Mn Sn Alloys Research Articles

Improved phase stability and mechanical properties in Ni-Mn-Sn-B Alloys: Experiments and first-principles calculations

The impact of boron microalloying on the performance of NiMnSn shape memory alloys was investigated using a combination of simulation and experimental methods. The simulation results reveal that B atoms tend to occupy the tetrahedral interstitial positions composed of Ni and Mn. Furthermore, the doping of B atoms not only increases the lattice constant and cell volume of the alloys, but also enhances the phase transition temperature and reduces the thermal hysteresis. The doping of B can enhance the phase stability of austenite and reduce total magnetic moments in the Ni–Mn-Sn alloy. Experimental investigations were conducted on (Ni43Mn47Sn10)100-XBX (X=0,1.5,3) alloys, and findings corroborate the simulations, confirming that B element doping elevates the phase transition temperature, lattice constant, and cell volume, while diminishing the thermal hysteresis. Furthermore, boron microalloying contributes to improved mechanical properties. At a B doping level of 3%at, the annealed alloy compressive strength increases by 125%, reaching 578 MPa, with a fracture strain of 6.7%. However the mechanical properties of the as-cast alloy surpass those of the annealed state, with the compressive strength of the same-component cast alloy reaching 1080 MPa, and a fracture strain of 7.9%, marking an 87% improvement over the annealed state.

Unraveling magnetic properties and martensitic transformation in Mn-rich Ni–Mn–Sn alloys: first-principles calculations and experiments

Unraveling magnetic properties and martensitic transformation in Mn-rich Ni–Mn–Sn alloys: first-principles calculations and experiments

Factors influencing the martensitic transformation in Ni–Mn–Z (Z = Ga, Sn) Heusler alloys

The martensitic transition temperature of the Ni–Mn–Z (Z = Ga, In, Sn or Sb) generally scales with the average valence electron per atom ( e/a ) ratio. The e/a ratio can be increased either by increasing Ni content in lieu of Mn or Z (Ni-rich) or by substituting Mn for Z (Mn-rich). While the Mn-rich alloys display the expected scaling behaviour of the martensitic transition temperature, the Ni-rich alloys, with the exception of Z = Ga alloys, do not exhibit any dependency on the e/a ratio. By carefully studying and comparing the structure, local structure and the physical properties of the Ni-rich and Mn-rich Ni–Mn–Ga and Ni–Mn–Sn alloys, the cause of the difference in behaviour is identified. The off-stoichiometry brought about by increasing the Ni or Mn content, results in the formation of a new local structural environment in addition to the Heusler-like environment. If either of the two local structural environments is martensitic, then the resulting Ni-rich or Mn-rich alloy also exhibits martensitic transformation.

One-step additive manufacturing of Ni–Mn–Sn alloys with a large elastocaloric effect

The one-step laser powder bed fusion method, without the need for heat treatment, successfully produces a microstructure containing austenite phase in NiMnSn samples. An impressive elastocaloric temperature change of 6.7 K was obtained.

Revealing microstructures evolution and dynamic recrystallization mechanisms of Mg–Sn–Mn alloy during compressive deformation at elevated temperature

The flow behavior of as-extruded Mg–3Sn-1.5Mn (wt.%) alloy was systematically researched via isothermal compression tests. The compressive temperatures (T) were from 250 °C to 400 °C, the strain rates were from 0.001 s−1 to 1s−1 and the true strain reached 0.69. Based on compression curves, flow stress apparently rose with increasing strain rate and/or decreasing temperature. Combined with the analysis of microstructure and processing map, the optimum working parameter was determined in the range of 350–400 °C, 0.01–1 s−1. According to electron backscatter diffraction (EBSD) analysis results, texture intensity significantly decreased and the basal (0001)//ED texture had transformed to basal <0001>//CD texture after compressive deformation obviously. Furthermore, the typical discontinue dynamic recrystallization (DDRX) and continue dynamic recrystallization (CDRX) were largely believed to be the major DRX mechanisms in Mg–3Sn-1.5Mn alloy. Both increasing temperature and decreasing strain rate had obvious influence on the degree of DRX. The activated slip systems in deformed grains were determined by the analysis of the in-grain misorientation axis (IGMA). As deformation temperature elevated, pyramidal <c+a> slip greatly activated and dominated compressive deformation.

