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Herein, the quality and accuracy to manufacture delicate parts from NiTi powder using electron beam powder bed fusion (EB-PBF) technology is investigated. Therefore, benchmarks with thin cylinders and thin walls are designed and fabricated using two distinct scan strategies of EB-PBF manufacturing (i.e., continuous melting and spotmelting) with different process parameter sets. After these optimizations, four different lattice structures (i.e., octahedron, cell gyroid, sheet gyroid, and channel) are manufactured and characterized. It is shown both continuous melting and spot melting modes are able to manufacture lattices with relative densities over 97%. And as-built lattice structures exhibit an excellent pseudoelasticity up to 8% depending on the design of the structure, e.g., the channel structure shows more deformation recoverability than the cell gyroid. This is attributed to the integrity of geometry as well as compressive mode of the mechanical loading. Of course, the compressive strength and ultimate compressive strength also increase with the increasing volume fraction. Moreover, the spotmelting can be used as an engineering tool to customize a delicate beamshaped structure with a superior pseudoelasticity. [ABSTRACT FROM AUTHOR]

The review summarizes the progress achieved in the surface modification of NiTi shape memory alloys (SMAs) with laser and electron beams in terms of their compliance with the requirements for biomedical devices and implants. The main provisions of the standards regulating this area of activity are aggregated. The production routes for manufacturing bulk items from NiTi SMAs are described. Since the formation of surface alloys on NiTi SMAs is now an intensively growing area of research, the influence of additional alloying elements on their functional properties is also discussed. The common patterns of interaction of laser and electron radiation with NiTi SMAs are specified. The typical requirements for surface layer conditions and conventional methods for their modification are reported. The results of various laser processing methods, differing in energy parameters, atmospheres and beam scanning algorithms, are summarized. They include remelting, annealing, nitriding, shock peening, alloying and texturing. In addition, some data on the modification and alloying of the surface layers with high-current pulsed electron beams are integrated. Finally, the aggregated information is compared and analyzed from the point of view of its prospects in these research areas. [ABSTRACT FROM AUTHOR]

Introduction: Modern endodontics aims to decrease the bacterial load from the complex endodontic space. Over the years, improvements in the operative phases have led to a considerable increase in the success rate of endodontic treatments. The shaping phase has seen the development of new techniques supported by technological innovations that have led to higher treatment predictability. Endodontic instruments have experienced a series of changes that have led to modifications in their design, surface treatments, and heat treatments. The clinical use of rotating nickel–titanium instruments has become widespread and consolidated, a success due primarily to the alloy's mechanical characteristics, which are superior to steel ones, but also to innovations in instrument design. The advent of the Ni-Ti alloy has kept the concepts and requirements of shaping the same but has modified its implementation in endodontics. Aim: The following review followed the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) protocol. The research question focused on Ni-Ti endodontic instruments whose cyclic fatigue was evaluated by analyzing cyclic fatigue strength and the incidence of fracture. Results: At the end of the research, 10 systematic reviews and 1 randomized controlled trial were included in this comprehensive review. The most frequently analysed alloys were M-wire, conventional Ni-Ti, and CM-wire. In seven articles, instruments made of M-wire alloy were used; in eight articles, instruments made of conventional Ni-Ti; and in seven articles, instruments made of CM-wire alloy. Conclusions: The technological evolution of Ni-Ti alloys has led to the development of increasingly high-performance endodontic files that are resistant to cyclic fatigue during clinical practice and have greater resistance to sterilisation practices, making treatment easier and more predictable over time. In particular, heat-treated nickel-titanium root canal instruments present greater resistance to cyclic fatigue than untreated ones and those used with reciprocating kinematics concerning continuous rotation. [ABSTRACT FROM AUTHOR]

Comprehensive characterizations of the superelastic and elastocaloric effects of NiTi and NiTi-based shape memory alloys (SMA) in the operation temperature region are highly desirable for using them in elastocaloric coolers with a large temperature lift. In this article, we report the superelastic and elastocaloric effects of a commercially available superelastic polycrystalline NiTi SMA tube with an outer diameter of 5 mm and a wall thickness of 1 mm between 293 and 330 K. The NiTi tube sample was subjected to a training of 250 cycles to stabilize its superelastic and elastocaloric effects. We observed that temperature dependencies existed for both superelastic and elastocaloric effects of the NiTi tube, and stress–strain curves differed much between isothermal and adiabatic loading conditions. The largest temperature rise and temperature drop measured at 293 K under an applied strain of 3.66% and a strain rate of 0.1 s−1 during loading and unloading were 21 and 11 K, respectively. The loading conditions (loading function and holding time) also impacted the superelastic effect of the NiTi tube. We identified two major reasons for the irreversibility of the adiabatic temperature change: the hysteresis heat dissipation and the temporary residual strain after unloading, and they affected the cooling performance of the elastocaloric cooler in different ways. We investigated the dependencies of the superelastic and elastocaloric effects on the maximum applied strain and the temperature distribution on the NiTi tube during loading and unloading. The results are beneficial to the modeling of elastocaloric coolers with large temperature lifts. [ABSTRACT FROM AUTHOR]

Rapid methods for assessing the fatigue properties of materials have been developed, among which the self-heating method stands out as particularly promising. This approach analyzes the thermal signal of the specimen when subjected to cyclic loading. In this research, the self-heating method was utilized for the first time with laser powder bed fusion (LPBF) of NiTi alloys, examining two specific loading conditions: loading ratios of 0.1 and 10. A thorough examination of the material self-heating behavior was conducted. For comparative purposes, conventional fatigue tests were also conducted, alongside interrupted fatigue tests designed to highlight the underlying mechanisms involved in high cycle fatigue and potentially self-heating behavior. The investigation revealed several key mechanisms at play, including intra-grain misorientation, the emergence and growth of persistent slip bands, and the formation of stress-induced martensite. These findings not only deepen our understanding of the fatigue behavior of LPBF NiTi alloys but also highlight the self-heating method potential as a tool for studying material fatigue. [ABSTRACT FROM AUTHOR]

