phd thesis on shape memory alloy

The constitutive modeling of shape memory alloys

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This dissertation presents a one-dimensional thermomechanical constitutive model for shape memory alloys based on basic concepts of thermodynamics and phase transformation kinetics. Compared with other developed constitutive relations, this thermomechanical constitutive relation not only reflects the physical essence of shape memory alloys, i.e., the martensitic phase transformation involved, but also provides an easy-to-use design tool for engineers. It can predict and describe the behavior of SMA quantitatively. A multi-dimensional constitutive relation for shape memory alloys is further developed based on the one-dimensional model. It can be used to study the mechanical behavior including shape memory effect of complex SMA structures that have never been analytically studied, and provide quantitative analysis for many diverse applications of shape memory alloys.

A general design method for shape memory alloy actuators has also been developed based on the developed constitutive relation and transient thermal considerations. The design methodology provides a quantitative approach to determine the design parameters of shape memory alloy force actuators, including both bias spring SMA force actuators and differential SMA force actuators.

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A Computationally Efficient Free Energy Model for Shape Memory Alloys - Experiments and Theory

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Applications of Shape Memory Alloys: A Review

Shape memory alloys (SMAs) impart a potential application in a wide range in micro- and nano-industrial world. Classic properties such as free recovery or pseudo-elasticity still needed further specifications in smart materials or micro-actuators applications. Nowadays, a primary goal is achieved that these materials offer a price-competitive advantage compared to other functional materials design. Among all types of functional SMAs, NiTi-based SMA attracted much attention in the rapidly growing field of micro-electro-mechanical-systems (MEMS) and bio-MEMS. This paper points out different products of Ni-Ti based SMAs. This will be illustrated by describing some device-based applications realizing why they are successful than that of other micro-instruments

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An attempt has been made to correlate shape memory behavior and the micromechanical characteristics of the martensite crystals in the polycrystalline microstructure of thermally and thermo mechanically processed nearly equi-atomic Ni
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A Short Review on the Microstructure, Transformation Behavior and Functional Properties of NiTi Shape Memory Alloys Fabricated by Selective Laser Melting

Xiebin wang.

1 Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials (Ministry of Education), Shandong University, Jingshi Road 17923, Jinan 250061, China

2 School of Materials Science and Engineering, Shandong University, Jingshi Road 17923, Jinan 250061, China

Sergey Kustov

3 Departament de Física, Universitat de les Illes Balears, Cra Valldemossa km 7.5, E07122 Palma de Mallorca, Spain; [email protected]

4 ITMO University, Kronverkskiy av. 49, 197101 St. Petersburg, Russia

Jan Van Humbeeck

5 Department of Materials Engineering, KU Leuven, Kasteelpark Arenberg 44, B3001 Heverlee, Belgium; [email protected]

Due to unique functional and mechanical properties, NiTi shape memory alloys are one of the most promising metallic functional materials. However, the poor workability limits the extensive utilization of NiTi alloys as components of complex shapes. The emerging additive manufacturing techniques provide high degrees of freedom to fabricate complex structures. A freeform fabrication of complex structures by additive manufacturing combined with the unique functional properties (e.g., shape memory effect and superelasticity) provide great potential for material and structure design, and thus should lead to numerous applications. In this review, the unique microstructure that is generated by selective laser melting (SLM) is discussed first. Afterwards, the previously reported transformation behavior and mechanical properties of NiTi alloys produced under various SLM conditions are summarized.

1. Introduction

Near equiatomic NiTi shape memory alloys (SMAs) could appear in a B2 structured austenite (A), a B19’ structured martensite (M) or a rhombohedral R-phase, depending on the thermal or mechanical conditions [ 1 ]. The thermoelastic martensitic transformation between the abovementioned phases gives rise to the shape memory effect and superelasticity, which makes NiTi SMAs able to recover large deformations of up to 10% [ 2 , 3 , 4 ]. Due to the unique functional properties, together with the good biocompatibility [ 5 ], low stiffness [ 6 , 7 ], excellent corrosion resistance [ 8 ], high damping properties [ 9 , 10 ], and the excellent strength and ductility (tensile elongation >30% [ 11 , 12 ]), NiTi SMAs are the most promising functional metallic materials for practical applications in both medical (e.g., stents, guide wires) [ 13 , 14 , 15 ] and non-medical fields [ 16 , 17 , 18 ].

The demand for complex or customized NiTi SMA devices will increase remarkably in the future with the development of technologies in such fields as aviation and aerospace, personalized medical care, etc. However, fabrication of complex NiTi structures via conventional processing techniques (e.g., machining and welding) is difficult [ 19 , 20 , 21 , 22 , 23 ]. This difficulty is mainly caused by the high work hardening, high toughness, high strength, and high ductility (total tensile strain up to 70% [ 12 ]) of NiTi SMAs [ 24 ].

