Effect Of Mn Content Research Articles

Effect of Mn content on low-cycle fatigue behaviors of low-carbon bainitic steel

The microstructures and low-cycle fatigue behaviors of steels with different Mn contents subjected to continuous cooling heat treatment processes (from Ms +10°C to Ms −20°C) are examined. Phase transformation testing results show that the steel without Mn exhibits short transformation time and short incubation period. When Mn content increases from 1.8% to 3.2%, bainite transformation time is prolonged, especially incubation period. The microstructure of the steel without Mn is mainly grain boundary allotriomorphic ferrite, while the other three steels with Mn consist of bainitic ferrite plate and retained austenite. Mn is an essential element used to obtain lower bainite. The low-cycle fatigue of the steels undergoes three stages, namely, cyclic hardening, saturation or cyclic softening, and fracturing. Higher elongation of the steel without Mn is beneficial to improve fatigue life under plastic strain amplitudes. The Coffin–Manson formula and damage hysteresis model are then used to evaluate the fatigue performances of the steels. It shows that the steel with 2.3% Mn exhibits higher fatigue damage capacity (W0) with a considerable damage transition exponent (β) than the other three steels. This result attributes to the largest distribution of high-angle misorientation of in the bainitic steel with 2.3% Mn.

Effects of Mn doping on dielectric properties and energy-storage performance of Na0.5Bi0.5TiO3 thick films

Lead-free Na0.5Bi0.5Ti1−xMnxO3 (NBTMnx, x=0, 0.01, 0.03 and 0.05) ferroelectric thick films have been fabricated on LaNiO3/Si(100) substrate by using a polyvinylpyrrolidone-modified sol-gel method and the effects of Mn content on their microstructure, dielectric properties and energy-storage performance were investigated. Compared with the pure Na0.5Bi0.5TiO3 (NBT) thick films, NBTMnx thick films exhibited a large enhancement in dielectric properties and energy-storage performance. Particularly, a giant recoverable energy-storage density (W) of 30.2J/cm3 and the corresponding efficiency (η) of 47.7% were obtained in NBTMn0.01 thick film at 2310kV/cm. Moreover, the NBTMn0.01 thick film displayed good energy-storage stability over a large temperature range at different frequency.

Effects of Mn Content on the Warm Stretch-Flangeabiliy of C-Si-Mn TRIP-Aided Steels

Effects of Mn content on warm stretch-flangeability are investigated using 0.2%C–1.5%Si–(1.5–5.0)% Mn transformation-induced plasticity (TRIP)-aided sheet steels with annealed martensite matrix. Warm hole-expansion at 150–250 °C after hole-punching at 25 °C enhances the stretch-flangeability of 3 and 5% Mn steels. The warm stretch-flangeability increases with the Mn content. The superior warm stretch-flangeability of hole-punched 5% Mn steel is caused by its large localized ductility on expanding, which results primarily from the stabilization of its large quantity of retained austenite and its fine microstructure. Use of hole-drilling instead of hole-punching at 25 °C further increases the stretch-flangeability and raises the optimum expanding temperature to 250–300 °C.

An efficient catalyst of manganese supported on diatomite for toluene oxidation: Manganese species, catalytic performance, and structure-activity relationship

The work reports the preparation of diatomite-supported manganese catalysts by deposition-precipitation method, and their application for toluene oxidation. Microstructure and morphology of catalysts were investigated by Powder X-ray diffraction pattern (PXRD), thermogravimetric (TG), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and nitrogen (N2) adsorption-desorption isotherms. Temperature-programmed reduction (TPR) and temperature-programmed surface reaction (TPSR) were used to analyze the reducibility of Mn species and the reactivity of surface oxygen species, respectively. The characterization results reveal that the manganese species were mainly in the phase of amorphous MnO2 and Mn2O3 on the diatomite, and the manganese species were successfully loaded on diatomite surface and filled in pores. With the increase of Mn content, the catalytic activity enhanced, due to the increase of surface oxygen species as adsorption-reaction sites. The Mn4+ played an important role in the superior catalytic activity towards toluene. The catalyst also displays high stability and superior activity towards toluene oxidation, which presents an applied interest. The effect of Mn content on the catalytic activity of catalysts was discussed in view of reaction mechanism and variations of physicochemistry properties.

