MnSi Research Articles

Preparation of Si–Mn/biochar composite and discussions about characterizations, advances in application and adsorption mechanisms

A novel Si–Mn binary modified biochar composite material (SMBC) was prepared after being sintered 450 °C for 2 h. The crystal structure, surface functional groups, surface morphology and element composition, specific surface area and pore structure were characterized by XRD, FTIR, XPS, SEM + EDS and BET etc. The results showed that the surface of SMBC was rough and loose, and the specific surface area increased to 35.4284 m2/g. Si and Mn were uniformly attached to the surface of biochar in the form of SiO2, MnOx, MnSiO3. Batch adsorption experiments showed that SMBC had a higher removal efficiency (139.06 mg/g, above 98%) for Cu(II) when the dosage was 2 g/L and pH = 6. The cycle experiments showed that SMBC had good reusability, and its regeneration efficiency still reached 80.24%. The leaching amount of Mn (0.65 mg/L) was greatly reduced and avoid second-pollution resulted from ion exchange, which was attributed to the existence of Si–O–Mn bonds, and they could help Mn adhere to the surface of biochar more stable. The adsorption process was dominated by single-layer chemical adsorption and mainly occurred in the membrane diffusion stage. Cu(II) mainly formed -COOCu, -OCu, Cu(OH)2, Cu(OH)2CO3, Si–O–Cu, Mn–O–Cu by the mechanisms such as precipitation (4.74%), ion exchange (13.81%), complexation and physical adsorption (total 81.45% of the two mechanisms). Among them, complexation was dominant in the adsorption process.

Xenon plasma focussed ion beam preparation of an Al-6XXX alloy sample for atom probe tomography including analysis of an α-Al(Fe,Mn)Si dispersoid

A Xe plasma Focussed Ion Beam instrument was used to prepare in-situ specimens for Atom Probe Tomography from a bulk sample of an aluminium 6XXX alloy. The nature and distribution of precipitates and solute clusters observed in the alloy are not observed to differ between standard electropolishing methods and Xe plasma preparation. Enabled by site specific specimen preparation, analysis of an α-Al(Fe,Mn)Si dispersoid shows segregation at the phase boundary and in the shell of the dispersoid.

The Effect of Bridge Geometry on Microstructure and Texture Evolution During Porthole Die Extrusion of an Al–Mg–Si–Mn–Cr Alloy

The Effect of Bridge Geometry on Microstructure and Texture Evolution During Porthole Die Extrusion of an Al–Mg–Si–Mn–Cr Alloy

Microstructure evolution and mechanical properties of low-silicon cast aluminium alloys with varying Mn contents

ABSTRACT The influences of Mn level (0–0.8 wt%) on the microstructure and mechanical properties of as-cast and T6 heat-treated low-silicon cast aluminium alloys were investigated. The results indicated that the addition of 0.5% Mn completely transformed the needle-like β-Fe phase in as-cast condition into a small-sized π-Fe phase, and the π-Fe phase was fully dissolved after T6 heat treatment. The as-cast and T6 heat-treated alloys with 0.5% Mn achieved the best combination of strength and ductility. However, an excess addition of Mn reduced the mechanical properties due to the occurrence of coarse π-Fe phase (as-cast state), α-Al(Fe, Mn)Si phase (T6 heat-treated state) and eutectic Si. With the increase of Mn content from 0 to 0.8%, the fracture modes of the as-cast alloys changed from intergranular + cleavage fracture to intergranular + quasi-cleavage fracture; The fracture modes of the T6 heat-treated alloys underwent a transition from intergranular + cleavage fracture to quasi-cleavage fracture and then to intergranular + cleavage fracture.

