Cr Mn Alloys Research Articles

Achieving high strength and high elasticity of Cu–Ni–Cr–Mn alloy by synergistic effect of multi-scale precipitates

The microstructural evolution, precipitation behavior and mechanical properties of Cu–19Ni–6Cr-xMn (x=0, 1, 3, 5, 7, 9 wt%) alloys were examined in the presence of solution treatment, cold rolled treatment and aged treatment. The results show that aged Cu–19Ni–6Cr–7Mn alloy exhibits superior mechanical properties with a hardness of 379 HV, tensile strength of 1012 MPa, and elastic modulus of 149.5 GPa, which is the maximum reported value for elastic modulus of copper alloys. The Mn element promotes the uniform distribution of the precipitates and grain refinement. Thermodynamic calculations indicate that the formation of the NiMn precipitates takes precedence over the NiCr-rich precipitates in this alloy. Three typical precipitates were detected in the Cu–19Ni–6Cr–7Mn alloy, including submicron-sized Cr-rich precipitates (>500 nm), nano-sized bcc-Cr precipitates (30–70 nm), and nano-sized NiMn precipitates with L12 ordered structure (3–5 nm). Precipitation plays a major role in improving the strength of the alloy. The synergistic effect between multi-scale precipitates, high-density dislocations, and solution strengthening has achieved significant breakthroughs in mechanical properties which open up new possibilities for engineering applications requiring high-strength and high-elasticity copper alloys.

Antiferromagnetic Cr-Mn alloys: Crystal structure, magnetic anisotropy, and exchange bias in magnetron-sputtered polycrystalline thin films

In this paper we study the formation of the antiferromagnetic Cr-Mn alloys with body-centered cubic crystal structure, and their capability to act as a pinning layer for the exchange bias effect in magnetron-sputtered polycrystalline films. By means of X-ray diffractometry, executed in different geometries, we perform a thorough analysis of Ta/Cr-Mn/Ta films, which results in the construction of a room-temperature phase diagram of Cr-Mn. These results combined with magnetic measurements of films with adjacent antiferromagnetic Cr-Mn and ferromagnetic Fe20Ni80 layers allow us to establish the conditions for the observation of the exchange bias effect, the maximum blocking temperature Tb of which can be as high as 540 K. Employing a specialized measurement protocol, we estimate the effective anisotropy constant Keff, whose values help to explain thickness dependence of the exchange bias field in structures with a Cr-Mn pinning layer.

Influence of Ni additions on microstructure, non-magnetic properties, and wear resistance of Fe–Mn-Cr alloy deposited by metal-cored arc welding

Influence of Ni additions on microstructure, non-magnetic properties, and wear resistance of Fe–Mn-Cr alloy deposited by metal-cored arc welding

The deterministic effect of laser energy density on the microstructures of novel duplex stainless steel fabricated via in-situ alloying in laser powder bed fusion

Distinctive microstructures and distributions of novel duplex (ferrite δ + austenite γ) stainless steel can be fabricated using in-situ alloying of Fe–Cr–Mn alloy and pure Ni powders by tuning laser energy density in powder bed fusion. At low-level energy density (∼60 J/mm3), ferrite solidification dominates and results in bimodal ferrite of columnar and equiaxed grains. At medium energy density (∼100 J/mm3), fine acicular Widmanstätten austenite satisfying the Nishiyama-Wassermann orientation relationship was produced within the coarse grains of δ, which is the predominant phase although ferrite and austenite solidification occur. At high-level energy density (∼194 J/mm3), ferrite and austenite solidification occur and the resultant microstructure consists of nearly equivalent fine equiaxed-grained δ and γ. The key difference in the microstructure was attributed to the different melt pool overlapping and types, which can be characterized by the size and local ratio of Cr equivalent (Creq) and Ni equivalent (Nieq) values (Creq/Nieq). The melt pool characteristics fundamentally determine the local solidification and transformation mode at different energy densities. The testing results have shown that the novel duplex stainless steel possesses excellent mechanical properties compared to conventionally-manufactured counterparts.

