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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

Achieving Superior Two-Way Actuation by the Stress-Coupling of Nanoribbons and Nanocrystalline Shape Memory Alloy

Inspired by the driving principle of traditional bias-type two-way actuators, we developed a novel two-way actuation nanocomposite wire in which a massive number of Nb nanoribbons with ultra-large elastic strains are loaded inside a shape memory alloy (SMA) matrix to form a continuous array of nano bias actuation pairs for two-way actuation. The composite exhibits a two-way actuation strain of 3.2% during a thermal cycle and an actuation stress of 934 MPa upon heating, which is about twice higher than that (~500 MPa) found in reported two-way SMAs. Upon cooling, the composite shows an actuation stress of 134 MPa and a mechanical work output of 1.08*106 J/ m3, which are about three and five times higher than that of reported two-way SMAs, respectively. It is revealed that the massive number of Nb nanoribbons in compressive state provides the high actuation stress and high work output upon cooling and the SMA matrix with high yield strength offers the high actuation stress upon heating. Compared to traditional bias-type two-way actuators, the two-way actuation composite with small volume and simple construct is in favour of the miniaturization and simplification of actuators.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Influence of Thermomechanical Treatment on Structural-Phase Transformations and Mechanical Properties of the Cu–Al–Ni Shape-Memory Alloys

Using the methods of optical and electron microscopy and electron and X-ray diffraction analyses, the influence of thermomechanical treatment on the mechanical properties, average grain size, and structural and phase transformations is investigated in the Cu–Al–Ni triple alloys exhibiting a shape memory effect. In the alloys under study with a fixed content of 3wt% Ni the concentration of aluminum was varied from 9 to 14 wt%. It is shown that in the alloys subjected to thermal treatment, including forging and homogenizing annealing using controlled recrystallization in the austenitic state followed by quenching, the grain-boundary disintegration and segregation disappear. It is found out that the microstructure of the alloys in the hot-forged and hardened states with the content of aluminum 9–10 wt%. consists of the grains of the average dimensions within 60–80 μm, with the content of aluminum 10–12 wt% – 100–350 μm, while in the alloys with the content of aluminum up to 14 12 wt% the average grain size reaches 1 mm. According to the data of mechanical testing at room temperature, with a decrease in the content of aluminum the ultimate tensile strength (σ{sub UTS}), the yield strength (σ{sub М}) and the relative elongation (δ) increase. An improvement of the mechanical properties of the alloys is attributed to the grain structure refinement of the β{sub 2}-austenite and package substructure of the β'{sub 1}-and γ'{sub 1}-martensites as the content of aluminum in the alloys decreases. For instance, in the fine-grained alloys containing 9.2 and 9.5 wt% Al the value of relative elongation remains at a high level (>10%), while for the other alloys with 10–14 wt% Al it does not exceed 5%. As the content of aluminum in the alloys decreases, the character of the specimen fracture under uniaxial tension changes (from brittle to ductile).

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Martensite crystal structure in Ru-based high temperature shape memory alloys

Highlights: • A three level twinned microstructure is recognized in the β″ phase. • Wavy contrast boundaries which are typical for translation interfaces • Displacements are translations of tetragonal β′ phase, lost during transformation. • Six times bigger monoclinic cell is characterized by the disappearance of 5 translations. - Abstract: High temperature shape memory alloys RuNb and RuTa were investigated by X-ray diffraction in order to determine the structure of the low temperature β” martensite. Powder X-ray diffraction and Rietveld analysis confirm the monoclinic symmetry and allow a precise determination of the atom positions. The low temperature microstructure is the result of a martensitic transformation from a tetragonal β′ martensite. The analysis of how it is controlled by the space groups of the two phases and by their relative orientation is performed by transmission electron microscopy. A three level twinned microstructure is recognized in the β” phase. The investigation at the smallest scale twins reveals the presence of wavy contrast boundaries which are typical for translation interfaces. High resolution transmission electron microscopy images, accompanied by phase contrast imaging analysis, have been used to determine the translation vectors associated to the interfaces. These displacements are the translations of the tetragonal β′ phase which are lost during the transformation. The combination of X-ray diffraction and transmission electron microscopy investigation allows the suggestion of a global distortion mechanism that explains the atomic displacements in the β” form.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Study of the microstructure evolution of heat treated Ti-rich NiTi shape memory alloy