Phase transformation in Fe–Mn–Si SMA/WC composite coating developed by laser cladding

A Fe–Mn–Si shape memory alloy/nano-WC (SMA/WC) coating was prepared by laser cladding on the surface 304 stainless steel. The phase composition, stress-induced phase transformation mechanism, microstructure, microhardness and wear resistance were analyzed by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), microhardness tester and friction tester, respectively. Results show that γ austenite, ε martensite and Fe6W6C phase appear in the composite coating, and the coating is composed of planar crystals, cell crystals, fine dendritic crystals and fine equiaxed grains from binding zone to surface region. The residual stress leads to the entanglement and accumulation of dislocations in the austenite grain boundaries, which in turn induce martensite deformation. The martensite phase of the annealed composite coating disappeared, and the microstructure showed austenite morphology. The SMA/WC coating has higher microhardness and excellent wear resistance due to the occurrence of γ austenite → ε martensite transformation. Furthermore, the addition of WC increases the microhardness of the coating by more than 2 times, and reduces the friction coefficient and the wear loss by about 1/4 and 2/3 respectively.

Analysis on the hot deformation flow stress curves of novel 6082 aluminium alloys with Mn addition

Two types of 6082 alloy, base alloy free of Mn and novel 0.75Mn alloy with an addition of 0.75% Mn, were prepared. A heat treatment of 450 °C for 6 h was performed, during which large numbers of α-Al (Fe, Mn) Si dispersoids precipitated in 0.75Mn alloy. Uniaxial compression tests were carried out and a series of flow stress curves were obtained at temperature range of 400-550 °C and at strain rate range of 0.001s-1-1s-1. The results revealed an impressive difference between the flow stress curves of base and 0.75Mn alloy that after the yield plateau, the flow stresses of base alloy remained fairly steady at certain levels while the flow stress in 0.75Mn alloy decreased along with strain until the end of deformation. The reason for the decrease of flow stress in 0.75Mn alloy was neither the dissolution of dispersoids nor the dynamic recrystallization. The decrease of flow stress was attributed to the loss of Mn solid solution strengthening effect based on the Mn diffusion rate-controlling mechanism and “pipe diffusion”.

Microstructures and mechanical properties of dispersoid-strengthened 6082 aluminum alloy plate produced by vacuumed centrifugal casting

A dispersoid-strengthened 6082 alloy was prepared using vacuum centrifugal casting. The casting pipe was split into two halves along the axial direction, then every single half of the pipe was flattened and was treated as a slab and was subsequently generated to the conventional rolling to produce plate. The microstructure and the mechanical properties of the inner, middle, and outer layers of the pipe was studied. The results shows that the intermetallic in the as-cast microstructure was gradient distributed, the number density of intermetallic decreased and the average size increased from outer layer to inner layer. After heat treatment, area fraction of the α-Al(Fe, Mn)Si dispersoid zone and the number density of dispersoid increased gradually from outer layer to inner layer. After rolling, the high temperature strength of the plates decreased and the elongation decreased from the outer layer to the inner layer.

Development of technology for production of K52 strength class steels with low chromium content, cold and corrosion resistant in conditions of the casting and rolling complex

The results of experimental testing of production in the conditions of a casting and rolling complex (CRC) Vyksa Steel Works (VSW) of rolled products with a thickness of 8–10 mm with a reduced chromium content of strength class K52 to meet the requirements of the new guidelines of Rosneft on the corrosion resistance of metal in acidic environments. Based on the C–Mn–Si–Nb alloying system, a new chemical composition of steel with a reduced chromium content (0,40%) has been developed that provides a set of consumer properties — strength (tensile strength — 530–550 MPa, yield strength — 450–470 MPa), ductility (elongation — 28–34%), cold resistance (T50 below –80°C) and corrosion resistance against hydrogen cracking (CLR = 0%, CTR = 0%) and general corrosion in a CO2-containing medium (the rate of general corrosion is not more than 0,2 mm/year). It is shown that the variation of the chromium content in the range of 0,4–0,7% does not significantly affect the rate of general corrosion both under the influence of 5% sodium chloride solution and 5% sodium chloride solution with the addition of 0,40% sodium acetic acid solution when kept in an aggressive environment for 96 hours.

