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Microstructure and defects strongly affect martensitic transformations in metallic alloys. Significant progress has been made in understanding the atomic-level processes that control the role of grain boundaries and precipitates in these solid-to-solid phase transformations. Yet, the role of dislocations and their structures on martensitic transformation temperature and the resulting microstructure remains unclear. Therefore, we used large-scale molecular dynamics simulations to study the forward and reverse transformation of a martensitic material modeled after Ni63Al37 under cyclic thermal loading. The simulations reveal that dislocations in the austenite phase act as one-dimensional seeds for the martensite phase, which is present at temperatures significantly above the martensite start value. We find a reduction in the dislocation density during cyclic thermal loading, which results in the increase in martensite and austenite transition temperatures, in agreement with experiments. Importantly, we extracted a critical martensitic nuclei size for developing stable domains and found that relatively low dislocation densities are needed to grow independent martensitic variants resulting in a multi-domain structure. [ABSTRACT FROM AUTHOR]

Utilizing molecular dynamics simulation, this study aims to explore the phase transformation behavior of porous nanocrystalline (NC) NiTi shape memory alloys (SMAs) when subjected to cyclic deformation. The influences of porosity and cyclic deformation on the phase transformation of NC NiTi SMAs are examined and discussed. The simulation results show that the increase in the porosity and number of cycles leads to a decrease in both the critical phase transformation stress and peak stress whereas an increase in the residual martensite, phase boundary, and interstitial atoms; the related results can be supported by previous experiments. After cyclic deformation, the reduction in the potential energy for the entire system during the tensile phase occurs at an earlier stage, indicating that the martensitic transformation occurs earlier as the number of cycles increases. Notably, the dissipated energy demonstrates a decrease with an increasing number of cycles, and the potential energy during the austenite elastic unloading stage undergoes a transition from a decreasing to an increasing trend due to the presence of residual martensite increasing with the number of cycles. [ABSTRACT FROM AUTHOR]

Electro-chemical machining (ECM) can safely be categorized as being a unique unconventional machining technique, in which the role of thermal defects are not involved. The NiTiCo shape memory alloy has high yield strength coupled with good resistance to aggressive aqueous environments, which makes it a potential candidate for use in several bio-medical applications. This research concentrates on electro-chemical machining of a NiTiCo alloy. Taguchi's Design of Experiment (DOE) containing three-parameters and three-factors was used to conduct the experimental study. The influence of concentration of the sodium chloride electrolyte, voltage, and frequency on output characteristics, such as (i) material removal rate (MRR), (ii) surface roughness (SR), and (iii) over-cut (OC), was analyzed. Experimental outputs revealed the voltage (45.29%) to be the most influential among the three controlling parameter. Grey relational analysis (GRA) was utilized to discover the ideal parametric relation and optimize machining characteristics. [ABSTRACT FROM AUTHOR]

The effect of interstitial hydrogen on the elastic properties of bcc Fe, bcc Fe–Cr, and bcc Fe–Ni was investigated using density functional theory calculations. Our results indicate that the elastic moduli decrease linearly with increasing hydrogen concentration. The consequences of hydrogen for the mechanical properties of bcc Fe, bcc Fe–Cr, and bcc Fe–Ni were analyzed, considering various factors such as the ideal shear stress, Peierls stress, number of dislocation pile-ups, and critical crack growth lengths. At the same hydrogen concentration, compared to the bcc Fe and bcc Fe–Ni systems, fewer dislocation pile-ups and shorter critical crack growth lengths can facilitate the nucleation and propagation of cracks in the bcc Fe–Cr system. Finally, we propose a mechanism to explain the influence of Cr and Ni on hydrogen embrittlement. [ABSTRACT FROM AUTHOR]

Aim: This study was twofold: (i) it aimed to investigate the morphometric changes of three temperature‐sensitive nickel–titanium (NiTi) instruments at different temperatures, and (ii) to conduct an in vivo real‐time analysis of intracanal temperature changes. Methods: Changes in the shape and length of XP‐Endo Shaper, XP‐Endo Finisher, and XP‐Endo Finisher‐R were evaluated in real time whilst heated in a temperature‐controlled water bath from 22 to 45°C. Instruments were fixed to a laminated water‐resistant 1 mm graph paper attached to a stone block. Instruments were imaged whilst subjected to increasing temperature using a digital camera attached to an operating microscope. From recorded videos, still frames were extracted at 10‐s intervals and changes in the length and shape of each instrument were measured and changes were plotted against time. Moreover, the intracanal temperature of distal roots of lower molars was measured in vivo for patients attending the clinic for non‐surgical root canal treatments. The temperature was measured using a K‐type thermocouple probe inserted into the mid‐root level after irrigating the canal with a solution set at room temperature (22°C) or heated to 45°C. The intraoral and intracanal temperatures were recorded using a video camera for 180 s at 5‐s intervals to plot the change in the intraoral and intracanal temperature, after both irrigation solution temperatures, with time. Results: The shape transformation of XP‐Endo Shaper began at 31.5 ± 2.0°C and reached its optimal transformation at 35.1 ± 1.0°C. For the Finisher and Finisher‐R, shape transformations began at 29.2 ± 1.9 and 26.9 ± 2.2°C reaching the optimal transformation at 33.9 ± 1.4 and 32.7 ± 1.7°C, respectively. The average decreases in lengths of XP‐Endo Shaper, Finisher, and Finisher‐R after full transformation were 0.43 ± 0.23, 1.07 ± 0.22, and 1.15 ± 0.22 mm, respectively. The intracanal temperature reached 32.9 ± 0.8 and 33.2 ± 1.0°C after 3 min of application of irrigation solutions set at 22 or 45°C, respectively. Conclusion: The tested instruments exhibited diverse changes in their shapes and lengths at varying temperatures. Despite the temperature of the irrigation solution, the intracanal temperature consistently remained lower than the intracanal temperature once equilibrium was reached. This highlights the importance of considering the temperature of irrigation solution during in vitro testing of endodontic instruments. [ABSTRACT FROM AUTHOR]

Pain often occurs after root canal treatment due to unavoidable mechanical or chemical damage. The purpose of the present study was to investigate the efficacy of a nickel-titanium (NiTi) device combined with ultrasonic irrigation and multiple antibiotic creams in the treatment of periapical inflammation of deciduous teeth, so as to improve the understanding of root canal treatment and optimize clinical practice. Evaluation of efficacy was conducted using X-rays and the Visual Analog Scale. This treatment significantly reduced pain and also improved patient compliance and treatment outcomes. The findings of the present study may have scientific and clinical significance for optimizing root canal treatment in pediatric dentistry and requires further in-depth research in clinical practice. These outcomes may provide potential new ideas and directions for improving patients' quality of life and the efficacy of clinical treatment and have further impacts on future related research and medical practice. [ABSTRACT FROM AUTHOR]

