Mn Si Cr Research Articles

Evolution of shape memory effect with aging time during aging after pre-strain in Fe–Mn–Si–Cr–Ni–C shape memory alloys

The shape memory effect of Fe–Mn–Si–Cr–Ni–C shape memory alloys could be significantly improved by aging after pre-strain, because a high density of directional Cr23C6 particles is precipitated. However, the variation of shape memory effect under a large deformation-strain with aging time is not evident in the Fe–Mn–Si–Cr–Ni–C alloys subjected to aging after pre-strain. In order to clarify the above issue, the effect of aging time on the microstructures and the recovery-strain under a large deformation-strain of 7.5% for the Fe–Mn–Si–Cr–Ni–C alloy subjected to aging for 10–300 min after 10% pre-strain at room temperature was systematically investigated by XRD, SEM, EBSD, and EPMA. When the aging time was 30 min, the maximum recovery-strain of 5.4% was achieved. The recovery-strain increased from 4.9% to 5.4% when the aging time was extended from 10 min to 30 min. It is attributed to that the fraction of twin boundaries, inhibiting stress-induced ε martensitic transformation, decreased from 19.1% to 14.2%, as the precondition that the density of stacking faults, promoting stress-induced ε martensitic transformation, remained nearly constant. When the aging time was extended from 30 min to 180 min, the recovery-strain decreased from 5.4% to 4.6% due to both the decrement of stacking faults and the increment of twin boundaries.

Strain localization at longitudinal weld seams during plastic deformation of Al–Mg–Si–Mn–Cr extrusions: The role of microstructure

The current work was motivated by the increasing use of hollow aluminum extruded profiles for automotive applications and the need for a better understanding of the mechanical response of extrusion seam welds. Two Al–Mg–Si alloys were studied, one without Mn and one with 0.5 wt%Mn and 0.15 wt%Cr. A high temperature homogenization was applied, resulting in a high density of α-Al(Fe,Mn)Si dispersoids in the Mn containing alloy, and an essentially dispersoid free microstructure in the other. The alloys were extruded through a simple porthole die (with two ports) to produce a strip with a centerline weld seam. The Mn free extrudate had a recrystallized grain structure whereas the Mn and Cr containing material was unrecrystallised. There were significant spatial variations of microstructure between the weld seam and surrounding regions, in particular the crystallographic texture. Tensile tests were conducted with the loading direction perpendicular to the weld seam using digital image correlation (DIC) to characterize the local strain distribution. Strain localization and final fracture occurred at weld seam for the unrecrystallized material whereas these occurred away from the weld line in the recrystallized case. The role of local crystallographic texture was examined through polycrystal plasticity simulations using the visco-plastic self consistent code (VPSC). These simulations indicated that the weld seam region was mechanically stronger than the surrounding region for the recrystallized alloy and correspondingly weaker for the unrecrystallized case, thereby rationalizing the experimental results of strain localization and final fracture location.

Composition of Non-Metallic Inclusions and Microstructure of Electric Arc Coating Formed Using the Flux-Cored Wire of Fe–C–Si–Mn–Cr–Mo System

Composition of Non-Metallic Inclusions and Microstructure of Electric Arc Coating Formed Using the Flux-Cored Wire of Fe–C–Si–Mn–Cr–Mo System

Structure and Composition of the Arc Sprayed Coatings Formed Using a Flux Cored Wire of the Fe–C–Si–Mn–Cr–Ni–Mo System

Structure and Composition of the Arc Sprayed Coatings Formed Using a Flux Cored Wire of the Fe–C–Si–Mn–Cr–Ni–Mo System

Microstructure and Deformation Characteristics of Mn–Si–Cr Ultra-high Strength Steel

Microstructure and Deformation Characteristics of Mn–Si–Cr Ultra-high Strength Steel

Experimental study and thermodynamic analysis on the selective oxidation of DP1180 dual‐phase steel

