Browsing by Subject "microstructures"
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Item Additive Manufacturing of High-Entropy Alloys - A Review(University of Texas at Austin, 2017) Cui, Wenyuan; Zhang, Xinchang; Liou, FrankHigh-entropy alloys have attracted increasingly interest due to their unique compositions, microstructures and mechanical properties. Additive manufacturing has been recognized as a promising technology to fabricate the high-entropy alloys in the recent years. The purpose of this paper is to review the current research progress in high-entropy alloys by additive manufacturing process. It will first highlight the important theory of the high-entropy alloys. The next aspect is to summarize current additive manufacturing methods applied for the high entropy alloys. At last, the correlation between the microstructures and the mechanical properties of the high-entropy alloys will be examined and discussed.Item Comparison of Microstructures and Mechanical Properties for Solid Cobalt-Base Alloy Components and Biomedical Implant Prototypes Fabricated by Electron Beam Melting(University of Texas at Austin, 2010-09-23) Gaytan, S.M.; Murr, L.E.; Martinez, E.; Martinez, J.L.; Machado, B.I.; Ramirez, D.A.; Medina, F.; Collins, S.; Wicker, R.B.The microstructures and mechanical behavior of simple, as-fabricated, solid geometries (with a density of 8.4 g/cm3), as-fabricated and fabricated and annealed femoral (knee) prototypes all produced by additive manufacturing (AM) using electron beam melting (EBM) of Co-26Cr-6Mo-0.2C powder are examined and compared in this study. Microstructures and microstructural issues are examined by optical metallography, SEM, TEM, EDS, and XRD while mechanical properties included selective specimen tensile testing and Vickers microindentation (HV) and Rockwell C-scale (HRC) hardness measurements. Orthogonal (X-Y) melt scanning of the electron beam during AM produced unique, orthogonal and related Cr23C6 carbide (precipitate) cellular arrays with dimensions of ~2μm in the build plane perpendicular to the build direction, while connected carbide columns were formed in the vertical plane, parallel to the build direction.Item The Effects of Specimen Dimensions on the Mechanical Behavior of EBM Produced Ti6Al4V Alloys(University of Texas at Austin, 2009-09) Kircher, R.S.; Christensen, A.M.; Wurth, K.W.There are several published studies investigating the microstructures and mechanical properties obtained during additive manufacturing of Ti6Al4V alloys utilizing the Electron Beam Melting (EBM) technique. These studies have concentrated on conventional testing coupon sizes and configurations which allowed for a direct comparison to the properties of conventionally produced Ti6Al4V alloys. One of the many benefits of the EBM process is that it allows the manufacturer to produce components in sizes and configurations unachievable by conventional methods. It becomes important to understand and verify the microstructures and mechanical performance of these smaller components in a manufacturing environment, requiring the use of non‐conventional testing configurations. This paper presents case-studies involving the production and testing of non-standard samples and how these samples compare to conventional E8 testing coupons. Differences in mechanical performance were observed and are most likely due to the unique characteristics of EBM produced materials.Item Functionally Optimized Ceramic Structures(1998) Gasdaska, C.; Clancy, R.; Ortiz, M.; Jamalabad, V.; Virkar, Anil; Popovitch, DraganThe feasibility of using the Fused Deposition of Ceramics (FDC) process to rapidly fabricate functional quality advanced ceramic components has been demonstrated multiple extrusion heads enable the deposition of spatially engineered ceramic microstructures on the scale of 250 um. This unique capability of FDC allows components to be built with combinations of materials and properties that are difficult or impossible to produce using conventional fabrication processes. Some concepts will be presented, along with examples of multiple material laminates produced using FDC. Strength data will be presented which demonstrates the performance improvement possible using spatially engineered microstructures.Item Investigation of Support Materials for Use in Ultrasonic Consolidation(University