Background: The behavior of shape memory alloys that admit large reversible deformations in response to thermal excitation has been extensively studied in recent years. Yet, the number of works dealing with springs made from these alloys is rather limited in spite of their attractiveness in various applications. Objective: To bridge this gap we designed and constructed an experimental system for characterizing the behavior of the springs. It enables precise control of the three state variables: temperature, elongation, and force. Methods: Control of the sample temperature is achieved by immersing it in a water-filled thermal bath, where the water temperature is adjusted using a thermoelectric Peltier device. A tension-compression motorized unit sets the spring elongation and a force gauge is used for measuring the force exerted on the spring. The data is continuously monitored and acquired with a self-coded LabVIEW program. An important aspect is the calibration procedure developed for identifying the spring load-free state and ensuring the repetitiveness of the measurements. Results: Experiments in which the elongation or the force were measured as a function of the temperature demonstrate the role of the phase transformations. Isothermal experiments enabled to characterize the variations of the force versus the elongation at different temperatures. Conclusions: The proposed system facilitates the execution of highly accurate experiments through which the complex history-dependent behavior of shape memory springs can be revealed and studied. [ABSTRACT FROM AUTHOR]

We report unique two-step strain glass transition toward different local strain states in NiTi, i.e. R and B19′ strain glasses. This unique transition is evidenced by dynamic mechanical analysis and in-situ HR-TEM. A comprehensive phase diagram is established to illustrate diverse transition pathways and corresponding tunable superelastic properties. This pathway exploits the integrated transition of different phases, lowering the transition energy barrier, yielding superelasticity with large recoverable strain (6%), ultralow modulus (24 GPa) and robust cyclic and wide-temperature stability. Our investigation provides fresh insights into continuous transition pathways among different strain glass states to achieve exceptional properties in shape memory alloys. [ABSTRACT FROM AUTHOR]

Because nickel-titanium (NiTi) alloys have unique functions, such as superelasticity, shape memory, and hysteresis similar to bone in the loading-unloading cycles of their recoverable deformations. They likely offer good bone integration, a low loosening rate, individual customization, and ease of insertion. Due to the poor processability of NITI, traditional methods cannot manufacture NiTi products with complex shapes. Orthopedic NiTi implants need to show an adequate fracture elongation of at least 8%. Additive manufacturing can be used to prepare NiTi implants with complex structures and tunable porosity. However, as previously reported, additively manufactured NiTi alloys could only exhibit a maximum tensile fracture strain of 7%. In new reports, a selective laser melting (SLM)–NiTi alloy has shown greater tensile strain (15.6%). Nevertheless, due to the unique microstructure of additive manufacturing NiTi that differs from traditional NITI, the biocompatibility of SLM-NITI manufactured by this new process requires further evaluation In this study, the effects of the improved NiTi alloy on bone marrow mesenchymal stem cell (BMSC) proliferation, adhesion, and cell viability were investigated via in vitro studies. A commercial Ti-6Al-4V alloy was studied side-by-side for comparison. Like the Ti-6Al-4V alloy, the SLM-NiTi alloy exhibited low cytotoxicity toward BMSCs and similar effect on cell adhesion or cell viability. This study demonstrates that the new SLM-NiTi alloy, which has exhibited improved mechanical properties, also displays excellent biocompatibility. Therefore, this alloy may be a superior implant material in biomedical implantation. [ABSTRACT FROM AUTHOR]

The irregular solutions of the stationary Schrodinger equation are important for the fundamental formal development of scattering theory. They are also necessary for the analytical properties of the Green function, which in practice can greatly speed up calculations. Nevertheless, they are seldom considered in numerical treatments because of their divergent behavior at origin. This divergence demands high numerical precision that is difficult to achieve, particularly for non-spherical potentials which lead to different divergence rates in the coupled angular momentum channels. Based on an unconventional treatment of boundary conditions, an integral-equation method is here developed which is capable of dealing with this problem. The available precision is illustrated by electron-density calculations for NiTi in its monoclinic B19' structure. [ABSTRACT FROM AUTHOR]

Titanium (Ti) is generally considered as an ideal bipolar plate (BPP) material because of its excellent corrosion resistance, good machinability and lightweight nature. However, the easy-passivation property, which leads to increased interfacial contact resistance (ICR) and subsequently decreased cell performance, limits its large-scale commercial application in proton exchange membrane fuel cells (PEMFCs). In this paper, we proposed a NiTi alloy prepared by suction casting as a promising bipolar plate for PEMFCs. This NiTi alloy exhibits significantly decreased ICR values (16.8 mΩ cm2 at 1.4 MPa) compared with pure Ti (88.6 mΩ cm2 at 1.4 MPa), along with enhanced corrosion resistance compared with pure nickel (Ni). The superior corrosion resistance of NiTi alloy is accredited to the nobler open circuit potential and corrosion potential, coupled with low corrosion current densities and passive current densities. The improved ICR can be interpreted by the existence of high-proportioned metallic Ni in the passive film, which contributes to the reduced capacitance characteristic of the passive film (compared with Ti) and enhances charge conduction. This work provides a feasible option to ameliorate BPP material that may have desirable corrosion resistance and ICR. [ABSTRACT FROM AUTHOR]

In realistic applications, shape memory alloys are mostly under cyclic loading and, thus, fatigue failure is the major mode of failure in these components. Fatigue mainly starts from a nano- or micro-defect studying which is not feasible using experiments. Thus, Molecular Dynamics (MD) simulations are useful for obtaining understanding of the underlying mechanisms leading to failure of the part. In this study, MD simulations were performed on single crystal NiTi models containing a middle crack subjected to cyclic tensile loading in different crystallographic orientations (i.e., [100], [110] and [111]) at two austenitic temperatures. The orientation dependence of the fatigue behavior of NiTi was observed to be significant. The crack did not propagate significantly under [100] and [110] loading due to the stress-induced martensitic phase transformation at the crack tip. The formation of the martensite at the crack tip acted as a barrier to crack propagation. On the other hand, the crack grew significantly in the model loaded along [111] crystallographic orientation. The crack growth was accelerated when the crack met the {110}<111> slip system which is favorable for austenite with B2 crystal structure. In addition, the effect of temperature on the fatigue crack growth of NiTi was studied at 500 K and 550 K, both being above the austenite finish temperature. The results indicated a slower crack growth rate in NiTi at a higher temperature. [ABSTRACT FROM AUTHOR]