Microstructure and Mechanical Properties of Cu—Al Alloy Deposited by Additive Manufacturing

In this work, Cu—4.9% Al alloy with little Si (the weight percentage is 1.3%) and little Mn (the weight percentage is 0.8%) was deposited by wire arc additive manufacturing. Microstructure and properties of the deposited alloy was investigated. Microstructural characterization was done using optical microscopy, scanning electron microscopy and transmission electron microscopy. Microstructural investigation revealed that aluminum was enriched at the interlayer (i.e. inside the deposited layers), whereas silicon and manganese were found enriched at the border layers (i.e. at the border of the deposited layers). Evaluation of the mechanical properties showed that the deposited sample had good strength and ductility. The addition of silicon effectively improved the hardness and tensile strength properties of the deposited alloy.

Fracture Behavior and Mechanical Properties of a Thermomechanical TRIP Steel Under Simulated Heat Treatment Conditions

In this research, hypereutectoid Si–Mn TRIP steel was prepared via casting method followed by thermomechanical processing and different heat treatments. Subsequently, fracture behavior and mechanical properties of the prepared steel were investigated. The time–temperature–transformation curves of the specimens were predicted by a simulation software. Their mechanical properties were studied through tensile, hardness, and impact tests. The microstructure and fracture behavior of the specimens were evaluated using an optical microscope, scanning electron microscope and fractographic analysis. Results indicated that the heat-treated sample containing a multi-phase microstructure of bainite, martensite, pearlite and retained austenite, had the highest ultimate tensile strength around 1,300 MPa. The software predictions of the heat treatments were in good accordance with the microstructural results. The samples have undergone thermomechanical process and heat treatment including isothermal transformation showed brittle behavior with intergranular and cleavage fracture surfaces. In addition, the two-stage quenching cycles resulted in dual-phase microstructure composed of martensite embedded in retained austenite with a combination of brittle and ductile fracture behavior.

Sliding wear of medium-carbon bainitic/martensitic/austenitic steel treated by short-term low-temperature austempering

A medium-carbon Si–Mn–Ni–Cr–Mo alloyed (300M) steel was austempered for various short periods at its martensite-starting temperature of 285 °C to seek improved sliding wear resistance as compared to the traditional martensitic and bainitic steels. Reciprocating sliding wear tests were performed against a WC/Co ball counterpart at a constant load of 49 N. The samples were characterised using field emission SEM, XRD and hardness testing. The associated wear mechanisms were analysed using SEM and cross-sectional TEM. The results revealed that a short austempering time of 6 min produced refined arrays of initial nano-bainitic ferrite laths and inter-lath filmy austenite and the majority martensite and retained austenite, while the majority of the microstructure remained martensitic with retained austenite. The hardness was unchanged to that of the as-quenched martensite of 6.4 GPa. Simultaneously the wear coefficient decreased by 41% from 2.67 to 1.58 × 10-15 m3N-1m-1, which is also superior to both the tempered martensite at 1.65 × 10-15 m3N-1m-1 and the lower bainite at 1.87 × 10-15 m3N-1m-1. Increasing the austempering time to 20 and 60 min resulted in wear coefficients of 1.38 and 2.18 × 10-15 m3N-1m-1, respectively. The improved wear resistance has been explained by the wear induced microstructure evolution, especially the carbon partitioning induced stabilisation of retained austenite. The high-stress sliding wear was found to be dominated by severe shear deformation, which resulted in a nano-laminate structured top layer. Delamination wear was found to take place within the embrittled nano-laminates.

Phase Selection in Mn–Si Alloys by Fast Solid‐State Reaction with Enhanced Skyrmion Stability