In this paper, the evolution of microstructure and mechanical properties in the Fe-28Ni-20Co-11.5Al-2.5Ta-0.05B (at.%) alloy were systematically studied. The findings elucidate that the absence of thermoelastic martensitic transformation following cyclic loading signifies the lack of superelasticity in solid solution state. Subsequent to the 72 h aging process at 600°C, the emergence of small (4 ± 2 nm) Ni3Al precipitates with an L12 structure was observed within the grains. The degree of misfit between the precipitate and matrix was found to be only 0.28%. The precipitates contribute to the strength through ordering strengthening, ultimately increasing the strength of austenite. In the method this study introduces, there is neither a need for significant cold rolling deformation and prolonged annealing to form specific recrystallization texture nor preparation of large grain sized specimens equivalent to single crystals. The coherent relationship between the Ni3Al phase and matrix induces the occurrence of thermoelastic martensitic transformation, which results in a 1.3% superelasticity. [ABSTRACT FROM AUTHOR]

NiTi shape memory alloys have been extensively studied owing to its superelasticity. However, the application of coarse-grained NiTi alloys is limited due to their low superelastic stress and poor superelastic stability after cyclic deformation, which mainly because of their low yield strength. In this study, large deformation cold-drawing and low-temperature annealing were used to obtain nanocrystalline (NC) Ni51Ti49 (at.%) wire specimen (average grain size ~ 14 nm). After twenty cycles of loading (up to 6%)–unloading, the Ni51Ti49 alloy has a superelastic stress of 1051 MPa, a residual strain of 0.66% and a superelastic stress reduction rate of 9%, which is obviously superior to NC NiTi with the same grain size, as well as previous coarse-grained NiTi alloys. We have suggested that this mainly stems from the NiTi matrix that was considerably improved by the synergistic enhancement of high-density grain boundaries and doped Ni atoms in NC Ni51Ti49 SMAs, reducing plastic deformation and showing high superelastic stability. [ABSTRACT FROM AUTHOR]

This study presents an experimental characterization of the interface strength of the shape memory alloy hybrid composite (SMAHC) consisting of the two‐way effect NiTi shape memory alloy (SMA) wire structured by electrochemical etching and the surrounding thermoset matrix. Mechanically induced, in situ thermally induced, and cyclic load‐increase pull‐out tests consistently reveal that SMAHC with structured SMA wires outperforms those with as‐delivered SMA wires by a substantial factor of 2.6–2.7 in interfacial strength — the critical factor governing the overall performance and functionality of the composite. Analyzing the force–displacement curves from mechanically induced pull‐out tests demonstrates that structuring the SMA wire surface leads to a significantly increased elastic energy to initiate a crack and achieve complete failure. SMA wires with structured surfaces continue transferring load even after the initial interfacial failure due to the presence of intact mechanical interlocking sites. The cyclic load‐increase pull‐out test confirms that SMA wires with structured surfaces exhibit a significantly higher load‐bearing capacity, withstanding more load levels and demonstrating greater force of the first failure. Furthermore, in thermally induced pull‐out tests with structured SMA wires, a re‐initiation of failure from the lower side follows an initial failure progression at the SMA wire entry point. [ABSTRACT FROM AUTHOR]

As it is known, controlling NiTi alloy's microstructure is an urgent problem in additive manufacturing, which directly affects the mechanical properties of the alloy. In laser‐directed energy deposition (LDED) technology, the simultaneous powder feeding equipment with double powder barrels can effectively control the material ratio and realize the generation of NixTi1−x alloys with different atomic ratios. First, the performance differences of NiTi alloy under different thermal treatments are explored. Based on this, the optimal thermal treatment process is used to adjust the microstructure of NiTi alloy fabricated by LDED by changing the Ni/Ti atomic ratio to improve mechanical properties. The results indicate that Ni4Ti3 precipitates can induce the R phase, change the phase transition, and improve the mechanical properties in Ni‐rich NiTi alloys. Besides, the mechanical properties of NixTi1−x alloy can be enhanced by adjusting the Ni/Ti atomic ratio to change the content of Ni4Ti3 precipitates. Ni52Ti48 alloy has a tensile strength of 771 MPa, an elongation of 11.6%, and a recovery rate of 95.2%. [ABSTRACT FROM AUTHOR]

The specific damping capacity variation of heat-treated NiTi was observed during a pseudoelasticity test. The detailed B2 → R-phase transformation process in cold-drawn NiTi wires undergoing middle-temperature aging was studied via X-ray diffraction, transmission electron microscope, and internal friction technique. Results show that, as aging time increased at 450 °C, the dynamic phase transition splitting from B2 → R to B2 → R1 and B2 → R2 became evident. However, such a splitting process was not observed for the sample after aging at 400 °C. The reason for R-phase generation is attributed to non-uniformly distributed stress fields. The splitting of the internal friction peak, in conjunction with high-resolution transmission electron microscope and mechanic results, suggests a substantial occurrence of short-range segregation of Ni atoms in the B2-NiTi matrix. Furthermore, the specific damping capacity (SDC) exhibits a gradual increase with prolonged annealing time. Specifically, the sample with significant dynamic phase transition splitting reaches an SDC value of 0.60. [ABSTRACT FROM AUTHOR]

A Fe-30.5wt%Ni-0.155wt%C alloy was annealed at two different temperatures to produce two different austenite grain sizes. In the coarse-grained specimen, hierarchical configurations of variants are formed and carefully analyzed using EBSD. These typical patterns result from the alternate formation of two perpendicular plate groups of variants over several length scales, and two distinct types of mechanical couplings are shown to occur sequentially in the process of the transformation of an austenitic grain. In the fine-grained specimen, the martensite start temperature is depressed below liquid nitrogen temperature, and the martensitic transformation can only occur under stress assistance. Grain size reduction brings about a dramatic change in the morphology of martensite and its configurations. Martensite is fully twinned, and martensite variants arrange themselves into self-accommodating configurations involving all four variants of the same plate group. Those specific configurations share striking similarities with those usually encountered in conventional shape memory alloys. The reversion of such microstructures upon heating is believed to be at the origin of the observed shape memory effect. [ABSTRACT FROM AUTHOR]

