Incorporating grain-level residual stresses and validating a crystal plasticity model of a two-phase Ti-6Al-4 V alloy produced via additive manufacturing

• Published in: Journal of the mechanics and physics of solids Vol. 121; pp. 447 - 462
• Main Authors: Kapoor, Kartik, Yoo, Yung Suk Jeremy, Book, Todd A., Kacher, Josh P., Sangid, Michael D.
• Format: Journal Article
• Language: English
• Published: London Elsevier Ltd 01.12.2018; Elsevier BV
• Subjects: Additive manufacturing; Alloying additive; Computer simulation; Critical components; Crystal plasticity finite element modeling; Cyclic loads; Damage detection; Damage localization; Digital image correlation; Digital imaging; Dislocations; Electron backscatter diffraction; Electron imaging; Finite element method; Image resolution; Laser beam melting; Manufacturing; Materials fatigue; Nucleation; Plastic deformation; Plastic properties; Residual stress; Strain localization; Ti-6Al-4 V; Titanium alloys; Titanium base alloys; Transmission electron microscopy; Vanadium; Ti-6Al-4 V; Transmission electron microscopy; Additive manufacturing; Crystal plasticity finite element modeling; Digital image correlation; Residual stress
• ISSN: 0022-5096; 1873-4782
• DOI: 10.1016/j.jmps.2018.07.025

•Explicitly modeled α and β phases of Ti-6Al-4 V with a realistic FE mesh.•Residual stresses initialized via GNDs, obtained from EBSD characterization.•TEM indicates higher amount of < c + a > dislocations than < a > type dislocations.•Good agreement between CPFE simulations and HR-DIC experiments.•Strain localization predominantly takes place at prior β grain boundaries. Titanium alloys, produced via additive manufacturing techniques, offer tremendous benefits over conventional manufacturing processes. However, there is inherent uncertainty associated with their properties, often stemming from the variability in the manufacturing process itself along with the presence of residual stresses in the material, which prevents their use as critical components. This work investigates Ti-6Al-4 V produced via selective laser melting by carrying out crystal plasticity finite element (CPFE) simulations and high-resolution digital image correlation (HR-DIC) on samples subject to cyclic loading. This is preceded by detailed material characterization using electron backscatter diffraction, back-scattered electron imaging and transmission electron microscopy, whose results are utilized to inform the CPFE model. A method to incorporate the effect of grain-level residual stresses via geometrically necessary dislocations is developed and implemented within the CPFE framework. Using this approach, grain level information about residual stresses obtained spatially over the region of interest, directly from the experimental material characterization, is utilized as an input to the model. Simulation results match well with HR-DIC and indicate that prior β boundaries play an important role in strain localization. In addition, possible sites for damage nucleation are identified, which correspond to regions of high plastic strain accumulation. [Display omitted]