Martensitic evolution in Ti-rich NiTi alloy, Ti50.5Ni49.5, has been investigated as a function of annealing, solution treatment and a combination thereof and a detailed electron microscopic investigation carried out. Self-accommodated martensite plates resulted in all heat treated samples. Martensitic < 011 > type II twins, which are common in NiTi shape memory alloys, was found in both as-received and heat-treated samples. Solution treated samples, additionally, showed {11-1} type I twinning was also found in samples that have been annealed after solution-treatment. Another common feature of the microstructure in both as-received and heat treated samples is the formation of Ti{sub 2}Ni precipitates. The size, number and dispersions of these precipitates can be controlled by resorting to a suitable heat treatment e.g. solution treatment.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Microstructures, Martensitic Transformation, and Mechanical Behavior of Rapidly Solidified Ti-Ni-Hf and Ti-Ni-Si Shape Memory Alloys

In this work, the microstructure and mechanical properties of rapidly solidified Ti{sub 50−x/2}Ni{sub 50−x/2}Hf{sub x} (x = 0, 2, 4, 6, 8, 10, and 12 at.%) and Ti{sub 50−y/2}Ni{sub 50−y/2}Si{sub y} (y = 1, 2, 3, 5, 7, and 10 at.%) shape memory alloys (SMAs) were investigated. The sequence of the phase formation and transformations in dependence on the chemical composition is established. Rapidly solidified Ti-Ni-Hf or Ti-Ni-Si SMAs are found to show relatively high yield strength and large ductility for specific Hf or Si concentrations, which is due to the gradual disappearance of the phase transformation from austenite to twinned martensite and the predominance of the phase transformation from twinned martensite to detwinned martensite during deformation as well as to the refinement of dendrites and the precipitation of brittle intermetallic compounds.

36 MATERIALS SCIENCE↗
DOE OSTI2017

Giant and reversible room-temperature magnetocaloric effect in Ti-doped Ni-Co-Mn-Sn magnetic shape memory alloys

The practical applications of magnetocaloric materials for magnetic refrigeration require not only large magnitude but also reversibility, as well as room-temperature operating temperature, of the magneto caloric effect. However, it is a complex problem to simultaneously meet these demands in the Heusler-type Ni-(Co)-Mn-X (X = In, Sn, Sb, Ga) magnetic shape memory alloys which are a promising candidate for magnetocaloric materials, owing to the interdependence of magnetostructural transformation parameters. In this work, through synergic tuning of magnetostructural transformation parameters via alloying with Ti in Ni 42-x Ti x Co 9 Mn 39 Sn 10 alloys, we achieved a large reversible room-temperature magnetocaloric effect. By alloying with a proper amount of Ti, the martensitic transformation temperature was brought down to room temperature and the sensitivity of transformation temperature to magnetic field change was greatly enhanced with the transformation entropy change still remaining a large value, while the thermal hysteresis and the transformation interval only slightly increased. Thus, the field required to induce the complete and reversible transformation was significantly reduced. As a result, a large reversible room-temperature magnetic entropy change ΔS m of 18.7 J kg -1 K -1 under 5 T was achieved in the Ni 41 Ti 1 Co 9 Mn 39 Sn 10 alloy. This is the first report on reversibleΔS m in Ni-Mn-Sn-based Heusler alloys and the ΔS m we achieved represents the highest reversible ΔS m under 5 T reported heretofore in Ni-Mn-based Heusler alloys. Furthermore, the Ni 41 Ti 1 Co 9 Mn 39 Sn 10 alloy shows good compressive properties and stable martensitic transformation during thermal cycling, beneficial for potential magnetocaloric applications. This study is instructive for the development of high-performance magnetocaloric materials for room-temperature magnetic refrigeration.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Processability and Material Behavior of NiTi Shape Memory Alloys Using Wire Laser-Directed Energy Deposition (WL-DED)