Effect of Mn-Content on the Deformation Behavior of Binary Ti-Mn Alloys

The effect of Mn-content on the deformation of Ti-Mn low cost alloy system was investigated. A set of alloys ranging in composition from 8 to 20 %wt Mn were produced. The alloys were subjected to solution heat treatment at 900 °C. Existed phases were evaluated through XRD and microstructure observation. The cold workability and the change in micro-hardness were studied. The results showed that β-phase is predominant in all alloys under study. Lower Mn-content alloys had poor cold workability, but higher Mn-content showed a drastic improvement reaches to around 95% cold working until certain composition then dropped. Change in micro-hardness with the Mn-content is hardly observed. On the other, the strain hardening effect generated from cold working enhances the micro-hardness significantly.

Optimization of Mn content for high strengths in high-speed extruded Mg-0.3Al-0.3Ca (wt%) dilute alloy

The effect of Mn content on mechanical properties and microstructure of Mg-0.3Al-0.3Ca-xMn (wt%, x=0, 0.2, 0.4, 0.8) dilute alloys extruded at a high die-exit speed of 60m/min has been investigated. The strengths of the as-extruded samples increased with increasing Mn content, and Mg-0.3Al-0.3Ca-0.8Mn (AXM030308) alloy exhibited the highest 0.2% proof stress of 190MPa. This is due to the formation of fine and strongly textured grain structure as well as the dispersion of high number density of Al-Mn particles. Subsequent solution treatment and peak aging resulted in further increase in strength. High number density of Guinier Preston zones (G.P. zones) were dispersed within fine grains with their [0001] axis normal to the extrusion direction in the peak aged Mg-0.3Al-0.3Ca-0.4Mn (AXM030304) alloy, exhibiting the highest 0.2% proof stress of 220MPa with reasonable tensile ductility of 22%, which are superior to those of a peak aged 6063 aluminum alloy.

SOME TRIBOLOGICAL INVESTIGATIONS ON ZINC BASE ALLOY

ZA-27 alloys reinforced by Mn-containing intermetallic compounds were prepared and effect of Mn content on impact strength, hardness, tensile strength, volumetric wear rate and surface roughness were examined. By adding Mn, Si, Cu, Mg into ZA-27, experimental alloys were fabricated by gravity die casting. The volume fraction and grain size of the Mn-containing intermetallic compound phases vary with the changing of Mn content. As the percentage of Mn increases the volume fraction and size of the precipitates increased. Volumetric wear rate of the reinforced ZA-27 alloys at room temperature were measured. The results show that the impact strength and hardness values are increased with increase in Mn up to 1%. Ultimate tensile strength and Volumetric wear rate decreased with increase in Mn up to 1 %. But surface roughness is decreases almost with increase in the Mn content. Better tribological properties of these alloys can be achieved at a Mn content of 1 %.

Non-Metallic Inclusions and Hot-Working Behaviour of Advanced High-Strength Medium-Mn Steels

AbstractThe work addresses the production of medium-Mn steels with an increased Al content. The special attention is focused on the identification of non-metallic inclusions and their modification using rare earth elements. The conditions of the thermomechanical treatment using the metallurgical Gleeble simulator and the semi-industrial hot rolling line were designed for steels containing 3 and 5% Mn. Hot-working conditions and controlled cooling strategies with the isothermal holding of steel at 400°C were selected. The effect of Mn content on the hot-working behaviour and microstructure of steel was addressed. The force-energetic parameters of hot rolling were determined. The identification of structural constituents was performed using light microscopy and scanning electron microscopy methods. The addition of rare earth elements led to the total modification of non-metallic inclusions, i.e., they replaced Mn and Al forming complex oxysulphides. The Mn content in a range between 3 and 5% does not affect the inclusion type and the hot-working behaviour. In contrast, it was found that Mn has a significant effect on a microstructure.