of Texas at Austin, 2009-09-15) Swank, M.L.; Strucker, B.E.This paper provides an overview of the need for supports and what characterizes a good support material for Ultrasonic Consolidation. The goal is to look at a broad range of possible support material choices and the benefits and drawbacks of each. By manually depositing support materials during a build, each material is evaluated for its performance for three different configurations: an enclosed pocket, freestanding rib, and open channel. These configurations represent commonly seen features that often need to be built using Ultrasonic Consolidation, but currently cannot be well constructed. The builds are constructed with 3003 Aluminum tapes at room temperature. Microstructures are also studied to evaluate the consolidated material.Item Laser Sintering of Pine/Polylatic Acid Composites(University of Texas at Austin, 2019) Zhang, Hui; Bourell, David L.; Guo, Yanling; Li, Jian; Zhang, Xiaodong; Zhuang, Yu; Li, ZhipengA new powder feedstock composed of sustainable and degradable biomass composite material was proposed for laser sintering technology in this research. This biomass mixture, abbreviated P-PLA, is made up of mechanically mixed polylactic acid (PLA) powder and pine powder. The proper processing parameters were determined based on the component thermal behavior and laser sintering testing: processing temperature 130-135°C, laser power 20-24 W, scan spacing 0.1-0.2 mm, scan speed 1.6-2.2 m/s and layer thickness 0.2mm. Laser-sintered P-PLA parts exhibited much better mechanical properties compared with pine/polyethersulfone copolyester (PCoPES) wood-plastic composite, with tensile strength 34-200% higher and flexural strength 92- 246% higher than values for laser-sintered P-CoPES. Results reveal that pine powder loading can reduce the shrinkage and deformation of laser-sintered P-PLA parts. Shrinkage decreased from 4% to 0.31-2.27% in the XY plane and from 3.25% to 0.13-2.25% in the Z direction.Item Line Scaling Effect On Grain Structure For Cu Interconnects(2009-06) Zhang, L. J.; Im, J.; Ho, P. S.; Zhang, L. J.; Im, J.; Ho, P. S.The effect of line scaling on Cu grain structures has been investigated by using both plan-view and cross-sectional transmission electron microscopy (TEM) techniques. Cu damascene lines with three different line widths of 850, 185 and 60 nm were studied. The plan-view TEM images revealed that the 850 nm lines had both polycrystalline and bamboo-like grain structures, whereas the 185 and the 60 nm lines had near bamboo-like structures. Statistical analysis was performed on the grain size distributions for both 185 nm and 60 nm lines. The results showed that the 185 nm lines followed a normal grain growth behavior, while the 60 nm lines deviated from normal grain growth with excessive small grains at the lower percentile which was attributed to scaling-induced small grain growth. Further analysis by cross-sectional TEM along the Cu trench line direction revealed that the 850 nm lines had bamboo-like structures across the thickness while the 185 nm and the 60 nm lines showed a combination of bamboo-like and multigrain structures with small grain clusters concentrated at the trench bottom.Item Microstructural and Mechanical Performance of Al2O3 Nanoparticle Reinforced 17-4 PH Stainless Steel Bulk Composite Parts Fabricated by Laser Engineered Net Shaping Process(University of Texas at Austin, 2016) Ning, Fuda; Hu, Yingbin; Liu, Zhichao; Wang, Hui; Cong, Weilong; Li, YuzhouAlloy 17-4 PH (AISI 630) is a precipitation-hardening martensitic stainless steel that has been extensively employed in the industries of aerospace, marine, and chemical. In this study, bulk parts of both 17-4 PH and Al2O3 reinforced 17-4 PH composites were fabricated on a steel substrate by laser engineered net shaping (LENS) process to investigate the effects of Al2O3 reinforcements on the part performance. The 17-4 PH powders were pre-mixed with Al2O3 nanoparticles by ball milling. The microstructures of both parts were observed using scanning electron microscopy and mechanical properties including microhardness and compressive properties were evaluated by means of a Vickers microhardness tester and a universal tester, respectively. The results indicate that Al2O3 reinforced 17-4 PH composite parts fabricated by LENS process exhibited superior