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In this paper, the wear resistance and microhardness of the hybrid and mono surface composite with Al–Mg–Mn alloy (AA5083) as the matrix material and SiC, Al2O3, Gr, and CNT as the reinforcement material was investigated experimentally. The surface composite was fabricated by friction stir processing (FSP). The microstructure of the prepared specimens was observed using optical microscopy. Mono reinforced surface composite and hybrid reinforced surface composite were tested for their microhardness and wear resistance before and after FSP and the results were compared. The surface composites showed uniform dispersion and finer grain size after FSP in comparison with the as-received AA5083. FSP aided the hybrid reinforced surface composite to increase the maximum microhardness value to 107.5 HV in SiC/Gr reinforcement as compared to the 89.11 HV in mono Gr reinforced surface composite and 75.15 HV in as-received AA5083. The hybrid surface composite also provided enhanced wear resistance in comparison with the mono reinforced surface composite and the base material. [ABSTRACT FROM AUTHOR]

The mechanical properties of an aluminum-manganese alloy and two aluminum-magnesium alloys, namely AMtsS, AMg5, and AMg6, at 4 K in a liquid helium environment were investigated. Their cylindrical specimens with a diameter of 5 mm, which had an annular notch with a depth of 1 mm and a radius of 6 mm, were tested for static tension. The testing machine stiffness was reduced from 14.5 to 8.4 and 3.8 MN/m. The study showed that the effect of hardening of cold-ductile metallic materials at a given temperature and in the presence of blunt notches with low stress concentration is completely neutralized with a decrease in the stiffness of the loading system and a corresponding increase in the stored elastic energy. The decrease in the ultimate strength of the notched specimen and the true rupture strength correlates with the decrease in the number of deformation jumps in the stress concentration zone. The results obtained are discussed, taking into account the conversion of the stored elastic energy in the specimen–machine system into the work of deformation during each act of discontinuous yielding and the reduction of the material's strain-hardening capacity at a small number of deformation jumps. [ABSTRACT FROM AUTHOR]

In this paper, the cracking of Al-Mn-Mg-Sc-Zr alloys prepared by selective laser melting (SLM) was comprehensively explored and the influence of process parameters on the generation and propagation of cracks was deeply studied. It was found that the higher laser power and volume energy density will lead to a decrease in the relative density of the material. The lower laser power or volume energy density will lead to cracking of the alloy. The microstructure analysis indicated that plenty of manganese-rich second phases precipitated at the bottom of the melt pool, which increased the tendency of cracking occurred at the bottom of the melt pool. Through the optimization of the process parameters, the SLM forming process parameters of the Al-5.22Mn-1.16Mg-0.81Sc-0.46Zr alloy are successfully obtained, and the crack-free tensile samples are prepared. The microstructure and mechanical properties of the as-deposited aluminum-manganese alloy is analyzed. The bottom and inside of the melt pool are equiaxed grains. The size of the equiaxial grains at the bottom of the melt pool is less than 2 μm, and the coarse equiaxial grains inside the melt pool are approximately 5 μm. As-deposited alloy has a room temperature tensile strength of 455.2 ± 0.7 MPa and elongation of 15.4 ± 0.3%. This study provides guidance for selective laser melting forming of high-strength aluminum-manganese alloy parts, and promotes the industrial production of high-strength aluminum alloy near net forming complex parts. [ABSTRACT FROM AUTHOR]

The physical properties desired for various applications of aluminum alloys are usually modified by tailoring their precipitation behavior during heat treatment. In this study, the precipitation behavior of a cast AlMn alloy annealed with two heating methods (electric resistance heating and radiative furnace heating) at different temperature has been studied through the electrical conductivity (EC) test, and scanning electron microscope. The impact of the two heating methods on the mechanical properties of the treated AlMn samples was evaluated through hardness and EC analysis. The results clearly show that under the conditions of electric resistance heating, the precipitation kinetics of the alloy is promoted. The mechanisms behind this phenomenon are discussed in detail. [ABSTRACT FROM AUTHOR]

Introduction: A tank used for the storage of aviation gasoline, equipped with a geodesic dome with a floating internal membrane system, reported serious corrosion damage to its floats, which caused them to be replaced in a short period of time. Objective: To analyze aluminum floats deterioration causes. Materials and Methods: During a visual inspection, corrosion products were collected and analyzed by IR spectrometry. Residual water samples were taken from the tank bottom for physicochemical analysis. Float component materials structural study was carried out, using a digital multichannel spectrometer and a metallographic microscope. Results and Discussion: Float failures occurred in cylindrical body in contact with the fuel, such as localized corrosion. The corroded material corresponded to the aluminum manganese alloy 3004, which was characterized by an important content of iron in its chemical composition and a microstructure with high density of intermetallic particles, in some micro locations forming clusters. Cavities were observed around some particles, and evidence of dissolution of the alloy matrix in a medium in which chloride ions were present. Conclusions: The results obtained indicated that in a medium with the presence of chloride ions, the formation of galvanic microcells between cathodic intermetallic particles of important dimensions and the alloy matrix was caused, which led to the formation of deep pits. [ABSTRACT FROM AUTHOR]

