Symposium: Neutron and X-Ray Studies for Probing Materials Behavior

Metallurgical and Materials Transactions A

, Volume 39, Issue 13, pp 3120-3133

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Measuring Stress Distributions in Ti-6Al-4V Using Synchrotron X-Ray Diffraction

  • J.V. BernierAffiliated withMaterials Modeling and Simulation Group, Engineering Technologies Division, Lawrence Livermore National Laboratory
  • , J.-S. ParkAffiliated withSibley School of Mechanical and Aerospace Engineering, Cornell University
  • , A.L. PilchakAffiliated withDepartment of Materials Science and Engineering, The Ohio State University
  • , M.G. GlavicicAffiliated withRolls Royce Corporation
  • , M.P. MillerAffiliated withSibley School of Mechanical and Aerospace Engineering, Cornell University Email author 

Abstract

This article presents a quantitative strain analysis (QSA) study aimed at determining the distribution of stress states within a loaded Ti-6Al-4V specimen. Synchrotron X-rays were used to test a sample that was loaded to a uniaxial stress of 540 MPa in situ in the A2 experimental station at the Cornell High Energy Synchrotron Source (CHESS). Lattice-strain pole figures (SPFs) were measured and used to construct a lattice strain distribution function (LSDF) over the fundamental region of orientation space for each phase. A high-fidelity geometric model of the experiment was used to drastically improve the signal-to-noise ratio in the data. The three-dimensional stress states at every possible orientation of each α (hcp) and β (bcc) crystal within the aggregate were calculated using the LSDF and the single-crystal moduli. The stress components varied by 300 to 500 MPa over the orientation space; it was also found that, in general, the crystal stress states were not uniaxial. The maximum shear stress resolved on the basal and prismatic slip systems of all orientations within the α phase, \( \hat \tau _{{\text{rss}}} , \) was calculated to illustrate the utility of this approach for better identifying “hard” and “soft” orientations within the loaded aggregate. Orientations with low values of \( \hat \tau _{{\text{rss}}} , \) which are potential microcrack initiation sites during dwell fatigue conditions, are considered hard and were subsequently illustrated on an electron backscatter diffraction (EBSD) map.