Efficient acquisition of interdiffusion coefficients matrices and atomic mobilities of fcc Co–Mn–Cr alloys by combining diffusion couple experiments and HitDIC software

Reliable diffusivities and atomic mobilities of fcc Co–Mn–Cr alloys are the important keystones for establishing the accurate diffusion database for CoCrFeMnNi high-entropy alloys and other relevant alloys, but they are still missing in the literature. In this paper, diffusion couple experiments together with High-throughput Determination of Interdiffusion Coefficients (HitDIC) software were employed to efficiently obtain diffusion descriptions of fcc Co–Mn–Cr alloys. Six diffusion couples were prepared and examined to provide the prerequisite composition profiles. Feature selection and regularization techniques in HitDIC software were adopted to extract the corresponding interdiffusion coefficients and atomic mobilities. A reliable set of diffusion descriptions of the fcc Co–Mn–Cr alloys were therefore obtained and verified. Investigations of the underlying composition- and temperature-dependent diffusion behaviors were enabled and demonstrated.

Thermodynamic and kinetic assessments in Co–Cr–Mn system using diffusion data

Atomic mobility and thermodynamic assessments of the fcc Co–Cr–Mn system were performed using the ternary diffusion data. Diffusion couples in the Co–rich region of the ternary fcc Co–Cr–Mn system were prepared and annealed at 900, 1050, and 1150 °C. The concentration profiles across the joint interface were measured using an electron probe microstructure analysis technique. The interdiffusivities were evaluated using the Whittle–Green method, and the atomic mobility parameters of the fcc phase were evaluated via numerical analysis of the diffusional flux. The thermodynamic parameters of the binary fcc Cr–Mn alloy were also determined using the CALPHAD method during the assessment of the mobility parameters in the Co–Cr–Mn system. The atomic mobility and thermodynamic descriptions obtained in this study were used to simulate the ternary concentration profiles. The excellent agreement between the experimental and simulated diffusion data validates the atomic mobility and thermodynamic parameters evaluated in this study.Graphical

Effect of grain size and second phase on the corrosion behavior of MIG-welded Al–Mg–Si–Mn–Cr alloy

Effect of grain size and second phase on the corrosion behavior of MIG-welded Al–Mg–Si–Mn–Cr alloy

Features of the manifestation of antiferromagnetism of the Cr-Mn alloy in the film composites of the (Cr-Mn)/Fe type

This paper presents a detailed study of the hysteresis properties of film structures based on bilayers of the Cr-Mn/Fe type. The temperature dependences of several parameters of the hysteresis loops of the Fe layers are determined for films varying in the composition and thickness of the Cr-Mn layer, as well as in the structure of buffer coatings. The compositional and temperature intervals of the existence of the antiferromagnetic ordering in the Cr-Mn layer and the related features of the temperature changes in the coercive force, its anisotropy in the plane of the films and the exchange bias field are established. The causal analysis of the established regularities is performed. Keywords: antiferromagnet, ferromagnet, bilayers, thickness, composition, temperature, texture, coercive force, exchange bias.

Effect of La Doping on Kinetic and Thermodynamic Performances of Ti1.2CrMn Alloy upon De/Hydrogenation.

Development of efficient hydrogen storage materials is one of the great challenges in the area of hydrogen energy and fuel cells. Herein, a La-doped Ti1.2CrMn alloy with high hydriding capacity (2.1 wt % H) and dehydriding capacity (1.8 wt % H) was successfully developed. The crystallographic characteristics, microstructural evolution, and hydrogen storage mechanisms of the alloy were investigated systematically. It was found that the introduction of La increased the cell volume of alloy and thus improved the hydrogenation kinetic, practical hydrogenation capacity, and cyclic property. The hydrogenation kinetic results of the La-doped alloy indicate that it exhibited a higher hydrogenation rate than that of the La-free alloy. It is ascribed to the formation of LaH3, which provides a fast diffusion channel for hydrogen atoms to enter the alloy matrix. The dehydrogenation enthalpy (ΔH) of the La-doped alloy was calculated by the van't Hoff equation and PCT curves to be ∼18.2 kJ/mol. The cycle test proves that the La-doped Ti1.2CrMn alloy, due to La addition, reduces the lattice expansion and lattice stress and exhibits excellent durability.