AbstractB20‐type transition‐metal silicides or germanides are noncentrosymmetric materials hosting magnetic skyrmions, which are promising information carriers in spintronic devices. The prerequisite is to prepare thin films on technology‐relevant substrates with magnetic skyrmions stabilized at a broad temperature and magnetic‐field working window. A canonical example is the B20‐MnSi film grown on Si substrates. However, the as‐yet unavoidable contamination with MnSi1.7 occurs due to the lower nucleation temperature of this phase. In this work, a simple and efficient method to overcome this problem and prepare single‐phase MnSi films on Si substrates is reported. It is based on the millisecond reaction between metallic Mn and Si using flash‐lamp annealing (FLA). By controlling the FLA energy density, single‐phase MnSi or MnSi1.7 or their mixture can be grown at will. Compared with bulk MnSi, the prepared MnSi films show an increased Curie temperature of up to 41 K. In particular, the magnetic skyrmions are stable over a much wider temperature and magnetic‐field range than reported previously. The results constitute a novel phase selection approach for alloys and can help to enhance specific functional properties, such as the stability of magnetic skyrmions.

Modified microstructures in proton irradiated dual phase 308L weldment filler material

The effect of proton irradiation on the microstructure of δ ferrite—γ austenite mixed phase 308L filler material in a 508–304 dissimilar metal weldment was investigated over a depth of 0 to 10 µm. Ni–Si–Mn G-phase precipitates were observed with SEM and TEM in δ ferrite but not in γ austenite. Our density functional theory based calculations show that the G/Fe interface energy in δ-Fe is significantly lower than that in γ-Fe (0.35 versus 1.25 J/m2), which provides a thermodynamics-based explanation for our experimental observations of preferential formation of G-phase in δ ferrite. STEM-EDS, TEM dark field imaging, and diffraction patterns confirmed the Ni–Si–Mn enriched precipitates were G-phase precipitates with a stoichiometry of Mn6Ni16Si7. Intragranular voids and Ni–Si enriched clusters were observed in irradiated γ austenite. Additionally, Ni and Si segregation was observed along the void interfaces. In both cases, Ni–Si clusters and segregation to voids, selected area diffraction patterns did not reveal the existence of a second phase. Proton irradiation induced Cr depletion and Si and Ni enrichment at γ−γ austenite grain boundaries that was characterized with STEM/EDS.

The effects of alloying elements on the peritectic range of Fe–C–Mn–Si steels

The peritectic reactions, liquid + δ-(ferrite) → γ(austenite) and the related casting problems during fast manufacturing process remain a big challenge for the compositional design and commercial production of high-quality Fe–C–Mn–Si steels. The precise prediction of the peritectic range of composition in steel is important in order to avoid the failure of casting and rolling; however, the effects of alloying elements on the peritectic range are unclear not only due to the large compositional space in alloyed steels but also its occurrence at high-temperature ranges, > 1400 °C. A combination of experimental measurements and thermodynamic modeling was employed to study the effects of alloying elements on the peritectic range for the wide composition ranges of Fe–C–Mn–Si steels. The phase transformation sequences and temperatures of two model Fe–C–Mn–Si steels were evaluated by differential scanning calorimetry (DSC) and in-situ confocal laser scanning microscope (HT-CLSM) and compared with thermodynamic calculation with TCFE9 database. The total number of 1680 phase diagrams is calculated by varying Mn from 0.3 wt% to 3.0 wt%, Si 0.05 wt% to 2.95 wt% and with and without a 0.02 wt% Ti addition. Using linear regression analyses for the calculations, we have predicted the correlation between peritectic ranges and the compositional space of Fe–C–Mn–Si steels. These results are effectively represented by contour plots and linear regression equations to predict the future outcomes of casting practice with their testing accuracy. It is also revealed that the peritectic ranges are influenced by complex elemental interactions, rather than the single-element effects of Mn, Si or Ti. The composition design of widely-applied Fe–C–Mn–Si steels is subject to a strict manufacturing restriction due to peritectic reaction and the related casting problems. This boundary condition is the topic of the current study.