Unlike the conventional processing techniques, additive manufacturing (AM), which fabricates certain components by adding layers of materials progressively, provides great potential to produce complex or customized parts [ 25 ]. Various metal AM techniques, e.g., Selective Laser Melting (SLM), Laser Powder Deposition, and Wire Arc Additive Manufacturing, have been developed in the past decades [ 26 , 27 , 28 ]. Among the AM techniques, SLM generally provides a better surface finish and geometrical accuracy [ 25 , 28 ], which are the main features required for NiTi devices (e.g., stents, actuators). As a result, the fabricating of NiTi parts by SLM has frequently been addressed.

The work on additively fabricating the NiTi parts by SLM starts from producing dense and porous-free parts by optimizing the SLM process. The input laser energy density, which is determined by the SLM process parameters, is normally used as a guide to produce dense parts. The energy density (volumetric energy density, E V , and linear energy density, E L ) can be simply estimated by:

where, P , v , h , and t represent the laser power, scanning velocity, hatch spacing, and layer thickness, respectively. The relative density of SLM fabricated NiTi parts benefits from the increase of energy density [ 29 ], like reported in other metallic materials [ 27 , 30 , 31 , 32 , 33 , 34 , 35 ], and a minimum energy density is required to produce fully dense (relative density > 99%) parts. As discussed in the work conducted by Haberland et al. [ 29 ], fully dense parts could be obtained when the energy density is higher than 200 J/mm 3 . The density of SLM produced parts will decrease slightly with an extra high energy density, due to the entrapping of gases, spatter, or improper closure of keyholes [ 33 , 36 , 37 , 38 , 39 , 40 , 41 ]. The optimization of SLM process to fabricate fully dense NiTi parts can refer to Ref. [ 24 , 29 ]. It is worth mentioning that various optimized energy densities for NiTi alloys have been reported in literature, from 55 to 300 J/mm 3 [ 24 , 29 , 42 , 43 , 44 , 45 , 46 , 47 , 48 , 49 ]. An even higher energy density of 595 J/mm 3 was used by Ma et al. [ 42 ], by reducing the hatch spacing. This indicates that many other factors have to be considered in order to optimize the SLM process, for instance, particle size, laser type, and spot size, as well as different combinations of SLM process parameters [ 50 ].

As compared with the samples that are produced via conventional approaches, the SLM fabricated parts show unique microstructure. On the other hand, the phase transformation behavior and functional properties, which are key factors affecting the practical applications of NiTi SMAs, are very sensitive to the change of microstructure [ 1 , 2 ]. Therefore, it is essential to understand the interrelation between SLM process and the resulted microstructure, and thus the phase transformation behavior and functional properties of the produced NiTi parts. In this review, the unique microstructure that is caused by SLM is discussed first. Afterwards, the previous works on explaining the phase transformation behavior, as well as improving the tensile properties of SLM fabricated NiTi parts, are summarized.

2. Microstructure

NiTi alloy powders are exposed to the laser beams with high energy density during SLM. The powders are heated up rapidly to a temperature above melting or even boiling points. When the laser beam moves away, the melt solidifies quickly due to the very high cooling rate (up to 10 6 K·s −1 [ 51 , 52 ], depending on SLM process parameters and materials). This complex process, as shown schematically in Figure 1 , repeats during SLM, and the previously solidified materials undergo a cyclic heating/cooling process. The unique thermal history leads to complex microstructural evolution during SLM, which affects remarkably both the transformation behavior and functional properties of the NiTi parts. The possible microstructural variation that is caused by SLM could be summarized, as follows:

Equilibrium vapor pressures ( P eq ) of Ni and Ti over the liquid alloy for Ti-50.0 at % Ni alloy, which were calculated according to Ref. [ 54 ].

Oxygen, carbon, and nitrogen pickup in SLM fabricated NiTi parts [ 47 ] (with permission from SAGE Publications).