Hot deformation behavior and resultant microstructural evolution of dilute Mg–Bi–Sn–Mn alloy during hot compression

This study investigated the dynamic recrystallization (DRX) mechanism and hot-deformation behavior of the solution-treated Mg-0.5Bi-0.5Sn-0.5Mn (BTM000) alloy during hot compression at temperatures ranging from 175 to 225 °C with a strain rate of 0.001–1 s−1. Processing maps and constitutive equation were used for a detailed analysis. The results showed a strong correlation with a coefficient of 0.987669, indicating the accuracy of proposed method in predicting the hot deformation behavior. The average activation energy (Q) was found to be 139.10 kJ/mol, and the stress component (n) was calculated to be 7.96, suggesting that cross-slip is the primary deformation mechanism. Based on the processing maps, the most suitable processing conditions were found to be within the range of 210–290 °C with a strain rate of 0.37–1 s−1. At a low strain rate of 0.001 s−1, the dominant deformation mechanism observed was pyramidal <c+a> slip. However, at higher temperatures (175–325 °C) and a strain rate of 1 s−1, a transformation from basal <a> slip to a combination of basal <a> slip and pyramidal <c+a> slip was observed. Under low-temperature and low-strain-rate conditions (175 °C/0.001 s−1), continuous dynamic recrystallization (CDRX) was the dominant mechanism. In contrast, under other deformation conditions (175 °C/1 s−1, 325 °C/0.001 s−1, 325 °C/1 s−1), a synergistic effect between discontinuous dynamic recrystallization (DDRX) and CDRX was evident. Through quasi-situ kernel average misorientation (KAM) characterization, it was observed that the local storage energy associated with CDRX was significantly lower compared to the combination of CDRX and DDRX, indicating a higher likelihood of CDRX occurrence.

Electrodeposited Co–Mn–Sn multicomponent alloy as an efficient electrocatalyst for hydrogen evolution reaction

Despite having exciting material characteristics, the potential of multi-component alloys (MCAs) as electrocatalysts has not been fully realized. In this work, efficient binary and ternary MCA electrocatalysts containing inexpensive metals like Co, Mn and Sn have been prepared via the electrodeposition process. When tested for hydrogen evolution reaction (HER) in an alkaline medium, ternary Co–Mn–Sn alloy displayed enhanced activity with the lowest overpotential of 136 mV, a Tafel slope of 111 mV dec−1 and a very low charge transfer resistance, making it superior to the binary alloys (Co–Mn and Co–Sn), or the single metal catalysts (Co, Mn and Sn). The ternary alloy also displayed high electrochemical and structural stability, making it a viable electrocatalyst for the hydrogen economy.

Martensitic transformation near room temperature and hysteresis in (Ni–Co)50–Mn–Sn metamagnetic shape memory alloys

The martensitic transformation behaviors, magnetic properties, crystal structures, and entropy change (ΔS) of Ni50−xCoxMn50−ySny alloys were systematically investigated. Samples were prepared by induction melting, followed by solution heat treatment at 1273 K for 1 day and quenching. A magnetic phase diagram with a broad range of compositions was established, from which a series of alloys with varying Co concentrations was selected, such that their martensitic transformation starting temperatures (TMss) were near room temperature. The thermal and magnetic-field hystereses of these samples were systematically investigated, and a clear composition dependence was observed. The dissipation energy (Edis), which governs the transformation hysteresis, was found to be smaller for alloys with x = 5–8 than for those with x = 0–3. This behavior was found to originate from the difference in crystal structures of the martensite phases, i.e., the crystal structures of the martensite phases are 4O and 6M for x = 0–3 and x = 5–8, respectively. Moreover, the geometric compatibility between the parent and martensite phases was found to be the direct cause of the difference in dissipation energy in Ni–Co–Mn–Sn alloys.