Morphologies and Compositions of α–Al15Fe3Si2-Type Intermetallics in Al–Si–Fe–Mn–Cr Alloys

Morphologies and Compositions of α–Al15Fe3Si2-Type Intermetallics in Al–Si–Fe–Mn–Cr Alloys

A Study on the Microstructures and Mechanical Properties of Ni-Cr-Mo-V Low Alloy Steels

Ni-Cr-Mo-V steel alloys for high-speed railway brake discs were prepared to investigate the effect of alloying element contents on the microstructure and mechanical properties. The Cr, Mo, Mn alloying elements were incorporated into the steel alloys, which contained low carbon content in the range 0.16 wt.% ~ 0.21 wt.% to provide sufficient hardenability. The steel alloys were austenitized at 940<sup>o</sup>C for 1 hour and quenched, and tempered at 610<sup>o</sup>C. Microstructural study showed a tempered martensitic microstructure with different sized austenite grains and packets. C-Mo alloy with high Mo content and the smallest prior austenite grain size showed the highest hardness and tensile strength. But, the alloy exhibited lower impact toughness than low Mo content alloys. The lowest tensile strength of the low Mo content Mn-Cr alloy, at room temperature and elevated temperature of 600<sup>o</sup>C, was 1053.4 MPa and 667.2 MPa, respectively. The grain refinement in the C-Mo alloy was considered to be due to the solute drag effect of the Mo element. The absorbed impact energy increased with tempering temperatures, but the impact energy of the three alloys had lower values than the generally guaranteed impact energy of the currently used disk. The low impact toughness of the Mo containing alloys was attributed to the higher Si content and higher tempered hardness of the alloys. A higher thermal conductivity and lower thermal expansion coefficient were obtained in the high Mo content C-Mo alloy, which had a higher Ac3 transformation temperature.

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

Analytical solution for interdiffusion in multicomponent systems and its application in high entropy alloys

In the present work, an analytical solution is derived for the diffusion equation as applicable to a multicomponent diffusion couple with a constant set of interdiffusion coefficients. The multicomponent diffusion equation was first decoupled using similarity transformation of the interdiffusivity matrix. The decoupled equation was then solved for the boundary conditions pertaining to an infinite diffusion couple, in general, containing n diffusing components by using Laplace transform. It is shown that the analytical solution derived here deduces to the forms specifically applicable to binary and ternary systems available in the literature. The analytical solutions were then applied to reproduce the concentration profiles developed in experimental diffusion couples prepared with quaternary Fe–Ni–Co–Cr and quinary Fe–Ni–Co–Cr–Mn alloys. The determination of the sets of 9 quaternary and 16 quinary interdiffusion coefficients in the said couple was done experimentally using Kirladly’s approach and was independent of the closed form solutions derived here. The constant sets of quaternary and quinary interdiffusion coefficients determined at approximately equi-molar compositions in the two systems were used in the present work to reproduce the concentration profiles in these couples, having reasonably large differences in the terminal alloy concentrations. It was found that the concentration profiles calculated using the solutions developed here agree very well with the experimental profiles developed in all three quaternary and all four quinary couples. The excellent agreement between the experimental and theoretical profiles not only validates the closed form solution developed here but also highlights the constancy of interdiffusivities over reasonably large composition ranges in such systems. This is significant as it enables the use of analytical solutions of the diffusion equation for modeling various processes in such concentrated multicomponent alloys.

Stability, rigidity and thermal vacancies evolution in Fe–Cr–Mn alloys with C and N additions: DFT and Wagner-Schottky model investigations

The pseudo-potential Density Functional Theory (PP-DFT) combined with the statistical Wagner-Schottky model, are applied to study the Fe-xMn-(26-x)Cr–5Mo–3Cu-0.6C-0.7 N austenitic alloys (x = 6, 9, 12 and 15 wt%). The obtained results show that the rigidity and the thermal vacancy behavior is very sensitive to the system composition. The overall system stability is found to be governed by the presence of nitrogen. Both carbon and nitrogen favor the vacancy creation at T∼1200K and prevent the thermal vacancy activation at T∼1600K. Interestingly, beyond 1273K, carbon atom could migrate toward the substitution sites while nitrogen atoms do not leave their favorable octahedral sites.