• (3) Precipitation . During SLM, the fabricating parts are heated up due to the heat transferred from the melt pool and heat affected zone. In Ni-rich NiTi alloys, the precipitation of Ni 4 Ti 3 phase may occur at a temperature as low as 473 K [ 65 , 66 ]. As a result, during fabricating Ni-rich NiTi parts, the formation of Ni 4 Ti 3 precipitates may occur, which will significantly affect both the phase transformation behavior and mechanical performance of NiTi alloys. The Ni 4 Ti 3 precipitation in SLM fabricated Ni-rich NiTi parts have been proposed in many studies [ 42 , 43 , 56 , 63 , 67 ]. Ni 4 Ti 3 precipitates with the size <2 nm have been observed by means of high-resolution transmission electron microscopy [ 42 , 56 ]. As the presence of N 4 Ti 3 particles significantly influences the performance of NiTi alloys [ 1 ], it is essential to study the size and distribution of Ni 4 Ti 3 particles under different SLM process conditions. The formation of other precipitates e.g., Ti 2 Ni, was also reported [ 42 , 57 , 68 , 69 ].
• (4) Strong texture . During SLM, the grains grow along the direction of the maximum temperature gradient, which is normally the same direction as the build direction (BD) [ 28 ]. The easy growth direction of the body centered cubic (BCC) crystals is <100> [ 28 ]. At elevated temperatures, near equiatomic NiTi alloys are in a B2 ordered austenite phase with BCC crystal structure [ 1 ]. Therefore, a strong <100> B2 //BD (build direction) can be developed in SLM fabricated NiTi parts [ 43 , 67 , 70 ]. The strong texture will significantly influence the functional properties of NiTi alloys, as the transformation strain depends strongly on the crystallographic orientation [ 1 ]. It has been frequently reported that the texture characteristics (e.g., intensity or type of texture) depends highly on the SLM process conditions [ 28 , 71 ]. Therefore, it is suggested that future work is required to study the effect of the SLM process conditions on the texture characteristic of NiTi alloys and its influence on the functional properties.
• (5) High density of dislocations . High density of dislocations could be introduced by SLM, due to the rapid cooling [ 42 , 72 , 73 , 74 ]. It has recently been reported that the dislocation network introduced by SLM could improve both the strength and ductility of the 316 L stainless steels, i.e., breaking the strength-ductility trade-off [ 72 , 73 ]. High density of dislocations has been reported in the SLM fabricated NiTi parts [ 42 , 56 ]. Moreover, the density of dislocations depends highly on the SLM process. For instance, Ma et al. [ 42 ] reported that the density of dislocations decreases with the decrease of hatch spacing from 35 to 120 μm, which probably is due to the recovery of dislocations that is caused by more re-melting and re-heating cycles when producing with smaller hatch spacing.
• (6) Residual stresses . The locally melted metal is deposited on a relatively cold substrate (or previously consolidated layers), leading to a steep thermal gradient, which can surpass 10 7 K·s −1 and 10 7 K·m −1 [ 75 ]. As a result, the residual stress could be built up inside the SLM fabricated parts [ 28 , 76 , 77 , 78 ]. The accumulated residual stress can cause distortion, geometric failure, delamination of layers, deterioration of fatigue and fracture resistance, as well as the increase of anisotropy of the mechanical properties of SLM fabricated parts [ 28 , 76 , 77 ]. According to the Clausius-Clapeyron type dependence of MTTs on stress [ 79 ], the accumulation of residual stresses will assist the martensite transformation.
• (7) Inhomogeneous grain size distribution . Due to the complex thermal history, the microstructure with inhomogeneous grain size distribution is normally observed in the SLM fabricated parts [ 57 , 71 , 80 , 81 ]. The mechanical performance will be affected remarkably by the inhomogeneous microstructure [ 81 , 82 , 83 ].
• (8) Microstructural heterogeneity . The materials at different position of SLM fabricated parts will experience a different thermal history. For instance, the first deposited layers will experience a fast cooling due to the cold substrate, as well as more reheating cycles, as compared with the top layers. Therefore, the heterogeneous microstructure (e.g., inhomogeneous Ni distribution, thermal stress state, grain size) is developed in the SLM fabricated parts [ 24 , 84 ]. The microstructural heterogeneities will significantly affect the transformation behavior and mechanical properties of SLM that are produced NiTi parts [ 84 ].

Schematic of the melt pool behavior of the selective laser melting process.

3. Phase Transformation Behavior

The “Martensitic Transformation Temperatures (MTTs)” are critical factors affecting practical applications of NiTi alloys, as they determine the temperature range on which shape recovery occurs. The transformation behavior of NiTi alloys is very sensitive to microstructural changes (e.g., presence of dislocations or precipitates). SLM process gives rise to a unique microstructure, being strongly affected by SLM process parameters. Therefore, it is essential to understand how the transformation behavior of NiTi parts reacts to the variations of the SLM process parameters.

As compared with starting NiTi powders, the SLM fabricated parts normally show higher transformation temperatures [ 29 , 49 , 62 , 85 , 86 ], an example could be found in Figure 6 of Ref. [ 29 ]. The increase of transformation temperatures is likely due to the Ni evaporation during the SLM process [ 29 , 47 , 56 , 87 , 88 ]. It seems that with a high Ni-rich starting powder (e.g., Ti-50.7 at % Ni), the shift of transformation temperatures is more obvious than that with a less Ni-rich powder (e.g., Ti-50.2 at % Ni) [ 29 , 63 ]. Therefore, it is important to carefully select the composition of the starting powders, in order to produce NiTi parts with the desired functional properties at the envisaged temperature range.

It has frequently been reported that MTTs increase with the increase of energy density [ 24 , 29 , 42 , 48 , 56 , 57 , 63 , 87 , 89 ]. Moreover, this increase of MTTs is more obvious in the Ni-rich samples than in the Ti-rich samples [ 63 ]. The precipitation of Ni-rich Ni 4 Ti 3 particles is also a possible reason for the increase of MTTs [ 42 ], because the formation of Ni 4 Ti 3 particles leads to Ni-depletion from the matrix [ 1 , 2 ]. However, the Ni 4 Ti 3 precipitates are normally very small in SLM fabricated NiTi alloys [ 42 , 56 ], and nano-sized Ni 4 Ti 3 precipitates indeed suppress martensite transformation (MT), instead of promoting MT, due to the intense lattice distortion that is caused by the coherency between Ni 4 Ti 3 and B2 matrix [ 90 , 91 , 92 ].

