This study investigates the effects of external magnetic fields (0–9 T) applied during a 30 min tempering treatment on the microstructure and mechanical properties of HT-9 ferritic/martensitic steels. Electron backscatter diffraction (EBSD) analysis reveals no significant changes in grain size, crystallographic texture, or grain boundary character distribution following magnetic-field-assisted tempering. However, grain orientation spread and kernel average misorientation analyses indicate a reduction in local lattice distortion and residual strain with increasing magnetic field strength. Transmission electron microscopy (TEM) observations show that carbides at grain boundaries become finer and more spherical after tempering under magnetic field, while carbides within the matrix exhibit minimal changes. Thermodynamic estimations suggest that the applied magnetic field increases the ferrite/carbide interfacial energy by up to approximately 7%, promoting carbide refinement and morphological evolution. Magnetic-field-assisted tempering results in an increase in yield strength, reaching a maximum value of 959 MPa at 6 T. No further increase in strength is observed at 9 T, suggesting a possible saturation of the magnetic-field-induced strengthening effect. These results demonstrate that magnetic-field-assisted tempering can modify carbide precipitation behavior and local strain distribution in HT-9 steel without significantly altering its grain structure.

The influence of magnetic fieldMagnetic fields-assisted aging on the microstructural evolution of AA7075 alloy was investigated using atom probe tomographyAtom probe tomography (APT). The mechanical propertiesMechanical properties of precipitation-hardening AA7075 alloys are primarily governed by the nucleation, growth, coarsening, and distribution of precipitates formed during artificial aging. In this study, the combined effects of aging time and externally applied magnetic fieldMagnetic fields in precipitate morphology and composition were investigated by APT after they were artificially aged at 120 °C for selected durations of 1, 4, and 24 h under 0 and 3 T. Detailed analysis of precipitate size, shape, and number density was conducted, while compositional changes were evaluated through bulk composition measurementsMeasurements and proxigram concentration profilesProfile across precipitate interfaces. The results show that precipitates become larger with longer aging time and that the application of a magnetic fieldMagnetic fields alters the chemical compositionChemical composition within the precipitate cores, which in turn modifies their growth behavior and morphology. These findings demonstrate that artificial aging under magnetic fieldMagnetic fields could provide a potential pathway for tailoring precipitation kinetics and microstructural features in precipitation-hardened aluminum alloysAluminum alloy.

This study investigates the influence of Magnetic Field-Assisted natural aging on the mechanical properties of AA7075 aluminum alloys. Specimens that were naturally aged under a 3 T magnetic field for up to 168 hours exhibited hardness increases of up to 13.8% compared with those naturally aged under conventional (0 T) conditions. Furthermore, specimens subjected to 24 hours of natural aging under magnetic field followed by artificial aging at 120 °C for 72 hours under 3 T demonstrated a pronounced enhancement in peak hardness, along with a reduction in the required aging time. These results indicate that the application of a magnetic field during the NA process accelerates precipitation kinetics and enhances the strength of these alloys. Overall, magnetic field-assisted aging presents a promising strategy to improve mechanical performance along with significant reductions in processing time for AA7XXX-series aluminum alloys.

Additive manufacturing (AM) is redefining the design space of NiTi shape memory alloys (SMAs), enabling architected geometries and spatially tailored functionality not accessible through conventional processing. However, the extreme thermal gradients and rapid solidification inherent to AM fundamentally reshape transformation thermodynamics, microstructure, and functional reliability. This review synthesizes current understanding of process-structure-property relationships across laser powder bed fusion, electron-beam powder bed fusion, directed energy deposition, and solid-state AM routes, framing them within a unified thermal-compositional landscape.NiTi performance in AM cannot be evaluated solely through densification metrics. Instead, subtle variations in local energy distribution, evaporation-driven nickel redistribution, oxygen uptake, and crystallographic texture govern transformation temperatures, anisotropy, and superelastic stability. A curated database compiled from over 300 studies is used to perform cross-study statistical mapping, revealing that energy-density metrics are non-unique descriptors, where identical nominal values can produce divergent phase states depending on melt-pool mode and time-temperature history. Texture control via build orientation and scan strategy has emerged as a powerful lever for engineering anisotropic functional response, while post-build heat treatments enable secondary-phase tuning but remain highly sensitive to as-built chemistry.Looking forward, the field is transitioning from empirical parameter optimization toward physics-informed and data-driven design frameworks. Standardized reporting of composition shifts, thermal history, and transformation metrics is needed to enable cross-platform comparability. Integration of in situ monitoring, predictive modeling, and curated databases offers a pathway toward closed-loop control of transformation behavior. Establishing thermodynamically grounded design principles will be essential for translating AM NiTi into reliable biomedical, aerospace, and adaptive structural applications. This framework provides a basis for rational process design and standardized reporting in AM NiTi systems.

