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Developing an accurate means of classifying defects, such as crystal-originated pits, surface-adhered foreign particles, and process-induced defects, using scanning surface inspection systems (SSIS) is of paramount importance because it provides the opportunity to determine the root causes of defects, which is valuable for yield enhancement. This report presents a novel defect classification approach developed by optimizing the linear-based channeling (LBC) and rule-based binning (RBB) algorithms that are applied to a commercially available SSIS (KLA-SP5), in combination with test sample selection including the signature defect patterns associated with the typical crystal growth process. The experimental results demonstrate that defect classification is possible with an accuracy and purity above 80% using the LBC algorithm and 90% using the RBB algorithm.

The Ni-Mn-Ga ferromagnetic shape memory alloys (FSMAs) are a group of active materials that undergo martensitic transformations (MTs) induced by temperature, stress and/or magnetic fields, resulting in large recoverable mechanical deformations. Their fast response and high energy density make them ideal candidates for implementation in sensors and actuators. Recently, the development of high-temperature FSMAs (HTFSMAs), working at temperatures over 373 K, has become an important task to meet the current requirements of modern technologies. The magnetic and magnetoelastic properties of FSMAs are very sensitive to the interactions between the magnetic moments of atoms that, in turn, depend on the atomic positions within the lattice. Here we investigate a series of the polycrystalline Ni45Mn25-xGa20Co5Cu5Fex (x = 0, 1, 2 and 5 at%) HTFSMAs. Their MT and Curie temperatures, the crystal structures of the martensitic and austenitic phases, the temperature evolutions of the lattice parameters of both phases and the atomic site occupancies have been studied by means of powder neutron diffraction measurements, complemented by standard characterization techniques. Based on the atomic site occupancies and additional measurements of the saturation magnetization, the influence of the structure and atomic ordering on the magnetism in these materials is analysed. The most promising candidate for high temperature magnetic actuation is the alloy with Fe 5 at%, following a combination of the high MT and Curie temperatures, around 370 K and 440 K, respectively, with a low tetragonality ratio, c/a approximate to 1.16, in the proximity of MT. (C) 2020 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

We report on low twinning stress of 0.2 MPa for type 1 twin boundaries with rational (101) twinning plane and 0.1 MPa for type 2 twin boundaries with rational [(1) over bar 01] twinning direction, in Ni2MnGa0.8Fe0.2 seven-layer modulated martensite exhibiting about 12% stress-induced strain. The studied samples were free of compound twins with (100) and (110) twinning planes. The martensite lattice is monoclinic and shows a long-period commensurate modulation with wave vector q=(2/7)g(110), where g(110) is the reciprocal lattice vector. The investigated alloy has high potential for practical applications due to the low twinning stress and the elevated Curie point T-C=400 K. (C) 2019 Acta Materialia Inc. Published by Elsevier Ltd.

We study Young’s modulus and damping of 10M martensite in Ni50.0Mn28.4Ga21.6 magnetic shape memory alloy using a sample without a/c twin boundaries (TBs) and maximum or zero shear stress in a/b twinning planes. Damping is ~300 times higher and modulus ~3.5 times lower when shear stress acts on a/b TBs. Ultrahigh damping and low modulus are insensitive to magnetic field, show strong strain amplitude nonlinearity and are attributed to stress-induced motion of a regular system of mobile a/b TBs. Near the reverse transformation, E001 modulus without contribution of TBs is ~10 times higher than reported previously for 10M polyvariant sample.

We study temperature, magnetic field and strain amplitude dependences of the Young's modulus and ultrasonic absorption in the cubic phase of stoichiometric Ni2MnGa single crystal, using longitudinal oscillations (90 kHz) along [100] direction. We show that the additional softening of the Young's modulus below the Curie temperature, usually considered as elastic premartensitic phenomenon, originates instead from conventional microeddy current relaxation associated with individual domain wall motion. In general, existing controversial experimentally observed damping and “elastic” softening behaviours are controlled by a combination of micro- and macroeddy current relaxations, operating at different spatial scales and over distinct frequency ranges.