Therefore, the Ni loss that is caused by evaporation is likely the main reason for the increase of MTTs. It is suggested that more Ni is evaporated with the increase of energy density, leading to the decrease of Ni/Ti ratio and thus the increase of MTTs. Similar results have been reported in laser welding of NiTi alloys [ 20 , 93 , 94 ]. Zamani et al. [ 93 ] found that the MTTs increase with the increase of laser power, indicating the increase of Ni loss with the increase of input energy. Oliveira et al. [ 94 ] reported that the MTTs increase gradually from base materials to the weld centreline, which can be attributed to the increase of Ni loss with the increase of laser energy, as the laser energy increases from heat affected zone to the center of the melt pool.

However, it was frequently observed that the MTTs differ largely between samples fabricated under similar energy density, but with different SLM process parameters [ 43 , 45 , 46 , 49 ], indicating that the physics behind the observed phenomenon in SLM fabricated NiTi alloy is rather complex. Moreover, it was also reported that the samples, which were produced with very low energy density, show a lower transformation temperature than the MTTs of the powders [ 29 , 63 ]. Therefore, the Ni loss by evaporation is not the only reason for the variation of MTTs with respect to the change of energy density (or SLM process parameters).

In our previous work [ 45 , 46 ], the variation of MTTs was also observed in the samples produced with the same energy density (100 J·mm −3 ) but different process parameters, as shown in Figure 4 a. The MTTs, which are defined as the temperature of the transformation peaks ( Mp ), change from 205 to 277 K under different SLM process conditions. Solution treatment (1273 K for 2 h) reduces the transformation interval for all the samples, but the temperatures of the transformation peaks remain essentially unaffected. This indicates that the variation of MTTs is mainly due to the modification of Ni/Ti ratio, instead of the presence of precipitates, internal stress, or dislocations, because the solution treatment could dissolve the Ni 4 Ti 3 precipitates, annihilate dislocations, as well as eliminate largely the internal stresses.

DSC (Differential Scanning Calorimetry) curves of the as-built (AB) and solution treated (ST, 1273 K for 2 h) NiTi samples produced by various SLM processes under ( a ) high O 2 and ( b ) low O 2 conditions. The green dash line guides the transformation peaks of the solution treated samples. P , v , and h represent the laser power, scanning velocity, and hatch spacing, respectively. (Modified after [ 45 ]).

Figure 4 b shows another set of samples, which were produced with the same SLM process parameters as the samples in Figure 4 a, but under a lower oxygen level. As compared with the samples produced under high oxygen level ( Figure 4 a), a much narrower variation of MTTs (between 233 and 261 K) was observed [ 45 ]. This indicates that the oxygen pickup remarkably influences the transformation behavior of the SLM fabricated NiTi parts. Therefore, it is essential to control the oxygen level of the chamber during the SLM process.

By comparing the transformation behaviour of the samples before and after solution treatment (1273 K, 2 h), we could conclude that the variation of MTTs of NiTi samples that were produced under different SLM conditions is mainly due to the modification of effective Ni/Ti ratio. Feasible reasons for the modification of Ni/Ti ratio are: (i) Ni evaporation, which decreases the Ni/Ti ratio; (ii) oxygen pickup, which binds Ti and thus results in an increase of the effective Ni/Ti ratio; and, (iii) formation of Ni 4 Ti 3 precipitates changing the Ni/Ti ratio of the matrix. The competition between the above effects determines the variation of MTTs.

It is rather difficult to quantify the Ni loss or oxygen pickup in experiments, because these characteristics are influenced by many factors, e.g., melt pool size, the maximum temperature of melt pool, the exposure time of the melts to atmosphere, and the oxygen content of the chamber. Therefore, simulation work, e.g., the model proposed by Khairallah et al. [ 37 ], is highly relevant to reveal the relation between SLM process and the loss of Ni or Ti.

The precipitation of Ni 4 Ti 3 particles, presence of dislocations and residual stresses, as well as the microstructural heterogeneity also affect the transformation behavior (e.g., multiple transformation peaks, broadening transformation peaks) of as-fabricated NiTi parts. Thus, the effect of solution treatment and subsequent aging treatment on the transformation behavior and the mechanical properties of SLM fabricated NiTi parts are also worth studying.

4. Tensile Properties

One of the most challenging tasks in SLM of NiTi SMAs is to produce NiTi parts with good functional and mechanical properties. This is currently the main issue that hampers the practical application of SLM fabricated NiTi parts.

