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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
DOE OSTI2018

Interfacial structure and bonding mechanism of weld seams during porthole die extrusion of aluminum alloy profiles

Highlights: • Interfacial structures and bonding mechanisms of extrusion welds were studied. • Interfacial grain boundaries, amorphous layers and voids were found. • Bonding mechanisms in the absence/presence of a gas-pocket were proposed. • Voids closure, oxide films breaking and grain boundaries migration were discussed. - Abstract: Fine nanostructures of bonding interfaces of weld seams formed by porthole die extrusion in the absence/presence of a gas-pocket behind the bridge of the extrusion die were systematically studied to understand the underlying interfacial bonding mechanisms. Interfacial grain boundaries, nanoscale amorphous layers, and three kinds of new interfacial structures were found. Specifically, it was found that, in the absence of a gas-pocket behind the bridge, there are two distinctly different interfacial structures. For the first kind of bonding interface, interfacial grain boundaries exist in contact areas and micro-voids exist in non-contact areas. For the second kind of bonding interface, there are no interfacial grain boundaries in contact areas and only nanoscale micro-voids exist in non-contact areas. In the presence of a gas-pocket behind the bridge, nanoscale voids and amorphous layers exist at the bonding interface. It was also found that the formation of gas-pockets can be avoided by increasing the depth of the welding chamber, and the increase of the welding chamber's depth and extrusion speed also contributes to the volume reduction of micro-voids and the migration of grain boundaries at the bonding interface, so as to improve the welding quality of weld seams. Based on the experimental findings, two interfacial bonding mechanisms corresponding to the absence/presence of a gas-pocket are proposed. The specific behavior of micro-asperities contact, micro-voids closure, oxide films breaking and interfacial grain boundaries migration are described, and the solid-state bonding process during porthole die extrusion is revealed from the micro-nano scales.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2025

Design and Development of a Fixtureless, Pass-through Machine Tool for Extrusion Machining

The aerospace, construction/architecture, and transportation manufacturing industries rely heavily on the mass production of near-net shape metallic and composite extrusions. While the production of raw extrusions is a relatively fast process, adding functional features such as holes and slots require additional time, cost, and energy to produce. To compensate for the inherent flexibility of extrusions, conventional machining requires rigid purpose-built fixtures for operations such as trimming, drilling and thinning. This approach requires that the machine tools be as large or larger than the parts themselves. This results in the need for excess shop floor space, energy for auxiliary equipment and motion systems, and significant capital expenditure. Considerable engineering expense and time involved in the designing, building, and proving out of part-specific fixtures for holding the components in specific configurations while machining add to the overall manufacturing cost. The primary objective of the technical collaboration between Oak Ridge National Laboratory and Fairmount Technologies (FT) is to improve the XM-3, a fixtureless CNC milling machine designed by FT. The machine was developed to trim, drill, and thin extrusions without part specific fixturing to make the manufacturing process more efficient and flexible. Dynamic measurements of the existing structure were collected, and modeling efforts were made to evaluate optimal machining parameters for the current system. Areas of improvement to increase the system stiffness, manufacturability, and machining efficiency were evaluated and highlighted for the next generation design. The impact of this effort may enable agile manufacturing across the commercial and defense aerospace industries, and other industries where extrusions are utilized like in the construction, architecture, and transportation industries.

42 ENGINEERING↗
DOE OSTI2019

System and process for formation of extrusion products

Devices and processes for performing shear-assisted extrusion include a rotatable extrusion die with a scroll face configured to draw plasticized material from an outer edge of a billet generally perpendicularly toward an extrusion orifice while the extrusion die assembly simultaneously applies a rotational shear and axial extrusion force to the billet.

Lavender, Curtis A.↗
DOE OSTI2021

Chapter 6 - Polymer and composites additive manufacturing: material extrusion processes

This chapter focuses on material extrusion additive manufacturing (AM) processes for polymers and composite materials. Different extrusion AM platforms, along with their operating mechanism concepts, processing capabilities, and limitations, are discussed here. This chapter also covers state-of-the-art developments in new areas such as hybrid systems, integrated systems, and automation, which facilitate the integration of extrusion-based AM processes into smart manufacturing or Industry 4.0. Following this, a comprehensive discussion on materials development, criteria for successful printing of different materials (thermoplastics, thermosets, and their composites), key factors influencing printing, and material-related challenges in extrusion AM is presented. Finally, a brief overview of current and future potential applications of material extrusion AM technology is provided.