Deformation rearranges the crystal lattice in magnetic shape memory alloys, which changes all anisotropic properties of the material. This study investigates leveraging the deformation-induced change of magnetic permeability for a strain measurement technique. A Ni-Mn-Ga single crystal placed inside a doubly wound coil with a primary and a secondary winding was used as a strain sensor. An AC voltage excited the primary coil and the secondary voltage was measured as the sample was strained from 0 to 5.2%. This method varies from other methods that utilize complex magnetic circuits, require high magnetic fields, or other sensing methods such as Hall probes. When the sensor element was tested statically by compressing the element manually against a bias magnetic field perpendicular to the load axis, the voltage output varied from 129.7 mV to 164.2 mV. The dynamic performance of the sensor was tested by cycling the element between 25 and 100 Hz in compression against a bias magnetic field in a displacement controlled magneto-mechanical test system. The bias magnetic field was varied from 0.2 to 0.8 T (0.16 to 0.64 MA/m) while the cyclic displacement was varied from 0.5 to 4.5% strain. The voltage amplitude of the signal in the secondary coil increased with decreasing tensile strain. The full scale RMS voltage at a 200 mm stroke increased from 53.0 mV to 78.4 mV as the bias magnetic field decreased from 0.8T to 0.2 T. As the element was compressed, there was no difference in the sensor output voltage between the static and dynamic tests. When the element expanded during unloading, the voltage output of the sensor from the static test matched the voltage output during compression. For the dynamic testing, the voltage output of the sensor exhibited a hysteresis from the loading voltage output, the hysteresis increased when the strain rate increased.

Concentrated on additive manufacturing, this chapter discusses materials research in the Manufacturing 4.0 context. In addition to providing a brief review on stimuli-responsive materials and their applications under Manufacturing 4.0, this chapter also looks ahead and discusses in detail the recent developments in additive manufacturing of machines, particularly machines based on the special characteristics of certain stimuli-responsive materials, such as thermally activated shape memory alloys, magnetic shape memory alloys and magnetocaloric materials. Furthermore, this chapter emphasizes possible future directions for the additive manufacturing of metallic materials in general.

The aim of this study is to respond to the educational needs of the future, considering automation and robotics. It is inevitable that automation and robotics are changing our lives and they create challenges for the future work life and education. In this study, we investigate what is the educational background of the unemployed people who are in danger of being replaced by automation and what is their educational resilience for adapting work life changes. The data of this study consist of the latest PIAAC data (The Programme for the International Assessment of Adult Competencies). Based on the research we develop a model for re-educating the people who have lost their jobs. peerReviewed

We have studied a tailoring effect of Mn or Ga replacement by Cu in two Ni43Co7Mn20-xFe2Ga21Cu7+x (x = 0.25, 0.5, 0.75, and 1.0 at. %) and Ni43Co7Mn20Fe2Ga21-xCu7+x (x = 0.5, 1 and 1.5 at. %) magnetic shape memory alloys with non-modulated tetragonal martensite, to increase the magnetic actuation temperature. A direct correlation between tetragonality ratio (c/a) and the martensitic (MT) and Curie temperatures (TC) has been disclosed in both alloys series. Some of the studied alloys show a combination of high MT temperature (>370 K) and TC (>430 K), which extends the reported composition range of high temperature ferromagnetic shape memory alloys.

Magnetic shape memory (MSM) alloys have a high potential as an emerging class of actuator materials for a new generation of fast and simple digital components. In this study, the MSM alloy Ni50.5Mn27.5Ga22.0 was built via laser powder bed fusion ( L -PBF) using gas atomized powder doped with excess Mn to compensate for the expected evaporation of Mn during L -PBF. The built samples were subjected to stepwise chemical homogenization and atomic ordering heat treatments. The experiments followed a systematic experimental design, using temperature and the duration of the homogenization treatment as the varied parameters. Overall, the produced samples showed only a minor variation in relative density (average density ~98.4%) and chemical composition from sample to sample. The as-built material showed broad austenite-martensite transformation and low saturation magnetization. The crystal structure of the as-built material at ambient temperature was a mixture of seven-layered modulated orthorhombic (14 M) and five-layered modulated tetragonal (10 M) martensites. Notably, ordering heat treatment at 800 °C for 4 h without homogenization at a higher temperature was enough to obtain narrow austenite-14 M martensite transformation, Curie temperature, and saturation magnetization typical for bulk samples of the same composition. Additionally, homogenization at 1080 °C stabilized the single-phase 14 M martensite structure at ambient temperature and resulted in considerable grain growth for homogenization times above 12 h. The results show that post-process heat treatment can considerably improve the magneto-structural properties of Ni-Mn-Ga built via L -PBF.