Pulsed anodization of a nearly equiatomic NiTi alloy in HNO3 leads to the formation of a nearly Ni‐free oxide layer, resulting in the suppression of Ni‐ion release from the alloy surface. The core technology involves introduction of a lower‐voltage period, which promostes chemical reactions between the alloy and electrolyte, to obtain a surface layer with better corrosion protection. In this study, a higher voltage of 3.5 V was applied, and the lower voltage was varied within 0–3.5 V. As the lower voltage was increased, nanometer‐sized pores present on the anodized surface gradually expanded, while the layer thickness decreased. Although the corrosion protectivity of the layer did not change significantly during the electrochemical experiments, the amount of Ni‐ion released into the physiological solution significantly decreased when the voltage was below 1.8 V. X‐ray photoelectron spectroscopy analyses revealed the presence of Ni (OH)2 on the topmost surface, and its concentration decreased at a voltage <1.8 V. Lower voltages affected the concentration of Ni (OH)2 on the topmost surface and thus considerably influenced the Ni‐ion release behavior. These findings will contribute to the production of NiTi alloys with improved biocompatibility. [ABSTRACT FROM AUTHOR]

This study presents experimental results on the effect of loading frequency during low‐cycle fatigue on the fracture mechanism and properties of pseudoelastic NiTi wire. The uniaxial tensile tests were performed in stress‐controlled mode over the 0.1–10 Hz frequency range. It was shown that the number of cycles before specimen failure decreased with increasing frequency from 0.1 Hz to 1 Hz but increased at frequencies above 1 Hz. It was fractographically shown that fatigue striations were observed on the fracture surfaces of specimens tested at all loading frequencies. A new type of fatigue striations was described on fracture specimens tested at frequencies up to 1 Hz. They are characterized by different spacing between successive striations with a change in the slope of the fracture at the transitions between them. This feature may be associated with forward and reverse phase transformations during half‐periods of loading and unloading of nitinol. Highlights: Dissipated energy and residual strain of nitinol decrease with increasing frequency.The residual strain and fatigue life of nitinol is frequency dependent.A new type of fatigue striations of various spacing was found at frequencies below 1 Hz.The spacing of striations changes due to alternate crack growth in martensite or austenite. [ABSTRACT FROM AUTHOR]

In the present study, the capacity of two commercial NiTi and NiTiCu shape memory alloy (SMA) wires to develop work-generating (WG) and constrained-recovery (CR) shape memory effects (SMEs), as well as the capacity of a commercial NiTiFe super-elastic wire to act as cold-shape restoring element, have been investigated. Using differential scanning calorimetry (DSC), the reversible martensitic transformation to austenite of the three NiTi-based wires under study was emphasized by means of an endothermic minimum of the heat flow variation with temperature. NiTi and NiTiCu wire fragments were further tested for both WG-SME and CR-SME developed during the heating, from room temperature (RT) to different maximum temperatures selected from the DSC thermograms. The former tests revealed the capacity to repetitively lift various loads during repetitive heating, while the latter tests disclosed the repetitive development of shrinkage stresses during the repetitive heating of elongated wires. The tensile behavior of the three NiTi-based SMA wires was analyzed by failure and loading–unloading tests. The study disclosed the actuation capacity of NiTi and NiTiCu shape memory wires, which were able to develop work while being heated, as well as the resetting capacity of NiTiFe super-elastic wires, which can restore the initial undeformed shape of shape memory wires which soften while being cooled down. These features enable the design of a robotic gripper based on the development of NiTi-based actuators with repetitive action. [ABSTRACT FROM AUTHOR]

Nitinol alloys are widely utilized across various fields owing to their exceptional elasticity and shape memory characteristics. Their low thermal conductivity, high strength, and high toughness pose significant challenges to conventional machining technologies. To address these challenges, several non-conventional machining processes such as electrical discharge machining have been developed. This study introduces an innovative approach that combines the use of insulated coated electrodes with multi-energy field-assisted electrical discharge machining to improve the application of electrical discharge machining in machining deep microporous. We investigated the effects of the insulated electrode and multi-energy field on surface morphology, taper accuracy, diameter cutting, and the thickness of the recast layer in detail. The findings suggest that the insulated coated electrode combined with multi-energy field-assisted electrical discharge machining achieves better taper accuracy and lower diameter cutting, resulting in a smoother surface and a more uniform, thinner recast layer compared to traditional electrical discharge machining. [ABSTRACT FROM AUTHOR]

Zinc–iodine (Zn–I2) batteries are promising, low‐cost and safe aqueous rechargeable energy storage devices. An iodide shuttle‐induced corrosion and poor zinc (Zn) stripping/plating often result in a limited battery lifetime, urges the development of multifunctional Zn anodes. To overcome these problems, here multifunctional Zn‐anode is demonstrated with shape‐programmability and uniform Zn morphology along low‐indexed (002) crystal plane, achieved by electrodepositing Zn on nitinol alloy (nickel–titanium, NiTi). It is found that the surface oxide layer on NiTi supports the uniform Zn deposition with densely packed and planar film formation that leads high corrosion resistance, while adopts the shape‐memory function. NiTi‐based device achieves extremely steady performance, benefiting from uniform and planar Zn morphology during cycling, whereas the Zn‐based device short‐circuits due to dendritic development under severe iodide corrosion. It is also demonstrated a flat‐shape‐programmed flexible pouch cell Zn–I2 battery (SP‐ZIB), which performs well in bent mode, recovers its original flat shape at elevated temperature, and shows consistent performance for validated cycles. The shape‐memory function of NiTi makes this Zn–I2 battery advanced by flexibility and shape‐programmable features. This study represents fresh insight for using smart materials as multifunctional features for the next‐generation Zn‐I2 batteries. [ABSTRACT FROM AUTHOR]

Objective: To evaluate the differences in frictional resistance between in-house 3D-printed resin brackets (IH3DBs) and two types of commercially available brackets in combination with three different archwires. Methods: Friction tests were performed using a dynamometer and a millimetre sled to simulate first premolar post-extraction space closure. Three different brackets, namely PRIMO metallic brackets, Crystal composite brackets and in-house 3D-printed brackets, were tested in combination with three different archwires (0.016-inch NiTi, 0.019 × 0.025-inch NiTi and 0.019 × 0.025-inch SS). Statistical analysis was performed to verify the differences in friction among the bracket and archwire combinations. For all the tests, the significance level was set at p < 0.05. Results: There were significant differences among the three brackets tested with both the 0.016-inch NiTi and 0.019 × 0.025-inch SS archwires (p = 0.026 and p = 0.017, respectively). Only tests with the 0.019 × 0.025-inch NiTi archwire yielded no statistically significant differences between the groups. The composite bracket generated clinically and statistically more friction than both the IH3DB and metallic bracket, with no differences between the latter two. Conclusions: The IH3DBs demonstrated comparable frictional resistance properties to the metal brackets and better than the composite brackets with all the archwires tested. [ABSTRACT FROM AUTHOR]