The selective oxidation process of dual‐phase 1180 steel was investigated in this study. Annealing was carried out in Cr/Cr2O3 Rhines pack at 820°C for 60, 120, and 240 s, under the oxygen partial pressures of 10−23, 10−25, and 10−29 atm, respectively. Field emission scanning electron microscopy (FE‐SEM), electron backscattered diffraction (EBSD), and X‐ray photoelectron spectroscopy (XPS) were used to analyze the experimental results. The oxides involved SiO2, MnO, MnSiO3, Mn2SiO4, and MnCr2O4. The amount of oxides augmented along with the increasing oxygen partial pressure. The Fe–Mn–Cr–Si–C–O2 oxidation diagram was calculated by thermodynamic software and was used to explain the selective oxidation process of dual‐phase 1180 steel. Experimental results combined with the thermodynamic computations well.

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

On the Significance of Thermal Deformation and Dynamic Recrystallization on Flow Behavior of 25Mn2Si2Cr Bainitic Alloy

Thermal deformation characteristics, dynamic recrystallization behavior, and processing map of 25Mn2Si2Cr high strength bainitic steels are elucidated during wide temperature range (850–1100 °C) and strain rate (0.1–10 s−1) from flow behavior. Thermomechanical analysis by Thermo‐Calc software indicates that microstructure during thermal deformation is austenite, which is conducive to dynamic recrystallization. Phenomenological constitutive equations of thermal deformation, dynamic recrystallization equation, and processing map are established to predict flow behavior. The experimental results indicate that deformation temperature and strain rate have significant effect on thermal deformation process. Flow stress increases with decrease in deformation temperature and increase in strain rate. Increasing deformation temperature and decreasing strain rate promote dynamic recrystallization occurrence. However, the grain size increases with increase in deformation temperature. Thermal simulations predict that optimum thermal deformation parameters are deformation temperature (950–1000 °C), strain rate (0.25–5 s−1) and deformation temperature (850–950 °C), strain rate (1–5 s−1) for processing of Mn–Si–Cr bainitic steels.

Fe–Mn–Si–Cr–Ni based shape memory alloy: Thermal and stress-induced martensite

The determining role of C- and Si-content on the shape memory effect of Fe–Mn–Si–Cr–Ni alloys, where Si was partly replaced by Co. In this regard, three alloys, Fe–15Mn–5Si–8Cr–5Ni, Fe–15Mn–5Si–8Cr–5Ni-0.1C, and Fe–15Mn–3Si–8Cr–5Ni-0.1C–2Co were designed to simultaneously study the shape memory effect and mechanical properties in relation to the microstructure. The microstructure of the alloys after cold rolling and annealing was analyzed by EBSD and X-ray diffraction techniques. The results indicated that grain size and the addition of C influenced the shape memory effect of Fe–Mn–Si–Cr–Ni-based memory alloy. With the increase of grain size, the annealing twin density was decreased, reducing the constraint on phase transformation of γ-austenite to ε-martensite. Furthermore, the austenite stability was decreased, such that the martensite-content was increased, and then reduced the shape memory effect of the experimental alloy. With the addition of C, the content of thermally-induced martensite was reduced, and the probability of stress-induced transformation of martensite to obtain α′-martensite was reduced, with consequent enhancement of the shape memory effect for the experimental steel. Additionally, the strength of parent phase was enhanced by the addition of C, and the plastic deformation by slip during stress-induced martensite was minimized, leading to low α′-martensite content and promotion of reversal of stress-induced martensite.

Characterization of retained austenite in a low carbon high strength Mn–Si–Cr steel

The microstructure and the mechanical properties of the low carbon high strength (LCHS) Mn–Si–Cr steel treated by the novel quenching and dynamic-partitioning (QDP) process are investigated in detail. All samples exhibit a better performance of tensile strength and impact toughness compared with conventional LCHS steels. The higher impact toughness is closely related to the stability of retained austenite (RA), which is determined by the morphology and the carbon content. The filmy RA between martensite laths as well as the nano-sized RA inside martensite laths can effectively improve toughness. The crystallographic features of the RA are studied in depth and the crystal plane indices of facets are accurately characterized. The near-coincidence-sites (NCS) model is applied to further analyze the interfacial structures of the nano-sized RA in the given orientation relationship. The observed facets tend to contain the high-planar density of NCS clusters. The study provides some references for the research on the phase transformation of high-strength steels.

