Using digital image correlation for characterizing the elastic and plastic parameters of ultrafine-grained Al 1050 strips fabricated via accumulative roll bonding process

Abstract

In the present article, digital image correlation (DIC) system has been utilized to determine the elastic and plastic parameters of ultrafine grained (UFGed) Aluminum 1050 strips fabricated via accumulative roll bonding (ARB) procedure during the uniaxial tensile test. At first, elastic and plastic parameters such as elastic modulus, Poisson ratio, strength coefficient, strain hardening exponent, anisotropy coefficient and yield stress of ARBed specimens have been extracted in different ARB passes. ARB process is an exceptional process to fabricate ultrafine-grained and nanostructured sheet metals and composites. Using of UFGed materials in various industries requires accurate identification of their mechanical and physical properties. Elastic modulus and anisotropy are the most important mechanical parameter for structural design and forming process respectively. The ARB process has been done up to seven passes by the value of 50% thickness reduction during rolling in every ARB pass at the ambient temperature. Results exhibited which via rising the ARB passes, as expected the elastic parameters did not change much, but all of the plastic parameters and crystallite size changed. The values of the ultimate tensile strength (UTS) and yield stress (YS) increased sharply but strain hardening exponent and elongation at first pass decreased severely and then from third to the seventh pass increased continuously. Due to the gradient of applied shear components in the thickness direction during rolling, the anisotropy coefficient is one of the most important parameters for severe plastic deformation based on rolling. In this paper, for the first time anisotropy variations in the tensile test were continuously determined and the results of the DIC demonstrated that changing of the anisotropy in each pass were different and via raising the value of applied strained the amount of anisotropy coefficient reduced.