Mn Si Alloys Research Articles

Formation and evolution of inclusions in Q355B steel deoxidised with silicon and manganese

Q355B is extensively utilised owing to its superior mechanical properties. Nevertheless, the inclusions generated during the deoxidation process with aluminium and the treatment with calcium in steelmaking can profoundly influence these properties. Consequently, this study explores the inclusions formed during the manufacturing process of Q355B utilising silicon–manganese deoxidation alloys in an industrial setting. Furthermore, this research evaluates the deoxidation efficacy of the silicon–manganese alloy and elucidates the fluctuations in oxygen and nitrogen concentrations throughout the entire process. This study further investigates the types, number density, size, morphology and transformation processes of the inclusions generated throughout the Q355B production using silicon–manganese deoxidation alloy; additionally, electrolytic treatment was performed on the cast billets to extract large inclusions. The findings reveal that the deoxidation efficiency of the SiMn alloy is enhanced at relatively low temperatures and with a high manganese-to-silicon ratio. The predominant cause for the increase in total oxygen content in the molten steel during the smelting process is the exposure of the molten steel to secondary oxidation. Manganese–silicon deoxidation adequately fulfils the production requirements for Q355B. Oxide inclusions predominantly comprise Si–Mn-type oxides and their evolved inclusions; during the evolution process, aluminium-containing spinels generate calcium aluminium silicates in conjunction with CaO present in the slag. The number density of inclusions consistently decreases; however, it may subsequently increase due to secondary oxidation and slag entrapment. Throughout the evolution process, inclusions continuously aggregate and grow, resulting in an increasing proportion of large inclusions, while small-sized sulphide inclusions precipitate during the continuous casting process. The analysis of the isothermal ternary phase diagram of the slag system, in conjunction with the electrolytic results of the cast billets, confirms the occurrence of secondary oxidation and slag entrapment during the smelting process. Thermodynamic software calculations elucidate the formation and evolution of composite inclusions, offering critical insights for composition control to mitigate the associated hazards of composite inclusions. Thermodynamic and kinetic calculations of precipitates clarify the solidification conditions and temperature required for the precipitation of MnS, demonstrating that the size of the precipitates is negatively correlated with the cooling rate and positively correlated with the concentration of the strongly segregated element sulphur.

Laser Powder Bed Fusion of Fe–Mn–Si based shape memory alloys with high performance at room and cryogenic temperature

A Fe–Mn–Si based alloy with high shape memory effect (SME) and mechanical performance at both cryogenic and room temperature was fabricated by laser powder bed fusion (LPBF) with blended elemental powders. The effect of laser power on the elemental uniformity, microstructure, SME, strength of the as-built sample was investigated. The developed alloy shown superior SME under high laser power, due to the fully transformation of initial bcc phase to the stable fcc phase during the cooling process. The developed Fe–Mn–Si alloy shown high shape recovery rate of 63 % and 92 % after ∼0.05 bending strain at room and cryogenic temperature, respectively. The as-built samples had characteristic microstructure of small fcc phase grains and high density of stacking faut and twins. The as-built sample exhibited room/cryogenic tensile strength as high as 962MPa/1372 MPa, respectively, with considerable plasticity. This work provides foundations for fast development of high performance additively manufactured shape memory alloy (SMA).

Tailoring the stability of iron carbides to enhance the mechanical performances of Fe–C–Mn–Si alloys

Tailoring the stability of iron carbides to enhance the mechanical performances of Fe–C–Mn–Si alloys

Reverse ε→γ transformations of temperature-induced and stress-induced martensites in Fe–Mn–Si alloys with shape memory effect

In this work we argue that the reverse martensitic transformation (MT) of the stress-induced martensite (SIM) of Fe–Mn–Si-based alloys for moderate prestrains occurs in essentially thermoelastic-like way, in contrast to non-thermoelastic MT of temperature-induced martensite (TIM). We compare, using a number of complementary experimental techniques, the temperatures and the kinetics of the reverse ε→γ martensitic transformation of SIM and TIM for commercial and model Fe–Mn–Si alloys after various thermomechanical treatments. We claim that two studied phenomena are generic in Fe–Mn–Si-based alloys of different compositions and microstructure: first, opposite to the conventional effect of stabilization of martensite by prestrain, the reverse MT during heating of alloys prestrained in bending and tension starts well below (up to 100 K) the start temperature of the reverse MT for the TIM of the same alloy. The difference between engineering temperatures of the start of the reverse transformation, As, for SIM and TIM reaches ca. 50 K, pointing to a need to consider different As for TIM and SIM, AsTIM and AsSIM. Second, the reverse transformations of TIM and SIM show very different kinetics. The reverse MT of SIM is diffuse over the temperature range exceeding 100 K. The reverse MT of TIM, on the contrary, is well localized within the temperature range of ca. 20 K. The experimental observations can be interpreted assuming that, due to the differences in the formation mechanisms of SIM and TIM, the latter shows non-thermoelastic behaviour, whereas the SIM shows similarities with the thermoelastic martensites stabilized by prestrain.