Effect of Chemically Active Medium on Magnetic Characteristics of Soft Magnetic Co-Based Amorphous Alloy

The interaction of the ribbon surface with acetone and its effect on the magnetic characteristics of ribbon are studied in this work using the example of soft magnetic Co-based AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) amorphous alloy. The studies show the different effect of acetone treatment of ribbon on the magnetization distribution and magnetic permeability of material in states differing in the sign of saturation magnetostriction. The treatment of the ribbon in the state with λs > 0 favors the increase in both the volume of domains with the orthogonal magnetization and the magnetic texture sharpness in the ribbon plane; in the state with λs < 0, the treatment favors the decrease in both the volume of domains with the orthogonal magnetization and magnetic texture sharpness and an increase in the maximum magnetic permeability. This can result from the predominantly planar anisotropic compressive stresses induced in the ribbon by catalytic oxidation and hydrogenation of acetone.

Effect of boron on microstructure evolution and properties of wear-resistant cast Fe–Si–Mn–Cr–B alloy

The purpose of this study was to clarify the effect of boron content on the microstructure evolution, mechanical properties, and three-body abrasive wear property of as-cast Fe–Si–Mn–Cr–B alloys, and to reveal the wear mechanism of Fe–Si–Mn–Cr–B alloys. The results indicated that the microstructure of the Fe–Si–Mn–Cr–B alloy was mainly composed of bainite, retained austenite (RA), M3B2, and M2B (M stands for the metal atom, in this case, it refers to Fe, Cr, and Mn). With the increase of boron content, the volume fraction of the boride phase increased, the morphology of the boride phase was dominated by fishbone, the microhardness of the boride phase and the macrohardness of the alloy increased, and the wear resistance of the alloy was significantly enhanced. Compared with the 0.5wt.% B alloy, the macrohardness of the 2.0wt.% B alloy was increased by 19.5%, the maximum microhardness of the boride phase reached 1440 HV0.2, the Charpy impact toughness was reduced by 45%, and the wear resistance was increased by 268%. The morphology, content and distribution of the boride phase play a key role in improving the hardness and wear resistance of the alloy. The synergy between the high-hardness boride phase and the softer metal matrix phase, which was composed of bainite and RA, gave the alloy excellent wear resistance. The main wear mechanisms of the alloy were abrasive wear and fretting wear.

On the significance of C and Co on shape memory performance of Fe–Mn–Si–Cr–Ni shape memory alloy

Fe–Mn–Si bearing shape memory alloys are used as structural and functional materials, and have the potential for application in industrial and architectural fields. Fe–Mn–Si–Cr–Ni based shape memory alloys were selected to elucidate the impact of C and Si content on shape memory effect, where Si was replaced by Co. In this regard, Fe–15Mn–5Si–8Cr–5Ni, Fe–15Mn–5Si–8Cr–5Ni-0.1C, and Fe–15Mn–3Si–8Cr–5Ni-0.1C–2Co alloys were designed to simultaneously elucidate the shape memory effect (SME) and mechanical properties in relation to the microstructure. The study indicated that the addition of 0.1 wt% C significantly improved the SME of Fe–Mn–Si–Cr–Ni alloy, and the shape recovery rate of Fe–15Mn–5Si–8Cr–5Ni-0.1C alloy aged at 750 °C for 4 h was maximum at 55.45%. The content of thermally-induced martensite was reduced, which led to decrease in the probability of α′-martensite formation, and promoted inverse transformation of stress-induced martensite and enhanced the shape memory effect. In addition, the strength of the parent phase was enhanced by segregation of elements during aging. Furthermore, the plastic deformation involving slip during stress-induced martensitic transformation was reduced. The reduced content of α′-martensite promoted reversal of stress-induced martensite. On the other hand, Co increased the stacking fault energy and reduced nucleation of stress-induced martensite, such that the number density of stacking faults decreased the shape memory effect of the experimental steel.

