Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “Tensile testing”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

Laser Powder Directed Energy Deposition of Steels for Nuclear Applications

This comprehensive investigation examines the structure–property relationships in two nuclear alloy systems—Alloy 709 (A709) austenitic stainless steel and Grade 92 (G-92) ferritic/martensitic (F/M) steel—manufactured via directed energy deposition (DED) for sodium-cooled fast reactor applications. This study establishes the fundamental mechanisms for controlling microstructures for optimizing the mechanical performance of additively manufactured nuclear materials through systematic heat treatment optimization and multiscale characterization. As-deposited A709 steel develops a complex multiscale strengthening architecture consisting of a fine cellular solidification structure with diameter of 2-3 µm within10–50 µm grains, elevated dislocation densities from rapid thermal cycling, and grain boundary precipitates that activate concurrent Hall–Petch, dislocation, and precipitation hardening mechanisms to achieve exceptional properties [yield strength (YS): 603 MPa, ultimate tensile strength (UTS): 844 MPa, Vickers hardness: 220 HV] that achieve a 44% superior strength compared to that of the wrought material. Heat treatments produce different results. Solution annealing (SA) dissolves the cellular structure and reduces the hardness to 190 HV. Precipitation treatment (PT) keeps the cellular structure but adds carbides, allowing the hardness to reach 205 HV. The best approach combines both treatments (SA+PT) and creates uniform precipitate distributions with M 23 C 6 carbides at the grain boundaries and MX carbonitrides in the matrix, achieving a hardness of 195 HV. However, directional differences persist, with a 12%–15% strength variation between orientations due to the inherited layered microstructural architecture that survives aggressive heat treatment. While tensile testing at 550°C demonstrates 40%–50% thermal softening with dynamic strain aging, DED A709 steel still maintains a 71% higher YS than that of the wrought material. Ion irradiation studies (100–400 dpa) of DED A709 steel reveal progressive radiation damage with increasing void density and radiation-induced segregation causing nickel enrichment and chromium depletion, which will ultimately compromise mechanical properties. As-deposited G-92 exhibits exceptional strength (UTS: 1650–1700 MPa, 430 HV) through a complex microstructure containing both ferrite and martensite phases, a high geometrically necessary dislocation (GND) density (17.04×10 14 /m 2 ), and fine carbides. Heat treatments create distinct changes. Normalizing produces fresh martensite with the highest hardness (460 HV) and an increased GND density (20.23×10 14 /m 2 ). Tempering develops dual precipitation systems and reduces the hardness to 290 HV. The optimal approach uses sequential normalizing plus tempering, achieving balanced properties with the lowest hardness (250 HV) and a reduced GND density (11.01×10 14 /m 2 ). A processing-dependent anisotropy is observed: horizontal specimens achieve superior ductile behavior, while vertical specimens exhibit brittle failure. A tempering heat treatment successfully mitigates this anisotropic behavior by transforming the hard martensitic as-deposited structure into tempered martensite enabling both horizontal and vertical specimens to exhibit similar stress–strain characteristics with visible necking behavior. Remarkably, testing at 550°C reveals a reversal in the anisotropy, where as-deposited specimens achieve near isotropy with superior thermal stability (a 15%–20% strength reduction), while tempered specimens develop an orientation dependence with a 25%–30% strength reduction. Both alloy systems demonstrate that DED processing creates specimens with a superior strength through refined microstructural features, though with distinct strengthening mechanisms—austenitic through cellular structures and precipitates versus F/M through phase transformations and precipitates. Heat treatment optimization requires alloy-specific approaches, with A709 benefiting from controlled precipitation while G-92 requires careful phase transformation control. The results show that DED manufacturing can produce nuclear materials with exceptional performance, but directional effects and temperature-dependent behavior must be carefully considered for reactor component design and qualification.

22 GENERAL STUDIES OF NUCLEAR REACTORS↗
DOE OSTI2024

Materials Characterization: A Primer for Solid Phase Processing Applications

The Pacific Northwest National Laboratory (PNNL) undertook the Materials Characterization, Prediction, and Control (MCPC) Laboratory Directed Research and Development (LDRD) Project to advance understanding of nuclear material processing and enable multifold acceleration in the development and qualification of new material systems produced via advanced manufacturing methods, such as solid phase processing, for use in national security and advanced energy applications (Smith 2021). As a two-year LDRD investment requiring focused research, the MCPC project applied only a subset of the wide range of available destructive and nondestructive characterization methods to provide data to the predictive modeling and data analytics tasks. The purpose of this report is to review a wide range of destructive and nondestructive characterization methods that are relevant in solid-phase processing (SPP) applications, but not necessarily applied in the MCPC Project as a guide to the planning of characterization activities in future research. Particular attention is given to measured characteristics that can correlate to other material characteristics, with a particular interest in nondestructive evaluation (NDE) that can be applied to samples obtained in the MCPC Project. Destructive examinations include tensile tests, optical and electron microscopy, micro-hardness, and residual stress tests. NDE tests include surface visual inspection, eddy current examination for cracks, 4-point potential drop, ultrasound, x-ray, and computed tomography.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Gaseous Hydrogen Embrittlement of L-PBF Ni-Based Superalloys for Service in Natural Gas Turbines