In this study, the through-thickness mechanical properties of a 32 mm thick hot rolled 7075 aluminum plate were measured with microscale uniaxial tensile tests. The mechanical strength across the thickness of the plate exhibited a complex M-shaped profile, with the maximum yield strength and ultimate tensile strength of 440.45 MPa and 493.81 MPa respectively attained at 11 mm depth from the surface of the plate. Representative samples from 0, 4, 11 and 16 mm depths were investigated to understand the influence of the precipitate distribution on the evolution of through-thickness mechanical properties in this alloy. The size and distribution of the microscale (>50 nm) and nanoscale (<20 nm) precipitate phases were quantified with a combination of large area scanning electron microscopy (SEM) and small angle x-ray scattering (SAXS) techniques and correlated with through-thickness mechanical properties obtained through microscale tensile testing. The nanoscale precipitate density as investigated with SAXS showed that the 11 mm depth had the highest volume fraction (0.0086) in comparison to the other representative depths. Moreover, the quench and temper processes were modeled using the precipitation module of Thermo-Calc with various assumptions about cooling rate and microstructure and they were found to be in good agreement with the experimental findings.

Machine learning (ML) has emerged as a promising tool for the design of multicomponent alloys due to their vast design spaces. Quaternary NiTiHfPd shape memory alloys (SMAs) possess unique potential to be employed in high-temperature actuation as well as damping systems. This study presents a machine learning approach using the currently available limited data regime to accelerate research on NiTiHfPd SMAs. To this end, a database of transformation temperatures of NiTiHfPd SMAs was compiled and expanded through compositional and post-processing features of the alloys. Various ML algorithms were utilized to predict the austenite finish temperature of NiTiHfPd SMAs and then validated through experiments.

This study explored the influence of magnetic fieldMagnetic field annealing in achieving enhanced mechanical propertiesMechanical properties in terms of yieldYield strength and microhardnessMicrohardness in 7075 aluminum alloyAluminum alloys. A custom-built 9 Tesla (T) superconducting magnetic system was employed during the agingAging of the samples at 120 °C without (0-T) and with (3-T) magnetic fieldMagnetic field to promote the precipitation and growth of strengthening phases. Mechanical propertiesMechanical properties measured with the aid of micromechanical tensile and Vickers hardnessHardness tests showed a 9

This study presents the shape memory behavior of Ni-rich NiTi shape memory alloy fabricated by Laser Powder Bed Fusion Additive Manufacturing (L-PBF-AM) before and after post-processing heat treatment. The microstructural features and thermo-mechanical responses were systematically investigated to understand the effects of processing on the behavior of the specimens. It was shown that the L-PBF-AM process improves the functionality of NiTi components by illustrating perfect superelastic behavior at higher-temperature windows compared to the casted ingot. In addition, it was revealed that shape memory responses were tailored by altering hatch distance, which significantly controls the texture formation along the building direction. After post-processing treatments, transformation temperatures were increased, hysteresis was decreased, and the strength of the samples was significantly improved. The aged L-PBF-AM sample with a smaller hatch distance (80 µm) and intense [001] texture illustrated perfect superelastic behavior with a recoverable strain of 7

Shape memory alloys are a unique class of materials that are capable of large reversible deformations under external stimuli such as stress or temperature. The present study examines the phase transformations and mechanical responses of NiTi and NiTiHf shape memory alloys under the loading of a spherical indenter by using a finite element model. It is found that the indentation unloading curves exhibit distinct changes in slopes due to the reversible phase transformations in the SMAs. The normalized contact stiffness (F/S2) of the SMAs varies with the indentation load (depth) as opposed to being constant for conventional single-phase materials. The load-induced phase transformation that occurred under the spherical indenter was simulated numerically. It is observed that the phase transformation phenomenon in the SMA induced by an indentation load is distinctly different from that induced by a uniaxial load. A pointed indenter produces a localized deformation, resulting in a stress (load) gradient in the specimen. As a result, the transformation of phases in SMAs induced by an indenter can only be partially completed. The overall modulus of the SMAs varies continuously with the indentation load (depth) as the average volumetric fraction of the martensite phase varies. For NiTi (Ea > Em), the modulus decreases with the depth, while for NiTiHf (Ea < Em), the modulus increases with the depth. The predicted young modules during indentation modeling agree well with experimental results. Finally, the phase transformation of the SMAs under the indenter is not affected by the post-yield behavior of the materials.