The NiTi alloy has attracted significant interest owing to its notable wear and corrosion resistance, suggesting the significant promise of utilizing additively manufactured NiTi alloys in tribological applications. In this study, dry sliding wear tests with sliding velocity of 0.1 m/s for total distance of 250 m at room temperature, 50 °C, 100 °C, and 200 °C were carried out on samples of NiTi alloy samples fabricated using laser powder and laser wire directed energy deposition (LP-DED and LW-DED) processes. Enhanced friction and wear behavior of LP-DED samples were captured at lower temperatures due to higher hardness and the stable dominating NiTi B2 austenite phase in the sample microstructure as confirmed from x-ray diffraction (XRD) analysis. Accumulated transferred material at lower temperatures played a crucial role in modifying the wear mechanisms. However, at higher temperatures both LP-DED and LW-DED samples presented similar wear mechanisms. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Orofacial Orthopedics/Fortschritte der Kieferorthopadie is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Vacuum induction melting is a more energy-efficient process for the preparation of a titanium alloy with good homogeneity and low cost. But the crucial problem for this technology is in developing a crucible refractory with high stability. In the present work, a novel (Ca,Sr,Ba)ZrO3 crucible was prepared by slip casting and its performance in melting NiTi alloy was studied. The results showed that a single solid solution was formed with a homogeneous distribution of metal elements after sintering at 1500 °C. It was found that the total content of oxygen and nitrogen remaining in the TiNi alloy after melting in the (Ca,Sr,Ba)ZrO3 crucible was 0.0173 wt.%, which fulfills the ASTM standard on biomedical TiNi alloys. The good resistance of the (Ca,Sr,Ba)ZrO3 crucible to molten NiTi has a relationship with the sluggish diffusion effect of high-entropy ceramics. This study provides insights into the process of designing highly suitable crucible material for melting a NiTi alloy. [ABSTRACT FROM AUTHOR]

In this paper, a CatBoost model for predicting superelastic strains of alloys was established by utilizing features construction and selection as well as model filtering and evaluation based on 125 existing data points of superelastic titanium alloys. The alloy compositions of a TiNbMoZrSnTa system were optimized and three nickel-free titanium alloys with potentially excellent superelastic properties were designed using the Bayesian optimization algorithm using a superelastic strain as the optimization target. The experimental results indicated that only Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn exhibited clear superelasticity due to the absence of relevant information about the alloys' β stability in the machine learning model. Through experimental optimization of the heat treatment regimens, Ti-12Nb-18Zr-2Sn and Ti-12Nb-16Zr-3Sn ultimately achieved recovery strains of 4.65% after being heat treated at 853 K for 10 min and 3.01% after being heat treated at 1073 K for 30 min, respectively. The CatBoost model in this paper possessed a certain ability to design nickel-free superelastic titanium alloys but it was still necessary to combine it with existing knowledge of material theory for effective utilization. [ABSTRACT FROM AUTHOR]

NiTi alloy has unique shape memory effect and superelasticity, but low strength limits its application. TiC has been identified as a suitable reinforcing phase for NiTi shape memory alloys (SMAs) since it does not undergo interface reactions and has a minimal impact on the shape memory effect. In this study, NiTi SMAs with 5 wt.% TiC addition are prepared by Laser Engineered Net Shaping (LENS). The incorporation of TiC and the fast cooling rate of LENS process generate significant residual stress, thus, heat treatment at 600 and 800 °C are performed for residual stress control. After heat treatment, the stress-induced martensite caused by residual stress disappears, where residual stress of NiTi SMAs decreases by 50-60% when compared to the sample without heat treatment. The optimal yield strength of 531 MPa is 47.1% higher than that of pure NiTi SMAs (361 MPa). Besides, NiTi SMAs undergoes a one-step phase transformation from austenite to martensite, while a two-step transformation including austenite-R phase-martensite is observed after heat treatment. [ABSTRACT FROM AUTHOR]

The objective was to evaluate the effect of glide path and coronal flaring on the dentin volume removal and percentage of touched walls in curved canals using two heat-treated rotary files. The mesiobuccal canal of forty-eight, randomly selected, extracted mandibular molars was divided into two groups of 24 each, according to the type of instrument used (RACE EVO and EdgeSequel rotary files). Each group was further divided into three subgroups; Group (A): Control using one file shaped to 04/30, Group (B) with a glide path (EdgeGlidePath (EGP)), and Group (C): with a glide path and coronal flaring (EGP and EdgeTaper Platinum (ETP) SX file respectively). The root canals were then instrumented using the assigned instruments. The assessment was carried out using micro-CT. The comparison of the mean values of the tested groups about dentin volume removal and percentage of untouched walls did not reach statistical significance (p<0.05). Glide path and coronal flaring had an insignificant effect on the dentin volume removal and percentage of untouched walls in curved canals. [ABSTRACT FROM AUTHOR]

Objective: The electrochemical dissolution method of instrument retrieval emphasizes on the dissolution of the instrument rather than sacrificing dentine. Most of the studies conducted for electrochemical dissolution used fluoride-containing electrolytes and were performed inside a beaker. In this study, we used chloride-based fluids as electrolytes. Materials and Methods: Fifty extracted mandibular first premolars were divided into five groups based on the electrolytes used. Canals were enlarged to ProTaper Universal F2, and files were intentionally broken inside the canal. These specimens were subjected to electrochemical characterization by applying the potential of 9V for 20 min. Optical images were taken to assess the change in surface topography. The results were analyzed statistically by one-way analysis of variance (analysis of variance [ANOVA]). Results: The rate of dissolution based on the electrolyte used decreased in the following order, viz. Tyrode's solution>artificial saliva>normal saline>Ringer's lactate/physiological serum. Conclusion: Apart from fluoride, chloride-based electrolytes could be an efficient alternative. [ABSTRACT FROM AUTHOR]

