. Box 9001, Beer-Sheva 84190, Israel S. Ifergane Á N. Eliaz (&) The Materials and Nanotechnologies Program, Tel-Aviv University, Ramat Aviv, Tel-Aviv 69978, Israel e-mail: neliaz@eng.tau.ac.il Z. Barkay The Wolfson Applied Materials Research Centre, Tel-Aviv University, Ramat Aviv, Tel-Aviv 69978, Israel 123 J Mater Sci (2010) 45:6345–6352 DOI 10.1007/s10853-010-4596-z