This work explores the underlying origins for an experimentally-observed correlation between the cyclic pseudoelastic response of Ni50.8Ti49.2 and the hatch spacing used in Laser Powder Bed Fusion (LPBF). In particular, an increase in hatch spacing from 80 to 180 µm produces a transition during cycling from a more flag-shaped to a linear pseudoelastic response, thus spanning a range of potential applications. These observations are studied through the development of a microstructural model that incorporates single crystal pseudoelastic constitutive behavior, texture, plasticity, and residual stress from the LPBF process. The model predicts that an increase in <111> and other non-<001> texture components, observed experimentally at larger hatch spacing, promotes stress redistribution between texture components, leading to greater strain ratcheting for larger hatch spacing and a more linearized stress-strain response after cycling. More generally, the model predicts that the design space for pseudoelastic response – including recoverable strain, linearization, and strain ratcheting – can be systematically varied through control of texture and residual stress from the LPBF process, leading to variations in recoverable strain and ratcheting by up to 4 %. The results suggest a rich design space for architected shape memory alloy materials and structures produced by LPBF.

Ultra-high strength of NiTiHfPd alloys have been promising for specific application areas of SMAs. Thus, the main objective of this study is to further understand the high strength behavior of the alloys through experimental and theoretical studies. Shape memory response of an ultra-high strength Ni45.3Ti29.7Hf20Pd5 alloy was systematically investigated after aging at 550 °C for 5 h via constant-stress temperature cycling and constant-temperature stress cycling experiments. Shape memory behavior under a wide range of compressive stress levels from 300 to 1200 MPa was reported before and after stress cycling of 5000 times. The alloys showed a reversible strain of 1.3

Shape Memory Alloys (SMA) have unique characteristics to memorize their original structure and retain them when activated by heat or stress, however, there still much to be done in terms of fatigue life and phase modifiability. In this project, we propose a tunable treatment method using shockwaves created by nanosecond and picosecond pulsed lasers assisted with magnetic field to create 3-D structures on NiTi SMA. When the laser pulse hits the surface, its energy is partially absorbed, which ablates the surface resulting a plasma plume. By confining the plasma using dielectric medium and magnetic field, the shockwave is tuned for vertical transfer of the pressure gradient on the surface. Optical profilometer and SEM results confirm that the shockwave pressure became uniform when magnetic field was used. The less heat affected zones on the crater, and equal depth across the crater indicates a stable surface morphology due to magnetic field. Moreover, Shape-memory properties were also investigated with differential scanning calorimetry (DSC) measurements of NiTi samples, and the results indicate significant phase broadening, reaching up to 33% from the initial, and shifts in austenitic and martensitic phases of 5 °C. The tunability of the shockwave using magnetic field and water confinement expands the usage in treatment and imprinting of SMAs for biomedical and industrial applications.

In this study, the effects of minor palladium (3 and 5 at.%) addition to ternary NiTiHf shape memory alloy (SMA) were investigated to design a high-temperature NiTiHfPd SMA. While most of the reported NiTiHfPd SMAs contain (Ni+Pd)-rich compositions, the (Ti+Hf)-rich compositions have not been studied to the same extent. This study investigates two new NiTiHfPd compositions and their shape memory effect at elevated temperatures. To this end, two Ni47.3Ti29.7Hf20Pd3 and Ni44.3Ti31.7Hf20Pd5 alloys were fabricated and characterized in terms of microstructure, transformation temperatures, and shape memory behavior in as-cast and aged conditions. The results demonstrated that even a minor addition of Pd could drastically alter the operating temperatures and shape memory effect of NiTiHf SMAs. The metallographic studies revealed the presence of a high volume fraction of secondary phases in the microstructure of Ni44.3Ti31.7Hf20Pd5 that consequently created a matrix leaner in (Ti+Hf) compared to Ni47.3Ti29.7Hf20Pd3. As a result, the Ni44.3Ti31.7Hf20Pd5 was found to be more responsive to precipitation hardening. The evaluation of the shape memory effect of the alloys displayed remarkable strength and strain recovery capability of the quaternary NiTiHfPd at a temperature range above 200 °C with thermal hysteresis as small as 25 °C.