Objective: Evaluating the canal-centering and apical transportation ability of endodontic file systems working with different kinematics but of similar cross section. Materials and Methods: Sixty human maxillary first molar mesiobuccal (MB) roots were assigned to three experimental groups based on instrumentation techniques: Reciproc Blue (RB), Mtwo (M2), and OneShape (OS). Pre- and post-instrumentation micro-computed tomographic analysis was performed. Centering ability and apical transportation were analyzed at 3 mm, 6 mm, and 9 mm short of the apex. Statistical analysis was conducted using Mann-Whitney U test and Kruskal-Wallis test. Results: OS showed better canal-centering ability than RB and M2 at 3 mm, 6 mm, and 9 mm. No significant difference among the tested groups was observed during the assessment of apical transportation (P < 0.05). Conclusion: The systems evaluated safely prepared curved MB canals with minimal canal transportation. OS showed superior canal-centering ability compared to the other two groups. [ABSTRACT FROM AUTHOR]

This work explores the influence of a pre-engineered notch on the electromagnetic radiation (EMR) parameters in NiTi shape memory alloy (SMA) during tensile tests. The test data showed that the EMR signal fluctuated between oscillatory and exponential, signifying that the specimen's viscosity damping coefficient changes during strain hardening. The EMR parameters, maximum EMR amplitude, and average EMR energy release rate remained constant initially but rose sharply with the plastic zone radius with progressive loading. It was postulated that new Frank–Read sources permit dislocation multiplication and increase the number of edge dislocations participating in EMR emissions, leading to a rise in the value of EMR parameters. The study of the correlation between EMR emission parameters and the plastic zone radius before the crack tip is a vital crack growth monitoring tool. An analysis of the interrelationship of the EMR energy release rate at fracture with the elastic strain energy release rate would help develop an innovative approach to assess fracture toughness, a critical parameter for the design and safety of metals. The microstructural analysis of tensile fractures and the interrelation between deformation behaviours concerning the EMR parameters offers a novel and real-time approach to improve the extant understanding of the behaviour of metallic materials. [ABSTRACT FROM AUTHOR]

Nickel‐titanium alloys are produced via laser metal deposition using titanium carbide and titanium diboride as nucleating agents to refine the grain structure. The optimal process parameters are determined by analyzing the quality of the alloy formation. X‐ray diffraction confirms the simultaneous presence of the B19′ martensitic phase and B2 austenitic phase in the nickel‐titanium alloy fabricated by laser metal deposition. Tensile testing is performed on the samples at room temperature. The results show that adding mass fractions 0.9 % titanium carbide and titanium diboride effectively refines the grain size of the nickel‐titanium alloy fabricated by laser metal deposition, leading to improved tensile properties. Specifically, the addition increases the tensile strength by 40 % and 70 %, and the elongation by 50 % and 60 %. [ABSTRACT FROM AUTHOR]

Background: Comprehensive datasets quantifying the coupled thermo-mechanical and electrical properties of shape memory alloys (SMAs) are lacking, as are standardized techniques for robust characterization. This hampers accurate modeling and design of SMA-based components. Objective: This work develops an automated experimental system to enable simultaneous measurement of stress-strain-temperature behavior and electrical resistivity evolution in NiTi SMA wires under controlled stress conditions. Methods: Customized test frames apply precise mechanical stresses while allowing for in situ electrical measurements and infrared imaging during complete thermal cycling protocols. Specialized instrumentation including a Keithley 2002 multimeter, Agilent E3631A programmable power supply, and FLIR A615 thermal camera are integrated with LabVIEW-based software routines for complete automation of the characterization process. Rigorous metrology principles are implemented throughout the measurement procedure to improve accuracy, repeatability, and consistency compared to prior manual techniques. Results: Extensive datasets are generated which reveal pronounced stress-dependencies in key SMA material parameters including transformation temperatures, recoverable strain, and electrical resistivity. A 3D regression model describes the comprehensive relationship between resistivity, temperature, and applied stress across the entire characterization domain. Conclusions: The automated measurement framework and methodology establishes a foundation for high-fidelity, reliable acquisition of coupled SMA property data. This will enable more accurate modeling and design of components and systems incorporating SMA actuation or sensing functions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin University of Science & Technology is the property of Journal of Harbin University of Science & Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

It is generally believed that oxygen in NiTi alloys exists only as Ti4Ni2O. In this work, the possibility of interstitial oxygen has been investigated by experiment and modelling. The sintered elemental NiTi alloys with different oxygen contents were prepared to investigate the relationship between the Ni equivalent (Nieq) and peak transformation temperature (Mp). The results showed at the same Nieq, the Mp was considerably higher than the value reported in the literature. The NiTi matrix with different oxygen contents was observed using atomic probes. Oxygen was found to be uniformly distributed throughout the matrix. The number of independent O atoms and Ti–O clusters increased with increasing oxygen content. Density functional theory was used to calculate the solid solution energy and the formation energy of NiTi superlattice with interstitial oxygen. Oxygen could exist stably in the interstices. The formation energy of interstitial oxygen in NiTi[O] was always higher than that of Ti4Ni2O, which suggested Ti4Ni2O may be the final equilibrium state. However, interstitial oxygen is still an important form existed in the non-equilibrium state, such as powder metallurgical NiTi. The results of this study provide a new basis for predicting the Mp of Ni–Ti–O systems. [ABSTRACT FROM AUTHOR]