Kishore, Vidya↗
DOE OSTI2019

Microstructure and mechanical properties of pure copper wire produced by shear assisted processing and extrusion

Shear assisted processing and extrusion (ShAPE) process can consolidate powdered materials and simultaneously extrude wire or tube with improved properties. We successfully produced copper wire extrusions from powder and solid materials for the first time. The extrusion pressure of ShAPE process is at least two times less than that required for conventional extrusion. We used optical microscopy to inspect and validate the integrity of extrudates. It shows that the microstructure was refined and dynamically recrystallized to equiaxial grains. Compared to the annealed copper wire, ShAPE processed wire has 80% higher yield strength, 15% higher ultimate tensile strength and 20% higher ductility. These were correlated with refined grain size and sub-structuring observed via electron backscatter diffraction (EBSD) and transmission electron microscopy (TEM).

Copper, Wire, Shear Assisted Processing and Extrus↗
DOE OSTI2018

Co-Extrusion of Zr Lined U-Zr Alloy Characterization Report

A feasibility study was undertaken to assess the feasibility of co-extruding U-10Zr and U-6Zr with a zirconium barrier on the outside surface. A U-10Zr and U-6Zr billet was cast, machined, and sealed in a zirconium can. The can was extruded with an extrusion ratio of approximately 35.5. After extrusion the extruded rods were sectioned for easier handling, radiographed, and metallographically examined. Radiography showed the rods to be solid with the exception of one location in the U-6Zr rod. Metallography showed the expected deformed microstructure in the longitudinal direction, although this was much less noticeable in the U-6Zr structure. Also seen in both rods microstructure was a zirconium gradient; the zirconium concentration was higher near the zirconium liner as compared to the interior of the rod. Based on the successful extrusion co-extrusion of U-Zr alloys with a zirconium liner is feasible.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗
DOE OSTI2021

Shear Assisted Processing and Extrusion of Thin-Walled AA6063 Tubing

Shear Assisted Processing and Extrusion (ShAPE) was used to fabricate thin-walled AA6063 tubing with improved mechanical properties compared to conventional extrusion. Namely, tensile properties for ShAPE extrusions after T5 heat treating far exceed conventional T5 properties and are on par with T6 tensile properties. Die rotational speed did not affect tensile properties, although increased extrusion speed did lead to moderate increases in elongation.

Friction Extrusion, ShAPE, AA 6063, friction stir ↗
DOE OSTI2019

Dynamic Recrystallization and Metal Flow Behavior of AZ31 Magnesium Alloy Bending Products Processed by Staggered Extrusion

Traditional curved products are obtained in two steps, which consist of an extrusion process and a bending process. There are many bottlenecks to this, such as long processing cycle, low efficiency, and difficulty in controlling the product quality. In this paper, a new staggered extrusion (SE) process was proposed to obtain magnesium alloy bending products. Bending products can be extruded by a staggered punch which has a step-like structure at one end. The experimental results show that with increased staggered distance (h) of the punch, the bending height of the bending products increased significantly. Compared with traditional extrusion, the grains of the bending products obtained by SE are refined. The increase in h is one of the reasons for the asymmetric distribution of axial velocity at the die exit of AZ31 magnesium alloy bending products. The asymmetric distribution of the flow velocity field of bending products during SE is one of the contributors for the bending characteristics to the bending products. The SE enables the use of extrusion in many applicable fields and enriches the types of bending products.