This study systematically evaluates the effects of laser powder bed fusion additive manufacturing (L-PBF-AM) parameters (hatch spacing and laser power) on the thermomechanical behavior and microstructure of Ni50.8Ti49.2 shape memory alloy. The samples were fabricated with hatch spacings from 40 to 240 mu m and laser powers of 50 and 100 W at a constant scanning speed of 125 mm/s, resulting in parts with volumetric energy density levels from 55 to 666 J/mm(3) and two sets of linear energy densities of 0.4 and 0.8 J/mm. The results showed a reduced melt pool size and discontinuity of scan tracks with decreased laser power. Additionally, the porosity level was increased with larger hatch spacing and lower laser power. More notably, the transformation temperatures increased, and the critical stress, recoverable strain, and functional stability of samples improved with lower hatch spacing, where the recovery ratio of up to 90% was observed, regardless of the employed laser power. This study also discussed the relationship between the fabrication process and texture formation in the L-PBF-AM process. The advantage of L-PBF-AM was revealed in tailoring the microstructure from highly textured samples in [1 1 1] or [001] direction when hatch spacing lower than laser beam focused was employed, to the appearance of equiaxed solidification front with island grains and random orientations.

In this study, the effects of cryogenic and flood cooling on the surface integrity of Inconel 718 are investigated for face turning with four selected cutting speeds of 25, 50, 75 and 100 m/min. Surface integrity of machined samples was characterized in terms of surface morphology, sub-surface microstructure, microhardness, x-ray diffraction textures, and residual stresses. While the differences between cryogenic and flood cooling were relatively limited for the majority of surface integrity metrics, a substantially increased (+80% vs flood condition) nanolayer depth was observed at the highest cutting speed of 100 m/min with cryogenic cooling. Additionally, cryogenic cooling resulted in slightly improved surface roughness and slightly increased compressive residual stress, particularly at elevated cutting speeds. Nb-rich secondary phases were detected after machining for all conditions, however, cryogenic cooling and low cutting speed led to reduced mixing of these nanocrystalized phases in the recrystallized surface layer. Based on these observations a and qualitative model for surface generation and nanocrystallization under flood and cryogenic machining conditions was proposed. Overall, the effect of cryogenic cooling on nanolayer generation was most pronounced at elevated speeds, suggesting the potential for cryogenic cooling to allow for more aggressive, yet sustainable, processing strategies with improved surface integrity.

This study is the first study on the compressive and tensile stress-strain revealing the deformation anisotropy among laser powder bed fusion NiTi parts fabricated with the same process conditions. We investigated the effects of building orientation on the microstructure and the resulting shape memory properties. To this end, three orientations were selected, namely 0, 45, and 90-degree, measured from the build plate and fabricated with the same process parameters. A strong (001) texture was formed along the building direction for all of the samples; a different texture could however be observed along the loading direction (LD). Samples fabricated with 45-degree showed a texture of (110) along the LD, as confirmed through X-ray diffraction and backscattered diffraction while 0 and 90 samples still had the (001) texture along with the LD. These texture variations created anisotropic compression-tension behaviors with deformation patterns consistent with single crystals. The (001) -textured parts showed higher strength and lower transformation strain (2.87% @ 200 MPa in tension for 0 degrees) while the (110) samples showed higher transformation strain at lower stresses (5.31% @ 150 MPa in tension for 45 degrees). (c) 2021 Elsevier B.V. All rights reserved.