One of the most important challenges in endodontics is to have files that have excellent flexibility, toughness, and high fatigue life. Superelastic NiTi alloys have been a breakthrough and the new R-phase NiTi alloys promise to further optimize the good properties of NiTi alloys. In this work, two austenitic phase endodontic files with superelastic properties (Protaper and F6) and two austenitic phase files with the R-phase (M-wire and Reciproc) have been studied. The transformation temperatures were studied by calorimetry. Molds reproducing root canals at different angles (30, 45, and 70°) were obtained with cooling and loads simulating those used in the clinic. Mechanical cycles of different files were realized to fracture. Transformation temperatures were determined at different number of cycles. The different files were heat treated at 300 and 500 °C as the aging process, and the transformation temperatures were also determined. Scanning and transmission electron microscopy was used to observe the fractography and precipitates of the files. The results show that files with the R-phase have higher fracture cycles than files with only the austenitic phase. The fracture cycles depend on the angle of insertion in the root canal, with the angle of 70° being the one with the lowest fracture cycles in all cases. The R-Phase transformation increases the energy absorbed by the NiTi to produce the austenitic to R-phase and to produce the martensitic transformation causing the increase in the fracture cycles. Mechanical cycling leads to significant increases in the transformation temperatures Ms and Af as well as Rs and Rf. No changes in the transformation temperatures were observed for aging at 300 °C, but the appearance of Ni4Ti3 precipitates was observed in the aging treatments to the Nickel-rich files that correspond to those with the R transition. These results should be considered by endodontists to optimize the type of files for clinical therapy. [ABSTRACT FROM AUTHOR]

This study aims to examine the effects of milling time on the morphological, structural, and magnetic properties of nanostructured Ni50Ti50 powders prepared by high-energy mechanical alloying using a Fritsch Pulverisette 7 planetary ball mill. Scanning electron microscopy and electron dispersive X-ray spectroscopy, results revealed a novel particle folding phenomenon during high-energy milling, significantly diverging from conventional welding and fracture processes. With increasing milling time, it was observed reduced particle size, and enhanced spherical equiaxial morphology, alongside a mixture of the amorphous phase, NiTi-martensite (Ms), NiTi-austenite (As), and solid solution phases (SS). Rietveld refinements of X-ray diffraction patterns and magnetic measurements highlighted the critical role of the amorphous phase in determining the Ms and Mr values of synthesized Ni50Ti50 powders. After 72 h of milling, the coercive field increased to 285.8 Oe, and the martensitic phase proportion reached 21.58%. [ABSTRACT FROM AUTHOR]

In an effort to enhance the quality of mechanized endodontic instruments, various thermal treatment methods, and design modifications have been suggested. However, upon evaluation, these endodontic instruments may exhibit microscopic irregularities. The objective of this in vitro study was to analyze the cutting capacity, surface finish, and mechanical properties of Nickel-Titanium 25/.04 Rotate (VDW GmbH, Munich, Germany) and LOGIC 2 (Easy Equipamentos Odontológicos, Belo Horizonte, MG, Brazil) rotary instruments. Twenty rotary instruments were divided into 2 groups: GR, the group with ROTATE instruments (n = 10); and GL2, the group with LOGIC 2 instruments (n = 10). They were evaluated for roughness, using a profilometer, for bending resistance, buckling resistance, and cutting capacity using a universal testing machine, as well as for torsional strength (torque and angular deflection) using a torquemeter. The instruments were visualized before and after the mechanical tests through scanning electron microscopy. GR showed better surface finish in terms of roughness, greater cutting capacity, and greater angular deflection than GL2 (P <.05). However, GL2 showed better flexibility than GR (P <.05). GL2 and GR did not show statistically significant differences in terms of buckling and torque (P >.05). The ROTATE and LOGIC 2 rotary instruments differed in their surface finish, cutting capacity, and mechanical properties, except for their buckling resistance and required fracture torque. [ABSTRACT FROM AUTHOR]

Nitinol alloy is widely utilized across various industries due to its special properties. In this paper, the compound effects of two kinds of energy fields on material removal rate (MRR), hole wall quality, machining accuracy, and recast layer in ultrasonic combined magnetic field assisted EDM (UV-MFEDM were studied and analyzed. In addition, the influence of magnetic field intensity on the efficiency and accuracy of micro-hole machining is analyzed systematically. The results show that the surface quality of the micropore is significantly improved, the MRR is increased by 31.6%, the taper of the micropore is reduced by nearly 30%, the overcut diameter is reduced by nearly 23%, the recast layer is more uniform and the thickness of the recast layer is reduced by nearly half. Appropriate magnetic field intensity proves beneficial for improving micro-hole machining efficiency while reducing both taper angle and diameter overcut of micro-holes. [ABSTRACT FROM AUTHOR]

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Exploring shape memory alloys (SMAs) is like diving into a world of material magic, especially when combined with additive manufacturing techniques. This detailed assessment delves into the fascinating realm of additive manufactured SMAs, examining their complex fabrication processes, captivating internal structures, wide-ranging applications, and unique properties. It is remarkable to observe how the combination of metals, particularly nickel and titanium, creates the very essence of SMA's capabilities and various other material combination for novel SMAs. Additional insights are provided regarding how additive manufacturing parameters and appropriate post-treatments can enable these materials to accomplish extraordinary functionalities. These SMAs also possess the ability to recollect and move, demonstrating superelasticity and the capacity to regain their original shape in various capacities. However, there are promising prospects for the development of novel SMA mixtures, enhanced post-treatments methods, and even more intelligent and responsive products with dimensional accuracy and uniformity. This work presents insights on opportunities in industries for resilient materials, ranging from everyday devices to the immense expanse of space and the human body. Even with the advancements, there is still work to be done in continuously improving their design and pocket comfort. This review not only presents information but also envisions a future in which additive manufactured SMAs are central to advancements in engineering and other fields.