A novel auto-aspirated sparger is examined experimentally in a closed-loop reactor (CLR) at lab scale using particle image velocimetry, high-speed camera and oxygen mass transfer rate measurements. State-of-the-art 3D printing technology was utilized to develop the sparger design in stainless steel. An insignificant change in the bubble size distribution was observed along the aerated flow, proving the existence of a low coalescence rate in the constraint domain of the CLR pipeline. The studied sparger created macrobubbles evenly dispersed in space. In pure water, the produced bubble size distribution from 190 to 2500 &mu, m is controlled by liquid flow rate. The bubble size dynamics exhibited a power-law function of water flow rate approaching a stable minimum bubble size, which was attributed to the ratio of the fast-growing energy of the bubble surface tension over the kinetic energy of the stream. Potentially, the stream energy can efficiently disperse higher gas flow rates. The oxygen transfer rate was rapid and depended on the water flow rate. The aeration efficiency below 0.4 kW/m3 was superior to the commonly used aerating apparatuses tested at lab scale. The efficient gas dissolution technology has potential in water treatment and carbon capture processes applications.

The temperature and field dependences of internal friction and Young’s modulus are studied using a high-resolution ultrasonic (90 kHz) technique in stoichiometric ferromagnetic Ni2MnGa shape memory alloy close to the premartensitic transformation temperature, TPM, in the demagnetized state and under moderate fields. Several new effects observed like an apparent Young´s modulus softening close to TPM under moderate fields, instead of the hardening outside this range, as well as existing controversies in the apparent elastic and anelastic properties of Ni2MnGa close to TPM are explained by microeddy and macroeddy current relaxations that to date have been disregarded.

We report on the observation of fully reversible magnetic-field-induced strain of 6% in a single-crystalline micropillar fabricated from a bulk Ni50Mn28.5Ga21.5 single crystal. Xe plasma source focused ion beam column milling technology was used to machine 50 × 50 × 100 μm3 cuboid pillars. The removal of about 2 μm of ion-beam-damaged surface layer enabled magnetic field actuation in pillars. Our results demonstrate the feasibility of manufacturing of micrometre-sized magnetic shape memory actuators by focused ion beam technique.

Precisely controlling the flow of fluids on a microscopic scale has been a technological challenge in the field of microfluidics. Active microfluidics, where a defined manipulation of the working fluid is necessary, requires active components such as micropumps or microvalves. We report on an optimized design of an integratable, wireless micropump made from the magnetic shape memory (MSM) alloy Ni–Mn–Ga. An external magnetic field generates a shape change in the MSM material, which drives the fluid in a similar fashion as a peristaltic pump. Thus, the pump does not need electrical contacts and avoids the mechanical parts found in traditional pumping technologies, decreasing the complexity of the micropump. With a discrete pumping resolution of 50–150 nL per pumping cycle, which is further scalable, and a pumping pressure well exceeding 2 bar, the MSM micropump is capable of accurately delivering the fluids needed for microfluidic devices. The MSM micropump is self-priming, pumping both liquid and gas, and demonstrates repeatable performance across a range of pumping frequencies. Furthermore, it operates simultaneously as both a valve and reversible micropump, offering superior possibilities compared to existing technologies within the flow rate range of 0–2000 µL/min. Due to its simplicity, this technology can be scaled down easily, which lends itself for future integration into lab-on-a-chips and microreactors for life science and chemistry applications.