The Metastability of Retained Austenite in Multiphase Steel during Abrasive Wear

This article presents the results of a study of the effects of the amount and metastability of retained austenite on the abrasive wear resistance of 0.55% C–Si–Mn–Cr–Mo–V–Nb steel subjected to Q&P treatment to obtain a heterogeneous martensite/bainite/austenite structure. The content of retained austenite varied from 13 to 28%, while the carbon content in austenite varied from 0.97 to 1.23%. The wear tests were carried out according to the three-body abrasion scheme using quartz or corundum as an abrasive. The microstructure and worn surface of the steel were examined using an electron scanning microscope and X-ray analysis. It has been established that during the transition from corundum to quartz the tendency of austenite to deformation martensitic transformation during wear decreased sharply. The wear of the steel is inversely proportional to its hardness and the amount of austenite that transforms to martensite during wear. The latter tendency is more pronounced under testing with a softer abrasive. In this case, Q&P treated steel is superior in wear resistance to martensite quenched steel.

Investigation of microstructure evolution and quench sensitivity of Al–Mg–Si–Mn–Cr alloy during isothermal treatment

The quench sensitivity of Al–Mg–Si–Mn–Cr alloy was studied through time-temperature-transformation (TTT) and time-temperature-property (TTP) curves. The high quench sensitive region ranges from 250 °C to 430 °C with nose temperature at about 350 °C, where the quenching rate is required to higher than 9 °C/s for avoiding the formation of quench-induced precipitates. B′(Al3Mg9Si7) precipitates from the supersaturated solid solution, and gradually transforms to equilibrium β (Mg2Si) and excess Si phase with increasing isothermal time at 350 °C. The loss of the solute atoms in matrix results in the reduction of the aging hardening precipitation and the formation of the precipitate-free zones (PFZs) during artificial aging. The nucleation rate of the quench-induced precipitation is studied by nucleation theory, and the phase transformation kinetics is analyzed through Avrami equation. The Al(MnCrFe)Si dispersoids, (sub)grain boundaries and dislocations are the preferential heterogeneous nucleation sites for quench-induced precipitation.

Bainitic Austempering Incorporating Quenching and Partitioning for Favorable Tuning of Microstructure and Mechanical Properties

A novel aspect of combining bainitic austempering with quenching and the partitioning process is addressed herein to obtain a favorable microstructure with desired mechanical properties. In this regard, Mn–Si–Cr–Al steel is first intercritically annealed at 840 °C and quenched to 140 °C after isothermal treatment at 360 °C for 15 min and then partitioned at 360 °C for 30 min. Multiphase microstructure containing ferrite, bainite, martensite, and retained austenite (RA) is obtained. Uniform elongation and total elongation increase appreciably from 11.5% to 20.5% and 21.0% to 28.3%, respectively, while maintaining near‐identical levels of tensile strength, compared with traditional bainitic austempering. The significant enhancement of tensile properties is attributed to the increase in volume fraction and mechanical stability of RA.

Influence of Polymer Coating on the Magnetic Characteristics of Ribbon of an Amorphous Cobalt-Based Alloy in the As-Quenched State

Samples of cobalt-based amorphous soft magnetic alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) with near-zero negative values of saturation magnetostriction were used to study the effect of a polymer coating (applied upon the production of magnetic screens) and of the conditions of its formation on the distribution of magnetization and magnetic properties. The coating was applied onto the ribbon in the as-quenched state at temperatures of 90–130°C. It has been shown that the polymer coating leads to an increase in magnetic permeability and to a good time stability of magnetic characteristics. With an increase in the temperature of the formation of the coating, its effect on the magnetic characteristics is weakened because of an increase of the Young modulus as a result of the heat treatment upon the production of the coating.

