2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Materials: Metals-Processing Strategies II
Program Organizers: Joseph Beaman, University of Texas at Austin
Wednesday 8:00 AM
August 16, 2023
Room: 616 AB
Location: Hilton Austin
Session Chair: Francisco Medina, University of Texas El Paso
8:00 AM
Effect of Initial Carbon Content on Tailoring the Mechanical Properties of Additively Manufactured Martensitic Ultra High-strength Steels: Stephanie Pestka1; Matthew Vaughan1; Sean Gibbons2; Philip Flater2; Alaa Elwany1; Ibrahim Karaman1; Raymundo Arryoave1; 1Texas A&M University; 2Air Force Research Laboratory
Laser powder bed fusion (L-PBF) of a newly developed martensitic ultra high strength steel (UHSS) known as AF96 has received notable attention due to its unique microstructure and superior mechanical properties. The current study investigates the influence of initial alloy carbon content on the mechanical properties of AF96 fabricated via L-PBF. A process parameter development study was first performed to determine optimal processing parameters that result in near defect-free as-printed parts. Test specimens were then fabricated using optimized parameter combinations for mechanical and microstructural characterization. This process was completed for three compositions of AF96 powder containing varying amounts of initial carbon content. Preliminary results show a significant increase in both yield strength and ultimate tensile strength with increasing initial carbon content.
8:20 AM
Effectiveness of Ex-situ Heat Treatment of L-PBF AM 17-4PH Stainless Steel Specimens Intentionally Exposed to Different As-built Thermal Histories: C. Hasbrouck1; Joseph Bartolai1; Darren Pagan1; Simon Miller1; 1The Pennsylvania State University
The presented research demonstrates the effectiveness of H900 heat treatment in eliminating microstructural and mechanical property differences between additively manufactured 17-4PH stainless steel samples of varying thermal histories. For this effort, 17-4PH stainless steel was manufactured using laser-based powder bed fusion on an EOS M280 machine in two geometries: ASTM Standard E8 subsize rectangular tensile specimen geometry with thicknesses of 2mm and 6mm. Thermal histories were manipulated by adding secondary laser passes on each layer at varying levels of reduced power. All samples were heat treated after the build following H900 procedures. No mechanical property or microstructural differences were discovered through uniaxial quasi-static tensile testing and electron backscatter diffraction.
8:40 AM
Effect of Process Parameters on Microstructure and Properties for the Application of 316L Additively Manufactured Medical Device Components: Fabienne Riester1; 1KARL STORZ SE & Co. KG
Additive manufacturing using laser powder bed fusion (LPBF) provides a great potential for the serial production in medical technology. In addition to the design freedom, function integration and weight optimization, the processability of biocompatible materials such as SS316L is particularly crucial. The good corrosion resistance and sufficiently high material characteristics serve as a basis for the optimization of further properties through the targeted variance of process parameters.For the application of additive manufacturing of 316L stainless steel by LPBF for medical instruments, the influences of the process parameters on the microstructure and the relevant component properties of surface roughness and density are investigated. By means of statistical evaluations, laser focus, filling contours and remelting are considered in addition to the most influential parameters of laser power and scanning speed. Finally, a set of process parameters is defined, which serves as a basis to produce a medical product.
9:00 AM
The Influence of Heat Treatments on the Microstructure and Tensile Properties of Additively Manufactured Inconel 939: Rukesh Gusain1; Mohammad Dodaran1; Paul Gradl2; Shuai Shao1; Nima Shamsaei1; 1Auburn University; 2NASA Marshall Space Flight Center
The variations in microstructure and tensile behavior of laser powder bed fusion Inconel 939 subjected to three different heat treatments are investigated in this study. The heat treatment schedule involves combinations of annealing temperature and soaking time, followed by multi-stage aging. The subsequent microstructural changes were analyzed using scanning electron microscopy. Tensile tests were performed at room temperature to examine the influence of the resultant microstructure on the mechanical behavior. The microstructural analysis showed that the higher solution temperatures led to the partial removal of dendritic microstructure and resulted in better homogenization, which was not so significant at the lower solution temperatures studied. Moreover, variations in the distribution of precipitates with aging temperature were also observed in this study. The optimal heat treatment schedule, which yielded a superior combination of strength and ductility, was identified in this study.
9:20 AM
Exploring IN718 Alloy Production with Bidirectional Raster and Stochastic Spot Melting Techniques using an Open-source Electron Beam Melting System: Shadman Nabil1; Cristian Banuelos1; Brandon Ramirez1; Alex De La Cruz1; Kurtis Watanabe1; Edel Arrieta1; Ryan B Wicker1; Francisco Medina1; 1University of Texas at El Paso
This study compares the fabrication of IN718 alloy using bi-directional raster and stochastic spot melting techniques with the open-source FreemeltOne Electron Beam Melting (EBM) system. The research aimed to produce dense parts using both scanning strategies, employing custom python code for raster melt beam path generation and PixelMelt software for stochastic spot melting. After optimizing process parameters, 10mm builds for each scanning strategy were fabricated, and their microstructure, hardness, and density were analyzed using optical microscopy and Scanning Electron Microscopy (SEM), vickers microhardness scale, and a pycnometer. The findings reveal valuable insights into the effects of scanning strategies on the microstructure, hardness, and density of IN718 alloy components, advancing additive manufacturing knowledge.