The stress-induced martensitic transformations and superelasticity behavior in the NiTi alloy with a single crystal model and a twist grain boundary bicrystal model at different temperatures are studied using molecular dynamics simulations. An atomic tracing method is proposed to identify specific numbers of B19′ martensite variants. Under uniaxial compressive loading, the stress-induced martensitic transformation takes place accompanied by the formation of <011>M type II twins, and the deformation process can be divided into three distinct stages based on microstructure evolution and average atomic total energy. It is found that the twist grain boundary induces an increase in the martensite start temperature, which is consistent with the experimental results. There is no residual B19′ martensite at the end of the unloading process, and the irrecoverable strain mainly results from plastic deformation at the grain boundary through the analysis of atomic local shear strains and has hardly changed with increasing deformation temperature. Remarkably, the grain boundary brings about the acceleration of martensite nucleation and an earlier occurrence of stress plateau. Further simulation results manifest that the presence of the twist grain boundary leads to weakened temperature dependence of martensitic transformation stress and a reduction in the hysteresis loop area. [ABSTRACT FROM AUTHOR]

In this study, hydroxyapatite (HA) incorporated in mesoporous SiO 2 particles (SiO 2 /HA) was initially synthesized using a soft template method. The resulting structure owned a high surface area (796.62 m2 g-1) and a substantial pore volume (0.757 cm3 g-1). The TEM and FESEM images indicated that the synthesized mesoporous particles possessed a spherical morphology, with a diameter of approximately 200 nm, and pores of slit-shape. The mission was to improve the surface characteristics of NiTi implants by composite coatings. This investigation emphasized specifically the impact of different concentrations of mesoporous SiO 2 /HA particles within the electrolyte on the properties of HA/mesoporous composite coatings. The surface characteristics of the coatings were examined using ATR-FTIR, FESEM, EDS, AFM, and hydrophilicity measurements. Furthermore, the osteogenic activity of the coatings was evaluated by culturing the osteosarcoma cell line SAOS-2 on the coated samples. The introduction of mesoporous particles resulted in a decrease in the coatings' surface roughness along with an improvement in their wettability. Moreover, there was an enhancement in the cell viability (99% after 7 days), proliferation, adhesion, and growth of SAOS-2 cells at the optimized concentration of mesoporous SiO 2 /HA particles (1000 mg/L). DAPI images illustrated that the mesoporous particles did not cause any adverse impact on the cellular nuclei. Finally, in the apoptosis test, the composite coating displayed a reduced number of necrotic cells compared to the pure HA coating. [ABSTRACT FROM AUTHOR]

To explore a new method to improve the wear resistance of TiNi shape memory alloy (SMA), Ti-50.8Ni alloy was treated by the method of ultrasonic surface shot peening. The microstructure evolution, hardness, and tribological behaviors have been further investigated to evaluate the effect of ultrasonic surface shot peening (USSP). The surface microstructure can be refined to some extent while the basic phase composition has little change. USSP can facilitate the martensitic transformation in the surface layer, which benefits improving the surface hardness. Additionally, the hardness of Ti-50.8Ni alloy increases first and then decreases with the increase of applied load, but the USSP-treated alloy tends to be more sensitive to load. USSP treatment can improve the wear resistance and reduce the coefficient of friction (COF) in case of a low sliding wear speed of 5 mm/s. However, the tribological properties of USSP-treated alloy are reversely worse in the case of 10 mm/s. This is mainly attributed to the combined effect of stress-induced martensite transformation and degeneration resulting from the frictional heating during the dry sliding wear process. [ABSTRACT FROM AUTHOR]

Introduction: Retrograde intrarenal surgery (RIRS) is associated with complications, many of which are related to the intrarenal pressure (IRP). We aim to describe the design of a novel isoprenaline-eluting guidewire ("IsoWire") and present the results from the first in vitro release studies and the first animal studies showing its effect on IRP. Materials and Methods: The IsoWire comprises a Nitinol core surrounded by a stainless-steel wire wound into a tight coil. The grooves created by this coil provided a reservoir for adding a hydrogel coating into which isoprenaline, a beta-agonist, was loaded. Animal studies were performed using a porcine model. For the control, IRP, heart rate (HR), and mean arterial pressure (MAP) were measured continuously for 6 minutes with a standard guidewire in place. For the experiment, the standard hydrophilic guidewire was removed, the IsoWire was inserted into the renal pelvis, and the same parameters were measured. Results:In vitro analysis of the isoprenaline release profile showed that most (63.9 ± 5.9%) of the loaded drug mass was released in the 1st minute, and almost all of the drug was released in the first 4 minutes exponentially. Porcine studies showed a 25.1% reduction in IRP in the IsoWire that released 10 μg in the 1st minute; however, there was a marked increase in HR. The average percentage reduction in IRP was 8.95% and 21.3% in the IsoWire that released 5 and 7.5 μg of isoprenaline, respectively, with no changes in HR or MAP. Conclusions: The IsoWire, which releases 5 and 7.5 μg of isoprenaline in the 1st minute, appears to be safe and effective in reducing the IRP. Further studies are needed to establish whether the isoprenaline-induced ureteral relaxation will render easier insertion of a ureteral access sheath, reduce IRP during sheathless RIRS, or even promote the practice of sheathless RIRS. [ABSTRACT FROM AUTHOR]

In this research, titanium alloys including smart nitinol (NiTi) were studied. The (NiTi) alloy tends to emitting (Ni) toxic ions due to its low resistance to corrosion within the body conditions over time. For (NiTi) coating process, the magnetron plasma sputtering (DC) technique was used with Aragon gas ratio of (90%) and Oxygen of (10%) in order to coat the alloy with Tantalum and its Oxide (Ta2O 5) thin films. This is one of the methods used to improve the biocompatibility and better adhesion stability of the membrane on the (NiTi) surface, since Tantalum and its oxides are biocompatible and are not affected by the body fluids. Hardness, corrosion and biocompatibility were tested. The results showed improvement in the nominated properties using this coating technique. The hardness for the non-coated sample was (630 Kgf/mm 2) , meanwhile, the coated sample recorded (762 Kgf/mm 2) using sputtering power of (25 W) with a thickness of (226 nm). Tantalum and its precipitated oxides on a pillar of thickness (90.4–226 nm) also exhibited a biocorrosion enhancement, when it was immersed in a Simulated Body Fluid (SBF). The corrosion rate for the non-coated sample was (1.204 × 10 − 2) , meanwhile for the coated sample, its value was (3.453 × 10 − 5) at sputtering power of (15 W), considered as the lower corrosion rate. The scanning electron micrographs also showed an increase in the biocompatibility for the coated nitinol alloys (NiTi) in comparison with the non-coated, ones since it showed a clear formation of Hydroxyapatite (HA) on the sample surface after immersion in the SBF. This behavior was confirmed by the XRD measurements, which presented higher HA peaks on the coated samples surface in comparison with the non-coated samples. [ABSTRACT FROM AUTHOR]