Efforts to improve efficiency of industrial gas turbine engines have focused on increasing operating temperatures by use of fuel-flexible gas blends. Ni-based superalloys are susceptible to hydrogen embrittlement (HE), leading to potential risk of premature component failure. Certain turbine components exposed to hydrogen-rich environments are manufactured from additive processes like laser powder bed fusion (L-PBF). The HE susceptibility was evaluated for three Ni-based superalloys: solid solution strengthened Alloy 625, γ’/γ’’-precipitation strengthened Alloy 718, and γ’-precipitation strengthened Haynes® 282®. L-PBF samples were pre-charged under medium and high pressure gaseous hydrogen before tensile testing at temperatures up to 260 °C using a fast strain rate. Selected samples were subjected to a service conditioning heat treatment prior to hydrogen charging to evaluate the change in susceptibility after prolonged service. The susceptibility to HE and HE mechanisms of these three alloys is compared.

additive manufacturing↗
DOE OSTI2024

Lattice Design and Advanced Modeling to Guide the Design of High-Performance Lightweight Structural Materials

Lightweight structural materials are required to increase the mobility of fission batteries. The materials must feature a robust combination of mechanical properties to demonstrate structural resilience. The primary objective of this project is to produce lightweight structural materials whose strength-to-weight ratios exceed those of the current widely used structural materials such as 316L stainless steels (316L SS). To achieve this, advanced modeling and simulation tools were employed to design lattice structures with different lattice parameters and different lattice types. A process was successfully developed for transforming lattice-structures models into Multiphysics Object Oriented Simulation Environment (MOOSE) inputs. Finite element modeling (FEM) was used to simulate the uniaxial tensile testing of the lattice-structured parts to investigate the stress distribution at a given displacement. The preliminary results showed that the lattice-structured sample displayed a lower Young’s modulus in comparison with the solid material and that the unit cell size of the lattice had a minimal effect. The novelty here is to apply up-front modeling to determine the best structure for the application before actually producing the sample. The approach of using modeling as a guiding tool for preliminary material design can significantly save time and cost for material development.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Deformation Behavior of β Phase in a WE54 Magnesium Alloy

Second phases play a significant role in the development of high-performance magnesium alloys with rare earth elements. Here, in situ tensile tests combined with synchrotron radiation were carried out to investigate the deformation behavior of β phases in a WE (Mg–Y–Gd–Nd) alloy. By lattice strain analysis, it was found that micro load continuously transferred from the soft α-Mg matrix to the hard β phases during the whole plastic deformation, while this behavior was much more obvious at the beginning of deformation. Based on diffraction peak broadening, Williamson–Hall (W–H) plotting was used to study the microstrain of β phases. The results showed that the microstrain of β phases increased rapidly within 4% plastic strain and reached the maximum at plastic strain of ~6.5%. Since the β phases acted as hard phases, the microstrain was considered as a sign of the stress concentration near phase interfaces. It was also suggested that the effective release of local stress concentration at the β/α-Mg interface benefited the ductility of the WE alloy by the plastic deformation of β phases and phase interface sliding.

36 MATERIALS SCIENCE↗
DOE OSTI2021

The Role of Retained Austenite in Tempered Martensite Embrittlement of 4340 and 300-M Steels Investigated through Rapid Tempering

Tempered martensite embrittlement (TME) is investigated in two medium carbon, high strength steels, 4340 (low silicon) and 300-M (high silicon), via rapid (1, 10, or 100 s) and conventional (3600 s) tempering. Rapid tempering of 4340 diminishes the depth of the TME toughness trough, where improvements in impact toughness correspond to the suppression of retained austenite decomposition. In 300-M, retained austenite decomposition is suppressed to an even greater extent by rapid tempering. While toughness improves overall after rapid tempering, TME severity remains consistent in 300-M across the tempering conditions examined. Through interrupted tensile tests, it was found that the 300-M conditions that exhibit TME are associated with mechanically unstable retained austenite. Unstable retained austenite is shown to mechanically transform early in the deformation process, presumably resulting in fresh martensite adjacent to interlath cementite that ultimately contributes to TME. The present results emphasize the role of both the thermal decomposition and mechanical transformation of retained austenite in the manifestation of TME.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Neutron Imaging of Al6061 Prepared by Solid-State Friction Stir Additive Manufacturing