Laser powder bed fusion has been widely investigated for shape memory alloys, primarily NiTi alloys, with the goal of tailoring microstructures and producing complex geometries. However, processing high temperature shape memory alloys (HTSMAs) remains unknown. In our previous study, we showed that it is possible to manufacture NiTiHf HTSMA, as one of the most viable alloys in the aerospace industry, using SLM and investigated the effect of parameters on defect formation. The current study elucidates the effect of process parameters (PPs) on the functionality of this alloy. Shape memory properties and the microstructure of additively manufactured Ni-rich NiTiHf alloys were characterized across a wide range of PPs (laser power, scanning speed, and hatch spacing) and correlated with energy density. The optimum laser parameters for defect-free and functional samples were found to be in the range of approximately 60–100 J/mm3. Below an energy density of 60 J/mm3, porosity formation due to lack-of-fusion is the limiting factor. Samples fabricated with energy densities of 60–100 J/mm3 showed comparable thermomechanical behavior in comparison with the starting as-cast material, and samples fabricated with higher energy densities (>100 J/mm3) showed very high transformation temperatures but poor thermomechanical behavior. Poor properties for samples with higher energies were mainly attributed to the excessive Ni loss and resultant change in the chemical composition of the matrix, as well as the formation of cracks and porosities. Although energy density was found to be an important factor, the outcome of this study suggests that each of the PPs should be selected carefully. A maximum actuation strain of 1.67% at 400 MPa was obtained for the sample with power, scan speed, and hatch space of 100 W, 400 mm/s, and 140 µm, respectively, while 1.5% actuation strain was obtained for the starting as-cast ingot. These results can serve as a guideline for future studies on optimizing PPs for fabricating functional HTSMAs.

Effects of post-aging cooling rate (water quenched, WQ, and furnace cooled, FC) on the shape memory properties of polycrystalline Ni45.3Ti34.7Hf15Pd5 alloys were studied. Their functional properties such as transformation temperatures, hysteresis, elastic energy, superelastic behavior and recoverable strain were found to be closely related to the post-aging cooling rate. Martensite start temperature decreased from 77 degrees C for WQ sample to 22 degrees C for FC sample. Impressive shape memory effect was observed under a huge compressive stress of 1 GPa with recoverable strains of 2.2 % and 2.5 % for the water quenched and furnace cooled samples, respectively. While both WQ and FC alloys showed perfect superelasticity for a wide temperature range, the WQ sample showed superelasticity at higher temperatures above 100 degrees C.

An advanced direct imprinting method with low cost, quick, and minimal environmental impact to create a thermally controllable surface pattern using nanosecond and picosecond laser pulses is reported. Patterned micro indents were generated on shape memory alloys (SMA) and aluminum using nanosecond and picosecond laser operating at various wavelengths combined with suitable transparent overlay, a sacrificial layer of graphite, and copper grid. Laser pulses at different energy densities which generate pressure pulses up to a few GPA on the surface were focused through the confinement medium, ablating the copper grid to create plasma and transferring the grid pattern onto the surface. Scanning electron microscope (SEM), atomic force microscope (AFM), and optical microscope images show that various patterns were obtained on the surface with high fidelity. Optical profile analysis indicates that the depth of the patterned sample initially increases with the laser energy and later levels off. Our simulations of the laser irradiation process also confirm that high temperature and high pressure (up to 10 GPA) could be generated when laser energy of 2 J/cm2 is used. Experimental data is in good agreement with a theoretical simulation of laser-induced shock wave propagation inside the material. Stress wave closely followed the rise time of the laser pulse to its peak values and initial decay. Ongoing experiments on a different wavelength and confinement medium conditions and recovery ratio (ratio of the depth of cold indent to the depth of the initial indent) will also be presented.

Compressive behavior of Al/SiC functionally graded composites (FGCs) was experimentally investigated. The FGC specimens are composed of ceramic (SiC) and metal (Al) constituent, varying in a predetermined configuration through the plate thickness. The compressive tests of FGCs manufactured with powder stacking hot-pressing technique were performed at different temperatures ranging from 25 to 150 °C. Al/SiC functionally graded composite specimens having three different compositions: n = 0.1, n = 0.5 and n = 1, were produced and compared to each other. It was found that the compression behavior of the FGCs was highly affected by composition variation through sample thickness. The strength of the composites decreased with the testing temperature. On the other hand, yield strength and ultimate compressive strength values increased with compositional gradient. The ultimate compressive strength of the composites reached 300 MPa. A minimum absorbed energy during the compressive tests was 25.2 × 10−3 J/mm3 and 96.9 × 10−3 J/mm3 for the test temperatures of 25 °C and 150 °C, respectively, for the compositional gradient n = 1.