A three‐dimensional non‐isothermal phase field model of polycrystalline NiTi shape memory alloy (SMA) was established based on the Ginzburg–Landau's theory, which considered the interaction between crack growth and martensite transformation (MT). Then, the crack propagation of polycrystalline NiTi SMA and its dependence on the system's grain size and loading rate were studied by the phase field simulations. The results show that the proposed phase field model can characterize the MT behavior, temperature field changes, and stress‐displacement response of NiTi SMA during the crack growth with different grain sizes and loading rates. That is the higher the loading rate, the higher the fracture toughness is; the larger the grain size, the higher the fracture toughness is and the more significant the influence of grain boundary on the crack growth path becomes. Meanwhile, as the grain size increases, the fracture mode gradually changes from the transgranular fracture (for the fine‐grained alloy with a grain size ≈ 15 nm) to the intergranular one (for the coarse‐grained alloy with a grain size ≈ 100 nm). Highlights: The mechanisms for the rate dependence of crack propagation are clarified.The influence of the latent heat effect on crack propagation are clarified.The mechanisms for the toughening effects under different grain sizes are clarified.The mechanisms for the change in fracture mode are clarified. [ABSTRACT FROM AUTHOR]

In the present study, microstructure and cyclic tensile tests were used to measure the superelastic responses of Fe40.95Ni28Co17Al11.5Ta2.5B0.05 (at.%) shape memory alloys after 97% cold rolling. Cold-rolled samples underwent annealing heat treatment (1250 °C/1 h) followed by quenching in water or aging heat treatment (700 °C/6 h and 700 °C/12 h) followed by quenching in water. The microstructure results showed that the average grain size increased from 210 μm to 1570 μm as annealing times increased from 0.5 h to 1 h. X-ray diffraction (XRD) spectra for FeNiCoAlTaB (NCATB) showed that in cold-rolled alloys after solution, the strong peak was in the face-centered cubic (γ, FCC) <111> structure. In aged samples, a new peak (γ', FCC) emerged, the intensity of which increased as aging times rose from 6 to 12 h. Transmission electron microscope (TEM) images showed that the average precipitate size was around 10 nm in 700 °C/6 h specimens and 18 nm in 700 °C/12 h specimens. The precipitate was enriched in Ni, Al, and Ta elements and exhibited an L12 crystal structure. Tensile samples aged at 700 °C for 6 and 12 h exhibited recoverable strains of 1% and 2.6%, respectively, at room temperature. Digital image correlation (DIC) results for the sample aged at 700 °C for 12 h showed that two martensite variants were activated during the superelastic test. Such variants can form corresponding variant pairs (CVPs), which promote tensile deformation. The tensile sample exhibited a gradual cyclic degradation, and a large irrecoverable strain was observed after the test. This irrecoverable strain was the result of residual martensite, which was pinned by dislocations. [ABSTRACT FROM AUTHOR]

This article explores the use of shape memory alloy (SMA) materials in the creation of robot effectors. Specifically, we focus on the design and implementation of a gripper powered by nitinol springs. Nitinol, an alloy of nickel and titanium, can return to a pre-set shape when heated - a phenomenon known as the shape memory effect - which we utilize to control the gripper. The article showcases the design, construction, and testing of the gripper, including its speed and reliability in grasping different objects. Our findings indicate that the gripper was reliable solution, but further research is necessary to optimize its functions and control for more efficient results in practical applications. [ABSTRACT FROM AUTHOR]

This paper presents the design and analysis of a novel 3-degree-of-freedom (3-DOF) parallel manipulator equipped with self-sensing Ni-Ti (Nitinol) actuators. The manipulator's architecture and mechanical design are elucidated, emphasizing the integration of Nitinol actuators. The self-sensing technique implemented in a previous work was extended to a 20 mm actuator length, and the actuator was used to design the 3-DOF manipulator. Kinematic analyses were conducted to evaluate the manipulator's performance under various operating conditions. A dynamic model was implemented for the dynamic dimensioning of the actuators, which work synergistically with a bias spring. The manipulator was realized, and a control strategy was implemented. Experimental tests, although documenting some positioning accuracy issues, show the efficacy and potential applications of the proposed manipulator in robotics and automation systems, highlighting the advantages of self-sensing Nitinol actuators in small parallel manipulator designs. [ABSTRACT FROM AUTHOR]

Context: An unfavorable event that can hinder endodontic treatment and affect the outcome of root canal treatment is the separation of endodontic instruments. Endodontic instrument separation can occur due to clinical or metallurgical factors. Friction between the ultrasonic tip and the remaining dentin generates heat, which is subsequently transferred to the external root surface. Elevated temperatures exceeding 10°C above body temperature for more than a minute may result in injury to periodontal or bone tissue. Aim: The aim of this study was to evaluate and compare temperature rise on the external root surface of teeth during retrieval of broken NiTi instrument using two different ultrasonic tips and two power settings. Materials and Methods: In each group, a sample size of 8 was sufficient to attain a statistical power exceeding 90%, enabling the detection of a minimum mean difference of 0.9204 (delta) through a one-way ANOVA test at a 95% confidence level (alpha 0.05). After access opening and working length determination, samples were randomly distributed into two groups - Group 1 (A and B) - ProUltra tip at high and low power settings and Group 2 (A and B) - Cric Dental IR3 at high and low power settings. The temperature rise was measured using K-type thermocouple thermometer. The comparisons were analyzed using the Kruskal-Wallis test with pairwise comparisons using the Dunn's test. Results: Group 1A and Group 1B resulted in lower heat generation compared to Group 2A and 2B and its difference was statistically significant (P < 0.05). Minimum temperature rise is seen in the ProUltra group at lower power settings (Group 1A) at the apical level and maximum temperature rise is seen in the Cric Dental IR3 group at higher power settings (Group 2B) at the middle third level. Conclusion: It was found that there is a significant temperature rise seen when ultrasonic tips are used for the retrieval of separated files, especially at higher power settings. The ProUltra tip demonstrated the lowest temperature rise at lower power settings, particularly at the apical level, whereas the IR3 Cric Dental tip exhibited the highest temperature rise, notably at higher power settings and the middle third level. [ABSTRACT FROM AUTHOR]

