Regular Article

Investigation of strain redistribution mechanism in α titanium by image-based crystal plasticity analysis^★

¹ Department of Mechanical Engineering, Kitami Institute of Technology, Kitami 090-8507, Japan
² Department of Materials Science and Engineering, Kumamoto University, Kumamoto 860-8555, Japan
³ Department of Advanced Materials Science and Engineering, Faculty of Engineering Sciences, Kyushu University, Fukuoka 819-0395, Japan
⁴ Department of Control Engineering, National Institute of Technology, Kisarazu College, Kisarazu 292-0041, Japan

^a e-mail: kawano_y@mail.kitami-it.ac.jp

Received: 29 April 2019
Received in final form: 1 July 2019
Published online: 11 September 2019

Abstract

Mechanisms of strain localization and localized activation of slip systems in α titanium were investigated using a crystal plasticity finite element (CPFE) method. A microscopic image of polycrystalline α titanium was obtained by electron back scatter diffraction (EBSD), and the data was converted from the microscopic image into the geometric model for the CPFE analysis. The uniaxial tensile deformation of the model was numerically reproduced by the CPFE method employing a dislocation density based constitutive equation. The results showed that the strain distribution corresponds well with that obtained by the experiment when the ratio of critical resolved shear stress (CRSS) employed in the numerical simulation is basal:prismatic ⟨a⟩:1st-pyramidal ⟨a⟩:1st-pyramidal ⟨c + a⟩:2nd-pyramidal ⟨c + a⟩ = 1.0:1.0:1.3:2.0:2.0. Next, numerical simulations were performed by changing the ratio of CRSS among the slip systems but keeping all other conditions the same as those of the above uniaxial tensile analysis. The results showed that strain redistribution typically occurs between hard and soft regions with high and low CRSSs for the primary slip systems; this redistribution resulted in a localized higher strain and activation of slip systems. However, localized activation of slip systems was observed even in slip systems with higher CRSS; the mechanism could be explained by the strain redistribution in the tensile direction.