Utilizing additive manufacturing (AM) techniques with shape memory alloys (SMAs) like NiTi shows great promise for fabricating highly flexible and functionally superior 3D metallic structures. Compared to methods relying on powder feedstocks, wire-based additive manufacturing processes provide a viable alternative, addressing challenges such as chemical composition instability, material availability, higher feedstock costs, and limitations on part size while simplifying process development. This study presented a novel approach by thoroughly assessing the printability of Ni-rich Ni55.94Ti (Wt. %) SMA using the wire laser-directed energy deposition (WL-DED) technique, addressing the existing knowledge gap regarding the laser wire-feed metal additive manufacturing of NiTi alloys. For the first time, the impact of processing parameters—specifically laser power (400–1000 W) and transverse speed (300–900 mm/min)—on single-track fabrication using NiTi wires in the WL-DED process was examined. An optimal range of process parameters was determined to achieve high-quality prints with minimal defects, such as wire dripping, stubbing, and overfilling. Building upon these findings, we printed five distinct cubes, demonstrating the feasibility of producing nearly porosity-free specimens. Notably, this study investigated the effect of energy density on the printed part density, impurity pick-up, transformation temperature, and hardness of the manufactured NiTi cubes. The results from the cube study demonstrated that varying energy densities (46.66–70 J/mm3) significantly affected the quality of the deposits. Lower to intermediate energy densities achieved high relative densities (>99%) and favorable phase transformation temperatures. In contrast, higher energy densities led to instability in melt pool shape, increased porosity, and discrepancies in phase transformation temperatures. These findings highlighted the critical role of precise parameter control in achieving functional NiTi parts and offer valuable insights for advancing AM techniques in fabricating larger high-quality NiTi components. Additionally, our research highlighted important considerations for civil engineering applications, particularly in the development of seismic dampers for energy dissipation in structures, offering a promising solution for enhancing structural performance and energy management in critical infrastructure.

Dabbaghi, Hediyeh↗
DOE OSTI2018

Simultaneously achieved large reversible elastocaloric and magnetocaloric effects and their coupling in a magnetic shape memory alloy

Large reversible caloric effects covering a broad temperature region are essential for high-efficiency and environment-friendly solid-state caloric refrigeration that can potentially replace the traditional vaporcompression-based cooling technology. Here, we report the simultaneously achieved large reversible magnetocaloric and elastocaloric effects in a Ni 43 Co 6 Mn 40 Sn 11 magnetic shape memory alloy. A reversible near-room-temperature magnetic entropy change Δ S m of as high as 19.3 J kg –1 K –1 under 5 T was experimentally obtained and the corresponding adiabatic temperature change Δ T ad was estimated to be 7.7 K. Meanwhile, a large reversible elastocaloric effect with a directly measured Δ T ad up to 7.1 K was attained. The elastocaloric effect exhibits high cyclic stability with no apparent degradation during 380 cycles of loading and unloading. Furthermore, we propose and demonstrate the utilization of the multicaloric approach under the coupled uniaxial stress and magnetic field to enlarge the refrigeration temperature region of reversible caloric effects. By combining the reversible magnetocaloric and elastocaloric effects and the reversible multicaloric effect under the coupling of uniaxial stress and magnetic field in the hysteresis region, large reversible caloric effects covering a broad temperature region from 257 K to 383 K can be obtained. Finally, this study may pave the way for designing advanced caloric materials with cyclically stable and reversible large caloric effects and wide refrigeration temperature region for solid-state refrigeration.

36 MATERIALS SCIENCE↗
DOE OSTI2024

A crystal-plasticity-informed Gaussian Process Regression model to capture anisotropy in single crystal shape memory alloys

This work presents a machine learning (ML) framework that model the anisotropic actuation responses in a shape memory alloy. A Gaussian Process Regression (GPR) based ML model is trained on a set of different crystal orientations subjected to different actuation conditions. The training employed thermo-mechanical responses from a crystal-plasticity model that captures phase-transformation, stress-induced plasticity, and transformation-induced plasticity. Further, on training the GPR-ML model at fixed stress level for different orientations, it captured the thermo-mechanical responses accounting for the anisotropy, and predicted responses for new orientations with good accuracy. The GPR-ML model is able to capture the transformation temperature variations even when trained using multiple stress levels, and the transformation strain showed significant deviations. The developed GPR-ML model gave reasonable predictions for an unexplored sample set of orientations and loading conditions.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Shock-induced transformation of nitinol shape memory alloy: Effect of stress state on transformation