Is additive manufacturing (AM) a sustainable process? Can the process be optimised to produce sustainable AM parts and production techniques? Additive manufacturing offers the production of parts made of different types of materials in addition to the complex geometry that is difficult or impossible to produce by using the traditional subtractive methods. This study is focused on the optimisation of laser powder bed fusion (L-PBF), one of the most common technologies used in additive manufacturing and 3D printing. This research was carried out by modulating the build layer thickness of the deposited metal powder and the input volumetric energy density. The aim of the proposed strategy is to save the build time by maximizing the applied layer thickness of nitinol powder while retrieving the different AM part properties. The saving in the process time has a direct effect on the total cost of the produced part as a result of several components like electric energy, inert gas consumption, and labour. Nickel-rich nitinol (52.39 Ni at.%) was selected for investigation in this study due to its extremely high superplastic and shape memory properties in addition to the wide application in various industries like aerospace, biomedical, and automotive. The results obtained show that significant energy and material consumption can be found by producing near full dens AM parts with limited or no alteration in chemical and mechanical properties. [ABSTRACT FROM AUTHOR]

The mechanical behaviors of laboratory-fabricated steel and superelastic shape memory alloy (SMA) wire ropes are assessed in this study through a comprehensive approach encompassing both experimental investigations and finite element (FE) numerical simulations. The assessment of steel wire ropes involves experimental scrutiny under sinusoidal cyclic loading and natural earthquake loading conditions. In parallel, SMA wire ropes' behaviors are analyzed utilizing FE simulations employing the widely acknowledged ABAQUS software version 2020. The validation of all numerical simulations is undertaken against the experimentally observed behaviors. Moreover, full-scale steel wire ropes are subjected to shaking table tests to validate the simulations, facilitating a comparative analysis between the mechanical responses of SMA and steel wire ropes. The findings demonstrate that SMA wire ropes exhibit superelastic behavior akin to SMA wires, with marginal variations in overall response observed across distinct configurations, akin to steel wire ropes. Furthermore, augmenting the helix angle of SMA wire ropes results in reduced stress and increased strain when exposed to the El Centro earthquake scenario. Nevertheless, the mechanical response of SMA wire ropes closely mirrors that of a single wire. [ABSTRACT FROM AUTHOR]

Adjacent segment disease (ASD) is a prevalent complication following lumbar fusion surgery, representing a significant challenge in spinal surgery. This study aimed to assess the long-term outcomes of Nitinol spring rod semi-rigid fixation, a potential alternative to traditional rigid fixation, in reducing the incidence of ASD. This retrospective case study evaluated 89 patients who underwent lumbar or lumbosacral surgeries using a combination of Bioflex® (a Nitinol spring rod dynamic stabilization system) and an interbody cage over 10 years of follow-up. The fusion status, adjacent segment disc height, mechanical complications, and re-operation rates were analyzed. The cohort had a median follow-up duration of 13.0 years. All patients achieved solid fusion at the final follow-up visit. One patient underwent revision surgery for clinical ASD (1.1%), and no patients required revision surgery due to mechanical problems. Radiological evidence of ASD was observed in 16.9% of the patients. This study's findings suggest that semi-rigid fixation using Bioflex with an interbody cage is a possibly effective treatment strategy to prevent ASD. The technique potentially reduces the risk of ASD by allowing a degree of movement at the surgical site. [ABSTRACT FROM AUTHOR]

In the present investigation, continuous stiffness measurement (CSM) using nano-indentation technique has been employed to measure the hardness and strain rate sensitivity (SRS) parameter of Ti-6Al-2Mo-4Zr-2Sn (AM-Ti6242) alloy. The measured properties have been subjected to exploratory data analysis and interpreted based on local microstructure, composition and micro-texture. Very interestingly, the chemically homogeneous microstructure showed mechanical heterogeneity. The presence of the martensite phase and formation of the stress-induced nano-twins in the AM Ti6242 have been found to influence its nano-mechanical behaviour in a completely different way compared to the non-additively manufactured Ti6242. [ABSTRACT FROM AUTHOR]

This study investigates the microstructure and properties of functionally graded NiTi alloy bilayers. The NiTi layer is printed by laser powder bed fusion on a NiTiX (where X is Hf or Cu) substrate prepared by vacuum arc remelting. Specimens produced with different thicknesses of layers, but constant thickness ratio, are examined by optical and scanning electron microscopy prior to and postannealing process at 1000 °C for 16 h. Scanning electron microscopy– energy‐dispersive X‐ray spectroscopy and transmission electron microscopy studies reveal the presence of Ti2Ni and Ni4Ti3 precipitates in the as‐printed NiTi/NiTiCu samples and Ti2Ni type precipitates in as‐printed NiTi/NiTiHf. Digital image correlation quantifies residual strain in the as‐printed bilayer and enables strain relief to be monitored during heating. It has been shown that microcracks occurring along interfacial zones during the laser powder bed fusion are diminished after annealing heat treatment. The microcrack closure occurs by diffusion of third elements to the open microcracks, leading to precipitation and accumulation of third elements in the interfaces. Eventually, the as‐printed NiTi/NiTiCu sample displays two‐way shape memory effects with about 24.5% shape recovery. This work enhances understanding of controlling fabrication to yield tailored properties in additively manufactured functionally graded NiTi‐based materials. [ABSTRACT FROM AUTHOR]

A novel method of preparing continuous NiTif‐reinforced Ti/Al‐laminated composites is proposed via ultrasonic consolidation (UC) and vacuum hot pressing. The microstructure of the composites is characterized by X‐ray diffraction, scanning electron microscopy, and electron backscattering diffraction. The tensile properties of the composites are measured by a universal testing machine. Results indicate that the composite exhibits multilayer structure consisting of residual NiTi fiber, intermetallic compounds (IMCs) layer, reaction layer, Ti layer, and Al layer. The intermetallic layer is composed of Al3Ti and Al3Ni, and some Ni‐rich precipitates are dispersed in the matrix. And with the introduction of UC assisted, grain refinement occurs at the IMC/Al interface, texture variation emerges at the NiTi fiber/IMCs interface, and a weakening of texture strength is observed at both interfaces. Compared to NiTif‐reinforced Ti/Al‐laminated composites without UC assisted, both the tensile strength (from 872.4 to 826.5 MPa) and failure strain (from 17.5% to 20.4%) of NiTif‐reinforced Ti/Al‐laminated composites with UC assisted increase due to the contribution of UC assisted. The reinforcing and fracture mechanisms of the UC assisted are also discussed. [ABSTRACT FROM AUTHOR]