The effect of Tb substitution for Ni on microstructure, martensitic transformation and cyclic stability of elastocaloric effect in Ni–Mn–Sn magnetic shape memory alloys

Cyclic stability of elastocaloric effect is the key factor that restricts the elastocaloric cooling application of Ni–Mn–Sn alloys fabricated by the conventional melting technique. Element doping is an effective way to enhance the performance of materials. In this work, the effect of Tb substitution for Ni on martensitic transformation (MT) temperature, microstructure, mechanical properties and cyclic stability of elastocaloric effect in the Ni43.5–xTbxMn45.5Sn11 (x = 0, 0.6, 1.2 and 1.8) magnetic shape memory alloys has been investigated. MT temperatures increase with increasing x from 0 to 1.2 and then decrease with further increasing x to 1.8. The substitution of Tb for Ni introduces γ phase (Tb-rich second phase in Tb-doping alloys). The volume fraction of γ phase increases with increasing Tb content and thus the mechanical properties and the cyclic stability of elastocaloric effect increase with the increase of Tb content. Among these alloys, Ni42.3Tb1.2Mn45.5Sn11 alloy shows a large adiabatic temperature change of 10.0 K induced by applying the uniaxial stress of 550 MPa. In addition, a constant temperature change of 6.5 K shows no apparent degradation under the compressive stress of 350 MPa during 1000 cycles for this alloy. The excellent elastocaloric properties make this alloy a promising candidate for the room-temperature elastocaloric cooling application. The underlying mechanism of the enhanced cyclability of elastocaloric effect and mechanical properties is also revealed.

Achieving high strength-ductility synergy in a novel Mg–Bi–Sn–Mn alloy with bimodal microstructure by hot extrusion

A novel extruded Mg–5Bi–5Sn–1Mn alloy is developed and exhibits high yield strength (YS) of 446 MPa and ductility of 13.2%, resulting from the bimodal microstructure composed of coarse unDRXed grains with strong extrusion texture and dislocation storage capacity as well as ultra-fine DRXed grains (0.48 μm).

Martensitic transformation and mechanical properties of grain refined Ni–Co–Mn–Sn Heusler alloys via Cr doping

The influence of Cr doping for Mn on the structural, martensitic transformation and mechanical properties of Ni 43 Co 5 Mn 44-x Cr x Sn 8 (x = 0, 1.5, 3, 5, 6 and 6.5) alloys has been systematically investigated. The replacement of Mn by Cr changed the alloy microstructure from a single-phase martensite to a refined eutectic dual-phase microstructure consisting of a martensitic/austenitic matrix and a γ phase. The volume fraction of the γ phase increased progressively with increasing the Cr doping. The γ phase formation altered the composition and e/a ratio of the matrix phase. As a result, the martensitic temperatures and the entropy change of the transformation showed a decrease in these alloys. The Cr-doped eutectic Ni–Co–Mn–Sn alloy exhibited superior mechanical properties attributed to the well dispersed γ phase lamellar grains for effective crack retardation while retaining the metamagnetic phase transformation. The compressive strength and ductility of alloys are notably enhanced from 290 MPa to 1420 MPa and from 6.7% to 15.8% respectively with Cr doping from 0 at% to 6.5 at%.

Tailoring Mechanical Properties of Mg–Al–Zn–Sn–Mn Alloy by Multipass Equal Channel Angular Pressing

Tailoring Mechanical Properties of Mg–Al–Zn–Sn–Mn Alloy by Multipass Equal Channel Angular Pressing

Solute segregation assisted superplasticity in a low-alloyed Mg–Zn–Ca–Sn–Mn alloy

In this study, we are pleased to report a low-alloyed Mg–1.0Zn–0.45Ca–0.35Sn–0.2Mn (wt. %) alloy sheet fabricated by hot rolling, showing superplastic deformation ability with tensile elongation of ~410%±30% at 573 K and 1 × 10−3 s−1. The superplasticity is co-dominated by grain boundaries sliding (GBS) and solute drag creep. Unlike high-alloyed Mg alloys with dispersed precipitates, this low-alloyed system keeps its fine-grained microstructure by the co-segregation of Zn and Ca atoms at grain boundaries (GBs) coupled with a few precipitates. Although the co-segregation of Zn and Ca atoms at GBs are not favored for GBS, the resulting superior thermostability is of great importance to achieve superplastic deformation. Thus, we put forward a new path in achieving superplasticity in low alloyed Mg alloys by using a complementary thermodynamic and kinetic stabilization approach.