First-principles study of Mn alloying into Fe3AlC: Towards the improvement of ductility

The first-principle calculations based on density functional theory (DFT) have been used to investigate structural and mechanical properties of Fe24−xAl8C8Mnx alloys. The calculated lattice constants of Fe3AlC were in accord with experimental values, and its lattice deformation increased with the doped content of Mn increasing. The calculated formation enthalpy indicated that Mn atom is more likely to locate in the center of each face of the Fe3AlC crystal lattice, and the Fe24−xAl8C8Mnx is a stable compound. The effect of Mn atoms on the independent elastic constants and the polycrystalline elastic parameters were calculated and discussed, such as bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratio ν, anisotropy value A and Vickers hardness Hv. The effect of Mn content on the melting temperature of the Fe3AlC alloys was also investigated, which represents the high temperature property. In addition, the density of states, the electron density difference, the population analysis and magnetic moment were also calculated to explain the mechanism of the structural stability, the chemical bonding and magnetization mechanism for the Fe3AlC and the Fe24−xAl8C8Mnx alloys at the electron level.

Effect of Mn Contents on the Phase Transition of the High Entropy Alloy Prepared by Laser Cladding

Al1.3FeCoNiCuCr high entropy alloy (HEA) coatings were prepared by pre-placed laser cladding on 921A steel substrate, and the study on the phase transition of the Al1.3FeCoNiCuCr coating due to the introduction of Mn was conducted. The combination of TEM and XRD results showed that the Al1.3FeCoNiCuCr HEA coatings without Mn addition typically consisted of two kinds of grains, i.e., one is composed of only FCC phase, and the another is a mixture of BCC and FCC phases. The two phases were of similar ratio in the coatings, while nanoparticulate precipitates were observed in the bcc phase. When 3 wt. % Mn was introduced into the alloy, the coatings consisted of also FCC and BCC phase. However, most of the grains were in FCC phase, while the BCC phase with a lath shape only distributed between the FCC phases. High hardness nanobanded precipitates were observed in the FCC phase. It is clearly revealed that the phase structure of Al1.3FeCoNiCuCr coatings undergoes a dramatic transition due to the introducing of Mn.

Microstructure, mechanical and tribological properties of Mo2FeB2 based cermets with Mn addition

Mo2FeB2 based cermets with different Mn contents were prepared by in-situ reaction liquid sintering. The effects of Mn content on the microstructure, mechanical and tribological properties were investigated. The observation of microstructure showed that the hard phase particles were distributed uniformly in Fe based binder. The mechanical properties of the cermets increased with the increasing of Mn content, due to grain refinement and solid solution strengthening. The inter-granular fracture was the main fracture mechanism of the cermets. The tribological behavior of the cermets was closely related to their mechanical properties. The cermet with 5 wt.% Mn content showed the best wear-resistance owing to its superior comprehensive mechanical properties. The wear mechanisms of Mo2FeB2 based cermets under dry sliding were primarily caused by abrasive wear, accompanying adhesive wear and oxidation wear.

Effect of Mn substitution on structural and magnetic properties of ferromagnetic shape memory alloys

ABSTRACTThe structure and the magnetic transitions have been investigated as a function of Mn in stoichiometric Ni2MnGa heusler alloys. Particular attention is paid to examine the linear increase of martensite transformation temperature on substituting Mn for Ga. It is observed that the martensite temperature increases and Curie temperature decreases with the effect of Mn content. Room-temperature magnetic measurements show the composition-dependent characteristics with decreasing magnetic saturation values and increasing coercivity values due to decrease in the magnetic exchange interaction strength with increasing Mn in place of Ga. The scanning electron microscopy image confirms that the Mn-rich alloys have the martensitic plates.

