Shape memory behavior of NiTiHf alloys fabricated by selective laser melting

Toker, Guher P.; Nematollahi, Mohammadreza; Saghaian, Sayed Ehsan; Baghbaderani, Keyvan Safaei; Benafan, Othmane; Elahinia, Mohammad; Karaca, H.E.

doi:10.1016/j.scriptamat.2019.11.056

Cited by 39 publications

(12 citation statements)

References 34 publications

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“…The entire process is controlled by a chamber purged with inert gas (typically argon) to prevent oxidation during manufacturing. [29][30][31][32] The laser power (P), scanning speed (V), hatch spacing (H), and layer thickness (L) are the main effective process parameters. The volumetric energy density (VED) and linear energy density can be defined as…”

Section: Metallurgy and Biocompatibility Of Niti Smasmentioning

confidence: 99%

“…AM offers flexible processing to achieve near-net-shape parts with little to no postprocessing by providing a vast number of controllable parameters to tailor the final properties of the material. 31,33 Additive Manufacturing of NiTi Shape Memory Alloy for Biomedical Applications: Review of the LPBF Process Ecosystem BIOMEDICAL APPLICATIONS OF AM NITI One of the major and most important applications of conventionally fabricated NiTi is to form selfexpanding stents that enable transcatheter and minimally invasive solutions. Most cardiovascular stents have a mesh structure and provide the overall geometry of an artery or vein (similar to a thin, hollow tube).…”

Section: Metallurgy and Biocompatibility Of Niti Smasmentioning

confidence: 99%

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Additive Manufacturing of NiTi Shape Memory Alloy for Biomedical Applications: Review of the LPBF Process Ecosystem

Safaei

Abedi

Nematollahi

et al. 2021

JOM

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NiTi shape memory alloys (SMAs) are used in a broad range of biomedical applications because of their unique properties including biocompatibility and high corrosion and wear resistance as well as functional properties such as superelasticity and the shape memory effect. The combination of SMAs and additive manufacturing can lead to revolutionary changes to the uses of SMAs in the biomedical industry. This article discusses the potential biomedical applications of NiTi that benefit from the AM process. We share the lessons learned in processing NiTi alloys with a focus on the laser powder bed fusion (LPBF) technique. The manufacturability, build quality, stable phases and transformation temperatures, microstructure, thermomechanical properties, microstructure tailoring, and functional properties of NiTi alloys produced via AM processing are reviewed. Current challenges such as expanding the process window, controlling the chemistry, and the performance and property responses are discussed, and potential opportunities including alloy design are discussed.

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Section: Metallurgy and Biocompatibility Of Niti Smasmentioning

confidence: 99%

Section: Metallurgy and Biocompatibility Of Niti Smasmentioning

confidence: 99%

Additive Manufacturing of NiTi Shape Memory Alloy for Biomedical Applications: Review of the LPBF Process Ecosystem

Safaei

Abedi

Nematollahi

et al. 2021

JOM

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“…Atomization with the inert gas EIGA technique can produce a spherical powder that has low impurity content. In this study, a particle size distribution of 25-75 and 15-63 µm were used for NiTi and NiTiHf powder, respectively, to ensure followability and layer resolution [28,29]. An SLM machine (Phenix Systems PXM, [3D Systems], Rock Hill, SC, USA) equipped with a 300W Ytterbium fiber laser, was employed in this study to fabricate Ni 50.8 Ti 49.2 and Ni 50.4 Ti 29.6 Hf 20 parts.…”

Section: Materials Preparationmentioning

confidence: 99%

Additively Manufactured NiTi and NiTiHf Alloys: Estimating Service Life in High-Temperature Oxidation

et al. 2020

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In this study, the effect of the addition of Hf on the oxidation behavior of NiTi alloy, which was processed using additive manufacturing and casting, is studied. Thermogravimetric analyses (TGA) were performed at the temperature of 500, 800, and 900 °C to assess the isothermal and dynamic oxidation behavior of the Ni50.4Ti29.6Hf20 at.% alloys for 75 h in dry air. After oxidation, X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy were used to analyze the oxide scale formed on the surface of the samples during the high-temperature oxidation. Two stages of oxidation were observed for the NiTiHf samples, an increasing oxidation rate during the early stage of oxidation followed by a lower oxidation rate after approximately 10 h. The isothermal oxidation curves were well matched with a logarithmic rate law in the initial stage and then by parabolic rate law for the next stage. The formation of multi-layered oxide was observed for NiTiHf, which consists of Ti oxide, Hf oxide, and NiTiO3. For the binary alloys, results show that by increasing the temperature, the oxidation rate increased significantly and fitted with parabolic rate law. Activation energy of 175.25 kJ/mol for additively manufactured (AM) NiTi and 60.634 kJ/mol for AM NiTiHf was obtained.

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“…Samples were cut from the same fabricated ingot that was atomized to make the powder for the SLM fabricated samples. More information on the fabrication and mechanical responses were presented elsewhere [14,15]. Hereafter, "AM" and "CON" were used for additively manufactured and conventionally made ingot, respectively.…”

Section: Materials Preparationmentioning

confidence: 99%

High-Temperature Oxidation Kinetics of Additively Manufactured NiTiHf

Dabbaghi

Nematollahi

Baghbaderani

et al. 2020

Volume 1: Additive Manufacturing; Advanced Materials Manufacturing; Biomanufacturing; Life Cycle Engineering; Manufacturing Equ

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NiTi-based high-temperature shape memory alloys (HTSMAs) such as NiTiHf have been utilized in a broad range of applications due to their high strength and work output, as well as, their ability to increase the transformation temperatures (TTs). Recently, additive manufacturing techniques (AM) have been widely used to fabricate complex shape memory alloy components without any major modifications or tooling and has paved the way to tailor the manufacturing and fabrications of microstructure and critical properties of their final parts. NiTi alloys properties such as transformation temperatures can be significantly altered due to oxidation, which can occur during the manufacturing process or post-processing. In this work, the oxidation behavior of Ni-rich NiTi20Hf shape memory alloys, which was fabricated by the selective laser melting (SLM) method, is evaluated. Thermogravimetric analysis (TGA) is used to assess the kinetic behavior of the oxidation at different temperature ranges of 500, 700, and 900 °C for 20 hours in the air. After oxidation, to evaluate the microstructure and chemical composition X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy (EDS) was conducted. The isothermal oxidation kinetics of conventional NiTi20Hf alloys were studied, and the results were compared to AM samples. Results show a two-stage oxidation rate at which oxidation increased with the high rate at the initial stage. As the oxidation time increased, the oxidation rate gradually decreased. The oxidation behavior of NiTiHf alloys initially obeyed logarithmic rate law and then followed by parabolic rate law. SEM results showed the formation of a multi-layered oxide scale, including TiO2, NiTiO3, and Hf oxide.

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Shape memory behavior of NiTiHf alloys fabricated by selective laser melting

Cited by 39 publications

References 34 publications

Additive Manufacturing of NiTi Shape Memory Alloy for Biomedical Applications: Review of the LPBF Process Ecosystem

Additive Manufacturing of NiTi Shape Memory Alloy for Biomedical Applications: Review of the LPBF Process Ecosystem

Additively Manufactured NiTi and NiTiHf Alloys: Estimating Service Life in High-Temperature Oxidation

High-Temperature Oxidation Kinetics of Additively Manufactured NiTiHf

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