Background: This study aimed to compare the effect of heat treatment on the cyclic fatigue resistance of three different nickel-titanium rotary file systems: TruNatomy, HyFlex CM, and NeoEndo flex in simulated curved canals at two different radii of curvatures. Materials and Methods: A total of 60 NiTi rotary files of three types were used, and the samples were divided into three groups TruNatomy, HyFlex CM, and NeoEndo flex. All the instruments were subjected to cyclic fatigue testing using a stainless steel custom-made canal model with a 60° angle of curvature and two radii of curvature 5 mm and 3 mm; the number of cycles to fracture and length of the fractured segment was measured. The separated instruments were subjected to fractographic analysis under scanning electron microscope. Results: The number of cycles to failure to fracture a file at a 3 mm radius of curvature is significantly less as compared to a 5 mm radius of curvature (HCM > TRN > NE). Conclusion: Within the limitation of the present study, there was a positive correlation between the radius of curvature and fatigue life of NiTi files. [ABSTRACT FROM AUTHOR]

To functionalize the surface of the NiTi alloy, hybrid layers comprising nanometric silica and titanium oxides were synthesized. The TiO2–SiO2 nanosystem was chemically prepared and utilized for electrophoretic deposition (EPD) to create multifunctional layers on the alloy surface. The impact of pH on Zeta potential and ceramic particle size was explored to ensure a stable colloidal suspension for EPD, with optimal parameters established at a pH of approximately 6. A uniform layer was formed by applying a voltage of 40 V for 3 min, appearing as a thin film interspersed with regularly spaced larger agglomerates. The thin film primarily consisted of a minor fraction of defective rutile nanoparticles, accompanied by silica and carbon agglomerates from the nanosystem synthesis process. Heat treatment at 800 °C for 2 h induced significant structural changes, developing a novel-generation material with a different structure. An interlayer with strong Si–O–Ti connections was formed. Moreover, the mechanism of layer formation was extensively discussed. [ABSTRACT FROM AUTHOR]

The paper presents an identification process of model parameters of a thin nickel-titanium alloy wire based on experimental research. The wire made of NiTi alloy was subjected to a tensile test to obtain the stress-strain characteristic. Parameters of the non-linear material model were identified based on the obtained experimental results. The material model used in the conducted research may be used for simulation of the shape memory effect and pseudoelasticity of the shape memory alloy. The generated results of numerical simulations have a good approximation with the conducted experimental tests. [ABSTRACT FROM AUTHOR]

Introduction: Interest in self‑ligating brackets is generally smoother and more comfortable. Objectives: To compare rate of retraction and rotational control of maxillary canines with self‑ligating MBT brackets on one side and conventional MBT brackets on the other side of the maxillary arch. Materials and Methods: Ten subjects with a mean age range of 18 to 25 years were selected. For each patient in the maxillary arch, bonding was performed with 0.022‑inch slot conventional MBT brackets on one side and 0.022‑inch slot self‑ligating MBT brackets on the other side. Stainless steel 0.009‑inch ligatures are used for conventional ligation. Retraction of canines was performed with 0.019 × 0.025‑inch stainless steel wires using NiTi closed coil springs with eyelets of 12 mm and 9 mm. The force of retraction was measured using a dynamometer. Dental casts were made at each time interval to record the canine retraction rate (in mm) and rotation (in degrees). Results: The mean difference in the retraction rate was 0.045 mm/month between self‑ligating and conventional brackets, respectively (P > 0.05). The mean difference of total rotation of canines with self‑ligating and conventional brackets was 1.5°, which gives evidence that there was less rotation of canines with self‑ligating brackets. Conclusion: There was no statistically significant difference in canine retraction rates between conventional and self‑ligating brackets. Secure ligation with the self‑ligating brackets showed better rotational control than the conventional brackets. [ABSTRACT FROM AUTHOR]

Mechanical properties of nanocrystalline NiTi shape memory alloys (SMAs) change drastically with grain size. The present contribution develops a constitutive model to reproduce the grain size dependent superelastic behavior and tensile–compressive asymmetry observed in the experiments of nanocrystalline NiTi SMAs. Effects of grain size are incorporated in the developed model by introducing the intrinsic length scale accounting for the transformation hardening as well as the grain-core and grain-boundary phase. In this work, nanocrystalline NiTi SMA is regarded as a two-phase composite material made of inclusions of the grain-core phase dispersed in the grain-boundary phase acting as a matrix. A transformation function allowing for the description of fine-grain strengthening mechanism and tensile–compressive asymmetry is proposed. In the grain-core phase, the evolution law for transformation strain during the forward and reverse transformation is determined. Besides, the constitutive relation of the grain-boundary phase is assumed to be linearly elastic. Based on the equivalent secant bulk and shear modulus of the grain-core and grain-boundary phase, the stress–strain relationship of nanocrystalline NiTi SMAs is derived by using the extended Mori–Tanaka method. Comparisons between experimental and predicted results demonstrate that the proposed model has the ability to reproduce the grain size dependent deformation and asymmetric stress–strain behavior under tension and compression of nanocrystalline NiTi SMAs. In detail, it is found that critical transformation stresses for forward and reverse transformations, dissipation energy density, transformation strain hardening, and maximum transformation strain are sensitive to the grain size and stress states. [ABSTRACT FROM AUTHOR]

The NiTi alloy, known as Nitinol, represents one of the most investigated smart alloys, exhibiting a shape memory effect and superelasticity. These, among many other remarkable attributes, enable its utilization in various applications, encompassing the automotive industry, aviation, space exploration, and, notably, medicine. Conventionally, Nitinol is predominantly produced in the form of wire or thin sheets that allow producing many required components. However, the manufacturing of complex shapes poses challenges due to the tenacity of the NiTi alloy, and different processing routes at elevated temperatures have to be applied. Overcoming this obstacle may be facilitated by additive manufacturing methods. This article provides an overview of the employment of additive manufacturing methods, allowing the preparation of the required shapes of Nitinol products while retaining their exceptional properties and potential applications. [ABSTRACT FROM AUTHOR]