36 MATERIALS SCIENCE↗
DOE OSTI2018

What makes a material printable? A viscoelastic model for extrusion-based 3D printing of polymers

This paper presents a practical model for evaluating polymer feedstock materials as candidates for 3D printing across a variety of extrusion-based platforms. In order for a material to be successfully utilized for 3D printing operations, a series of fundamental conditions must be met. First, pressure-driven extrusion must occur through a given diameter nozzle at a specified flow rate. Second, the extruded material must form and sustain the desired shape. Third, the extruded structure must be able to bridge a specified gap and serve as a mechanically sound foundation for successive deposits. Finally, the deposited structure must be dimensionally stable during the transition to the final state (i.e. fully cured at room temperature). This article presents a framework for extrusion-based printing and a simple viscoelastic model for each of these conditions based on the rheological and thermo-physical properties of the candidate material and the processing parameters of the extrusion-based deposition platform. The model is demonstrated to be a useful tool for the evaluation of example test cases including: high temperature thermoplastics (polyphenylsulfone), fiber reinforced thermoplastics (acrylonitrile butadiene styrene), low-viscosity thermosets (epoxy resins), and thermoplastics with a high coefficient of thermal expansion (polypropylene).

36 MATERIALS SCIENCE↗
DOE OSTI2021

High speed manufacturing of aluminum alloy 7075 tubing by Shear Assisted Processing and Extrusion (ShAPE)

Shear assisted processing and extrusion (ShAPE) was used to extrude aluminum alloy 7075 tubing at speeds up to 12.2 m/min. This is in comparison to 2.0 m/min which is generally the limit for conventionally extruded 7075. The increased speed is primarily attributed to more extensive shear deformation, compared to conventional extrusion, which results in a high density of low angle grain boundaries that facilitate continued deformation and delay the onset of surface tearing. Mechanical testing after heat treating to the T6 condition gave an ultimate tensile strength of 565.3 ± 4.6 MPa, yield strength of 495.7 ± 8.7 MPa, and elongation of 16.8 ± 0.8%. Strength values exceed the ASTM minimum standard and are on par with ASM typical values, while elongation was substantially improved compared to 7 and 11% for the ASTM and ASM values respectively. Finally, it was observed that low temperature extrusion at 341 °C and 40 rpm gave superior material properties in the T6 condition compared to high temperature extrusion at 441 °C and 120 rpm due to variances in nanoscale second phase size and distribution.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Microstructure characterization of LAE442 magnesium alloy processed by extrusion and ECAP

The magnesium alloy LAE442 was processed by extrusion and equal channel angular pressing (ECAP) to achieve ultrafine grained microstructure. Detailed characterization of the microstructure was performed by scanning electron microscope, electron back scattered diffraction (EBSD) and transmission electron microscope. The initial, as-cast, microstructure consisted of large grains of ~ 1 mm. The grain refinement due to the processing by severe plastic deformation led to a decrease of the average grain size to ~ 1.7 μm after the final step of ECAP. A detailed characterization of secondary phases showed the precipitation of Al{sub 11}RE{sub 3}, Al{sub 2}Ca and Al{sub 10}RE{sub 2}Mn{sub 7} intermetallic phases. X-ray diffraction measurements proved that Li is dissolved within the magnesium matrix in the as-cast condition. Newly formed Al{sub 3}Li phase was observed after ECAP. The texture formation due to the extrusion and ECAP was different from that in the other magnesium alloys due to the activation of non-basal slip systems as a result of the decrease of the c/a ratio. - Highlights: • Combined extrusion and equal channel angular pressing results in significant grain refinement by factor 1000 approximately. • Al{sub 11}RE{sub 3}, Al{sub 2}Ca and Al{sub 10}RE{sub 2}Mn{sub 7} secondary phases are present in the as-cast material while Li was dissolved in the Mg matrix. • Extrusion and ECAP have no effect on the composition of the secondary phases but they influence strongly their distribution. • Texture evolution is affected by decrease of c/a ratio due to the presence of Li and resulting activation of non-basal slip.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Analysis of contact conditions and microstructure evolution in shear assisted processing and extrusion using smoothed particle hydrodynamics method