Research on the variation of the inclusion and sulfur content in Pipeline steel

Pipeline steel is widely used in various industries, and the sulfur content and inclusions in steel have a significant impact on performance, which determines whether the steel quality is qualified. The experiments were carried out to explore the sulfur content and inclusion evolution of pipeline steel which was deoxidized by Si–Mn–Al with “EAF-LF-VD-T-CC”. The samples of molten steel and slag were taken during the process of LF-VD-Tundish after EAF tapping. The kinetics model was established to simulate the desulfuration process of molten steel in actual production, obtaining a result which the error is within 3 ppm. It can be summarized that proper calcium treatment can transform the inclusion into a liquid inclusion, the value of [Ca] ranges from 25 to 45 ppm. Too high and lower calcium treatment can cause the compositions of inclusions to deviate from the liquid phase area, while too low calcium treatment will increase the overall size and density of the inclusions. In addition, the evolution of inclusion in steel at refining temperature and during solidification process was comprehensively calculated, considering all types of inclusions such as calcium oxide, magnesium oxide, aluminum oxide, calcium sulfide, spinel, calcium aluminate and liquid inclusion. The thermodynamic calculations are in good agreement with experimental results, which can predict the formation of the inclusions in Si–Mn–Al deoxidized pipeline steel.

Effect of Hot-Dip Galvanizing Process on Selective Oxidation and Galvanizability of Medium Manganese Steel for Automotive Application

A medium manganese steel with 7.5 wt.% Mn for automobile application was galvanized in a continuous Hot Dip Galvanizing (HDG) simulator under different galvanizing conditions. It was shown that the effects of dew point, annealing temperature and annealing atmosphere on the surface oxidation of steel could be comprehensively evaluated by the consideration of oxygen partial pressure P(O2). Although Mn2SiO4 was a thermodynamic stable phase when P(O2) varied from 10−28 to 10−21 atm, it was difficult to form Mn–Si–O composite oxide because there was no enrichment of silicon on the steel surface. So, this oxide was generally formed in the Fe substrate and had little effect on the galvanizability. With the increase in P(O2) above 10−25 atm, MnO particles in the form of the thermodynamic stable phase became coarser and tended to aggregate, which hindered the formation of a continuous inhibition layer, resulting in the defects of bare spots on the galvanized surface of the steel. When the oxygen partial pressure greater than 10−22 atm, film-like MnO layer was formed on the surface of steel sample, which obviously deteriorated the galvanizability. The galvanizability of the steel can be improved by the regulation of oxygen partial pressure; based on this, the reasonable zinc plating process parameters can be developed.

Metallogeny of a base metal sulfide-bearing magnetitite body from the Eretria mine, East Othris massif, Greece: Insights into an ancient seafloor hydrothermal system

Magnetite deposits comprise a very small volume of a serpentinized peridotite body that constitutes the Eretria chrome mine of the East Othris ophiolite in central Greece. Magnetite deposits have been examined to aid determination of their mode of occurrence, mineralogy and origin. Research attention has been focused on an ore body that consists of a ~30 cm-thick pod of semi-massive to massive magnetite (~75%–85% modal) hosted in a serpentinite shear zone. The silicate matrix of magnetitite (~10%–15% modal) is composed of unstrained serpentine, chlorite and subordinate amounts of andradite and actinolite. Base metal sulfides (BMS; ~5%–10% modal) and phosphates are dispersed between the magnetite grains. Variably altered Cr-spinel crystals are poikilitically enclosed within magnetite. The investigated ore samples show great variations in the Cu (890–9530 ppm), Ni (190–3260 ppm), Co (120–2180 ppm) and Zn (20–1240 ppm) contents. The δ18ΟSMOW value for magnetite from a magnetitite sample is −2.2‰.The undeformed nature of the silicate minerals in magnetitite points toward crystal growth from a post-magmatic fluid. The low Ni, Mn, Mg and high Si contents in magnetite suggest that it was not derived from fluids produced concurrent to serpentinization. The presence of phosphates, BMS and hydrosilicates suggest that the ore forming fluids were acidic and halogen-bearing. Our preferred hypothesis for the formation of magnetitite is that mixing of upwelling, metal-rich brines along the dilational segments of the host shear zone caused saturation of the ensuing fluids with Fe, which eventually prompted magnetite precipitation. The T estimates deduced from mineralogy, with an uppermost limit of ~460 °C required, and cessation of mineralization at ~150–100 °C, are consistent with the ambient T present within a cooling oceanic lithospheric slab. In analogy with some modern serpentinite-hosted BMS deposits at rifted settings, the BMS-bearing magnetitite of Eretria may represent part of an ancient seafloor hydrothermal system. Our study provides important insights into the initiation and episodicity of hydrothermal activity in oceanic settings.