Effects of Cr-addition on ageing response of an Al–Si–Mg die cast alloy

Chromium (Cr) is rarely added to Al–Si die cast alloys as it has a strong tendency to induce the formation of coarse-sized sludge particles. In the present study, high pressure die-cast samples made of Al-7wt.%Si–Cr–Mg alloys with varied Fe contents (0.11 wt%, 0.26 wt% and 0.32 wt%) were tensile tested under as-cast and T5 heat-treated conditions, in comparison to those made of Al-7wt.% Si–Mn–Mg alloy with a constant Fe content (0.11 wt%). The results demonstrated that under the as-cast condition, the Al–Si–Cr alloys with higher Fe contents can achieve comparable tensile properties as the Al–Si–Mn alloy with strictly controlled Fe level. However, after a T5 heat treatment (205 °C for 60 min), the increment in yield strength is less for the Al–Si–Cr alloys in relative to the Al–Si–Mn alloy, regardless of Fe contents. Scanning electron and scanning transmission electron microscopic characterizations were conducted on the as-cast and heat-treated microstructures, aiming to understand the undermined ageing response caused by Cr addition.

The nanoscale mechanisms of strengthening and ductility enhancement in an Al–Mg–Si–Mn alloy on processing by high-pressure torsion

In this work we show that high-pressure torsion (HPT) processing of an Al-1.0at%Mg-0.8at%Si-0.2at%Mn in T6 state causes an 81% increase in ultimate tensile strength (UTS) to reach 559 MPa, whilst, remarkably, retaining a very good ductility of 14%. After an initial decrease in ductility for up to 1 HPT turn, further deformation up to 5 turns remarkably causes increases in ductility as well as increases in hardness and UTS. Analysis by X-ray diffraction line broadening and transmission electron microscopy show that during HPT processing a high density of dislocations are produced, and the grain size decreases from 3 μm for T6 sample to around 286 nm for 5r-HPT sample. Atom probe tomography reveals solute atoms strongly segregate on ultrafine-grained boundaries for a 5r-HPT sample. A model for the strengthening mechanisms is established to evaluate contribution of dislocations, grain boundaries, solid solution atoms, precipitates and solute (co-)clusters. We show that in the HPT processed 6xxx-series Al–Mg–Si alloy the strengthening caused by solute segregation at dislocations and on grain boundaries is the dominant strengthening mechanism. This work illustrates a rare case of a beneficial concomitant increase of strength and ductility during HPT. The result is an AA6xxx material with strongly increased strength and very good ductility as compared to the widely employed commercially available AA6xxx-T6 alloys.

Coupled Effects of Temperature and Humidity on Fracture Toughness of Al-Mg-Si-Mn Alloy.

The combined effect of temperature and humidity on the fracture toughness of aluminium alloys has not been extensively studied, and little attention has been paid due to its complexity, understanding of its behaviour, and difficulty in predicting the effect of the combined factors. Therefore, the present study aims to address this knowledge gap and improve the understanding of the interdependencies between the coupled effects of temperature and humidity on the fracture toughness of Al-Mg-Si-Mn alloy, which can have practical implications for the selection and design of materials in coastal environments. Fracture toughness experiments were carried out by simulating the coastal environments, such as localised corrosion, temperature, and humidity, using compact tension specimens. The fracture toughness increased with varying temperatures from 20 to 80 °C and decreased with variable humidity levels between 40% and 90%, revealing Al-Mg-Si-Mn alloy is susceptible to corrosive environments. Using a curve-fitting approach that mapped the micrographs to temperature and humidity conditions, an empirical model was developed, which revealed that the interaction between temperature and humidity was complex and followed a nonlinear interaction supported by microstructure images of SEM and collected empirical data.

Microstructural characterization, oxidation behavior, and properties of a new Al–Cu–Ni–Mn–Si non-BCC high entropy alloy at 600, 700, and 800 °C

Non-BCC high entropy alloys have been created and characterized in their as-cast and oxidized condition. The effect of Si on the microstructures in Al–Cu–Ni–Mn alloy has also been explored. The microstructure remained unaltered by the addition of Si. It has been observed that the addition of Si only changes the composition of the three phases that have been identified. Three phases with elements rich in: (a) Ni, (b) Mn, and (c) either Al–Cu–Ni in quaternary alloy or Al–Cu–Mn in Si alloy have been observed. It is suggested that Si draws Ni out of solution for Al–Cu–Ni rich phase in preference for Mn. Macrohardness (HRB) of the two alloys and microhardness (HV) of the three phases were found to be HRB 74 for the Al–Cu–Ni–Mn alloy and HRB 114 for the Al–Cu–Ni–Mn–Si alloy; and HV 265 to HV 271 for the Al–Cu–Ni-Mn alloy phases and HV 411 to 968 for the Al–Cu–N–Mn–Si alloy phases.

