Additive Manufacturing: Length-Scale Phenomena in Mechanical Response: Properties and Failure
Sponsored by: TMS Materials Processing and Manufacturing Division, TMS: Nanomechanical Materials Behavior Committee
Program Organizers: Meysam Haghshenas, University of Toledo; Andrew Birnbaum, Us Naval Research Laboratory; Robert Lancaster, Swansea University; Xinghang Zhang, Purdue University; Aeriel Leonard

Thursday 8:30 AM
March 23, 2023
Room: 23B
Location: SDCC

Session Chair: Kavan Hazeli, The University of Arizona; Mohsen Taheri Andani, University of Michigan


8:30 AM  
On the Melt Pool Dynamic of Metal Matrix Composites via Hybrid Additive Manufacturing: Laser Powder Bed Fusion and Ink-Jetting: Milad Ghayoor1; Omid Sadeghi1; Bryce Cox1; Joshua Gess1; Somayeh Pasebani1; 1Oregon State University
    In this study, the effect of the addition of reinforcement nanoparticles to the 316L matrix by adopting ex-situ and in-situ methods to produce 316L/Al2O3 nanocomposite was investigated. In the ex-situ method, the Al2O3 nanoparticles (NPs) were lightly mixed with 316L powder and processed by laser powder bed fusion. In the in-situ method, an ethanol-based ink containing Al13 nanoclusters (NCs) was added to 316L powder and then processed by laser. Both ex-situ and in-situ methods produced nanocomposites with Al-Si-Mn-O-enriched precipitations within the 316L matrix. The addition of NPs/NCs to the 316L matrix, altered the geometrical characteristic of the single-track melt pools. At a high laser power of 150 W, the Marangoni flow and the buoyancy force caused the nanoparticles to agglomerate and float to the top surface of tracks. Lastly, a hybrid LPBF+ink-jet printer was adopted to selectively change the composition of different zones by adding Al13 NCs ink to 316L

8:50 AM  
Dynamic Strength Performance of Additively Repaired Small-damage Sites in Stainless Steel: Jesse Callanan1; David Jones1; Saryu Fensin1; Daniel Martinez1; 1Los Alamos National Laboratory
    The increasing attention on metal additive manufacturing has led to attractive new possibilities in the field of crucial part repair which have the potential to reduce overall cost, reduce downtimes, and expand the range of options for application and material types. In this work, artificially damaged stainless steel samples were repaired with additive manufacturing technology and the mechanical properties were investigated. Various types of damage sites on the order of one cubic millimeter were inflicted on samples to replicate scratches commonly incurred during manufacturing or regular use of metal parts. The damage sites were repaired with pulsed laser deposition additive manufacturing, and the repaired samples were tested at dynamic strain-rates. Post-mortem metallography was used to study the links between repair processing methodology, microstructure, and mechanical performance. Results show that optimal process parameters are critical for realizing effective repairs due to the dependence of damage morphology on the resulting microstructure.

9:10 AM  
Investigation of The Effects of Size, Geometry, and Temperature in Additively Manufactured Titanium Alloy: Daniel June1; Andrew Wessman1; Kavan Hazeli1; 1The University of Arizona
    This study investigates the interplay between size, geometry, and temperature and their effects on the mechanical properties of Additively manufactured titanium alloys (Ti-6Al-4V). Quasi-static testing was conducted at ambient, 250, and 450 degrees Celsius temperatures, showing a decrease in elongation and an increase in strain-softening rates as sample thickness is reduced. Furthermore, comparisons made between test samples of flat and round samples indicated a further decrease in elongation and increased strain-softening for thin round samples , respectively. It was also noted that this trend becomes more apparent as the temperature is raised from 250 to 450 degrees Celsius. To determine the driving mechanisms responsible for this phenomenon, a microscopic examination of texture and grain morphology was conducted alongside surface roughness data as functions of sample thickness and geometry.