Shear assisted processing and extrusion (ShAPE) is a solid-phase processing technique that adds an additional shear force as compared with a conventional extrusion approach. Recently, ShAPE has demonstrated the capability of extruding high-performance aluminum alloy 7075 (AA7075) tubes at speeds up to 12.2 m/min without surface tearing. However, the relationship among the ShAPE processing parameters, thermomechanical conditions, contact conditions, heat generation, and microstructure evolution remains primarily empirical because an insightful understanding of the associated physics is still lacking. To help elucidate these relationships, this work proposes a thermomechanical meshfree model for the first time for ShAPE processing of AA7075 using the smoothed particle hydrodynamics (SPH) method. The meshfree model is first validated thoroughly by experimental data in terms of material flow, die face temperature, and extrusion force with various processing parameters. The validated model is then used to analyze the steady-state contact conditions and heat generation rates during ShAPE processing. Distributions of the average grain size of AA7075 being extruded are calculated using the SPH model output. The meshfree model results reveal that extrusions conducted at lower temperatures and higher strain rates yield more refined grains and possibly higher material strength, which is also consistent with the experimental observations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Porosity evolution during heating of copper made from powder by friction extrusion

Here, friction extrusion was used to compact and extrude solid copper rod from feedstock powders. Following extrusion, considerable porosity was observed throughout the extrudate cross section due to the entrained porosity in the feedstock material and the extrusion process. The thermal stability of the extrudate was investigated via a series of heat treatments. Porosity evolution exhibited three distinct stages—an unchanged plateau (0°C–300°C) followed by an abrupt increase (400°C–500°C) and ultimately a reduction, as the temperature increases (>500°C). The peak porosity measured was ~25%. The underlying driving force for pore evolution is described as the competition between the internal pore pressure, material strength, and sintering kinetics, as a function of temperature. The observed porosity evolution and driving force are not expected to be limited to copper. Thus, this manuscript reveals an important consideration regarding elevated-temperature thermal stability as advanced manufacturing methods involving direct powder extrusion are explored.

36 MATERIALS SCIENCE↗
DOE OSTI2017

PVC extrusion development and production for the NOvA neutrino experiment

We have produced large and highly-reflective open-cell PVC extrusions for the NOvA neutrino oscillation experiment. The extrusions were sealed, instrumented, assembled into self-supporting detector blocks, and filled with liquid scintillator. Each Far Detector block stands 15.7 m high, is 15.7 m wide and 2.1 m thick. More than 22,000 extrusions were produced with high dimensional tolerance and robust mechanical strength. This paper provides an overview of the NOvA Far Detector, describes the preparation of the custom PVC powder, and the making of the extrusions. As a result, quality control was a key element in the production and is described in detail.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2021

Eliminating Yield Anisotropy and Enhancing Ductility in Mg Alloys by Shear Assisted Processing and Extrusion

Solid phase processing techniques such as friction stir welding, Shear assisted processing and extrusion (ShAPE)/ friction extrusion and cold spray have been successfully demonstrated as promising thermomechanical methods to produce metallic materials with enhanced performance. In this study, AZ series with and without silicon, ZK60 Mg alloys in as-received forms (as-cast or as-extruded) were processed using Shear Assisted Processing and Extrusion (ShAPE). Microstructural characterization was performed using EBSD and TEM and revealed that as compared to the feedstock materials/ billets, friction extruded Mg alloys had more uniform microstructure, equiaxed grains, finer and homogeneously distributed precipitates and chemical homogeneity. It was also observed that basal planes were not oriented parallel to extrusion axis. As a result, rod products exhibited significantly reduced (in some cases eliminated) yield asymmetry and achieved enhanced ductility, which were uncommon or difficult to attain using conventional processing techniques. In addition, modified texture likely suppressed deformation twinning under compressive deformation.