Tailoring Mechanical Properties of Mg–Al–Zn–Sn–Mn Alloy by Multipass Equal Channel Angular Pressing

Herein, the influence of equal channel angular pressing (ECAP) routes, i.e., A and Bc, on the microstructure and texture evolution of a Mg–3.7Al–0.7Zn–0.8Sn–0.4Mn (wt%) alloy is investigated by scanning electron microscopy (SEM), electron backscatter diffraction (EBSD), and X‐ray diffraction (XRD). It is found that with increasing the number of ECAP passes, the area fraction of the dynamically precipitated secondary‐phase particles increases, whereas particle size becomes larger. After four and six passes of ECAP via route A, shear deformation induced by ECAP promotes the incline of c‐axes toward extrusion direction (ED). The optimum room temperature (RT) mechanical properties (yield strength of ≈225 MPa, ultimate tensile strength of ≈312 MPa, and elongation to fracture of ≈31.9%) are obtained after four passes of ECAP at 200 °C via route A. The improved strength results from fine dynamic recrystallization (DRX)/ed grains, nanoscale secondary‐phase particles, and basal texture. Herein, it is indicated that Mg–Al–Zn–Sn alloys have great potential as low‐cost high‐strength‐ductility wrought Mg alloys.

Martensitic Transformation and Crystalline Structure of Ni50Mn50−xSnx Melt-Spun Heusler Alloys

The structure and thermal behavior are key factors that influence the functional response of Ni–Mn–Sn alloys. The present study reports the production as well as the structure and thermal analysis of melt-spun (solidification rate: 40 ms−1) Ni50 Mn50−xSnx (x = 10, 11, 12 and 13 at.%) alloys. X-ray diffraction measurements were performed at room temperature. The austenite state has an L21 structure, whereas the structure of the martensite is 7M or 10M (depending on the Sn/Mn percentage). Furthermore, the structural martensitic transformation was detected by differential scanning calorimetry (DSC). As expected, upon increasing the Sn content, the characteristic temperatures also increase. The same tendency is detected in the thermodynamic parameters (entropy and enthalpy). The e/a control allows the development production of alloys with a transformation close to room temperature.

Development of low-alloyed Mg–Zn–Ca–Sn–Mn alloy with high strength-ductility synergy by sub-rapid solidification and hot rolling

Achieving high strength-ductility synergy is a great challenge in low-alloyed Mg alloys. In this work, a new Mg–1.0Zn–0.45Ca–0.35Sn–0.2Mn (wt.%, ZXTM1000) alloy was designed and fabricated by sub-rapid solidification (SRS) to overcome the dilemma. After hot rolling and annealing, the new alloy sheet exhibited an excellent tensile yield strength (YS, ∼270 MPa) and elongation (∼21%). Microstructure characterization revealed that the high YS was mainly attributed to the fine grains (∼3 μm) and high density of spherical Ca2Mg6Zn3, Mg2Ca, and α-Mn precipitates. Moreover, the homogeneous grain size distribution, weakened TD-split texture and the activation of multiple types of slips contributed to the enhanced ductility. The findings demonstrate an effective way to fabricate low-alloyed Mg alloys with high strength and ductility by combining the SRS and hot rolling.

Effect of Co substitution on the magnetic properties and magnetocaloric effects of Ni–Co–Mn–Sn alloys