Many studies, which were mainly focused on the compression mode, have been conducted to investigate the mechanical properties of SLM fabricated NiTi parts [ 24 , 29 , 43 , 47 , 49 , 60 , 62 , 67 , 68 , 70 , 85 , 95 , 96 , 97 , 98 , 99 ]. The effect of SLM process conditions on the functional properties of NiTi alloys under compression mode has been well studied and summarized, for example in Ref. [ 24 , 43 , 100 ]. The SLM fabricated NiTi parts normally show good mechanical properties under compression. The total compressive strain over 25% [ 60 , 63 , 98 ] and recoverable strain of up to 6% [ 43 ] have been reported, which are comparable to the conventionally fabricated NiTi samples. It was also found that the compressive properties of SLM fabricated NiTi alloys also benefit from aging treatment [ 24 , 70 , 101 ], the effect that is similar to that in NiTi produced by conventional techniques [ 65 , 90 ].

Besides compression, the tensile properties of NiTi parts are also important, because many NiTi devices work under tension or tension-distortion conditions. However, only very few studies tested the performance of SLM fabricated NiTi parts under tension [ 56 , 57 , 100 , 102 ] or bending [ 42 , 103 ]. Tensile properties are more sensitive to the defects generated by SLM (e.g., porosity, microcracks), leading to the low fracture strains and stresses under tension.

Recently, Sam et al. [ 56 ] investigated the tensile properties of NiTi samples fabricated with different energy densities by modifying the hatch spacing. A recoverable strain of around 5% has been obtained in the samples that were produced with certain SLM parameters ( Figure 5 a) [ 56 ]. It was also found that the sample fabricated with low energy density (with the hatch spacing of 120 μm) shows a larger recoverable strain than that fabricated with high energy density (with the hatch spacing of 35 μm) [ 56 ]. The detailed reason for the improvement of the tensile performance with a larger hatch spacing is not clear yet. It is suggested that future work is highly required to study the influence of SLM process conditions on the microstructure and thus the mechanical properties of NiTi alloys. Khoo et al. [ 100 ] reported a NiTi ribbon with transformation strain (under tension) of 4.6% ( Figure 5 b). The ribbon was fabricated by repetitive laser scanning, i.e., (partially) re-melting the previously deposited layer. It seems that re-melting could eliminate the defects (e.g., cracks, pores) and thus improve the tensile properties. However, only one layer was fabricated in this study. Future studies are required to investigate the effect of re-melting on the performance of SLM fabricated bulk parts.

( a ) Isobaric heating-cooling curves of a Ni 50.9 Ti 49.1 alloy fabricated with a small hatch spacing of 35 μm (black curve), and a large hatch spacing of 120 μm (blue curve). For both samples, the laser power (50 W), scanning sapped (80 mm s −1 ), and layer thickness (30 μm) were the same. The results of the conventionally fabricated Ni 50.9 Ti 49.1 (red curve) and a Ni 49.7 Ti 50.3 alloy after solution treatment (900 °C, 1 h, green curve) are also shown [ 56 ] (with permission from Elsevier Publisher); ( b ) Stress-strain curve of a NiTi ribbon fabricated by repetitive laser scan. A laser power of 25 W was used for the first scan, and the laser power of 60 W was used for the second scan [ 100 ] (with permission from Springer Nature).

In the work conducted by Hayat et al. [ 104 ], NiTi parts were fabricated while using Selective Electron Beam Melting (EBM), which offers a high vacuum circumstance during processing, and thus leads to low pick-up of O 2 and other impurities. Moreover, a preheating temperature of 750 °C kept during processing. However, the EBM fabricated sample shows only the tensile strain of 3.9%. This indicates that the contamination of O 2 may be not the main reason for deteriorating the tensile properties of NiTi alloys fabricated by SLM. Therefore, detailed research (e.g., in-situ TEM work) on finding the origin of the brittleness of SLM fabricated NiTi alloy is highly required, especially to compare the microstructure with the NiTi alloys that were fabricated via conventional approaches.

SLM gives rise to a unique microstructure, which will significantly affect the functional performance of NiTi parts. For instance, the strong texture leads to high anisotropy in the functional properties in different directions (with reference to the build direction). This has to be considered especially for the NiTi devices, which are designed for deforming at different directions. The pickup of oxygen and other impurities, and the presence of pores and micro-cracks will undermine the functional performance of NiTi parts, especially under tension. The inhomogeneous microstructure that is caused by SLM may lead to unpredictable mechanical behavior, as compared with the conventionally fabricated NiTi parts. It is suggested that future work is required to understand how the unique microstructure affects the functional performance of SLM fabricated NiTi parts.

5. Conclusions

In this brief review, previous studies on fabricating NiTi parts by SLM were summarized. SLM provides great potential for fabricating geometrically complex NiTi devices, which will significantly promote the practical applications of NiTi SMAs. SLM gives rise to a unique microstructure, which is highly sensitive to the change of SLM process parameters. The transformation behavior and functional properties of NiTi alloys are, in turn, very sensitive to the microstructural changes. Therefore, more systematic studies are necessary to establish the relation between the SLM process and resulting microstructure, as well as the functional performance of NiTi parts.