Additive manufacturing (AM) has gone through major developments in the past decade, enabling the rapid manufacture of complex geometries from traditional engineering materials. This study aims to facilitate the development and additive manufacturing of a new generation of fast and simple digital components with integrated magnetic shape memory (MSM) alloy sections that can be actuated by an external magnetic field. Here, we employ a systematic design of experiments (DoE) approach for investigating laser powder bed fusion (L-PBF) of a Ni-Mn-Ga based MSM alloy. The effects of the applied process parameters on the chemical composition and relative density are determined, and detailed investigations are conducted on the microstructural properties of the as-deposited material obtained using optimized parameters. The results show that although the L-PBF of Ni-Mn-Ga is characterized by an ever-present loss of Mn, deposition of Ni-Mn-Ga with a high relative density of 98.3% and a minimal loss of Mn at ∼1.1 at.% is feasible. The material produced in this manner was compositionally near homogenous and, in as-deposited condition, consisted of a mixture of 14 M and non-modulated (NM) martensites. However, combined measurements by the low-field ac magnetic susceptibility method (LFMS) and DSC revealed that the phase transformation of the as-deposited material from martensite to austenite, and vice versa, was broad and occurred in a paramagnetic state. Inspection by SEM revealed a layered microstructure with a stripe-like surface relief that originated from the presence of martensitic twins within the sample. Additionally, AFM and MFM measurements showed that in as-deposited Ni-Mn-Ga, there exists a weak MFM contrast that can be attributed to the twinned martensite having magnetic anisotropy. Overall, L-PBF shows high potential for the production of functional Ni-Mn-Ga based MSM alloys.

Ni–Mn–Ga single crystals were grown from an oriented seed using a modified Bridgman method. The grown crystals can be oriented very easily for final preparation of magnetic shape memory (MSM) elements with all faces parallel to {100}. The twinning stress depends on the orientation of the twin habit plane. For type I twin boundaries with traces perpendicular to the sample edge, the equivalent stress to move the twin boundary was 0.9 MPa. For type II twin boundaries with traces slightly inclined to those of type I twin boundaries, the equivalent stress to move the twin boundary was 0.01 MPa. The presented method of growing and processing Ni–Mn–Ga single crystals is more efficient than existing methods and produces high-quality MSM elements.

Present publication gives a detailed theoretical concept and also presents the relevant experimental results concerning the effect of the constant external stress on the magnetic-field-controlled strain response during the cycling in magnetic field in Ni–Mn–Ga. We also first consider in details the problems of hysteresis, total energy balance, energy losses, optimization of work output and estimation of thermodynamic efficiency for Ni–Mn–Ga based MSMAs. Simultaneously we give the most important information about the main structural, magnetic and mechanical properties related to a family of non-stoichiometric Ni–Mn–Ga alloys having three different type of martensite crystal structures.

Magnetic shape memory (MSM) materials provide a new way to produce motion and force. The material has also another interesting property: it is possible to monitor its shape by measuring its magnetic parameters. Based on this property, sensors and power generators can be made from the material. In this paper a new method for position sensing using MSM material is introduced and demonstrated. The size of an MSM element is changed in the air-gap of an inductor and the inductor's inductance is measured to see its dependence on the strain of the material. The physical background of the achieved signal is explained and a simple analytical formula for calculating the inductance as a function of the position is proposed. The calculated results are compared with the measured ones.

Ni–Mn–Ga alloys with different chemical compositions having cubic-7M martensitic transformation were studied. Despite of composition difference, low de-twinning stress (approximately 1–2 MPa) and magnetic-field-induced strain (MFIS) of approximately 10% at ambient temperature in a magnetic field order of 1 T were observed in 7M martensitic phase. The influence of magnetic field on stress–strain curves and temperature dependencies of de-twinning stress are also presented.

Present publication gives a detailed theoretical concept and also presents the relevant experimental results concerning the effect of the constant external stress on the magnetic-field-controlled strain response during the cycling in magnetic field in Ni-Mn-Ga. We also discuss the physical mechanism of this effect using our latest model developments. Simultaneously we give the most important information about the main structural, magnetic and mechanical properties related to a family of non-stoichiometric Ni-Mn-Ga alloys having three different type of martensite crystal structures.