A novel transient liquid phase bonding (TLP) method for obtaining high-temperature resistant diamond/Cu joint was designed. The joint was achieved through the isothermal solidification of Au–Si interlayer assisted by the diamond active modified layer and NiTi particles. The interfacial reaction mechanisms in the TLP process were systematically investigated in this study. The results shown that Ti 5 Si 3 C, CuTiSi and NiTiSi precipitated from the seam. Due to the precipitation of Si and the interdiffusion of Au–Cu, a ductile Au–Cu solid solution ((Au, Cu)ss) matrix formed. The shear strength of the diamond/Cu joint was notably affected by the holding time. The maximum room-temperature shear strength of 108 MPa was achieved when the joints were held at 600 °C for 60 min, and the high-temperature strength was still up to 22 MPa at 600 °C. The high strength of the joints was achieved because of (i) the elimination of the Cu(Au)–Si brittle phases, (ii) the NiTiSi whiskers pulling-out mechanism, and (iii) the moderate distribution of compounds at the diamond/seam interface. [ABSTRACT FROM AUTHOR]

Development of efficient photothermal catalysts made of earth-abundant elements is of prime importance for heterogeneous photocatalysis driven by solar light. Herein, we report for the first time the synthesis of NiTi@TiO 2 /Ni core-shell-satellite nanoparticles from pristine nitinol nanopowder (NiTi) by simple and easily scalable ultrasonically assisted hydrothermal treatment in pure water (T = 200 °C, P = 14 bar, f = 20 kHz, P ac = 17 W, τ = 3 h). Prepared material exhibits unique set of properties, such as strong capability of light-to-heat conversion, good magnetization, high stability, and remarkable thermally assisted photocatalytic hydrogen production (5.5 mmol h−1 g−1 at T = 90 °C). The core-shell-satellite morphology of NiTi@TiO 2 /Ni particles maximizes the contact area between the heat generating metallic core and photocatalytically active TiO 2 /Ni nanocrystalline shell providing the most efficient photothermal effect in the processes of H 2 production and CO 2 methanation without CO emission. In addition, significant magnetic susceptibility of the NiTi@TiO 2 /Ni nanoparticles allows their easy recovery from solution with an external magnetic field. Noncongruent surface oxidation of nanoalloys reported in this work paves the way to the preparation of new generation of catalysts with advanced photothermal properties. [Display omitted] • NiTi@TiO 2 /Ni photocatalyst was prepared from NiTi nanopowder by ultrasonically assisted hydrothermal treatment in water. • Obtained material exhibits strong capability of light-to-heat conversion, good magnetization, and high stability. • NiTi@TiO 2 /Ni nanoparticles exhibit remarkable activity for thermally assisted photocatalytic hydrogen production. • This material enables CO 2 methanation by in situ generated hydrogen in aqueous solutions. [ABSTRACT FROM AUTHOR]

The advent of additive manufacturing (AM) has dramatically shifted the manufacturing sector conceptualization, design, and creation of products. AM can facilitate the production of complicated geometries and create functioning components with distinctive features for aerospace and automotive applications. However, defects such as pores, voids, interfaces, and inclusions can impair the quality and functionality of AM components. Vibration analysis (VA) has become a popular tool for the dynamic qualification and testing of products and nondestructive testing, but the literature lacks a comprehensive review of VA applied to AM. Hence, in this article, recent advances in the application of VA for identifying and characterizing flaws in metal alloys, including titanium, aluminum, and nickel‐based alloys produced by AM, are summarized. In this review, studies on defects such as porosity, cracks, and inclusions and their effect on VA are also included. Herein, this article concludes with a discussion of the limitations of VA for defect characterization and future research directions. Overall, VA is a promising nondestructive testing method for quality assurance in AM and offers insights on overcoming the difficulties for further development and application of this technology. [ABSTRACT FROM AUTHOR]

This study endeavors to comprehensively explore and elucidate the seamless integration of NiTi shape memory alloys (SMAs) into multifaceted applications through the utilization of novel joining techniques. The primary focus lies in the utilization of wire arc additive manufacturing (WAAM) to deposit Nitinol (NiTi) onto Copper (Cu), thereby introducing a transformative approach for their integration into electro-mechanical systems and beyond. Through a detailed examination of the NiTi/Cu bimetallic junction, using advanced analytical techniques including SEM, XRD, and DSC analyses, this research aims to unravel the intricate complexities inherent within the interface. The SEM images and X-ray patterns obtained reveal a complex and nuanced interface characterized by a broad mixed zone comprising various constituents, including Ti(Ni,Cu)2, pure Cu, Ti2(Ni,Cu)3 precipitates, and Ni-rich NiTi precipitates. The DSC results, showcasing low-intensity broad peaks during thermal cycling, underscore the inherent challenges in demonstrating functional properties within the NiTi/Cu system. Recognizing the critical importance of an enhanced martensitic transformation, this study delves into the effects of heat treatment. Calorimetric curves post-annealing at 500 °C exhibit distinct transformation peaks, shedding light on the intricate influence of NiTi layer distribution within the junction. The optimal heat treatment parameters for NiTi/Cu junction restoration are meticulously explored and determined at 500 °C for a duration of 12 h. Furthermore, the study offers valuable insights into optimizing NiTi–Cu joints, with micro-hardness values reaching 485 HV and compressive strength scaling up to 650 MPa. These significant findings not only hold promise for diverse applications across various industries but also pave the way for further research directions and explorations into the realm of SMA integration and advanced joining methodologies. [ABSTRACT FROM AUTHOR]

This document is a special issue of the journal "Materials" that focuses on the recent progress in the structure transition, processing, characterization, and applications of metallic materials. The issue includes research papers on various topics such as the development of dispersion-strengthened copper alloys, the characterization of carbide precipitation in steel, the effect of magnetic fields on aluminum bronze, and the enhancement of impact toughness in cast iron through heat treatment. The issue aims to provide comprehensive and up-to-date information for researchers, engineers, and industry experts in the field of metallic materials. [Extracted from the article]

