Control of Ni-Ti phase structure, solid-state transformation temperatures and enthalpies via control of L-PBF process parameters

Chekotu, Josiah Cherian; Goodall, Russell; Kinahan, David J.; Brabazon, Dermot

doi:10.1016/j.matdes.2022.110715

Cited by 23 publications

(5 citation statements)

References 46 publications

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“…The work done by the material ( Q out ) can be determined by calculating the area contained within the martensitic transformation region (enclosed by the loading and unloading curve) on the stress–strain curve. This is also referred to as the dissipated energy per cycle or enthalpy [ 103 ]. Q out is the latent heat energy required for the martensitic transformation (obtained from Differential Scanning Calorimetry analysis).…”

Section: Discussionmentioning

confidence: 99%

Influence of Structural Porosity and Martensite Evolution on Mechanical Characteristics of Nitinol via In-Silico Finite Element Approach

et al. 2022

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Nitinol (NiTi) alloys are gaining extensive attention due to their excellent mechanical, superelasticity, and biocompatibility properties. It is difficult to model the complex mechanical behavior of NiTi alloys due to the solid-state diffusionless phase transformations, and the differing elasticity and plasticity presenting from these two phases. In this work, an Auricchio finite element (FE) model was used to model the mechanical behavior of superelastic NiTi and was validated with experimental data from literature. A Representative Volume Element (RVE) was used to simulate the NiTi microstructure, and a microscale study was performed to understand how the evolution of martensite phase from austenite affects the response of the material upon loading. Laser Powder Bed Fusion (L-PBF) is an effective way to build complex NiTi components. Porosity being one of the major defects in Laser Powder Bed Fusion (L-PBF) processes, the model was used to correlate the macroscale effect of porosity (1.4–83.4%) with structural stiffness, dissipated energy during phase transformations, and damping properties. The results collectively summarize the effectiveness of the Auricchio model and show that this model can aid engineers to plan NiTi processing and operational parameters, for example for heat pump, medical implant, actuator, and shock absorption applications.

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Section: Discussionmentioning

confidence: 99%

Influence of Structural Porosity and Martensite Evolution on Mechanical Characteristics of Nitinol via In-Silico Finite Element Approach

et al. 2022

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“…One of the phenomena that occur during the additive manufacturing of Nitinol products using the SLM method is the loss of nickel in the matrix [15][16][17][18][19][20] due to its evaporation. The loss is dependent on the process parameters and results in a temperature shift of the martensite -> austenite transformation towards higher temperatures, compared to transformations in the output powder.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Ageing on Phase Transformations and Nanoindentation Behaviour in Ni-Rich NiTi Alloys

Ratajski,

Bałasz,

Mydłowska

et al. 2024

Preprint

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In the article, the results of research on a NiTi alloy with a high nickel content (51.7 at.%), produced using the additive technology SLM method and subjected to isothermal aging after so-lution annealing, are presented. The study involved the determination of the sequence of phase transformations occurring using differential scanning calorimetry (DSC), and the determination of the temperature range of these transformations. In parallel, the phase composition was determined using the XRD method; hardness and the Young’s modulus were also determined. The analysis of the DSC results obtained indicates the following characteristic features of the NiTi alloy, which change with ageing time: (1) during cooling (from +1500C to -500C), the type of transformation changes from a one-step transformation after solution annealing to a two-step transformation after the ageing process over 1, 20 and 100 hours at 500°C; (2) during heating (from -500C to +1500C) for all the samples, regardless of the ageing time, only a one-step transformation from martensite M(B19’) to austenite A(B2) is observed; (3) the temperature at which the transformation starts increases with the ageing time, (4) the width of the total temperature range of the transformation M(B19’)  A(B2) during heating changes from large (∆T=49,7°C), after solution annealing, to narrow (∆T=19.3°C and ∆T=17.9°C after 20 h and 100 h of ageing) and, most importantly, (5) a comparison with literature data shows that, irrespective of the composition of the NiTi alloy and the manufacturing technology of the alloy samples (regardless of the fact whether this was traditional or additive technology), a sufficiently long ageing process period leads to the occurrence of the martensite  austenite transformation in the same temperature range.

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“…One of the phenomena that occur during the additive manufacturing of Nitinol products using the SLM method is the loss of nickel in the matrix [15][16][17][18][19][20] due to evaporation. The loss is dependent on the process parameters and results in a temperature shift of the martensite → austenite transformation towards higher temperatures, compared to transformations in the output powder.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Ageing on Phase Transformations and Mechanical Behaviour in Ni-Rich NiTi Alloys

Ratajski,

Bałasz,

Mydłowska

et al. 2024

Materials

View full text Add to dashboard Cite

In this article, the results of research on a NiTi alloy with a high nickel content (51.7 at.%), produced using the additive technology SLM method and subjected to isothermal ageing after solution annealing, are presented. The study involved the determination of the sequence of phase transformations occurring using differential scanning calorimetry (DSC) and the determination of the temperature range of these transformations. In parallel, the phase composition was determined using the XRD method; the hardness and the Young’s modulus were also determined. The analysis of the DSC results obtained indicates the following characteristic features of the NiTi alloy, which change with ageing time: (1) During cooling (from +150 °C to −50 °C), the type of transformation changes from a one-step transformation after solution annealing to a two-step transformation after the ageing process over 1, 20, and 100 h at 500 °C; (2) during heating (from −50 °C to +150 °C) for all the samples, regardless of the ageing time, only a one-step transformation from martensite M(B19′) to austenite A(B2) is observed; (3) the temperature at which the transformation starts increases with the ageing time; (4) the width of the total temperature range of the transformation M(B19′) → A(B2) during heating changes from large (ΔT = 49.7 °C), after solution annealing, to narrow (ΔT = 19.3 °C and ΔT = 17.9 °C after 20 h and 100 h of ageing); and, most importantly, (5) a comparison with the literature data shows that, irrespective of the composition of the NiTi alloy and the manufacturing technology of the alloy samples (regardless of whether this was traditional or additive technology), a sufficiently long ageing process period leads to the occurrence of the martensite → austenite transformation in the same temperature range.

show abstract

Control of Ni-Ti phase structure, solid-state transformation temperatures and enthalpies via control of L-PBF process parameters

Cited by 23 publications

References 46 publications

Influence of Structural Porosity and Martensite Evolution on Mechanical Characteristics of Nitinol via In-Silico Finite Element Approach

Influence of Structural Porosity and Martensite Evolution on Mechanical Characteristics of Nitinol via In-Silico Finite Element Approach

The Effect of Ageing on Phase Transformations and Nanoindentation Behaviour in Ni-Rich NiTi Alloys

The Effect of Ageing on Phase Transformations and Mechanical Behaviour in Ni-Rich NiTi Alloys

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