Effect of Multidirectional Forging on the Microstructure and Mechanical Properties of the Al–Mg–Mn–Cr Alloy

The effect of multidirectional forging on the grain structure and parameters of secondary-phase particles in the Al–4.8Mg–1.2Mn–0.1Cr alloy has been investigated using the methods of the scanning and transmission electron microscopy. The multidirectional forging performed at a temperature of 350°C to a cumulative strain of 10.5 has resulted in a 1.5 decrease in average particle sizes of the manganese-bearing phases of crystallization origin and dispersoids and in the formation of a structure with a mean grain size of 1.7 µm. Multidirectional forging included in a sheet processing, in contrast to hot rolling, forms an equiaxed grain structure with a grain size of about 6 µm in recrystallized sheets and with enhanced strength characteristics.

Significant impact of cold-rolling deformation and annealing on damping capacity of Fe–Mn–Cr alloy

The influences of cold-rolling deformation and annealing on the damping capacity of Fe–19Mn–8Cr alloy were investigated. It was observed that the cold-rolled Fe–19Mn–8Cr alloy with a reduction of 10% showed the relatively excellent damping capacity because of the relatively more e-martensite and lower dislocation density, and the reduction of slopes of different damping curves increased along with increasing the cold-rolling reduction. Besides, the subsequent annealing process can further enhance the damping capacity. After 70% cold-rolling deformation, the austenite grain would grow up with the increase in the annealing temperature, which resulted in a significant change in the content and morphology of e-martensite influencing the damping capacity of the experimental steel. The damping capacity was optimum when annealed at 800 °C for 30 min, displaying that the size of e-martensite has a vital influence on the damping capacity of the experimental alloy. This study may enrich the fundamental knowledge about how to ameliorate the damping capacity of Fe–Mn–Cr damping steels.

Interdiffusion and atomic mobility in the bcc Ti–rich Ti–Cr–Mn system

In this work, ternary interdiffusivities in the bcc Ti–rich Ti–Cr–Mn alloys at 1273 K were determined by using the combination of the diffusion couple technique and the Matano–Kirkaldy method. Subsequently, on the basis of the presently obtained interdiffusivities along with the diffusivity and mobility parameters of binary sub–systems within the Ti–Cr–Mn system and thermodynamic descriptions for the bcc Ti–Cr–Mn system, the atomic mobilities of Ti, Cr and Mn in the bcc Ti–Cr–Mn alloys were assessed using the optimization module within the Thermo-Calc software package. Moreover, the comprehensive comparisons between the experimental diffusion properties (i.e., interdiffusivities, composition profiles, and diffusion paths) and the calculated/model–predicted data due to the present atomic mobilities were conducted in order to verify the reliability of the mobilities. At present, the atomic mobilities for the bcc Ti–Cr–Mn system can provide an accurate interdiffusivity matrix over a wide composition range.

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.

First report on entire sets of experimentally determined interdiffusion coefficients in quaternary and quinary high-entropy alloys

Abstract

Relationship between phase stability and mechanical properties on near/metastable β-type Ti–Cr-(Mn) cast alloys

The phase stability of near/metastable β-type Ti–Cr-(Mn) alloys with 4.06–13.46 wt% molybdenum equivalent fabricated by rapid solidification process were evaluated using several parameters, i.e. bond order, metal d-orbital energy level and molybdenum equivalent. The microstructural evolution of the near/metastable β-type Ti–Cr and Ti–Cr–Mn alloys was systematically investigated by using optical and transmission electron microscopies. With increasing molybdenum equivalent value in the Ti–Cr-(Mn) alloys, α’’ martensitic transformation and precipitation of athermal ω phase were strongly suppressed during rapid cooling. Based on microstructural investigation, the β phase stability of the alloys was evaluated using the phase stability index diagram using bond order, metal d-orbital energy level parameters. Moreover, the microstructural evolution depending on the phase stability of Ti–Cr-(Mn) alloys strongly affected to mechanical properties and trade-off behavior between strength and plasticity. Based on these microstructural evolutions and mechanical properties of the Ti–Cr-(Mn) alloys, the phase stability and a relationship between phase stability and mechanical properties of near/metastable β-type titanium alloys were systemically investigated.