Solid-state Friction Stir Additive Manufacturing has recently gained attention as a result of its capacity to fabricate large-scale parts while preserving the mechanical properties of the feedstock material. However, the correlation between the quality of layer-by-layer bonding of the deposited metal and processing parameters has remained unknown. Neutron imaging techniques, with 90% total transmission per cm, are employed for Al6061 parts fabricated by MELD ® Technology as a non-destructive evaluation approach for the first time to investigate the layer-by-layer structure of a stadium-shaped ingot in different sections. The post-processed results show the fabricated parts with an optimized set of processing parameters are void-free. However, the hydrocarbon-based feedstock lubricant segregates between the layers, which consequently may lead to non-uniform weaker mechanical properties along the build direction and stimulate crack initiation during mechanical loading. The tensile test results show 14% lower strain-to-failure values in alleged contaminated areas in transmission imaging results. Additionally, layer bonding is significantly impacted by hot-on-hot and hot-on-cold layer deposition schemes, especially for larger layer thicknesses.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Tensile Performance Sensitivity to Variations of Standard 17-4 PH Heat Treatments on LPBF-Produced Material

Standard heat treatments for metals of a particular composition are typically designed with the assumption of a conventional starting microstructure, such as that produced by casting or wrought processing. When applied to metals fabricated by Laser Powder Bed Fusion (LPBF) metal additive manufacturing (AM), these heat treatments can produce inconsistent performance due to the unique as-built microstructures. This study investigates how modifications to standard heat treatments for 17-4 PH steel influence the microstructure and mechanical properties of LPBF-fabricated material. Specimens were produced and subjected to varying solutionizing and homogenizing treatments followed by standard aging treatments. Microstructures were characterized using optical microscopy, Electron Backscatter Diffraction (EBSD), and X-ray diffraction (XRD), and mechanical properties were evaluated through uniaxial tensile testing. Based on these results, recommendations are provided for achieving improved wrought-like performance in LPBF 17-4 PH steel.

17-4 PH↗
DOE OSTI2020

Styrene-Based Elastomer Composites with Functionalized Graphene Oxide and Silica Nanofiber Fillers: Mechanical and Thermal Conductivity Properties

The mechanical and thermal conductivity properties of two composite elastomers were studied. Styrene–butadiene rubber (SBR) filled with functionalized graphene oxide (GO) and silica nanofibers, and styrene–butadiene–styrene (SBS) block copolymers filled with graphene oxide. For the SBR composites, GO fillers with two different surface functionalities were synthesized (cysteamine and dodecylamine) and dispersed in the SBR using mechanical and liquid mixing techniques. The hydrophilic cysteamine-based GO fillers were dispersed in the SBR by mechanical mixing, whereas the hydrophobic dodecylamine-based GO fillers were dispersed in the SBR by liquid mixing. Silica nanofibers (SnFs) were fabricated by electrospinning a sol–gel precursor solution. The surface chemistry of the functionalized fillers was studied in detail. The properties of the composites and the synergistic improvements between the GO and SnFs are presented. For the SBS composites, GO fillers were dispersed in the SBS elastomer at several weight percent loadings using liquid mixing. Characterization of the filler material and the composite elastomers was performed using x-ray photoelectron spectroscopy, x-ray diffraction, transmission electron microscopy, scanning electron microscopy, thermogravimetric analysis, dynamic mechanical analysis, tensile testing, nanoindentation, thermal conductivity and abrasion testing.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Stable, Ductile and Strong Ultrafine HT-9 Steels via Large Strain Machining

Beyond the current commercial materials, refining the grain size is among the proposed strategies to manufacture resilient materials for industrial applications demanding high resistance to severe environments. Here, large strain machining (LSM) was used to manufacture nanostructured HT-9 steel with enhanced thermal stability, mechanical properties, and ductility. Nanocrystalline HT-9 steels with different aspect rations are achieved. In-situ transmission electron microscopy annealing experiments demonstrated that the nanocrystalline grains have excellent thermal stability up to 700 °C with no additional elemental segregation on the grain boundaries other than the initial carbides, attributing the thermal stability of the LSM materials to the low dislocation densities and strains in the final microstructure. Nano-indentation and micro-tensile testing performed on the LSM material pre- and post-annealing demonstrated the possibility of tuning the material’s strength and ductility. The results expound on the possibility of manufacturing controlled nanocrystalline materials via a scalable and cost-effective method, albeit with additional fundamental understanding of the resultant morphology dependence on the LSM conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Ultrasonic Additive Manufacturing

Ultrasonic additive manufacturing (UAM) is a solid-state hybrid manufacturing technique that leverages the principles of ultrasonic welding, mechanized tape layering, and computer numerical control (CNC) machining operations to create three-dimensional metal parts. This article begins with a discussion on the process fundamentals and process parameters of UAM. It then describes metallurgical aspects in UAM. The article provides a detailed description of a wide range of mechanical characterization techniques of UAM, namely tensile testing, peel testing, and pushpin testing. The article ends with information on sensor embedding.

