Environmental Degradation of Additively Manufactured Alloys: AM Materials and Aqueous Corrosion - Part I
Sponsored by: TMS Structural Materials Division, TMS: Corrosion and Environmental Effects Committee, TMS: Additive Manufacturing Committee
Program Organizers: Kinga Unocic, Oak Ridge National Laboratory; Jenifer Locke, Ohio State University; Sebastien Dryepondt, Oak Ridge National Laboratory; Michael Kirka, Oak Ridge National Laboratory; Xiaoyuan Lou, Purdue University; Brendy Rincon Troconis, University of Texas at San Antonio; Luke Brewer, University of Alabama

Wednesday 2:00 PM
March 17, 2021
Room: RM 20
Location: TMS2021 Virtual

Session Chair: Jenifer S. Locke , The Ohio State University; Xiaoyuan Lou, Auburn University


2:00 PM  
Comparing Corrosion of Alloys Made by Additive Manufacturing and Traditional Methods: Sohrab Ghiasi1; Vineeth Kumar Gattu2; William Ebert2; J Ernesto Indacochea1; 1University of Illinois at Chicago; 2Argonne National Laboratory
    Additive manufacturing (AM) is being used to produce large, complex and high-demand alloys parts for a wide range of industrial applications in corrosive environments. Confidence in the long-term performance of these materials requires a clear understanding of the relationships between processing methods, product microstructure, and corrosion performance. We have evaluated the microstructures and electrochemical corrosion behaviors of commonly used Ti-based and Co-based alloys made by additive manufactured and traditionally methods by using potentiodynamic scans and potentiostatic methods. Changes in the electrical properties of the corroded surfaces were measured by using electrochemical impedance spectroscopy and changes in the surface microstructures were evaluated by using scanning electron microscopy. Differences in the test responses and corrosion behaviors will be discussed and related to the microstructures and process methods.

2:20 PM  
Anisotropic Electrochemical Response of Laser Powder Bed Additively Fused Ti6Al4V in Chloride Medium: Sangram Mazumder1; Mangesh V. Pantawane1; Yee-Hsien Ho1; Narendra B. Dahotre1; 1University of North Texas
    The present research aims in investigation and analysis of spatial variation in electrochemical behavior of Ti6Al4V additively printed by laser powder bed fusion, also known as LPBF. Electrochemical behavior of the LPBF printed Ti6Al4V was evaluated by potentiodynamic polarization measurements and electrochemical impedance spectroscopy, at various regions along the build direction, in chloride containing medium. Varying electrochemical behavior was further characterized using scanning electron microscopy and X-ray diffraction which confirmed the variation in (002) texture in the build plane of LPBF printed Ti6Al4V. Also, a Multiphysics computational models developed by finite element method was used in understanding the thermokinetics of the LPBF printed Ti6Al4V and was also conducive in apprehending the spatial variation of electrochemical behavior.

2:40 PM  
Simulation of the Effect of Corrosion on the Mechanical Properties of Porous Mg Scaffolds Fabricated by Power Bed Laser Fusion for Biomedical Applications: M. Marvi-Mashhadi1; Muzi Li2; Wahaaj Ali2; Carlos González3; Javier Llorca3; 1Carlos III University; 2IMDEA Materials Institute; 3IMDEA Materials Institute & Technical University of Madrid
    Porous scaffolds of WE43 Mg alloy for biomedical applications were manufactured by power bed laser fusion. The effect of corrosion in a simulated body fluid on the mechanical properties was ascertained by means on compression tests and the degradation was analyzed by means of X-ray computed tomography. The mechanical behavior was analyzed by means of the finite element method. Corrosion of Mg as a function of time was included through a phenomenological diffusion-based model that can take into account both uniform and pitting corrosion. The model parameters in terms of the strength of Mg and the corrosion rate were determined by comparison with experimental data in Mg scaffolds and they were used to analyze the effect of porosity and strut dimensions on the mechanical behavior of the scaffolds as a function of the corrosion time. This information was used to establish the optimum scaffolds dimensions for bone healing applications.

3:00 PM  
Characterization of Corrosion Behavior in Additively Manufactured Al-6061 RAM Processed by Laser Powder Bed Fusion (L-PBF): Hamidreza T-Sarraf1; Nikhilesh Chawla2; 1Purdue University; 2Arizona State University
    The prospect of producing net shape Al-alloys via laser powder bed fusion (L-PBF) has the potential to provide cost effective components. However, L-PBF processed high strength Al-alloys, produced principally with the same compositions of the wrought alloys lead to hot tearing and undesirable mechanical properties due to interdendritic shrinkages formed during rapid solidification. Reactive additive manufacturing (RAM) technique has overcome this weakness by adding reactive particles as grain modifier into the feedstock powder. However, the influence of these particles on the corrosion performance of L-PBF processed Al-alloy is still unknown. In this work, the corrosion behavior of Al-6061 manufactured by RAM technique was studied over ten days of exposure in a 0.5 M NaCl solution. The microscopic observation and electrochemical data revealed that microstructural modifier particles acted as cathodic sites for corrosion attack. The influence of the microstructure on localized corrosion behavior and attack was characterized and will be discussed.

3:20 PM  
Effect of Heat Treatment on the Stress Corrosion Cracking Behavior of an Additively Manufactured 7050 Aluminum Alloy Produced by Selective Laser Melting (SLM): Kevin Chasse1; Crosby Owens1; Rupesh Rajendran2; Preet Singh2; 1Northrop Grumman Corporation; 2Georgia Institute of Technology
    An additively manufactured, high-strength 7050 aluminum alloy (Al-Zn-Mg-Cu) produced by selective laser melting (SLM) was evaluated for stress corrosion cracking (SCC) susceptibility in chloride-containing environments relative to an 7050 wrought plate. Alloys were overaged for different amounts of time to assess effect of heat treatment on SCC and localized corrosion. Constant extension rate testing (CERT) and sustained load testing were conducted in 3.5% NaCl. Coupons were characterized for evidence of SCC following the tests. Scanning vibrating electrode technique (SVET) was also used to assess the electrochemical behavior associated with microstructural features on select samples. Results of these experiments are showing that the SLM alloys are generally resistant to SCC in chloride environments in all heat treatments and are less susceptible than their 7050 wrought counterpart. Electrochemical potential differences near precipitates imply that extended overaging can increase localized corrosion susceptibility in chloride environments. Further work is ongoing for these materials.

3:40 PM  
Influence of Cold Spray Deposition Parameters on Pitting of AA2024: Ozymandias Agar1; Luke Brewer1; 1University of Alabama
    This presentation will describe how changes in cold spray parameters alter the pitting behavior of deposited AA2024 material (CS-2024). Cold spray is under development to repair corrosion damage in aircraft structures, but optimization for corrosion performance is still being investigated. A series of cold spray deposition parameters, including gas pressure (500, 600 and 700 psi), powder feed rate, and gun speed 100 or 200 mm/s were assessed. The pressure modified particle velocity, while the gun speed and powder feed rate modified the thickness deposited per layer. Subsequently, potentiodynamic polarization and five-day immersion tests were performed in aerated, artificial seawater, and compared against wrought AA2024-T3. Materials sprayed under different conditions showed similar potentiodynamic behavior. Pitting behavior, however, varied substantially with changes in spray conditions and correlated with microscale levels of deposit quality. Minimal pitting, even less than in wrought AA2024-T3, was observed for the CS-2024 which exhibited the least porosity.