9:30 AM  
Microstructure and Property Variations in Directed Energy Deposited 316L on Super-Austenitic AL6XN: Anna Rawlings1; Andrew Birnbaum1; John Steuben1; John Michopoulos1; 1U.S. Naval Research Laboratory
    Directed energy deposition (DED) allows for the generation of alloys with tailored compositions, and therefore, properties. In this study, a DED system is utilized to build a thin wall using 316L stainless steel powder on an AL6XN super-austenitic stainless steel baseplate. The extent of local mixing of baseplate and powder materials generated by successive melting and solidification cycles is examined by synchronous energy dispersive spectroscopy (EDS) with electron backscatter diffraction (EBSD). Additionally, microstructural and mechanical property responses along the part height as well as into the build plate resulting from compositional changes and thermal cycling are analyzed by phase indexing, kernel average misorientation mapping, and hardness evaluation via nanoindentation. Lastly, high-resolution characterization of individual layers is performed to investigate microstructural responses due to differing thermal conditions experienced by the center of the deposited bead compared to the bead exterior.

9:50 AM Break

10:10 AM  
High Temperature Laser Powder-bed Fusion Austenitic Steels with Outstanding Creep Strength: Sebastien Dryepondt1; Kinga Unocic1; Rangasayee Kannan1; Peeyush Nandwana1; Patxi Fernandez-Zelaia1; Michael Lance1; Lisa Debeer-Schmitt1; Ken Littrell1; 1Oak Ridge National Laboratory
     The formation of sub-grain cellular structures in laser powder bed fusion (LPBF) austenitic steels such as 316L due to extremely fast cooling rates is known to enhance room temperature strength. The nucleation of a high density of nano carbides or carbonitrides in the cell walls also offers the opportunity to develop advanced LPBF high temperature high strength austenitic alloys. 310 and 347-type steels fabricated by LPBF exhibited creep strength at 700-800°C along the build direction three to six times greater than the creep properties of cast counterparts. The lower creep strength observed perpendicular to the build direction was mainly attributed to the elongated grains along the build direction. SEM coupled with image analysis, TEM and in situ neutron SANS experiments were performed to investigate the microstructure evolution at 700-800°C of these non-equilibrium alloys. This research was sponsored by the DOE EERE Vehicle Technologies Office, Powertrain Materials Core Program

10:30 AM  
High Throughput Bending Creep Testing of a New High Strength Additively Manufactured A205 Alloy: Anup Kulkarni1; Praveen Ravanappa1; Dheepa Srinivasan1; Callie Benson2; Vikram Jayaram3; Praveen Kumar3; 1Pratt and Whitney Research and Development Center; 2Collins Aerospace; 3Indian Institute of Science Bangalore
    The bending and uniaxial creep behavior of A205 aluminum alloy printed by laser powder bed fusion was studied in the temperature range of 150-200°C and stress range of 100-250 MPa. During bending creep testing, digital image correlation was employed for mapping the strains at different locations in the small size cantilevers. The stress and strain fields vary across the length and thickness of the cantilever beam, which facilitates in obtaining multiple stress-strain rate data points from a single test. The steady state creep rates obtained from the bending creep tests were well in line with those measured from conventional uniaxial creep tests performed at equivalent stress and temperature, which validated bending creep as a high throughput testing method. The intragranular nanoscale precipitates of Al-Cu (’) and Al-Cu-Ag-Mg () were responsible for excellent creep resistance and thermal stability, which makes A205 an attractive material for high temperature aerospace applications.

10:50 AM  
Uniaxial Equivalence of Bending Creep in Additively Manufactured AlSi10Mg Alloy: Shobhit Singh1; Faizan Hijazi2; Vikram Jayaram3; Dheepa Srinivasan4; Praveen Kumar3; 1Indian Institute of Science, Bangalore; The University of Manchester; 2Indian Institute of Science Bangalore; 3Indian Institute of Science, Bangalore; 4Pratt and Whitney Research and Development Center
    Creep of additively manufactured AlSi10Mg hypoeutectic alloy, printed by laser powder bed fusion (L-PBF) is conducted in compression, tension and bending of cantilevers at 250oC. Digital image correlation is specifically utilized to extract strain profiles from bending cantilevers constrained at one end, which enables the acquisition of multiple strain-time creep curves from a single tested specimen. Uniaxial tests were performed between 75 to 140 MPa and the bending was conducted with loads to give stresses between 80 and 125 MPa, which far exceeds the actual service conditions. The uniaxial equivalent minimum creep rates obtained from the DIC-augmented bending creep appears to be in good agreement with the minimum creep rates from uniaxial experiments. Electron microscopic investigation gives evidence of the formation of nano-precipitates pinning the dislocations, probably causing the creep strengthening in this alloy. Additional coarsening of eutectic Si particles is also observed during creep.