• (1) SLM is a complex physical metallurgical process, which leads to the complex microstructural changes, including the variation of composition, formation of precipitations and dislocations, development of strong texture and residual stresses, and the microstructural heterogeneity. Systematic work is required to study the interrelationship between SLM process and resulted microstructure and related functional properties.
• (2) The phase transformation behavior are very sensitive to the SLM process conditions, even when fabricating under similar energy density level. Although the interrelationship between the SLM process and the transformation behavior of NiTi alloys is not clear yet, it may provide an effective way to tailoring the transformation temperature of NiTi alloys by tuning the SLM process parameters.
• (3) The compression properties of SLM fabricated NiTi alloys are comparable with the NiTi alloys produced via conventional approaches. However, the SLM fabricated NiTi alloys normally show a total elongation < 6% under tension. The origin of the brittleness of SLM fabricated NiTi alloy is not clear yet. Future work is highly required to study the formation of defects (e.g., voids, micro-cracks) under different SLM process conditions, and their influence on the functional performance of SLM fabricated NiTi alloys.

Acknowledgments

We could like to thank Jean-Pierre Kruth, M.; Speirs, S. Dadbakhsh (KU Leuven, Belgium), Xiaopeng Li (The University of New South Wales, Australia), Bey Vrancken (Lawrence Livermore National Laboratory, USA) and Zuocheng Wang (Shandong University, China) for discussions.

This work was funded by the National Key R&D Program of China (Grant No.: 2018YFB1105100), Shandong Provincial Natural Science Foundation, China (Grant No.: ZR201709180018), China Postdoctoral Science Foundation (Grant No.: 2017M622195), the Fundamental Research Funds of Shandong University, and the Research Foundation Flanders (FWO, Grant No.: G.0366.15N). The financial support from the Spanish Ministerio de Economía y Competitividad, Project MAT2014-56116-C04-01-R and by the Ministry of Education and Science of the Russian Federation, goszadanie No. 3.1421.2017/4.6 is also acknowledged.

Conflicts of Interest

The authors declare no conflict of interest.

Shape Memory Composites Based on Polymers and Metals for 4D Printing

Processes, Applications and Challenges

• © 2022
• Muni Raj Maurya 0 ,
• Kishor Kumar Sadasivuni   ORCID: https://orcid.org/0000-0003-2730-6483 1 ,
• John-John Cabibihan   ORCID: https://orcid.org/0000-0001-5892-743X 2 ,
• Shahzada Ahmad 3 ,
• Samrana Kazim 4

Center for Advanced Materials, Qatar University, Doha, Qatar

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Department of Mechanical and Industrial Engineering, Qatar University, Doha, Qatar

Upv/ehu science park, basque center for materials, application, leioa, spain.

• Provides a thorough overview of shape memory composites, their preparation techniques, and background information
• Analyzes shape memory polymers composites and metal alloys for various different applications
• Discusses the benefits, challenges, and future scope of shape memory materials and 4D printing

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Table of contents (18 chapters)

Front matter, advances in 4d printing of shape-memory materials: current status and developments.

• Muni Raj Maurya, Kishor Kumar Sadasivuni, Samrana Kazim, J. V. S. K. V. Kalyani, John-John Cabibihan, Shahzada Ahmad

Characterization Techniques for Shape-Memory Alloys

• Praveen K. Jain, Neha Sharma, Rishi Vyas, Shubhi Jain

Nitinol-Based Shape-Memory Alloys

• Mukesh Kumar

Molecular Dynamics Simulations for Nanoscale Insight into the Phase Transformation and Deformation Behavior of Shape-Memory Materials

• Natraj Yedla, Sameer Aman Salman, V. Karthik

Influences of Powder Size (SMAs) Distribution Fe–Mn/625 Alloy Systematic Studies of 4D-Printing Conceivable Applications

• S. Shanmugan

Copper-Based Shape-Memory Alloy

• Gopal Krushnaji Kulkarni, Girish Sambhaji Gund

Synthesis Techniques of Shape-Memory Polymer Composites

• Gautam M. Patel, Vraj Shah, Miral Vora

Wet Synthesis Methods of Shape-Memory Polymer Composites

• Ashok Bhogi, T. Rajani

Recent Progress in Synthesis Methods of Shape-Memory Polymer Nanocomposites

• Kalpana Madgula, Venkata Sreenivas Puli

Effect of Nano and Hybrid Fillers on Shape-Memory Polymers Properties

• G. V. S. Subbaroy Sarma, Murthy Chavali, Maria P. Nikolova, Gagan Kant Tripati

Meso, Micro, and Nano Particulate Filled Shape-Memory Polymers

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Fiber- and Fabric-Reinforced Shape-Memory Polymers

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Organic Shape-Memory Polymers and their Foams and Composites in Space

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Combination of Shape-Memory Polymers and Metal Alloys

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Devices and Sensors Based on Additively Manufactured Shape-Memory of Hybrid Nanocomposites

• Vinayak Adimule, Santosh S. Nandi, B. C. Yallur

Recent Developments on 4D Printings and Applications

• Deepalekshmi Ponnamma, M. Sai Bhargava Reddy, Muni Raj Maurya, Omkar Kulkarni, Manikant Paswan, Kishor Kumar Sadasivuni et al.