AbstractNi–Mn–Sn-based magnetic refrigeration materials have a coupling ability of structure transformation and magnetic transition to improve their magnetocaloric effects. In this work, the influence of the Co doping on Curie temperature, structure and magnetocaloric properties of Ni43-xCoxMn46Sn11 (x = 0, 1, 2, 3) alloys prepared by melt-spinning were investigated by means of X-ray diffraction, Differential Scanning Calorimetry and Vibrating Sample Magnetometry. It was found that the crystal structure of samples changes from 4O modulated martensite to L21 cubic austenite with increasing temperature. The magnetic phase diagram of Ni43-xCoxMn46Sn11 system was constructed from thermomagnetic curves. Increasing Co content enhanced the Curie temperature of L21 cubic austenite from 279 K to 354 K, however, shifted the transition temperature of martensitic down to lower temperature, 170 K. As for the sample with x = 3, it only has ferromagnetic–paramagnetic second order magnetic transition, and no structural transformation was observed. The sensitivity of martensitic transformation induced by magnetic field can be improved up to − 3.52 K · T−1. Under 0–5 T, the maximum values of magnetic entropy change, refrigerant capacity and the adiabatic temperature change are improved by 60.5%, 59.0% and 17.5%, respectively. The results indicate that the relatively large martensitic transformation sensitivity and magnetocaloric effects make these alloys good candidates in the range of 150–300 K.

Phase Transformations in Ni(Co)–Mn(Cr,C)–(In,Sn) Alloys: An Ab Initio Study

Abstract—The phase transformations in the Heusler alloys of Ni(Co)–Mn(Cr,C)–In and Ni(Co)–Mn(Cr,C)–Sn(Al) have been studied in this work using the density-functional theory. The possibility of martensitic phase transitions from the cubic L21-structure into tetragonal L10-state has been predicted, and the transition temperatures have been estimated. Energetically favorable magnetic configurations, lattice parameters, and magnetic moments of austenite and martensite phases have been determined. The Curie temperatures and elastic moduli of cubic phases of alloys have been calculated. In Ni–Mn–Sn alloys with Co addition, the effect of exchange-correlation functional on the ground state has been investigated.

ELECTROCATALYTIC ACTIVITY OF Ni–Mn–Sn ALLOY FOAMS FOR OXYGEN EVOLUTION REACTION (OER)

This study carried out to examine electrocatalytic activity of Ni–Mn–Sn alloy foams for oxygen evolution reaction (OER) in alkaline media. As the first step, Ni–Mn–Sn alloy foams were prepared of sulfate bath on copper substrate. Next, after optimization of electrodeposition condition by cyclic voltammetry (CV) test, foams were electrodeposited at different current densities 100, 120, 140 and 180[Formula: see text]mA[Formula: see text]⋅[Formula: see text]cm[Formula: see text]. Then, they were characterized by field emission scanning electron microscopy (FE-SEM) along with energy disperse x-ray spectroscopy (EDS) to investigate surface morphologies and chemical compositions. According to FE-SEM results, it was revealed that formation of foam like structures were due to the presence of dynamic hydrogen bubbles template (DHBT). To survey their structure, grazing incidence X-ray diffractometer (GIXRD) analysis was performed. The resulted diffraction pattern determined not only FCC nickel structure of foams, but also mixed phases composed. Following this, Ni–Mn–Sn alloy foams were placed in 0.1 M KOH and related CV tests were applied to measure their electrocatalytic activity for OER. This study demonstrated good electrocatalytic activity for Ni–Mn–Sn alloy foams by showing favorable oxygen evolution overpotenitals and Tafel slopes.

Analysis of Size Effects during Martensitic Transitions in Epitaxial Films and Microparticles of the Ni–Mn–Sn Alloy

The available literature data on the effect of the thickness of the epitaxial films and size of the crystallites in the microparticles of the Ni–Mn–Sn alloy powder on the parameters of the martensitic transitions in this alloy have been analyzed in the framework of the theory of defuse martensitic transitions (DMT), which is based on thermodynamic and kinetic ratios. The purpose of the analysis is to establish an explicit (functional) dependence of these parameters on the film thickness D and the size of nanocrystallites d in the film and microparticles. The results of the R-diffraction analysis show that internal elastic microdeformations and stresses arise in films and microparticles of the alloy powder due to the coherent coupling of the epitaxial film with a solid substrate or as a result of severe plastic deformation of the alloy during its grinding in a ball mill. The analysis shows that the local microstresses significantly affect the type of the dependence of the temperature interval (diffusity) ΔT of the transition on the size factors D or d. In the absence of microstresses, these dependences have the form ΔT ∼ 1/D2 or ΔT ∼ 1/d2. In the presence of microstresses, the temperature transition interval depends on the size factors as ΔT ∼ 1/D or ΔT ∼ 1/d.