ADVANCED MATERIALS & PROCESSES | SEPTEMBER 2024 15 The average twinned area fraction was 3.99 ± 2.8% and 4.55 ± 0.9% from the tensile test and PIP images, respectively. The larger twinned area fraction is observed in the PIP case, impacting the hardening capacity of WDED α-Ti at room temperature. Hence, the increased twin boundary density acts as a low- energy grain boundary, not blocking but reducing dislocation movement on the material. CONCLUSIONS The tensile-compressive asymmetry of single phase WDED α-Ti along the buildup was characterized by comparing experimental data from the uniaxial tensile test and the PIP technique. The combination of experimental results and optical microscopy techniques resulted in a characterization of the main deformation mechanisms under tensile vs. compressive stresses at room temperature. Samples exhibited two prominent deformation mechanisms: twinning and slip dislocations. Twins significantly influenced the material’s plasticity behavior, particularly its hardening capacity. Mechanical properties from the PIP resulted in higher UTS, which is primarily attributed to larger twin density. The larger formation of twins under compression emerges primarily from the complex stress condition under the indent and interaction with the compressive residual stresses resulting from multiple deposited layers on the buildup. ~AM&P For more information: Blanca Palacios, Ph.D. researcher, Cold Spray and Rapid Advanced Deposition Laboratory, Florida International University, 10555 W. Flagler St. EC 2400, Miami, FL 33174, 305.348.0198, bpala021@fiu.edu. References 1. A. Queguineur, et al., Wire Arc Additive Manufacturing of Thin and Thick Walls Made of Duplex Stainless Steel, Int. J. Adv. Manuf. Technol., 127, p 381-400, 2023, doi.org/10.1007/s00170- 023-11560-5. 2. J. Suryawanshi, et al., Tensioncompression Asymmetry and Shear Strength of Titanium Alloys, Acta Mater., 221, p 117392, 2021, doi.org/10.1016/ j.actamat.2021.117392. 3. D. John, et al., Profilometry-Based Indentation Plastometry for Evaluating Bulk Tensile Properties of AluminumSilicon Carbide Composites, Adv. Eng. Mater., 25(14), p 2201890, 2023, doi.org/ 10.1002/adem.202201890. 4. B. Palacios, et al., Role of Structural Hierarchy on Mechanics and Electrochemistry of Wire Arc Additive Manufactured (WAAM) Single Phase Titanium, J. Manuf. Process., 93, p 239249, 2023, doi.org/10.1016/j.jmapro. 2023.03.025. 5. L. Böhme, et al., Crystal C-axis Mapping of HCP Metals by Conventional Reflected Polarized Light Microscopy: Application to Untextured and Textured cp-Titanium, Mater. Charact., 145, p 573581, 2018, doi.org/10.1016/j.matchar. 2018.09.024. 6. Y.T. Tang, et al., Tensile-Compressive Asymmetry in Extruded AZ31B Rod and Its Effect on Profilometry-based Indentation Plastometry (PIP), Mater. Sci. Eng. A, 848, 2022, doi.org/10.1016/ j.msea.2022.143429. 7. A. Lama, et al., Macroscale Property Assessment and Indentation Characteristics of Thick Section Friction Stir Welded AA 5083, Mater. Sci. Eng. A, 880, p 145306, 2023, doi.org/10.1016/ j.msea.2023.145306. 8. F. Azarmi and I. Sevostianov, Evaluation of the Residual Stresses in Metallic Materials Produced by Additive Manufacturing Technology: Effect of Microstructure, Curr. Opin. Chem. Eng., 28, p 21-27, 2023, doi.org/10.1016/ j.coche.2019.12.004. Fig. 5 — Stress-strain curves resulting from the uniaxial tensile tests and PIP tests show the estimated anisotropy behavior of the WDED cp-Ti plasticity response. Fig. 6 — Optical micrographs of (a) tensile and (b) PIP samples used for the twinned area fraction calculations. Images were converted into 16 bits (grayscale pixels), twin regions were enhanced in Photoshop, and a threshold of 30% (darker shades/black) was used in ImageJ software to allow calculations under the same conditions. (a) (b)
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