The binary nickel–titanium (NiTi) alloy, "Nitinol", has become a prominent name in the medical device industry among medical device manufacturers. The unique properties of the material, such as the shape‐memory effect and pseudoelasticity, have earned the material increasing popularity for new product innovations. Among the various manufacturing processes available for metal alloys, laser micromachining has taken the lead for processing Nitinol‐based products. This literature review provides an analysis of the history and applications of Nitinol, an overview of the microstructure of the material, and a review of the current manufacturing methods for laser cutting medical‐grade Nitinol. A more in‐depth focus is placed on the realm of laser processing and the challenges associated with the manufacturing process. Ultrafast femtosecond pulse processing delivers promising results and quality for manufacturing Nitinol medical devices. However, there exists a need to investigate potential approaches to increase the cutting speed of the process to enhance throughput and stay competitive in a growing market due to the cutting speed being over 4‐times slower than long pulse cutting. Many tactics to address the problem are discussed, ranging from laser selection, processing parameters, and nontraditional laser machining approaches. [ABSTRACT FROM AUTHOR]

Nowadays, advanced engineering materials are gradually becoming more attractive to the industries because of their high fatigue strength, hardness, thermal shock resistance, attractive strength to weight ratio, etc. Aluminium metal matrix composites (MMCs) have such properties and good electrical conductivity. Therefore, wire electrical discharge machining (WEDM) was found to be a suitable process for machining of such materials. The open gap voltage, pulse-on-time, pulse-off-time, peak current, wire feed rate and wire tension were considered as input process parameters, and experiments were carried out on fabricated hybrid Al/(SiC+ZrO2+ NiTi)-MMC. Taguchi method-based L18 (21x37) mixed orthogonal array was employed for planning of experiments. The process parameters were optimised for material removal rate (MRR) and surface roughness (SR) heights. Confirmation results reveals 61.88%, −28.75% and −20.25% improvement in MRR, Ra and Rt respectively, over initial setting. From analysis of variance (ANOVA), open gap voltage and pulse-on-time were found significant parameters for MRR and SR. The mathematical models for MRR and SR were developed and confirmation test reveals good agreement of it with experimental results. Scanning electron microscopy images reveal that the recast layer thickness was 8.569 µm at optimal MRR setting and 6.113 µm at optimal surface roughness (Ra) setting. [ABSTRACT FROM AUTHOR]

Single-phase Mn50Ni40In10−xCux (x = 0, 1, 2, 4, 6, 8, and 10) Heusler alloys were synthesized by melt-spinning method. Martensitic transformation is retained within the whole composition range studied. The substitution of Cu for In leads to a drastic increase in the martensitic transformation temperature TM from below room temperature to above 750 K, and enhances the antiferromagnetic character of the martensite. The increase in TM is related to the increasing electron concentration e/a and decreasing cell volume V with Cu doping. The energy difference between martensite and austenite also increases with Cu doping, which tends to elevate the TM. Cu doping can enhance the metallic bonding character in NiMn-based magnetic shape memory alloys (MSMAs) and is a grain refining strategy of their ribbons. The oriented columnar grains in In-rich samples change to fine equiaxial grains in Cu-rich samples. All this has a positive effect on the strength and ductility. The tensile strength of the Mn50Ni40Cu10 ribbon is 3.6 times higher than that of Mn50Ni40In6Cu4. So, Mn–Ni–Cu can be a promising all-d-metal Heusler alloy platform for developing MSMAs with interesting properties. [ABSTRACT FROM AUTHOR]

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

The resistance of nickel–titanium endodontic instruments against cyclic fatigue failure remains a significant concern in clinical settings. This study aimed to assess the cyclic fatigue strength of five nickel–titanium rotary systems, while correlating the results with the instruments' geometric and metallurgical characteristics. A total of 250 new instruments (sizes S1/A1, S2/A2, F1/B1, F2/B2, F3/B3) from ProTaper Gold, ProTaper Universal, Premium Taper Gold, Go-Taper Flex, and U-Files systems underwent mechanical testing. Prior to experimental procedures, all instruments were meticulously inspected to identify irregularities that could affect the investigation. Using a stereomicroscope, design characteristics such as the number of spirals, length, spirals per millimeter, and average helical angle of the active blade were determined. The surface finishing characteristics of the instruments were examined using a scanning electron microscope. Differential scanning calorimetry was employed to establish the instruments' phase transformation temperatures, while energy-dispersive X-ray spectroscopy was utilized to analyze the elemental composition of the alloy. The instruments were subjected to cyclic fatigue testing within a stainless steel non-tapered artificial canal featuring a 6 mm radius and 86 degrees of curvature. Appropriate statistical tests were applied to compare groups, considering a significance level of 0.05. The assessed design characteristics varied depending on the instrument type. The least irregular surface finishing was observed in U-Files and Premium Taper Gold files, while the most irregular surface was noted in Go-Taper Flex. All instruments exhibited near-equiatomic proportions of nickel and titanium elements, whereas ProTaper Universal and U-Files instruments demonstrated lower phase transformation temperatures compared to their counterparts. Larger-sized instruments, as well as ProTaper Universal and U-Files, tended to display lower cyclic fatigue strength results. Overall, the design, metallurgical, and cyclic fatigue outcomes varied among instruments and systems. Understanding these outcomes may assist clinicians in making more informed decisions regarding instrument selection. [ABSTRACT FROM AUTHOR]

Nitinol, a biocompatible material, is gradually becoming famous for its superelasticity, shape memory and corrosion resistance behaviours. However, the lower machinability due to the strain-hardening effect and lower thermal conductivity is contrary to its adventitious properties. Therefore, EDM is a preferable machining process for materials like Nitinol. EDM, thermal processing, raises the concern of processing Nitinol with minimal variation of its well-known properties and economical machining process. Therefore, this article deals with multi-objective optimization through GRG-assisted GA of µ-EDM drilling of Ni51.58Ti48.34 alloy using a copper electrode and distilled water. It was found that discharge current and servo voltage significantly influence the responses. The GA, with the assistance of GRG, optimized the multiple responses (viz. MRR, TWR and DoT) and yielded a discharge current of 12 A, gap voltage of 40 V, discharge time of 2 µs, charging time of 9 µs and flushing pressure of 50 kg/cm2. The confirmatory experiment yielded MRR of 0.0036 g/min, TWR of 0.0038 g/min and DoT of 0.0089 radians. There were variations of the predicted and experimentally validated responses by − 2.78, 26.32 and 35.96% for MRR, TWR and DoT, respectively. [ABSTRACT FROM AUTHOR]

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]