Browsing by Author "Song, Jie"

Now showing 1 - 6 of 6
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    Corrosion Fatigue Characteristics of 316L Stainless Steel Fabricated by Laser Powder Bed Fusion
    Gnanasekaran, Balachander; Song, Jie; Vasudevan, Vijay; Fu, Yao (MDPI, 2021-06-29)
    Laser powder bed fusion (LPBF) has been increasingly used in the fabrication of dense metallic structures. However, the corrosion related properties of LPBF alloys, in particular environment-assisted cracking, such as corrosion fatigue properties, are not well understood. In this study, the corrosion and corrosion fatigue characteristics of LPBF 316L stainless steels (SS) in 3.5 wt.% NaCl solution have been investigated using an electrochemical method, high cycle fatigue, and fatigue crack propagation testing. The LPBF 316L SSs demonstrated significantly improved corrosion properties compared to conventionally manufactured 316L, as reflected by the increased pitting and repassivation potentials, as well as retarded crack initiation. However, the printing parameters did not strongly affect the pitting potentials. LPBF samples also demonstrated enhanced capabilities of repassivation during the fatigue crack propagation. The unique microstructural features introduced during the printing process are discussed. The improved corrosion and corrosion fatigue properties are attributed to the presence of columnar/cellular subgrains formed by dislocation networks that serve as high diffusion paths to transport anti-corrosion elements.
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    Ensuring Melt Track Width Consistency and Crack-Free Conditions Using Interpass-Temperature-Dependent Process Parameters for Wire-Arc-Directed Energy-Deposited Inconel 718
    Jimenez, Xavier A.; Song, Jie; Fu, Yao; To, Albert C. (MDPI, 2024-06-28)
    Melt track width can vary in a wire-arc-directed energy-deposited material (DED) using a constant set of process parameters, leading to a lower-quality build. In this work, a novel framework is proposed that uses the data from the process parameter development stage to create optimized process parameters for a target layer width at different interpass temperatures without hot cracking. Inconel 718 is used as the model material since it is known to suffer from hot cracking during DED processing. In the proposed framework, a process window containing a few sets of process parameters (torch travel speed and wire feed rate) is established for crack-free deposition of Inconel 718, and these parameters are used to create a small database. A linear regression model is then employed to generate interpass-temperature-specific optimized process parameters for a target melt track width. The results demonstrate that the proposed approach can reduce the melt track width variation in the deposited walls from 12% to 3% error on average under different printing conditions. It also demonstrates that interpass temperature (IPT) can be used as a controlled variable and the optimized process parameters as initial values when applying control techniques to the process.
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    Heat Treatment Effect on the Corrosion Resistance of 316L Stainless Steel Produced by Laser Powder Bed Fusion
    Sangoi, Kevin; Nadimi, Mahdi; Song, Jie; Fu, Yao (MDPI, 2025-01-04)
    This study explores the effect of heat treatment on the microstructural characteristics and corrosion resistance of 316L stainless steels (SSs) produced via laser powder bed fusion (L-PBF), focusing on anisotropic corrosion behavior—a relatively less explored phenomenon in LPBF 316L SSs. By systematically analyzing the effects of varying heat treatment temperatures (500 °C, 750 °C, and 1000 °C), this work uncovers critical correlations between microstructural evolution and corrosion properties. The findings include the identification of anisotropic corrosion resistance between horizontal (XY) and vertical (XZ) planes, with the vertical plane demonstrating higher pitting and repassivation potentials but greater post-repassivation current densities. Furthermore, this study highlights reductions in grain size, dislocation density, and melt pool boundaries with increasing heat treatment temperatures, which collectively diminishes corrosion resistance. These insights advance the understanding of processing–structure–property relationships in additively manufactured metals, providing practical guidelines for optimizing thermal post-processing to enhance material performance in corrosive environments.
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    Microstructures and Corrosion Properties of Wire Arc Additive Manufactured Copper–Nickel Alloys
    Song, Jie; Jimenez, Xavier A.; To, Albert C.; Fu, Yao (MDPI, 2024-02-14)
    The 70/30 copper–nickel alloy is used mainly in critical parts with more demanding conditions in marine settings. There is a need for innovative methods that offer fast production and cost-effectiveness in order to supplement current copper–nickel alloy manufacturing processes. In this study, we employ wire arc additive manufacturing (WAAM) to fabricate the 70/30 copper–nickel alloy. The as-built microstructure is characterized by columnar grains with prominent dendrites and chemical segregation in the inter-dendritic area. The aspect ratio of the columnar grain increases with increasing travel speed (TS) at the same wire feed speed (WFS). This is in contrast with the equiaxed grain structure, with a more random orientation, of the conventional sample. The sample built with a WFS of 8 m/min, TS of 1000 mm/min, and a track distance of 3.85 mm exhibits superior corrosion properties in the 3.5 wt% NaCl solution when compared with the conventional sample, as evidenced by a higher film resistance and breakdown potential, along with a lower passive current density of the WAAM sample. The corrosion morphology reveals the critical roles played by the nickel element that is unevenly distributed between the dendrite core and inter-dendritic area.
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    A phase field model to simulate crack initiation from pitting site in isotropic and anisotropic elastoplastic material
    Song, Jie; Matthew, Christian; Sangoi, Kevin; Fu, Yao (IOP Publishing, 2023)
    A multiphysics phase field framework for coupled electrochemical and elastoplastic behaviors is presented, where the evolution of complex solid-electrolyte is described by the variation of the phase field variable with time. The solid-electrolyte interface kinetics nonlinearly depends on the thermodynamic driving force and can be accelerated by mechanical straining according to the film rupture-dissolution mechanism. A number of examples in two- and three- dimensions are demonstrated based on the finite element-based MOOSE framework. The model successfully captures the pit-to-crack transition under simultaneous electrochemical and mechanical effects. The crack initiation and growth has been demonstrated to depend on a variety of materials properties. The coupled corrosion and crystal plasticity framework also predict the crack initiation away from the perpendicular to the loading direction.
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    Wire Direct Energy Deposition of Cobalt Iron Alloy
    Salah, Mohammad (Virginia Tech, 2025-01-23)
    The presented research explores the Wire-Laser Direct Energy Deposition of Fe17Co alloy for soft magnetic applications. Process parameters starting from power, feed speed, and feed/scan ratios were optimized where a high confidence multi-factor regression model was developed correlating the processing parameters to final bead dimensions. The model showed that increasing feed speeds led to an increase in bead height and a reduction in bead width while increasing feed/scan ratio resulted in an increase of bead height and width. Interlayer cooling time for multi-layer deposition was tested and revealed, through thermal camera measurement, that increasing interlayer cooling time leads to a higher cooling rate, and generally more stable printing process. Printed samples showed single phase BCC with fine equiaxed structure and high density (>98.5%) with no pores or cracks. ASTM A773 sample rings were printed and showed that for decreasing input energy (by decreasing power or increasing feed speed) leads to a finer grain structure. The average diameter grain size of the printed samples was 18.7 microns and grew to an average of 26.5 microns after a pre-anneal heat treatment at 700°C for 2 hours followed by 850°C for 10 hours. Furthermore, using interlayer cooling time, the thermal gradient of the samples throughout the printing was increased and lead to even finer grain structure. However, this lead to increased grain growth post annealing. Printed samples showed good magnetic properties, but slightly less than that of the commercial wrought material.