9:40 AM Break
10:10 AM
Effects of Build Orientation and Heat Treatment on the Porosity Distribution and Morphology within Inconel 625 Fabricated via Laser Powder Bed Fusion: Mohanish Andurkar1; Bart Prorok2; John Gahl3; Scott Thompson3; 1Kansas State University; 2Auburn University; 3University of Missouri
The effects of build orientation, i.e., vertical, or diagonal (45º), and heat treatment on the porosity characteristics within Inconel 625 (IN625) fabricated via laser powder bed fusion (L-PBF) was experimentally investigated. Selected samples were heat treated at 1050 ℃ for 1-hour to promote evolution of pores. X-Ray Computed Tomography (XCT) was performed on samples to generate three-dimensional porosity maps. Volume Graphics (VG) software was used to inspect and quantify porosity distributions. Results indicate that build orientation and heat treatment influence measured porosity count. As-built (no heat treatment) sample microstructure was observed to have lower porosity count when compared to heat-treated samples. The vertically built sample was observed to have lower porosity relative to its diagonally built counterpart. The porosity morphology or diameter was observed to vary after heat treatment. On the other hand, the sphericity of pores was not affected by different build orientation and heat treatment.
10:30 AM
Microstructural and Microhardness Variations of Laser Powder Bed Fusion (L-PBF) Additively Manufactured Inconel 718 Due to Machine Variability and Thickness for Aerospace Applications: Anannya Doris1; Leslie Trujillo1; Dana Godinez1; Edel Arrieta1; Ryan Wicker1; Paul Gradl2; Colton Katsarelis2; Francisco Medina1; 1University of Texas at El Paso; 2Marshall Space Flight Center, NASA
This paper reports on a study investigating the microstructure and microhardness of thin walls fabricated by Laser Powder Bed Fusion (L-PBF) from sixteen geometric feature build plates. The study evaluated any variance in those properties with the variation in thickness by characterizing the XY and YZ planes of seven thin walls of different thicknesses and the base parts. Electron Backscatter Diffraction (EBSD) analysis with inverse pole figure (IPF) mapping was done for four samples from four different machine manufacturers. From the EBSD grain boundary map, the microstructure is composed of equiaxed grains with a lower threshold angle with smaller grains in the border area. Compositional analysis for both the powders and the resulting fully heat-treated LPBF-ed material was analyzed for alloy element stability and contaminants using 10 gm samples. The paper concludes by showing the relationship between composition and microstructural properties.
10:50 AM
Numerical and Experimental Investigations on Manufacturability of Al-Si-10Mg Thin Wall Structures Made by LB-PBF: Mahyar Khorasani1; Martin Leary1; David Downing1; Stuart Bateman1; Eric MacDonald2; 1RMIT; 2The University of Texas at El Paso
This research aims to investigate the effect of power, inclination angle and the number of laser passes upon dimensional deviation, distortion and porosity of Thin Wall Structures (TWS) made by LB-PBF. Investigating the mentioned parameters is useful to determine the capability of LB-PBF to produce Al-Si-10Mg TWS as well as the manufacturability of these structures. To identify the effect of inclination angle, number of laser passes and laser power on dimensional deviation, distortion and porosity a full factorial Design of Experiments (DOE) has been selected. To discuss the results statistical analyses and simulation of LB-PBF are implemented. Simulations have been carried out using computational fluid dynamic software (Flow-3D V12) and the depth and width of the meltpool are predicted. The obtained dimensions of the melt-track are then generalised based on the thickness of the TWS to confirm the accuracy of the simulation.
11:10 AM
Controlling Chemical Composition Changes in Laser Powder Bed Fusion of AlSi10Mg: Bochuan Liu1; Gregory Gibbons1; 1University of Warwick
Due to the large energy input during the laser powder bed fusion process, some elements of metal alloy will reach vaporisation temperature. Significant difference between the volatility of various elements in the alloy may change the chemical composition after manufacturing. This study will use this preferential evaporation effect to control the final composition to a targeted value, potentially for alloy and component tracing. Microstructure and mechanical properties changes associated with various compositions will be investigated.
11:30 AM
Compositional Variation Effect on the Microstructure and Nanomechanical Properties of Additively Manufactured AlCuFeNiTi High Entropy Alloy: Sandeep Khadka1; Hubert Bilan1; Tao Ma2; Philip Yuya1; 1Clarkson University; 2University of Michigan
An equiatomic AlCuFeNiTi high entropy alloy (HEA) was successfully fabricated for the first time using pre-alloyed powder with directed energy deposition method. The alloy was characterized using microscopy techniques and nanoindentation to provide insight into the relationship between its microstructural and nanoscale mechanical properties. The microstructure has a dominant dendritic region with an ordered Heusler structure (L21) and an interdendritic region with FCC structure with traces of C14 Laves region. During solidification, dendritic fragmentation occurs, contributing to the alloy having mostly equiaxed grains rather than the commonly observed columnar grains. Nanoindentation results showed that the interdendritic regions present soft zone while Laves phase presents the hardest region. The presence of laves phase inside the grain boundaries strengthens the region. The results of the current study highlight the synthesis of an equiaxed HEA with one of the highest combinations of elastic modulus and hardness values determined using nanoindentation.