Niyanth S, Niyanth↗
DOE OSTI2021

Process Robustness of Friction Stir Dovetailing of AA7099 to Steel with In Situ AA6061 Interlayer Linking

Rolled homogeneous armor (RHA) steel was joined to aluminum alloy AA7099-T7451 with an interlayer of AA6061-T651 by single-pass friction stir dovetailing (FSD). The evolution of the AA7099/AA6061 and AA6061/steel interfacial microstructures and mechanical properties of the joints were examined. The AA6061 interlayer prevented Zn migration from the AA7099 to the steel during FSD and inhibited formation of brittle, Zn-rich, Fe-Al intermetallic compounds within the joint. The flow of the dissimilar aluminum alloys at the interface was controlled with a partially threaded friction stir welding pin and a dovetail geometric configuration optimized in previous work. The process robustness was explored to establish parameter windows by elucidating parametric effects on the relationship between process conditions and the joint’s microstructure and mechanical properties. Ranges of process forge force (50–70 kN) and interface temperature (475°C–515°C) consistently yielded joints with adequate performance. The load-carrying capacity in lap shear tensile tests was 2025 ? 100 N/mm.

Friction Stir Dovetailing, FSW, AA7099, AA6061, Ro↗
DOE OSTI2021

The Role of Interface in Additively Manufactured Interpenetrating Composites

Additively Manufactured Interpenetrating Composites (AMIPCs) are a relatively new metal-metal chain composite in development for use in high energy absorption systems. In this system, reinforcing phase of additively manufactured continuous lattice configurations 316L austenitic stainless-steel is in melt infiltrated with a matrix phase of A356 aluminum-silicon casting alloy. Measurements and observations of this material system have shown that weakly bonded or open/porous interface between the reinforcement and matrix phases exhibits dramatically different mechanical properties of AMIPCs, which is not currently well understood. In this work, Finite Element Models (FEM) are used to model the effects of interfaces between the composite phases. Mechanical tensile tests measurements of various composite volume fractions and varying degrees of casting infiltration are also examined and used to show consistency with the FEM results. The outcome provides insight into material design criteria and performance predictions for new hybrid material systems with exceptional damage tolerance.

Allen, Jason↗
DOE OSTI2023

Investigation of the Hydrogen Embrittlement of API 5L Natural Gas Pipeline Steels

Hydrogen ions produced during corrosion or through hydrogen blending into natural gas pipelines can lead to the degradation of ductility of metals used in these transmission pipelines. The effect of hydrogen on the mechanical properties of pipeline steels was studied for three grades of API 5L steels: X56, X65, and X100. These steels are either commonly used in or considered for use in natural gas transmission pipelines which are being considered for use in hydrogen blending. These steels were subjected to constant strain rate tensile testing after charging with electrochemically generated hydrogen. This presentation reports on work to extend the life of the natural gas pipeline network via understanding the effect of hydrogen embrittlement induced by corrosion processes.

Teeter, Lucas↗
DOE OSTI2026

INFLUENCE OF SUPPLEMENTARY ARGON GAS SHIELDING ON THE MICROSTRUCTURE AND MECHANICAL BEHAVIOR OF SS316L ADDITIVELY MANUFACTURED BY DIRECTED ENERGY DEPOSITION

The dissolution of atmospheric gases into parts additively manufactured by directed energy deposition (DED) has long been of concern, and stock shielding solutions have usually proven inadequate at fully removing atmospheric gases from weld beads. The objective of this work was to design a new supplementary argon gas shroud for a specific DED printer and evaluate its effect on microstructure and macroscopic properties of SS316L and the potential for printing more reactive metals such as Ti-6Al-4V. This was investigated by printing four SS316L sample blocks, two with and two without the shroud, each printed in two different orientations. These samples were subsequently evaluated with inert gas fusion (IGF), SEM/EDS imaging, and tensile tests. The shroud reduced oxygen content by 0.019-0.031%, and SEM imaging revealed fewer oxide inclusions. A more dramatic reduction of 0.13% oxygen and 0.171% nitrogen was observed by the inert gas fusion of Ti-6Al-4V samples. Overall, the results indicated the shroud was successful at reducing atmospheric gas uptake within the print region and may enable the printing of reactive metal powders in DED systems.