Heat treatment of the new high-strength high-ductility Al–Mg–Si–Mn alloys with Sc, Zr and Cr additions

Heat treatment of alloys of the Al–Mg–Si system essentially affects the age-hardening response and, accordingly, their final mechanical properties. However, the specific Mg/Si ratio in casting alloys makes age-hardening by heat treatment negligible. To improve the age-hardening response, the alloys were alloyed with Sc, Cr, Zr, and two types of heat treatment were applied: full T6 (solution treatment (ST), quenching, and artificial aging (AA)); and T5 with AA from the as-cast state. The microstructure after different heat treatment modes was observed by means of SEM and TEM. It was established that the main structural components that affect the mechanical properties of alloys after heat treatment are nanoscale precipitates and a coarse Al7Cr and Al3Zr intermetallic phases in the Cr- and Zr-containing alloys. The highest impact in terms of tensile properties was achieved in the Sc-containing alloys after T5 at 325 °C. Alloys with 0.2 wt% Sc exhibit the highest strength after T5 from as-cast state at 325 °C (up to 380 MPa) and highest elongation (up to 20%) after full T6 (ST 520 °C and AA 325 °C).

Gradient multilayer aluminium sheets used in automotive heat exchangers

The local electrochemical measurement and corrosion mechanism of the multi-layer aluminium sheets (AA4343/AA3xxx/AA4343 and AA7072/AA3xxx/AA4343) after brazing are determined by a combination of mechanical polishing and work function calculation based on density functional theory. The work functions of (100), (110), and (111) crystal planes of Si and α-Al(Fe,Mn)Si particles which are common in multi-layer aluminium sheets are calculated. The results demonstrate Si and α-Al(Fe,Mn)Si particles are considered to be cathodic with respect to the Al matrix, thus promoting cathodic reactions. The potential differences between the Si and α-Al(Fe,Mn)Si particles with respect to the Al matrix may lead to localized dissolution of the Al matrix. Besides, the microstructure and composition of multi-layered aluminium sheets are studied by optical microscopy, scanning electron microscopy, and glow discharge optical emission spectrometry and compared with those obtained for conventional multi-layer aluminium sheets (AA4343/AA3xxx/AA4343). The presence of the AA7072 layer reduces the outward diffusion of copper. In addition, the AA7072 sacrificial layer exhibits a large potential difference against the core material for a long time, thereby improving corrosion protection.

Microstructures and strengthening mechanisms of high Fe containing Al–Mg–Si–Mn–Fe alloys with Mg, Si and Mn modified

In this paper, two high Fe containing Al–Mg–Si–Mn–Fe alloys with Mg, Si and Mn modified were prepared, and their microstructures and mechanical properties were comparatively studied with a common applied alloy. Furthermore, the effects of alloying elements on their microstructures and the corresponding strengthening mechanisms were analyzed. It was found that the two Al–Mg–Si–Mn–Fe alloys exhibited good combination of strength and elongation in spite of their high Fe content. When compared with the common applied alloy, the yield strength of the two alloys was increased by 28 MPa and 50 MPa respectively, whereas the elongation was only slightly decreased. The higher strength of the two Al–Mg–Si–Mn–Fe alloys was mainly attributed to precipitation and solid solution strengthening which were substantially caused by the appropriated proportion of Mg and Si. Owing to the appropriate addition of Mn, no β–AlFeSi phases were found in the alloys, and the detriments of Fe were fully eliminated. The submicron scaled α–Al(FeMn)Si phases slightly improved the yield strength because of their contribution to grain refinement and dispersion strengthening. The results of this paper provide a valuable insight into the strengthening and industrial manufacturing of Al–Mg–Si alloys.