Three Ni-Mn-Ga alloys with different chemical compositions and nonmodulated tetragonal martensitic phase (NM) were studied. In two of the alloys, the polydomain nonmodulated tetragonal phase was obtained in cubic-tetragonal martensitic phase transformation at temperatures below and above Curie point, while in the third one, NM-phase is a result of intermartensitic transformation (7M-NM). Magnetic susceptibility and differential scanning calorimetry were used to study these phase transformations. X-ray diffraction, optical polarised microscopy and mechanical testing were used to study variant rearrangement in compression. Twinning strain approximately 19% was observed for all alloys. It was found also that twinning stress is high (approximately 6-18 MPa) and the alloys did not show detectable magnetic field-induced strain. The influence of magnetic field on stress-strain curves and temperature dependencies of twinning stress are presented.

This article briefly summarizes the mechanism of magnetic shape memory, main modeling principles and most important information about the main structural, magnetic and mechanical properties related to a family of non-stoichiometric Ni-Mn-Ga alloys. Depending on the martensite crystal structure these alloys are able to show a really giant (about 6% or 11%) strain response in a magnetic field less than 1 T.

In NiMnGa alloy the crystal structure of low temperature phase is strongly related to transformation temperature. In the present study three NiMnGa alloys with different transformation temperatures were studied. Alloy A has the martensitic start temperature (M s ) near ambient temperature and M s of Alloy B is near Curie point (T C ) whereas M s of Alloy C M s is well above T C . The crystal structures of three alloys were studied by X-ray diffraction in powder and bulk materials. The low temperature phase of single crystal in Alloy A was tetragonal phase with c a, and in Alloy C such a phase was tetragonal phase with c > a. The crystal structure of Alloy A in bulk material is in good agreement with powder diffraction, but in Alloys B and C there is a lack of conformity between bulk and powder. Furthermore, the difference of crystal structure in powder and bulk is discussed in more detail.

In the present paper some magnetomechanical properties of a near-stoichiometric Ni-Mn-Ga magnetic shape memory alloy are discussed. Two series of measurements were performed to study the magnetic field-induced stress as a function of the deformation rate as well as the magnetic field-induced strain as a function of mechanical stress applied in the direction opposite to the strain. The results indicate that the present alloy can be used as an actuator material for its ability to work against an external stress and produce strain. The discussion is extended to comparison of the present results with some recently obtained model calculations that show good correlation.

Magnetic-field-induced strain of approximately 10% is reported in Ni 48.8 Mn 29.7 Ga 21.5 alloy at ambient temperature in a magnetic field of the order of 1 T. It was confirmed by different experimental methods that the strain is contributed by twin boundary motion. The crystal structure of thermally-induced martensitic phase in this alloy was found to be close to orthorhombic one in temperature range from 245 K to 333 K. The lattice parameters are a=0.619 nm, b=0.580 nm, c=0.553 nm (relating to the cubic parent phase coordinates) at ambient temperature. Detailed x-ray study revealed seven-layer modulation along the (110) [110] p system. The results of mechanical tests and magnetic anisotropy property measurements are also reported. The necessary conditions for the observation of a giant magnetic field-induced strain in non-stoichiometric Ni 2 MnGa alloys based on the new experimental data are discussed.

During the last decade, NiMnGa alloys have drawn an increasing interest due to their shape memory properties, superelasticity and, lately, the magnetic field induced straining effect. Extensive studies have also been devoted to the martensitic transformations, the crystal structures of the martensites and the austenitic parent phases. It has been found that the martensite transformations in non-stoichiometric NiMnGa alloys are highly sensitive to the alloy composition. The properties of these alloys with different compositions have been studied with regard to mechanical, and actuation behaviour. However, the corrosion of these alloys has little studied. In the present work, the corrosion behaviour of three non-stoichiometric NiMnGa alloys having different compositions and martensitic structure are studied. Particular emphasis is given to the correlation between the corrosion resistance and the martensitic crystal structures of the alloys.

Single crystal samples of near-stoichiometric Ni 2 MnGa alloy with orthorhombic seven-layered martensitic structure have been investigated. Measured lattice parameters are a=0.619 nm, b=0.580 nm and c=0.553 nm (in coordinates of parent cubic phase) at ambient temperature. Giant magnetic-field-induced strain (MSM effect) of about 10% was observed in this phase. Microstructure change under applied magnetic field was studied by means of X-ray diffraction and optical microscopy methods. It was shown that the mechanism of MSM effect in seven-layered orthorhombic martensitic phase is similar to the mechanism found before in five-layered tetragonal martensite. Giant magnetic-field-induced strain in orthorhombic phase is caused by sample transformation from one single-variant state (a axis parallel to the field) by twinning ((101)[101] system) to another single-variant state (c axis parallel to the field).