Helvie, Kyle↗
DOE OSTI2023

Multifunctional Fiber-Reinforced Polymer Composites for Damage Detection and Memory

Self-structural health monitoring (SHM) functionalities for fiber-reinforced polymer composites have become highly sought after to ensure the structural safety of newly advancing components in the automotive, civil, mechanical, and aerospace industries. This paper introduces a self-damage detection and memory (SDDM) hybrid composite material, where the structural carbon fiber tow is transformed into a piezoresistive sensor network, and the structural glass fiber operates as electrical insulation. In this study, SDDM specimens were fabricated, and tensile and impact tests were performed. The tensile tests of SDDM specimens find two distinct loading peaks: first where the carbon fiber fails, and second where the glass fiber fails. A linear correlation was observed between the carbon fiber resistance and composite strain up to a threshold, beyond which a sharp nonlinear increase in resistance occurred. The resistance then approached infinity, coinciding with the first loading peak and failure of the carbon fiber elements. This demonstrates the potential for a damage early warning threshold. Additionally, the effect of stitching the sensor tow in a zig-zag pattern over a large area was investigated using tailored fiber placement (TFP) of 1-loop, 3-loop, and 5-loop specimens. Tensile testing found that increasing the number of loops improved the sensor’s accuracy for strain sensing. Furthermore, impact tests were conducted, and as the impact energy progressively increased, the sensor resistance permanently increased. This illustrates a capability for self-memory of microdamage throughout the life cycle of the structure, potentially useful for predicting the remaining life of the composite.

Demo, Luke B. (ORCID:0000000208806522)↗
DOE OSTI2022

Effects of surface treatments on ABS mechanical properties from fused filament fabrication

This paper examines the influence of surface treatments on the mechanical properties of acrylonitrile butadiene styrene (ABS) samples printed by fused filament fabrication (FFF). Prior efforts have applied brushing, painting, solvent dipping, infiltration, and vapor smoothing as post-processing surface treatments to improve the mechanical properties of FFF components. Additionally, because FFF can produce components with undesirable surface roughness, mechanical abrasion, epoxy coating, and acetone treatment may increase tensile strength by decreasing stress concentrations. Ridged surface texture may provide desirable tribological or handling properties. Based on these opportunities, this paper investigates abrasive media blasting, epoxy coating, acetone immersion, and ridged texturing surface treatments on the tensile strength and other mechanical properties of FFF ABS samples. ASTM D638-14 Type-I samples were printed, treated on all sample sides, and tested. From tensile tests, the elastic modulus, tensile strength, and fracture strain for both the untreated and treated ABS samples were calculated. For each sample, the surface finish and fracture macromorphology were observed with optical microscopy and the roughness values for the surface finish were calculated from profilometer data. Furthermore, samples were submerged in water and weighed periodically to measure mass changes due to water absorption. From surface profilometry and optical miscopy data, mechanical media blasting, epoxy coating, and immersion in all concentrations of acetone decreased surface roughness. Overall, on average, grit blasting with large beads and epoxy coating led to 2.6% and 1.2% increases in tensile strength, respectively; immersion in 40% acetone led to a 1.9% increase in tensile strength while treatment in 60% and 80% acetone decreased tensile strength by 4.9% and 1.9%, respectively. The study concludes that only grit blasting with large beads, immersion in 60% acetone, and the ridged texture significantly affected the tensile strength.

36 MATERIALS SCIENCE↗
DOE OSTI2021

A review of technologies for welding magnesium alloys to steels

Here we review various state-of-the-art methods for welding magnesium alloys and steels using different joint configurations. Microstructural characterizations indicate that four microstructures may form at the Mg/steel interface after welding: unwelded gap, metal oxides, solid solutions, or intermetallic compounds. Reaction products at the Mg/steel interface vary with different welding methods, alloying elements in base materials, interlayers or coatings applied, and preparations of base material before welding. Regarding mechanical property characterization, (a) lap tensile shear testing for lap-welded and spot-welded joints, (b) tensile testing for butt-welded joints and (c) fatigue properties of lap-welded and spot-welded joints are summarized and compared, separately. Reaction products at the Mg/steel interface are correlated with mechanical properties. Finally, ways to enhance Mg/steel joint strength, such as introducing interlocking features during friction stir lap and butt welding, are discussed.

Wang, Tianhao↗