Modern Approach Towards Additive Manufacturing and 4D Printing: Emerging Industries, Challenges and Future Scope

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Correction to: Characterization Techniques for Shape-Memory Alloys

• 4-D Printing
• Shape Memory Polymer Composites
• Shape Memory Metal Alloys
• Additive Manufacturing
• Shape Memory Effect

About this book

Shape Memory Composites Based on Polymers and Metals for 4D Printing is a thorough discussion of the physics and chemistry behind this developing area of materials science. It provides readers with a clear exposition of shape-memory-composite (SMC) preparation techniques for 3D and 4D printing processes and explains how intelligent manufacturing technology may be applied in fields such as robotics, construction, medical science, and smart sensors.

 This book provides practitioners, industrial researchers, and scholars with a state-of-the-art overview of SMP/SMA synthesis, additive manufacturing, modification in synthesis of SMCs for 4D printing, and their likely future applications.

Editors and Affiliations

Muni Raj Maurya, Kishor Kumar Sadasivuni

John-John Cabibihan

Shahzada Ahmad, Samrana Kazim

About the editors

Dr. Muni Raj Maurya is a Researcher at the Center for Advanced Materials, Qatar University, Qatar. His research interests include investigation of optical properties of semiconductor materials and the development of optically active nanostructures. His current research is focused on nanocomposites fabrication, modifications, designs and their applications especially sensors, photodetectors, wearable devices, 3D-Printing and flexible electronics.

Dr. Kishor Kumar Sadasivuni received his BSc and MSc degrees from Andhra University in 2006 and 2008, respectively and his PhD from the University of South Brittany, in 2012. He currently works at the Center for Advanced Materials, Qatar University. Dr. Sadasivuni has published over 200 articles in the international peer-reviewed journals and has edited over nine books. His achievements have been recognized by award, such as Tyre & Rubber Industry Leadership Acknowledgement Awards (TRILA): Young ResearchScholar of the Year 2017. He is also serving as a Managing Editor for the Emergent Materials journal (Springer) lead by Qatar University and Qatar Petroleum Company (QAPCO) and an Editorial Board Member of the Bulletin of Chemical and Pharma Research. He serves as a Guest Editor for Sensors & Transducers journal and a Lead Guest Editor for the International Journal of Materials Science and Applications

Dr. John-John Cabibihan received the Ph.D. degree in bioengineering, with a specialization in biorobotics, from Scuola Superiore Sant’Anna, Pisa, Italy, in 2007. From 2008 to 2013, he was an Assistant Professor with the Electrical and Computer Engineering Department, National University of Singapore. He is currently an Associate Professor with the Department of Mechanical and Industrial Engineering, Qatar University. Dr. Cabibihan is an inventor in 18 patent families and has over 150 peer-reviewed publications. He is an Associate Editor/Editorial Board Member of the IEEE Robotics and Automation Letters, Frontiers in Bioengineering and Biotechnology, International Journal of Advanced Robotic Systems, and SN Applied Sciences journal.

Shahzada Ahmad is a Professor at the Basque Center for Materials, Applications and Nanostructures (BCMaterials), University of Basque country, Spain. His research spans across the fields of physical chemistry, and materials science with a view to developing advanced materials for energy applications. He is an elected fellow of the European Academies and strong advocate for renewable energy.

Samrana Kazim is a Senior Researcher at the Basque Center for Materials, Applications and Nanostructures (BCMaterials), University of Basque Country, Spain. Her current research is focused on Designing, and characterization of nanostructured materials, hybrid inorganic–organic solar cells, and charge transport properties of organic semiconductor.

Bibliographic Information

Book Title : Shape Memory Composites Based on Polymers and Metals for 4D Printing

Book Subtitle : Processes, Applications and Challenges

Editors : Muni Raj Maurya, Kishor Kumar Sadasivuni, John-John Cabibihan, Shahzada Ahmad, Samrana Kazim

DOI : https://doi.org/10.1007/978-3-030-94114-7

Publisher : Springer Cham

eBook Packages : Engineering , Engineering (R0)

Copyright Information : The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Switzerland AG 2022

Hardcover ISBN : 978-3-030-94113-0 Published: 19 May 2022

Softcover ISBN : 978-3-030-94116-1 Published: 20 May 2023

eBook ISBN : 978-3-030-94114-7 Published: 18 May 2022

Edition Number : 1

Number of Pages : XIX, 412

Number of Illustrations : 42 b/w illustrations, 129 illustrations in colour

Topics : Manufacturing, Machines, Tools, Processes , Materials Science, general , Chemistry/Food Science, general , Structural Materials

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Search for dissertations about: "shape memory alloy"

Found 5 swedish dissertations containing the words shape memory alloy .