Effect of Mn Content on the Properties Affecting Shape Memory Behaviour of Cu-12Al-4Ni-10Zn Alloy

Effect of Mn Content on the Properties Affecting Shape Memory Behaviour of Cu-12Al-4Ni-10Zn Alloy

Effects of alloyed Mn on oxidation behaviour of a Co–Ni–Cr–Fe alloy between 1050 and 1250 °C

The effects of Mn content on the oxidation behaviour of a Co-base superalloy with compositions of Co–29Cr–21Ni–23Fe–2.2Nb–1.6Si–xMn (x=0, 0.5, 1, 2) (Co22 alloy for short, wt.%) have been studied. Isothermal oxidation behaviour was investigated, and it showed kinetics of the Mn-containing samples followed a two-stage parabolic law. In the absence of Mn, scales on Co22 alloys consisted mainly of Cr2O3 and SiO2, and small amounts of Fe–Cr, Ni–Cr spinel nodules formed on the surface. When Mn was added, a triple oxide layer could be observed, consisting of Mn–Cr spinel as outer layer, Cr2O3 as middle layer and SiO2 in the innermost layer.

Thermal and electrochemical properties of layered perovskite PrBaCo2−xMnxO5+δ (x = 0.1, 0.2 and 0.3) cathode materials for intermediate temperature solid oxide fuel cells

Layered perovskite PrBaCo2−xMnxO5+δ (PBCM-x, x = 0.1, 0.2 and 0.3) oxides have been synthesized and investigated as cathode materials for intermediate temperature solid oxide fuel cells (IT-SOCFs). The effects of Mn contents in PBCM-x materials on the crystal structure, chemical stability, thermal expansion coefficient (TEC) and electrochemical properties have been studied. XRD results have showed that the lattice parameters increase with x increasing from 0.1 to 0.3, although the crystalline structure does not change. The substitution of Co by Mn lowers the thermal expansion coefficient clearly. The average TEC decreases from 22.8 × 10−6 K−1 for PBCM-1 to 15.1 × 10−6 K−1 for PBCM-3 in the temperature range of 35–800 °C. The PBCM-x samples exhibit a semiconductor to metal transition. All the samples reach the general required electrical conductivity value of cathode material at the operating temperature range of 600–800 °C. Among the samples, PBCM-2 shows the best electrochemical performance. The single fuel cell with the configuration of PBCM-2/YSZ/Pt delivers the highest power density of 304.2 mW cm−2 at 800 °C.

The characterization of the coating formed by Microarc oxidation on binary Al–Mn alloys

In this study, effects of Mn content on behavior and properties of Microarc Oxidation (MAO) coatings produced on binary Al–Mn alloys and pure Al were investigated. Al–Mn alloys containing 1, 2, 4, 8 at.% Mn and pure aluminum produced using induction furnace under controlled atmosphere were coated in an alkaline electrolytic solution for 120 min. Surface roughness, thickness, microhardness, phase composition, microstructure and chemical composition of coatings were characterized by profilometry, Eddy Current test, microhardness measurement, XRD, SEM and SEM–EDS. All coatings composed of three regions: thin transition layer, dense inner region and porous loose outer region. Granular precipitates of α-Al2O3 were observed through dense inner region of coatings. With increasing Mn content, coating thickness increased from 111 μm to 169 μm. All coatings, regardless of substrate chemical composition, contained Al6Si2O13, γ-Al2O3, α-Al2O3 and considerable amount of amorphous phases. Increasing amount of Mn suppressed α-Al2O3 formation. It was seen that surface roughness and porosity formation tends to increase whereas the coating hardness tend to decrease with increasing Mn content. The coatings produced on Al–Mn alloys contained Mn along with Al, Si, O. The amount of Mn in the coatings increases with increase of Mn content in the substrates.

Effect of Mn content on structural, optical, opto-thermal and electrical properties of ZnO:Mn sprayed thin films compounds

Manganese-doped zinc oxide thin films (ZnO:Mn) at different percentages (0–3%) were deposited on glass substrates using a chemical spray technique. The effects of manganese element content on structural, optical, opto-thermal and electrical conductivity of ZnO:Mn thin films were investigated by means of X-ray diffraction, optical measurement, Photoluminescence spectroscopy and impedance spectroscopy. XRD analysis revealed that all films consist of single phase ZnO and were well crystallized in würtzite phase with the crystallites preferentially oriented towards (002) direction parallel to c-axis. Doping manganese resulted in a slight decrease in the optical band gap energy of the films and a noticeably change in optical constants. The UV peak positions for ZnO:Mn samples slightly red shift to the longer wavelength in comparison with the pure ZnO which can be attributed to the change in the acceptor level induced by the substitutional Mn2+ and the band-gap narrowing of ZnO with the Mn dopant. We have performed original AC and DC conductivity studies inspired from Jonscher and small polaron models. These studies helped establishing significant correlation between temperature and activation energy and Mn content. From the spectroscopy impedance analysis we investigated the frequency relaxation phenomenon and the circuit equivalent circuit of such thin films. Finally, all results have been discussed, as an objective of the actual work, in terms of the manganese doping concentration.