Shear Assisted Processing and Extrusion, SHAPE, ma↗
DOE OSTI2024

Vacuum-assisted extrusion to reduce internal porosity in large-format additive manufacturing

Large-scale 3D printing of polymer composite structures has gained popularity and seen extensive use over the last decade. Much of the research related to improving the mechanical properties of 3D-printed parts has focused on exploring new materials and optimizing print parameters to improve geometric control and minimize voids between printed beads. However, porosity at the microstructural level (within the printed bead) has been much less studied although it is almost universally observed at levels of 4 %-10 % when using fiber reinforced materials. This study introduces a vacuum-assist approach that minimizes internal porosity by removing ambient air from the interstitial space between pellets in the hopper and acts as a negative pressure vent for gases that evolve during the initial stages of single-screw extrusion. Vacuum-assisted extrusion was able to reduce porosity below 2 % across a wide range of processing parameters, moisture content, fiber reinforcements, and printing platforms. Specifically, when printing on a large-format extruder (Strangpresse Model-30), the vacuum-assisted extrusion reduced internal porosity by 35–75 % compared to conventional non-vacuum extrusion, and only pores with length scale > 2 microns are affected. The success of this approach prompted the design of a patent-pending continuous vacuum hopper relevant for large-scale 3D printing on commercial systems.

36 MATERIALS SCIENCE↗
DOE OSTI2019

On the Mechanism of Bilayer Separation by Extrusion, or Why Your LUVs Are Not Really Unilamellar

Extrusion through porous filters is a widely used method for preparing biomimetic model membranes. Of primary importance in this approach is the efficient production of single bilayer (unilamellar) vesicles that eliminate the influence of interlamellar interactions and strictly define the bilayer surface area available to external reagents such as proteins. Sub-microscopic vesicles produced using extrusion are widely assumed to be unilamellar, and large deviations from this assumption would dramatically impact interpretations from many model membrane experiments. In this work, using three probe-free methods—small-angle X-ray and neutron scattering (SAXS and SANS) and cryogenic electron microscopy (cryoEM)—we report unambiguous evidence of extensive multilamellarity in extruded vesicles composed of neutral phosphatidylcholine lipids, including for the common case of neutral lipids dispersed in physiological buffer and extruded through 100 nm diameter pores. In such preparations, only ~35% of lipids are externally accessible, and this fraction is highly dependent on preparation conditions. Charged lipids promote unilamellarity, as does decreasing solvent ionic strength, indicating the importance of electrostatic interactions in determining the lamellarity of extruded vesicles. Smaller extrusion pore sizes also robustly increase the fraction of unilamellar vesicles, suggesting a role for membrane bending. Taken together, these observations suggest a mechanistic model for extrusion, wherein formation of unilamellar vesicles involves competition between bilayer bending and adhesion energies. The findings presented here have wide-ranging implications for the design and interpretation of model membrane studies, especially ensemble-averaged observations relying on the assumption of unilamellarity.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2018

Enhanced strength and toughness in ultra-fine grained 99.9% copper obtained by cryo-hydrostatic extrusion

Highlights: • Cryo-HE can increase the yield strength of Cu by more than threefold. • In cryo-HE of Cu, the grain refinement is stronger by 30% than in room-HE. • Cryo-HE with post-annealing effectively creates a bimodal microstructure in Cu. • Short-term post-annealing applied to cryo-HE-treated Cu can double its ductility. • Grain refinement with recrystallization results in a slight increase of Cu toughness. - Abstract: Ultrafine grained 99.9% Cu with enhanced strength and toughness was produced by hydrostatic extrusion conducted at the temperature of liquid nitrogen. The cryo-extruded Cu has a tensile yield strength of 490 MPa, hardness of 145 HV0.2, and tensile fracture toughness of 39.5 MPa m{sup 1/2}, which means that their values increased by 380%, 185% and ~10%, respectively, compared to those of the starting material. The significant strengthening is due to the strong grain refinement to 320 nm and the high energy of defects stored during the processing at liquid nitrogen temperature. The short term post deformation annealing doubles the ductility of material even by above 10% of the elongation to fracture at a slight expense of the yield strength (485 MPa). The observed behavior of Cu can be explained in terms of its low stacking fault energy, the susceptibility to dynamic recrystallization within the working zone of the extrusion die, and the triaxial strain components with the very large strain gradients, combined with the significant adiabatic heating effect active during the hydrostatic extrusion. The better homogeneity of the grain refinement and the higher efficiency of the distribution of defects and of the energy storage accompanied by the decreased dislocation mobility during the cryo hydrostatic extrusion contributed to the higher strength.

36 MATERIALS SCIENCE↗