Experimental and Numerical Studies on Fe–Mn–Si Alloy Dampers for Enhanced Low-Cycle Fatigue Resistance

Experimental and Numerical Studies on Fe–Mn–Si Alloy Dampers for Enhanced Low-Cycle Fatigue Resistance

Diffusivity and atomic mobility in fcc Cu–Mn–Si alloys: measurements and modeling by CALTPP program

Diffusivity and atomic mobility in fcc Cu–Mn–Si alloys: measurements and modeling by CALTPP program

Kinetic Transition During Ferrite Growth Induced by Interfacial Solute Segregation in an Fe–C–Mn–Si Alloy

Kinetic Transition During Ferrite Growth Induced by Interfacial Solute Segregation in an Fe–C–Mn–Si Alloy

The Improved Mechanical Anisotropy of a Commercial Al–Cu–Mg–Mn–Si (2017) Aluminum Alloy by Cross rolling

The optimized thermomechanical process is an effective way to improve and control the properties of metallic alloys. Herein, the influence of unidirectional cold rolling and cross cold rolling on the texture and mechanical properties of a commercial AlCuMgMnSi (2017) alloy is investigated. The Al sheets successfully prepared by the three cold rolling methods have different dominant texture components, and show different texture transformation routes during solution and aging treatments. In addition, the influence of the rolling direction on the texture of the 2017 alloy is discussed. The cross‐rolled sheets subjected to artificial aging show the strongest yield strength of ≈366 MPa and ultimate tensile strength of ≈426 MPa, as well as excellent mechanical anisotropy. Its in‐plane anisotropy (IPA), , and Δr values are 0.7%, 0.576, and 0.042, respectively. The effects of texture and precipitates on the anisotropy of aged 2017 alloys are also discussed separately. This work may help to understand the relationship between rolling direction and the mechanical anisotropy of aluminum alloys and provide a basis for industrial production.

Non-metallic Inclusions in Different Ferroalloys and Their Effect on the Steel Quality: A Review

Ferroalloys have become increasingly important due to their indispensable role in steelmaking. In addition, the demand for improved steel qualities has increased considerably, which in turn highlights the quality of ferroalloys. This is due to the fact that the impurities in ferroalloys directly and significantly influence the quality of steel products. To gain a better understanding of the main trace elements and inclusions in ferroalloys (such as FeSi, FeMn, SiMn, FeTi, FeCr, FeMo, FeNb, FeV, FeB, some complex ferroalloys) and their behaviours in steel melt after the additions of these ferroalloys, information from a large number of previous results on this topic was extensively reviewed in this work. The applications of different ferroalloys and their production trends were discussed. In addition, the effects of some trace element impurities from ferroalloys on the inclusion characteristics in steel were also discussed. The possible harmful inclusions in different ferroalloys were identified. Overall, the results showed that the inclusions present in ferroalloys had the following influence on the final steel cleanliness: (1) MnO, MnS and MnO–SiO2–MnS inclusions from FeMn and SiMn alloys have a temporary influence on the steel quality; (2) the effect of large size SiO2 inclusions (up to 200 μm) in FeSi and FeMo alloys on the steel cleanliness is not fully understood. The effect of Al, Ca contents should be considered before the addition of FeSi alloys. In addition, Al2O3 inclusions and relatively high Al content are commonly found in FeTi, FeNb and FeV alloys due to their production process. This information should be paid more attention to when these ferroalloys are added to steel; (3) except for the existing inclusions in these alloys, the Ti-rich, Nb-rich, V-rich carbides and nitrides, which have important effects on the steel properties also should be studied further; and (4) specific alloys containing REM oxides, Cr–C–N, Cr–Mn–O, Al2O3, Al–Ti–O, TiS and Ti(C, N) have not been studied enough to enable a judgement on their influence on the steel cleanliness. Finally, some suggestions were given for further studies for the development of ferroalloy productions.

Electronic structure, magnetic properties, and elastic properties of full-Heusler alloys Cr2-xFexMnSi (x=0, 1, and 2)

In this study, we have systematically investigated the electronic structures, magnetic and elastic properties of the full-Heusler compounds Cr2-x Fe x MnSi (, 1, and 2) by density functional theory calculations using the CASTEP with the generalized gradient approximation for the exchange-correlation functional. Our calculation results show that the Cr2MnSi, CrFeMnSi and Fe2MnSi alloys exhibit excellent half-metallic materials, and half-metallic band gap will be larger as the number of Fe atoms increases. The magnetism originates from the spin contribution of Cr-, Fe- and Mn-d orbital electrons and the strong hybridization between them. The total magnetic moment of Cr2-x Fe x MnSi (, 1, and 2) remains an integer value when the lattice parameter is changed within a narrow range, and the range will be larger as the number of Fe atoms increases. Investigation of elastic properties shows that the Cr2-x Fe x MnSi (, 1, and 2) alloys are ductile and anisotropic materials.