Due to its numerous practical applications and intriguing phase transformation behavior, shape memory alloys (SMAs) have garnered significant research and development interests. In the past, most studies on the mechanical behavior of SMAs have been conducted under uniaxial stress loadings. Limited research on SMAs under shock loading has not provided conclusive results regarding their transformation behavior and transformation stress under such loading. Additionally, there is a lack of comprehensive understanding regarding the effects of different stress states on transformation behavior. The main objectives of this study are to address these issues. To achieve these objectives, a series of shock wave experiments were designed and conducted. Additionally, quasi-static and dynamic uniaxial stress experiments were carried out to establish a baseline for comparison. The results revealed that the transformation stress under dynamic uniaxial strain shock loading was approximately 1.92 GPa in contrast to 0.5 GPa (quasi-static) to 0.8 GPa (dynamic) observed in uniaxial stress loading. The transformation behavior exhibited noticeable rate sensitivity for both types of loading. There appeared to be a critical strain rate above which the austenite phase was driven to a metastable state. This estimated critical axial strain rate along the loading direction was approximately 2 × 10 3 /s–4 × 10 3 /s for uniaxial stress loading and approximately 2 × 10 6 /s for uniaxial strain loading. The apparent high transformation stress for uniaxial strain loading can likely be attributed to a combination of high-pressure confinement and high strain rate. Furthermore, determining their relative contributions remains an open issue.

36 MATERIALS SCIENCE↗
DOE OSTI2018

Plant-Based, Shape-Memory Material Could Replace Today’s Conductors

A novel approach that creates a renewable, leathery material—programmed to remember its shape—may offer a low-cost alternative to conventional conductors for applications in sensors and robotics. To make the bio-based, shape-memory material, Oak Ridge National Laboratory scientists streamlined a solvent-free process that mixes rubber with lignin—the by-product of woody plants used to make biofuels. They fashioned the leathery material into small strips and brushed on a thin layer of silver nanoparticles to activate electrical conductivity. The strips were stretched or curled and then frozen as part of the process to program the material to return to its intended shape, which occurs after the application of low heat. “The performance of this polymer can be tuned further,” said ORNL’s Amit Naskar. “Variant lignins can be used at different ratios, which determines the material’s pliability.” This research was sponsored by the Department of Energy’s Bioenergy Technologies Office.

15 GEOTHERMAL ENERGY↗
DOE OSTI2018

Fabrication and Properties of Composite Artificial Muscles Based on Nylon and a Shape Memory Alloy

This paper focuses on the design, fabrication and investigation of the mechanical properties of new artificial muscles formed by twisting and annealing. The artificial muscles designed by twisting nylon have become a popular topic in the field of smart materials due to their high mechanical performance with a large deformation and power density. However, the complexity of the heating and cooling system required to control the nylon muscle is a disadvantage, so we have proposed a composite artificial muscle for providing a direct electricity-driven actuation by integrating nylon and a shape memory alloy (SMA). In this paper, the design and fabrication process of these composite artificial muscles are introduced before their mechanical properties, which include the deformation, stiffness, load and response, are investigated. The results show that these composite artificial muscles that integrate nylon and a SMA provide better mechanical properties and yield up to a 44.1% deformation and 3.43 N driving forces. The good performance and direct electro-thermal actuation make these composite muscles ideal for driving robots in a method similar to human muscles.

36 MATERIALS SCIENCE↗
DOE OSTI2026

PET waste- and bio-derived imine vitrimers for shape-memory, intrinsic flame-retardant, and recyclable carbon fiber composites

Developing circular multifunctional vitrimers and carbon fiber–reinforced polymers (CFRPs) that are simultaneously recyclable, mechanically robust, and intrinsically flame retardant remains a major challenge. Here, in this study, we report multifunctional vitrimers and their carbon fiber–reinforced vitrimer (CFRV) composites, where the vitrimer design integrates closed-loop recyclability, enhanced interfacial adhesion, and intrinsic flame retardancy within a single materials platform. The vitrimer matrix is synthesized from post-consumer polyethylene terephthalate (PET) waste and a vanillin-derived phosphorus-containing crosslinker, forming an imine-based network. The resulting vitrimer resin exhibits high tensile strength, thermal healability, repeated reprocessability, programmable shape memory, and rapid chemical depolymerization under mild conditions. Amine-functionalized carbon fibers significantly improve fiber–matrix interfacial bonding, yielding CFRVs with tensile strengths up to 789 MPa and complete recovery of structurally intact fibers after chemical recycling. The phosphorus-rich aromatic network further imparts intrinsic flame retardancy, enabling self-extinguishing behavior without external additives. This work advances a materials design paradigm for next-generation multifunctional, sustainable vitrimers and CFRVs, while simultaneously addressing the recycling challenges associated with both plastic and CFRP waste.