microhardness and compressive properties as compared to pure 17-4 PH parts.Item A Microstructure and Hardness Study of Functionally Graded Materials Ti6Al4V/TiC by Laser Metal Deposition(University of Texas at Austin, 2015) Zhang, Jingwei; Zhang, Yunlu; Liou, Frank; Newkirk, Joseph W.; Brown-Taminger, Karen M.; Seufzer, Walliam J.Crack free functionally graded material (FGM) Ti6Al4V-TiC has been fabricated by laser metal deposition (LMD) using TiC and Ti6Al4V powder which were premixed for different ratios. This study focuses on the influence of laser processing parameters and TiC compositional distribution on microstructure, Vickers hardness and phase. The microstructure is analyzed by scanning electron microscopy (SEM), x-ray diffraction (XRD) and hardness tests. Primary carbide, eutectic carbide and unmelted carbide are found in the deposit area. When laser power increased, the primary and secondary dendrite arm spacing increased. The laser power and scanning speed did not influence the Vickers hardness distribution significantly.Item Microstructure and Mechanical Properties of Maraging Steel 300 After Selective Laser Melting(University of Texas at Austin, 2010-09-23) Yasa, E.; Kempen, K.; Kruth, J.-P.Selective laser melting (SLM) is an additive manufacturing process for the direct fabrication of prototypes, tools and functional parts. The process uses a high intensity laser beam to selectively fuse fine metal powder particles together in a layer-wise manner by scanning cross-sections generated from a three-dimensional CAD model. The SLM process is capable of producing near fully dense functional products without almost any geometrical limitation and having mechanical properties comparable to those produced by conventional manufacturing techniques. There is a wide range of materials that are suitable to be processed by SLM including various steels, Ti, Al and CoCr alloys. Being one of these materials, maraging steel 300 (18Ni-300) is an iron-nickel steel alloy which is often used in applications where high fracture toughness and strength are required or where dimensional changes have to remain at a minimal level, e.g. aircraft and aerospace industries for rocket motor castings and landing gear or tooling applications. To achieve its superior strength and hardness, maraging steel, of which the name is derived from ‘martensite aging’, should be treated with an aging heat treatment. In this study, the effect of the SLM parameters (scan speed and layer thickness) on the obtained density, surface quality and hardness of maraging steel 300 parts is investigated. Moreover, various aging heat treatments (different combinations of duration and maximum temperature) are applied on the SLM parts to achieve high hardness values. The mechanical testing of maraging steel 300 specimens produced by SLM and treated with an appropriate aging treatment is accomplished by impact toughness and tensile tests and compared to the results obtained using conventional production techniques. Additionally, the microstructures of as-built and heat treated parts are investigated.Item Simulation Of Coarsening During Laser Engineered Net Shaping(1997) Tikare, Veena; Griffith, Michelle; Schlienger, Eric; Smugeresky, JohnLaser Engineered Net_Shaping, otherwise known as LENSTM, is an advanced manufacturing technique used to fabricate complex near net shaped components directly from engineering solid models without the use of dies or machining. The ultimate objective ofthis project is to develop predictive simulation capability which will allow the LENSTM processors to determine fabrication conditions given the material, shape, and application ofthe final part. In this paper, we will present an incremental achievement to meeting the ultimate goal, a model capable ofsimulating the coarsening ofmicrostructural features under the unique thermal history to which a LENSTM part is subjected during processing. The simulation results show how grains ofvery different shapes and sizes form within the same deposition line. They also show that relatively minor changes in the dynamic temperature profile results in microstructures with vastly different characteristics. The implications ofthis work for LENSTM fabrication is that controlling the temperature profile is essential to tailoring the microstructure of a component to its application.