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.

A novel process on the recovery of zinc and manganese from spent alkaline and zinc-carbon batteries

Spent alkaline and zinc-carbon batteries contain valuable elements (notably, Zn and Mn), which need to be recovered to keep a circular economy. In this study, the black mass materials from those spent batteries are pyrometallurgically treated via a series of process steps in a pilot-scale KALDO furnace to produce an Mn–Zn product, a ZnO product, and an MnO (manganese monoxide) product, toward applications of Mn–Zn micronutrient fertilizer, zinc metal, and manganese alloy, respectively. After an oxidative roasting step, an Mn–Zn product, containing 43% Mn, 22% Zn, and negligible amounts of toxic elements (notably, Cd, Hg, and Pb), could be produced, being suitable for the micronutrient fertilizer application. After a reductive roasting step, a ZnO product and an MnO product are produced. The attained ZnO product, containing up to 84.6% ZnO, is suitable for zinc metal production when the leaching steps are taken to remove most of the Cl and F in the product. The attained MnO product, containing up to 91.7% MnO, is of premium quality for manganese alloy production, preferably for SiMn alloy production due to its low phosphorus content. The proposed application scenarios could substantially improve the recovery efficiency of those spent batteries.

Carbide formation and accumulation in SiMn furnaces

Recent excavations of Norwegian medium size SiMn furnaces have revealed spectacular amounts of carbide-rich materials accumulating on the sidewalls. In an excavated furnace from Eramet Kvinesdal, producing a 19%Si silicomanganese alloy prior shutdown, the sidewall materials contained silicon carbide in addition to SiMn alloy, slag and carbon. This contrasts with the large amounts of titanium carbides found in a furnace from Ferroglobe (Glencore then) which was producing 16%Si silicomanganese. The significant volume occupied by the carbides is likely to affect the flow of materials as well as furnace operation. It is therefore meaningful to understand how and when those carbides can form, especially concerning titanium carbide given the low content of titanium (about 0.3%) in the raw materials. The present study investigates the conditions under which TiC and SiC can appear in the furnace. Slag, alloy, and gas compositions were chosen to mimic industrial charges and were reacted between 1450 and 1650 °C. The reacted samples were further analysed by electron probe microanalysis with wavelength-dispersive X-ray spectroscopy (EPMA/WDS). Thermodynamic calculations were conducted using FactSage 8.0 and used for further reflection. The results indicate that TiC was formed by both precipitation and chemical reaction.

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).

New perspective on the interface reaction and morphology evolution in the reduction of manganese silicate for silicomanganese alloy production

SiMn alloy is the largest consumption product in the Mn series alloys. Manganese silicates generated during the pre-treatment procedures of manganese ores are the main ingredient for SiMn alloy production. However, conventional cognition is that manganese and silicon in the silicates are respectively reduced to Mn7C3 and SiC by carbon, and then the carbides interact to form alloy. In current study, pure MnSiO3 was synthesized firstly and then a new perspective on the interface reaction and morphology evolution for the reduction of pure MnSiO3 were investigated via XRD, SEM, XPS and thermodynamics analyses. Interface reaction showed that the MnSiO3 was firstly reduced to manganese carbides and SiO2, and then the SiO2 was further reduced by the carbides to generate SiMn alloy. The intermediate product Mn7C3 played a crucial role since the reduction of SiO2 by newly born Mn7C3 preferentially conducted than the carbon reductant. Morphology evolution of the interface between C and MnSiO3 as well as thermodynamic calculations of Mn-Si-O and Mn-Si-C-O systems were minutely clarified in this work to clarify the reduction mechanism. In addition, decomposition of SiMn alloy to SiC ceramic at 1700 °C was an important inducement to illustrate the frangibility of industrial SiMn alloy product.

Twins and polytypic stacking faults in the ν phase formed in rapidly quenched Mn-Si alloys

Mn-rich Mn-Si binary alloys containing the ν phase have been prepared by arc-melting and rapid-quenching methods. In comparison, twins and polytypic stacking faults (SFs) are observed in the rapidly quenched ν phase, and the atomic-scale structure properties of twins and SFs have been determined by using aberration-corrected scanning transmission electron microscopy techniques. Both twins and SFs break the crystallographic symmetry of the ν phase, and lead to reconstruction of the subunits of the ν phase at twin boundaries and SFs. On the basis of experimental results, new structural models are proposed to explain the twin and SFs formation in the rapidly quenched ν phase.