Bio-derived crosslinker↗
DOE OSTI2023

ReaxFF reactive force field model enables accurate prediction of physiochemical and mechanical properties of crystalline and amorphous shape‐memory polyurethane

Abstract We investigate reactive force field (ReaxFF) prediction of physiochemical and mechanical properties, and stimuli response behavior of a shape‐memory polyurethane (SMPU) rigid segment. We used SMPUs as a platform to link the rigid/hard segment domain crystallinity with properties that can also be experimentally measured. Specifically, we developed models for crystalline and amorphous forms of a common rigid segment of SMPUs, for example, 4,4′‐diphenylmethane diisocyanate (MDI) with n‐butanediol (BDO), denoted as MDI‐BDO. ReaxFF molecular dynamics simulations with equilibrium dynamics are performed by controlling mass, temperature, and pressure or volume to predict the structural and physiochemical properties of crystalline and amorphous rigid segments of SMPU systems, followed by simulating their XRD and FTIR patterns, respectively. Non‐equilibrium ReaxFF simulations are implemented by using uniaxial box deformation technique to study response‐behavior of crystalline SMPU under tensile loading and during stress‐relaxation. The model and simulation scheme presented in this study demonstrates a robust theoretical pathway toward application‐dictated, on‐demand design of high‐performance SMPUs in applications such as soft robotics.

Afroz, Mohammad M.↗
DOE OSTI2018

Shape memory and superelasticity of nanograined Ti-51.2 at.% Ni alloy processed by severe plastic deformation via high-ratio differential speed rolling

A novel method of producing nanograined Ni-rich superelastic NiTi alloys in sheet form was proposed using a combination of severe plastic deformation via high-ratio differential speed rolling (HRDSR) and post-deformation annealing. The HRDSR-processed microstructure was composed of heavily deformed austenite and martensite grains, and amorphous phases. After annealing at 673 K, the severely deformed microstructure with no functional properties evolved to the nanograined structure (20–70 nm) composed of austenite and martensite nanograins and sub-nanograins through static recovery or continuous static recrystallization process. The nanograined microstructure had a high resistance to martensitic transformation upon cooling and slip deformation during straining. As a result, the HRDSR-processed alloy annealed at 673K exhibited superior superelasticity compared to the alloys with coarse grains. At the higher annealing temperature of 873 K, the micron-sized recrystallized grains with low dislocations developed through discontinuous static recrystallization process. In this case, deformation during straining was governed by the detwinning of twinned martensite, and as a result, shape memory effect was more significantly pronounced than superelasticity.

36 MATERIALS SCIENCE↗
DOE OSTI2023

Caloric Effects Induced by Uniform and Non-uniform Stress in Shape-Memory Materials

A Ginzburg–Landau model is developed that is adequate to describe a square-to-rectangle martensitic transition with associated shape-memory and superelastic properties. Using this model we study caloric effects in the vicinity of the martensitic transition induced by stress and we compare the case of a uniform uniaxial stress and the case of a non-uniform continuous distribution of stresses that produce bending of the material. The former case corresponds to an elastocaloric effect and the latter corresponds to a flexocaloric effect. The aim of the work is to quantitatively compare both cases, which we show must be accomplished in terms of equal amounts of exchanged mechanical work. It is then obtained that the flexocaloric effect is more efficient for low exchanged work but less efficient for large exchanged work.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Design of High Temperature Ti-Pd-Cr Shape Memory Alloys with Small Thermal Hysteresis

The large thermal hysteresis (ΔT) during the temperature induced martensitic transformation is a major obstacle to the functional stability of shape memory alloys (SMAs), especially for high temperature applications. We propose a design strategy for finding SMAs with small thermal hysteresis. That is, a small ΔT can be achieved in the compositional crossover region between two different martensitic transformations with opposite positive and negative changes in electrical resistance at the transformation temperature. We demonstrate this for a high temperature ternary Ti-Pd-Cr SMA by achieving both a small ΔT and high transformation temperature. We propose two possible underlying physics governing the reduction in ΔT. One is that the interfacial strain is accommodated at the austenite/martensite interface via coexistence of B19 and 9R martensites. The other is that one of transformation eigenvalues equal to 1, i.e., λ2 = 1, indicating a perfect coherent interface between austenite and martensite. Our results are not limited to Ti-Pd-Cr SMAs but potentially provide a strategy for searching for SMAs with small thermal hysteresis.

Science & Technology - Other Topics↗
DOE OSTI2024

Elastomeric shape memory polymer composites

In accordance with one aspect of the presently disclosed inventive concepts, a product includes a porous three-dimensional (3D) printed polymer structure having elastomeric shape memory, where the structure includes a material comprising a plurality of gas-filled microballoons. The 3D printed polymer structure has hierarchical porosity.

Wu, Amanda↗