Significant attention has been directed to the need for a strong and lightweight welding technology for joining the NiTi shape memory alloys (SMAs) to stainless steel (SS). Dissimilar NiTi/SS joints suffer from the brittle and inevitable intermetallic compounds (IMCs) like TiFe, TiFe2, and FeNi that are formed during the welding process. To tackle this challenge, this study explores the use of an engineered magnetic field during the dissimilar laser welding of NiTi to SS. The presence of a magnetic field delivered a remarkable improvement in the tensile strength (over 452 MPa) of the joint, with a notable difference in the microstructure. The effect of the magnetic field on microstructure was investigated; material characterizations showed brittle IMC-free microstructure and a change in grain growth mechanism from columnar to cellular growth during the solidification. Further, fractography analysis proved a ductile failure mode at the joint. [ABSTRACT FROM AUTHOR]

The diffusion processes during the contact melting at the boundary of explosively welded VT1-0 titanium with CuNi19 (melchior) and CuNi45 (constantan) alloy composites were studied. Heat treatment of composites led to the formation of the interaction zone at the joint boundary. The interaction zone in VT1-0 + CuNi19 consists of TiCuNi and αTi + Ti2Cu(Ni) continuous layers as well as a mixture of TiNi(Cu) + TiCu(Ni) + Ti2Cu(Ni) intermetallics. It has been shown that an increase in the nickel content in the case of VT1-0 + CuNi45 composite leads to a decrease in the temperature of contact melting, a change in its mechanism, an increase in the titanium content in the interaction zone, and the appearance of additional Ti2Ni(Cu) intermetallic in its composition. [ABSTRACT FROM AUTHOR]

The triply periodic minimal surface (TPMS) structure of NiTi has gained significant attention owing to its potential for reusable buffer devices. However, the manufactured NiTi TPMS structure still faces challenges such as uneven pore distribution and numerous internal defects, primarily because of the lack of a design theory. Laser powder bed fusion technology has emerged as a promising approach for producing NiTi alloys and TPMS structures, affording substantial advantages. Thus, this study focused on designing and manufacturing three volume-fraction sheeted gyroid lattice structures by using laser powder bed fusion technology. Among the three structures, the VF15 gyroid lattice structure demonstrates the highest values for the compressive modulus (741.42 MPa), nominal yield strength (42.26 MPa), and ultimate yield strength (152.21 MPa). The findings highlight the effectiveness of laser powder bed fusion in preparing NiTi TPMS structures. In general, the utilization of laser powder bed fusion technology for fabricating NiTi TPMS structures combines the strengths of both the NiTi alloy and TPMS structures, resulting in outstanding buffering and shape memory capabilities. Therefore, the findings have potential applicability in efficient and secure reversible energy absorption devices. [ABSTRACT FROM AUTHOR]

Objectives: The reduction of resistance to sliding between the archwire and bracket promotes more seamless tooth movement, leading to a faster and improved orthodontic treatment experience. This research aimed to examine how the degradation of elastomeric modules, different ligation methods, bracket-wire angle, and wire type (nickel titanium, NiTi or stainless-steel, SS) impact the kinetic friction resulting from the interaction between NiTi or SS archwires and SS brackets. Materials and Methods: The current in vitro study was conducted on nine groups, including NiTi and SS archwires with three types of ligations (O-ring, figure of 8, and SS wire ligature) and two bracket-wire angles (0° and 10°). The kinetic friction in each group was measured using a Universal Testing Machine at four time intervals: baseline, day one, week one, and week four. Repeated measures ANOVA, Mauchly test of sphericity followed by the Greenhouse-Geisser test, and relevant post hoc tests were used for statistical analysis (P<0.05). Results: The authors found a decrease in kinetic friction in all types of ligations, which confirmed the effect of time on the degradation of ligation modules. The kinetic friction of figure of 8 ligations was higher than both O-ring and SS wire ligations. No difference was observed between O-ring and SS wire ligations. Furthermore, the bracket-wire angle did not affect friction. Conclusion: The authors suggest that the use of figure of 8 ligations in NiTi and SS wires should be limited due to their high friction and replaced with other types of ligations, if possible. [ABSTRACT FROM AUTHOR]

This study aimed to analyse the effect of chlorhexidine digluconate (CHX DG) mouthwash on the adhesion of oral bacteria to orthodontic appliances. The interactions of four bacteria (S. mutans, A. actinomycetemcomitans, S. oralis, and V. parvula) with two alloys (stainless steel [SS] and nickel-titanium [NiTi]) and three CHX DG solutions (commercial products Curasept and Perio Plus, and pure CHX DG, all with 0.12% active substance) were tested. The adhesive effect on the orthodontic wires was evaluated after 24 h for S. oralis and after 72 h for the other bacteria. The minimum bactericidal concentration of the solution for each bacterial strain was determined using the dilution method to test the antibacterial action. Salivary-pretreated orthodontic archwires were exposed to minimal bactericidal concentrations of solution and bacteria. Commercial antiseptic products, especially Perio Plus, showed a better inhibition of bacterial adhesion to both alloys than pure CHX DG solution (p < 0.05). A. actinomycetemcomitans was most inhibited in the adhesion of all bacteria by the CHX DG products. A greater inhibition of streptococci adherence was observed on SS, while that of A. actinomycetemcomitans was observed on NiTi. V. parvula inhibition was product-dependent. Although there were differences between the strains and the tested agents, it can be concluded that Perio Plus most effectively inhibited the adhesion of all tested bacteria to the SS and NiTi alloys. A. actinomycetemcomitans was most sensitive to all tested agents, while S. mutans showed the highest resistance. The effectiveness of the tested agents was better on NiTi alloys. [ABSTRACT FROM AUTHOR]

