Functionally graded NiTi alloy with exceptional strain-hardening effect fabricated by SLM method

Yang, Yuanzheng; Zhan, Jianbin; Sui, Jianbo; Li, C-Q.; Yang, Ke; Castany, Philippe; Gloriant, T.

doi:10.1016/j.scriptamat.2020.07.019

Cited by 32 publications

(10 citation statements)

References 26 publications

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“…Although a slight change in chemical composition is unavoidable during the L-PBF process, a compositional change of less than 0.1 wt.% of the NiTi alloy can result in a significant change in the SME and mechanical performance. [21,22] This behavior leads to a very narrow process window for the L-PBF of the NiTi alloy. Consequently, it is almost impossible to optimize the L-PBF conditions under which a NiTi alloy with the desired microstructure and chemical composition and high dimensional accuracy can be produced.…”

Section: Introductionmentioning

confidence: 99%

3D and 4D Printing of Complex Structures of FeMnSi‐Based Shape Memory Alloy Using Laser Powder Bed Fusion

Kim

Ferretto

Leinenbach

et al. 2022

Adv Materials Inter

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Section: Introductionmentioning

confidence: 99%

3D and 4D Printing of Complex Structures of FeMnSi‐Based Shape Memory Alloy Using Laser Powder Bed Fusion

Kim

Ferretto

Leinenbach

et al. 2022

Adv Materials Inter

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“…In recent years, the laser powder bed fusion (L-PBF) technique has attracted a lot of attention in the fabrication of NiTi parts [10][11][12][13], because of its ability to build parts with complex structures [14,15] and in situ tailorable microstructures [16,17]. For the fabrication of L-PBF NiTi parts, main processing parameters include laser power (P, W), scanning velocity (v, mm s -1 ), layer thickness (t, lm) and hatch distance (h, mm).…”

Section: Introductionmentioning

confidence: 99%

Controlling microstructure evolution and phase transformation behavior in additive manufacturing of nitinol shape memory alloys by tuning hatch distance

et al. 2022

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Laser powder bed fusion (L-PBF), categorized as additive manufacturing technique, has a capability to fabricate NiTi (Nitinol) shape memory alloys with tailorable functional properties and complex geometries. An important processing parameter, hatch distance (h), is often related to macroscale structural defects; however, its role on controlling the microstructure and functional properties is usually underestimated in L-PBF of NiTi. In this work, equiatomic NiTi (50.0 at% Ni) parts were fabricated with various hatch distances to tailor the microstructure and their shape memory characteristics. Contrary to what is observed in Ni-rich NiTi alloys, in this work, we demonstrate that phase transformation temperatures of L-PBF equiatomic NiTi do not decrease proportionally with hatch distance but rather relate to a critical hatch distance value. This critical value (120 μm) is derived from the synergistic effect of thermal stress and in situ reheating. Below this value, epitaxial grain growth and in situ recrystallization are enhanced, while above, irregular grains are formed and dislocations induced by thermal stresses decrease. However, the critical value found herein is characterized by high dislocation density and fine grain size, resulting in a superior thermal cyclic stability. The proposed finite element model is proven to be an effective tool to understand and predict the effect of hatch distance on grain morphology and dislocation density evolutions in L-PBF NiTi SMAs. In the present study, we provide a comprehensive understanding for in situ controlling L-PBF NiTi microstructure and functional characteristics, which contributes to designing 4-dimensional shape memory alloys.

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“…This demonstrates that LPBF is a feasible method to modify the Ni concentration and, thus, the transformation temperature of NiTi alloys. The layer-by-layer building permits the L-PBF method of fabricating NiTi specimens with different MTTs at different locations; thus producing the functionally graded NiTi alloys [ 42 , 43 ].…”

Section: Introductionmentioning

confidence: 99%

Structure, Martensitic Transformation, and Damping Properties of Functionally Graded NiTi Shape Memory Alloys Fabricated by Laser Powder Bed Fusion

Jiang

et al. 2022

Materials

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Besides the unique shape memory effect and superelasticity, NiTi alloys also show excellent damping properties. However, the high damping effect is highly temperature-dependent, and only exists during cooling or heating over the temperature range where martensitic transformation occurs. As a result, expanding the temperature range of martensite transformation is an effective approach to widen the working temperature window with high damping performance. In this work, layer-structured functionally graded NiTi alloys were produced by laser powder bed fusion (L-PBF) alternating two or three sets of process parameters. The transformation behavior shows that austenite transforms gradually into martensite over a wide temperature range during cooling, and multiple transformation peaks are observed. A microstructure composed of alternating layers of B2/B19′ phases is obtained at room temperature. The functionally graded sample shows high damping performance over a wide temperature range of up to 70 K, which originates from the gradual formation of the martensite phase during cooling. This work proves the potential of L-PBF to create NiTi alloys with high damping properties over a wide temperature range for damping applications.

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Functionally graded NiTi alloy with exceptional strain-hardening effect fabricated by SLM method

Cited by 32 publications

References 26 publications

3D and 4D Printing of Complex Structures of FeMnSi‐Based Shape Memory Alloy Using Laser Powder Bed Fusion

3D and 4D Printing of Complex Structures of FeMnSi‐Based Shape Memory Alloy Using Laser Powder Bed Fusion

Controlling microstructure evolution and phase transformation behavior in additive manufacturing of nitinol shape memory alloys by tuning hatch distance

Structure, Martensitic Transformation, and Damping Properties of Functionally Graded NiTi Shape Memory Alloys Fabricated by Laser Powder Bed Fusion

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