1. Heterogeneous Integration of Shape Memory Alloysfor High-Performance Microvalves

Author : Henrik Gradin ; Göran Stemme ; Peter Woias ; KTH ; [] Keywords : Microelectromechanical systems ; MEMS ; silicon ; wafer-level ; integration ; heterogeneous integration ; wafer bonding ; Au-Si ; eutectic bonding ; release etching ; electrochemical etching ; microvalves ; microactuators ; shape memory alloy ; SMA ; NiTinol ; TiNi ; NiTi ; cold-state reset ; bias spring ; gate valves ; wire bonding ;

Abstract : This thesis presents methods for fabricating MicroElectroMechanical System (MEMS) actuators and high-flow gas microvalves using wafer-level integration of Shape Memory Alloys (SMAs) in the form of wires and sheets. The work output per volume of SMA actuators exceeds that of other microactuation mechanisms, such as electrostatic, magnetic and piezoelectric actuation, by more than an order of magnitude, making SMA actuators highly promising for applications requiring high forces and large displacements. READ MORE

2. Wafer-level heterogeneous integration of MEMS actuators

Author : Stefan Braun ; Göran Stemme ; Martin A. Schmidt ; KTH ; [] Keywords : NATURVETENSKAP ; NATURAL SCIENCES ; Microelectromechanical systems ; MEMS ; silicon ; wafer-level ; integration ; heterogeneous integration ; transfer integration ; packaging ; assembly ; wafer bonding ; adhesive bonding ; eutectic bonding ; release etching ; electrochemical etching ; microvalves ; microactuator ; Shape Memory Alloy ; SMA ; NITINOL ; TiNi ; NiTi ; cold-state reset ; bias spring ; stress layers ; crossbar switch ; routing ; switch ; switch array ; electrostatic actuator ; S-shaped actuator ; zipper actuator ; addressing ; transfer stamping ; blue tape ; Computer engineering ; Datorteknik ;

Abstract : This thesis presents methods for the wafer-level integration of shape memory alloy (SMA) and electrostatic actuators to functionalize MEMS devices. The integration methods are based on heterogeneous integration, which is the integration of different materials and technologies. READ MORE

3. Integration and Fabrication Techniques for 3D Micro- and Nanodevices

Author : Andreas C. Fischer ; Frank Niklaus ; Karl F. Böhringer ; KTH ; [] Keywords : Microelectromechanical systems ; MEMS ; Nanoelectromechanical systems ; NEMS ; silicon ; wafer-level ; chip-level ; through silicon via ; TSV ; packaging ; 3D packaging ; vacuum packaging ; liquid encapsulation ; integration ; heterogeneous integration ; wafer bonding ; microactuators ; shape memory alloy ; SMA ; wire bonding ; magnetic assembly ; self-assembly ; 3D ; 3D printing ; focused ion beam ; FIB ;

Abstract : The development of micro and nano-electromechanical systems (MEMS and NEMS) with entirely new or improved functionalities is typically based on novel or improved designs, materials and fabrication methods. However, today’s micro- and nano-fabrication is restrained by manufacturing paradigms that have been established by the integrated circuit (IC) industry over the past few decades. READ MORE

4. Elastic properties and phase stability of shape memory alloys from first-principles theory

Author : Chun-Mei Li ; Levente Vitos ; Denis Music ; KTH ; [] Keywords : TEKNIK OCH TEKNOLOGIER ; ENGINEERING AND TECHNOLOGY ; Construction materials ; Konstruktionsmaterial ;

Abstract : Ni-Mn-Ga and In-Tl are two examples of shape memory alloys. Their shape memory effect is controlled by the martensitic transformation from the high temperature cubic phase to the low temperature tetragonal phase. Experimentally, it was found that the martensitic transformation, related to the elastic properties, is highly composition-dependent. READ MORE

5. Towards Unconventional Applications of Wire Bonding

Author : Stephan Schröder ; Frank Niklaus ; Michael Mayer ; KTH ; [] Keywords : TEKNIK OCH TEKNOLOGIER ; ENGINEERING AND TECHNOLOGY ; Micro-electromechanical systems MEMS ; heterogeneous 3D integration ; wire bonding ; wire integration ; transfer wafer bonding ; nondispersive infrared gas sensing ; low-stress packaging ; shape memory alloy SMA ; infrared IR emitter ; through silicon via TSV ; ethanol sensing ; nitric oxide gas sensing ; wafer-level ; chip-level ; Kanthal ; nickel chromium NiCr ; Electrical Engineering ; Elektro- och systemteknik ;

Abstract : This thesis presents novel heterogeneous integration approaches of wire materials to fabricated and package MEMS devices by exploring unconventional applications of wire bonding technology. Wire bonding, traditionally endemic in the realm of device packaging to establish electrical die-to-package interconnections, is an attractive back-end technology, offering promising features, such as high throughput, flexibility and placement accuracy. READ MORE

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