Several calcium-based compounds are used to reinforce NiTi composite, but their porous structure and high ceramic content degrade its mechanical characteristics. Therefore, the work aimed to combine reinforcement of NiTi composite using marble dust and nano-silver. The NiTiMDAg nanocomposites were successfully synthesized by the powder metallurgy process. A dense and smooth surface with a relative density of 94.93% was achieved for NiTiMD6Ag6 nanocomposite due to the effective interlocking and bonding provided by nano-silver. The XRD shows the formation of NiTi phase (B19′ and B2) and many other phases (i.e., Ni2Ti, Ni3Ti, Ni4Ti3, NiTi2 and NiTiO3). The combined reinforcement (i.e., marble dust and silver) enhances elastic modulus and strength of NiTiMDAg nanocomposite up to 5.63 GPa and 112.48 MPa, respectively. The results show that the Ni release reduced to 4.00 mg.l−1.cm2 and a uniform apatite formed on the NiTiMDAg nanocomposites. [ABSTRACT FROM AUTHOR]

Owing to the unique superelasticity of shape memory alloys (SMAs), the development of a theoretical model of its contact mechanics proves a challenge. This study compares and investigates the influence of superelastic material parameters on the uniaxial and nanoindentation behavior of a NiTi SMA based on the constitutive model and finite element simulation using the controlled variable method. The elastic modulus and phase transformation strain is found to influence the entire indentation process: The initial stress due to phase transformation when loading primarily affects the loading stage of the indentation curve and the starting stress of reverse phase transformation only affects the unloading stage. The superelastic modulus and Poisson's ratio have a negligible effect on the indentation behavior. Furthermore, the variation law and influence of superelastic material parameters of the NiTi SMA on its indentation behavior is systematically analyzed using an orthogonal design method. The results demonstrate that the elastic modulus and phase transformation strain significantly influence the maximum indentation force and indentation loss work, whereas the other superelastic material parameters have a negligible effect. The maximum indentation force is proportional to the elastic modulus and inversely proportional to the phase transformation strain, and the dissipated energy is proportional to the elastic modulus and the phase transformation strain. Moreover, the dissipated indentation energy decreases with an increase in the maximum indentation force. This study can guide the development of contact mechanics models for superelastic SMAs. [ABSTRACT FROM AUTHOR]

This study compared the fatigue resistance and elemental composition of two blue heat-treated nickel–titanium (NiTi) files used in root canal preparation as follows: Tia Tornado Blue (TTB) and Race Evo (RE) file systems. For cyclic fatigue testing, the two systems were tested where each file was rotated inside an artificial metal canal submerged in either sodium hypochlorite or saline solution until fracture. Time to fracture was recorded. For torsional fatigue testing, the file tip was secured while the file was allowed to rotate at a fixed rate until fracture. Torque at failure was recorded. The two experiments were performed at simulated body temperature and the length of fractured segments was measured. Statistical analysis was carried out with a significance level (p-value) set at 5%. The mean cycles to fracture for RE were superior to that of TTB irrespective of the solution used (p < 0.05). TTB's cyclic fatigue resistance decreased in NaOCl (p < 0.0001). RE demonstrated lower torque at failure (p = 0.002). All files were fractured at comparable lengths (p = 0.218). Although RE is considered more resistant to cyclic fatigue, it showed inferior torsional resistance compared with TTB. The NaOCl negatively affected the TTB's cyclic fatigue resistance. [ABSTRACT FROM AUTHOR]

The paper analyzes the occurrence of evenly spaced cracks on the surface of lamellar specimens of Fe-28Mn-6Si-5Cr (mass %) shape-memory alloy (SMA), during cold rolling. The specimens were hot rolled and normalized and developed cold rolling cracks with an approximate spacing of about 1.3 mm and a depth that increased with the thickness-reduction degree. At normalized specimens, X-ray diffraction patterns revealed the presence of multiple crystallographic variants of brittle α′ body-bcc martensite, which could be the cause of cold-rolling cracking. Both normalized and cold-rolled specimens were analyzed using scanning electron microscopy SEM. SEM micrographs revealed the presence of several crystallographic variants of α′-body-centered cubic (bcc) and ε hexagonal close-packed (hcp) martensite plates within a γ-face-centered cubic (fcc) austenite matrix in a normalized state. High-resolution SEM, recorded after 25% thickness reduction by cold-rolling, emphasized the ductile character of the cracks by means of an array of multiple dimples. After additional 33% cold-rolling thickness reduction, the surface of crack walls became acicular, thus revealing the fragile character of failure. It has been argued that the specimens cracked in the neutral point but preserved their integrity owing to the ductile character of γ-fcc austenite matrix. [ABSTRACT FROM AUTHOR]

Micro-electrical discharge machining (µ-EDM) is one the most favourable process to machine difficult to cut materials in micro-scale with higher accuracy and precision. In this paper, two multi-response optimisation tools called Taguchi's grey relation analysis (GRA) and response surface methodology (RSM)-based desirability function are used to evaluate optimised micro-machining parameters for minimal overcut and circularity error during µ-EDM of nickel-titanium (NiTi) shape memory alloy (SMA). Taguchi's GRA revealed that electrode material has the strongest influence on both the responses followed by capacitance and discharge voltage. ANOVA analysis established that electrode material has the highest percentage contribution of 40.15% on both the responses. The optimisation result obtained by Taguchi's GRA approach is validated by the RSM-desirability function-based technique. The final optimisation result (capacitance 155 pF, electrode material tungsten, discharge voltage 80 V) is a very close agreement with the literature model (capacitance 355 pF, electrode material tungsten, discharge voltage 80 V), with reference to the overcut and circularity error for the improvement of the dimensional accuracy of the micro-holes. Further, the response surface plots disclosed the variation of overcut and circularity error with the process parameters at various levels in a descriptive manner. [ABSTRACT FROM AUTHOR]