Modeling slip system strength evolution in Ti-7Al informed by in-situ grain stress measurements

Darren C. Pagan, Paul A. Shade, Nathan R. Barton, Jun Sang Park, Peter Kenesei, David B. Menasche, Joel V. Bernier

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54 Scopus citations

Abstract

Far-field high-energy X-ray diffraction microscopy is used to asses the evolution of slip system strengths in hexagonal close-packed (HCP) Ti-7Al during tensile deformation in-situ. The following HCP slip system families are considered: basal 〈a〉, prismatic 〈a〉, pyramidal 〈a〉, and first-order pyramidal 〈c+a〉. A 1 mm length of the specimen's gauge section, marked with fiducials and comprised of an aggregate of over 500 grains, is tracked during continuous deformation. The response of each slip system family is quantified using ‘slip system strength curves’ that are calculated from the average stress tensors of each grain over the applied deformation history. These curves, which plot the average resolved shear stress for each slip system family versus macroscopic strain, represent a mesoscopic characterization of the aggregate response. A short time-scale transient softening is observed in the basal 〈a〉, prismatic 〈a〉, and pyramidal 〈a〉 slip systems, while a long time-scale transient hardening is observed in the pyramidal 〈c+a〉 slip systems. These results are used to develop a slip system strength model as part of an elasto-viscoplastic constitutive model for the single crystal behavior. A suite of finite element simulations is performed on a virtual polycrystal to demonstrate the relative effects of the different parameters in the slip system strength model. The model is shown to accurately capture the macroscopic stress-strain response using parameters that are chosen to capture the mesoscopic slip system responses.

Original languageEnglish (US)
Pages (from-to)406-417
Number of pages12
JournalActa Materialia
Volume128
DOIs
StatePublished - Apr 15 2017

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Polymers and Plastics
  • Metals and Alloys

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