Fe-Mn-Si based alloys are known to possess some unique physical and mechanical properties. The main attention has been paid to shape memory effect in these alloys due to their great technological potential. It has been found in previous investigations of present authors that the mechanical and shape memory properties of Fe-Mn-Si based alloys can be improved by additional alloying by interstitial elements. However, the influence of carbon and nitrogen on corrosion resistance of these alloys is quite different. The aim of the present study was to clear up the difference of influence of nitrogen and carbon on the properties of Fe-Mn-Si based alloys with the help of internal friction the most sensitive to interstitial atoms method of investigation. In the present work, several Fe-Mn-Si shape memory alloys with various amounts of nitrogen and carbon are developed. The internal friction measurements have been carried out. The obtained internal friction data were compared with other properties of these alloys. The reasons of different influence of carbon and nitrogen on the properties of shape memory Fe-Mn-Si based alloys were discussed.

When cooling from high temperature, the material of composition Ni 48.5 Mn 30.3 Ga 21.2 undergoes several magnetic and structural transitions. The phases are, at high temperature austenitic cubic L2 1 phase; at 297 K 5-layered modulated tetragonal martensite; and below 210 K non-modulated tetragonal martensitic phase with c / a larger than unity. Five-layered martensite exhibits giant field-induced strain of about 6% (magnetic shape memory (MSM) effect). The mechanism of the MSM effect was substantiated by simultaneous measurement of the strain and magnetization.

A single-crystal samples of near-stoichiometric Ni 2 MnGa alloys with large magnetic field induced strain (MSM effect) at room temperature have been investigated. It was found that there is a reversible reorientation of easy magnetization direction and magnetic domain structure under applied magnetic field. By means of x-ray Laue diffraction method and difractometric analysis it was ascertained that these phenomena are connected with the growth of martensitic twin variant with the short crystallographic axis (c-axis) directed along the applied magnetic field. Furthermore, by means magneto-optical investigations we have found the correlation between martensitic microstructure and magnetic domain structure. The field-induced reorientation of martensite was able to change the dimensional lengths of the samples more than 4.5 %.

An effect of the magnetic field on the martensitic transformation and the change in the martensitic variants of the alloy Ni 2 MnGa containing (at%) 49.6 Ni, 28.4 Mn and 22.0 Ga was studied using X-ray diffraction. It is shown that the applied magnetic field induces martensitic transformation and initiates the development of a preferential martensitic variant. These processes are extended in time, which resembles the isothermal martensitic transformation observed in iron-based alloys. The kinetics of transformation under magnetic field and the after-effect when the field is taken out are studied. The kinetics is shown to depend on the orientation of the applied field in relation to the direction of easy magnetization 1 0 0 . The strain induced by the magnetic field is measured and the time dependence of the strain is found in consistence with the results of X-ray diffraction study.

Since the shape memory effect in various Fe-alloys was discovered some decades ago, these types of alloys have attracted increasing interest due to their good cold and hot workability, low cost and the potential of practical applications. At the early years after discovery, the alloys investigated were Fe-Mn or Fe-Mn-Si based steels, but the need of improving the recoverable strains and the strength properties has led to studying of Fe-Mn-Si-Cr-Ni and complicated chemical compositions. The final aim is to obtain a shape memory material that could be trained as a part of the conventional steel production line without separate training sequence and, furthermore, which could be applied in larger scale, for example, for pre-tensioning of concrete The present study was focused on Fe-Mn-Si-Cr-Ni based alloys with nitrogen contents up to 0.20% The aim of the nitrogen alloying was to decrease the amount of nickel and chromium and to improve the strength of the material with nitrides. The values obtained for different alloys were high - ultimate tensile strength could be as high as 1600 MPa, recoverable strain at average of 2-3 %, even 4.5%. The purpose of this study was to find optimum working parameters to obtain the best shape memory and strength properties for certain high nitrogen alloys.