Improvement of low temperature toughness of ferritic Mn steels by alloy modification

A study has been made on the effects of Mn content and addition of Al on the microstructure and mechanical properties of (4-6)Mn steels, with the aim of developing ferritic Mn steels having good combination of tensile properties and impact toughness. It has been shown that the reduction of Mn content to 6 wt% and lower from 8-12 wt% of conventional steels can effectively prevent the occurrence of intergranular fracture, which has been a major problem of (8-12)Mn steels with poor toughness at cryogenic temperature. While increasing Mn content in the binary (4-6)Mn steels results in an increase in strength and a decrease in impact toughness, the addition of 1Al to (4-6)Mn steels results in improvements in both strength and impact toughness as compared to those of the binary (4-6)Mn steels and the best impact toughness has been obtained in the as-rolled 1Al added 4Mn steel, whose microstructure consists of fine acicular ferrite grains.

The effect of Mn content on magnetism and half-metallicity of off-stoichiometric Co2MnAl

Using the first-principles calculations within density functional theory (DFT), we investigate the influence of Mn content on magnetism and half-metallicity of off-stoichiometric Co2MnAl. From our calculation, the Mn-poor structure most likely results from antisite disorders where Mn atoms are partially substituted by Co (CoMn antisite) or Al (AlMn antisite) due to their lower formation energy than the structure missing Mn atom. Besides, the half-metallicity is immune to AlMn antisite, while the impurity Co atom in CoMn antisite is responsible for the dramatic decrease in spin polarization. Besides, in the Mn-rich structure where excess impurity Mn occupy the Co sites, impurity Mn atom exhibits antiparallel coupling with other magnetic atoms, resulting in ferrimagnetism. With increasing of Mn content, the spin polarization of Mn-rich structure increases from 75% to 100%. When Mn content rises up to α = 1.875, the corresponding compound Co1.125Mn1.875Al owns the perfect spin polarization and stable half-metallicity due to the reason that its Fermi level is situated nearly in the middle of the spin down gap. Hence, a large tunneling magnetoresistance (TMR) of magnetic tunnel junctions (MTJs) could be obtained by using Mn-rich Co2MnAl electrode. Furthermore, when Mn content reaches up to α = 2, the compound converts to inverse Heusler compound Mn2CoAl with an unique band structure that the conduction and valence band edges of the spin up electrons touch at the Fermi level, it is therefore classified to be spin gapless semiconductors.

Effects of Mn Content on the Deformation Behavior of Fe–Mn–Al–C TWIP Steels—A Computational Study

This paper presents a double-slip/double-twin polycrystal plasticity model using finite element solution to investigate the kinetics of deformation twinning of medium manganese (Mn) twinning-induced plasticity (TWIP) steels. Empirical equations are employed to estimate the stacking fault energy (SFE) of TWIP steels and the critical resolved shear stress (CRSS) for dislocation slip and deformation twinning, respectively. The results suggest that the evolution of twinning in Fe–xMn–1.4Al–0.6 C (x = 11.5, 13.5, 15.5, 17.5, and 19.5 mass%) TWIP steels, and its relation to the Mn content, can explain the effect of Mn on mechanical properties. By comparing the double-slip/double-twin model to a double-slip model, the predicted results essentially reveal that the interaction behavior between dislocation slip and deformation twinning can lead to an additional work hardening. Also, numerical simulations are carried out to study the influence of boundary conditions on deformation behavior and twin formation. The nucleation and growth of twinning are found to depend on internal properties (e.g., mismatch orientation of grains and stress redistribution) as well as on external constraints (e.g., the applied boundary conditions) of the material.