Operational factors of new flux cored wires of the Fe–C–Si–Mn–Cr–Ni–Mo system for surfacing of protective plates of shearer cutting drums

Evaluation of the joint effect of the chemical composition of flux cored wires on the wear and hardness of the deposited layer was carried out using mathematical-statistical methods, allowing the influence of the chemical composition of the flux cored wires on the performance of the weld layer of the mining equipment to be revealed. According to the results of the multifactor correlation analysis, the dependences of the hardness of the deposited layer and its wear resistance on the mass fraction of elements included in the flux cored wires composition of the Fe-C-Si-Mn-Cr-Ni-Mo system were determined. The obtained dependences are used to predict the hardness of the deposited layer and its wear resistance when the chemical composition of the weld metal is changed. New, protected by patents of the Russian Federation, flux cored wires of the system Fe-C-Si-Mn-Cr-Ni-Mo for surfacing the mining equipment were developed.

Performance of Surface Layers Applied by New Powder Wire in Highly Abrasive Wear

The influence of chromium (in high concentrations) as a reducing agent in the manufacture of Fe–C–Si–Mn–Cr–Ni–Mo powder wire is studied. Metal layers are applied to St3 steel plates under An-26S flux, with preliminary heating of the basic metal to 250–300°C. Powder wire (diameter 5 mm) manufactured on a laboratory machine is applied by means of an ASAW-1250 welding system, in the following conditions: current 420–520 A; voltage 28–32 V; welding rate 7.2–9.0 m/h. After surfacing, the metal is cooled to room temperature. In producing the powder wire, the filler consists of PZhV1 iron powder (State Standard GOST 9849–86); FS75 ferrosilicon powder (State Standard GOST 1415–93); FKh900A high-carbon ferrochrome powder (State Standard GOST 4757–91); FMn78(A) carbon ferromanganese (State Standard GOST 4755–91); PNK-1L5 nickel powder (State Standard GOST 9722–97); FMo60 ferromolybdenum powder (State Standard GOST 4759–91); FV50U0.6 ferrovanadium powder (State Standard GOST 27130–94); PK-1U cobalt powder (State Standard GOST 9721–79); and PVN tungsten powder (Technical Specifications TU 48-19-72–92). Within the chosen concentration ranges, carbon, manganese, chromium, molybdenum, nickel, and to some extent vanadium increase the hardness of the applied layer and also decrease the wear rate of the samples. The low viscosity of the matrix prevents the retention of tungsten carbide at the surface. Consequently, wear occurs not by uniform abrasion of the surface but by the extraction of high-strength carbon particles from the matrix. As a result, new cracks are formed in the matrix, which accelerates its wear. Multifactorial correlational analysis yields dependences of the hardness and wear resistance of the applied layer on the mass content of the elements in the Fe–C–Si–Mn–Cr–Ni–Mo powder wire. These dependences may be used to predict the hardness and wear resistance of the applied layer with change in its chemical composition.

Temperature of the Formation of a Protective Polymer Coating and the Magnetic Properties of Cobalt-Based Amorphous Alloys

The influence of the polymer coating used in the manufacture of magnetic shields and of the conditions of its formation on the distribution of the magnetization and on the magnetic properties of shields has been studied. Samples of a ribbon of the Co-based soft-magnetic amorphous alloy AMAG-172 (Co–Ni–Fe–Cr–Mn–Si–B) with a saturation magnetostriction close to zero were used in the study. The coating was deposited in the temperature range of 90–130°C on the ribbon subjected to heat treatments in air that form a state with a negative saturation magnetostriction. The change of magnetic characteristics was investigated over a two year period. It has been shown that there is a temperature range in which a change in the sign of the saturation magnetostriction occurs upon the formation of the coating. This change is due to a change in the structural-phase state of the ribbon because of the diffusion processes that occur upon heating. The formation of the coating leads to a reduction in the maximum magnetic permeability; nevertheless, over a two year period, no decrease in μmax is observed in the ribbon with a coating formed in the 110–130°C temperature range.