In this work, bulk anisotropic Mn-Al-(C) magnets have been produced by hot-deforming arc-melted alloys. The hot-deformed magnets develop a texture in a plane perpendicular to the deformation direction. Optimum magnetic properties have been obtained in a magnet with nominal composition Mn53.5Al44.5C2 with values of remnant magnetization, coercivity, and energy product of 2.2 kOe, 3.3 kG, and 1.8 MGOe, respectively. A maximum coercivity of 2.8 kOe has been obtained in the magnet with composition Mn54.5Al43.5C2. Addition of C is effective in increasing the coercivity of the substituted alloy. [ABSTRACT FROM AUTHOR]

Permanent magnets constitute an important base for advanced technologies. Rare-earth-based alloys are currently the main permanent magnet materials. Due to the limited availability and high costs, these magnets are, as a rule, used in small items. In large-scale equipment (e.g., in generators, motors, including magnetic levitation transport devices), more affordable and cheaper materials are addressed. Manganese-based alloys, in particular, AlMn, may be regarded as examples of these materials. In Russia, extensive research activity into aluminum–manganese alloys was during the period from the 1960s to the 1990s [1–3]. In other countries this research activity has continued till now. More than one hundred articles were published during the last decade. Most of them address bulk and film samples of the metastable magnetic phase τ-AlMn. Our review focuses on an analysis and systematization of contemporary studies into the preparation and properties of manganese–aluminum alloys; perhaps, it will serve to popularize research into manganese-based intermetallics as promising materials for permanent magnets in Russia. [ABSTRACT FROM AUTHOR]

A color metallography using Weck's reagent was employed to investigate the characteristic microstructure of AlMnSi alloy strip fabricated by high-speed twin-roll casting. The microstructure of the strip consists of two components: solidified shells and a central band. By Weck's reagent etching, the colorful microstructure was obtained, and doughnut-like patterns were observed in the globular grains. Based on the presence of the patterns, the globular grains were divided into two types: Type-I and Type-II. Type-I grains exhibited the core-like structure. On the other hand, Type-II grains had no color contrasts in the grain. SEM-EDS analysis of Type-I grains revealed the high correlation between the obtained color and micro-segregation of Si. TEM and STEM analyses confirmed the formation of an amorphous film on the surface of Al substrate by the etching. The thickness of the film and the roughness of the Al substrate under the film were different from location to location. The local change of the film's features resulted in the different color in the optical microscopic image. Based on the microstructure observation, the origin of globular grains observed in the central band in the AlMnSi alloy strip was discussed in detail. [ABSTRACT FROM AUTHOR]

The tribological impact of the steel alloy employed as the work roll material during hot rolling on the surface quality and corrosion behavior of Al-Mn alloys was explored. AISI 52100, AISI D2 and AISI 440C steel work rolls with a surface roughness (Ra) of 0.1 µm were used to hot roll Al-Mn alloy specimens under similar conditions using a rolling tribo-simulator. Corrosion tests were then performed on the rolled Al-Mn specimens by immersing them in a 0.5 wt.% NaCl solution. Surface examination of the Al-Mn specimens after rolling revealed dark MgO-rich islands covering the surfaces of the AISI D2 and AISI 440C-rolled Al-Mn surfaces. These features were associated with the carbides observed protruding from the AISI D2 and AISI 440C steel surfaces. Subsequent corrosion tests revealed that these MgO-rich islands possessed a distinct influence on the corrosion behavior of the rolled Al-Mn surfaces. The frequency of occurrence and depth of the MgO-rich islands, which were dependent on the work roll material employed, influenced the initial and subsequent corrosion morphology detected on the Al-Mn surfaces. The preferential dissolution of the MgO-rich islands was detected as one of the corrosion mechanisms occurring during the early stages of corrosion. [ABSTRACT FROM AUTHOR]

Zirconium conversion coating (ZrCC) was prepared on aluminum-manganese alloy AA3005 by immersion in 200 ppm of H2ZrF6 bath for 10 min at room temperature. Potentiodynamic polarization curves and electrochemical impedance spectra were measured up to 10 and 40 days, respectively, in 0.5 M NaCl solution. Microstructural characterization of samples was carried out using scanning electron microscopy equipped with energy dispersive X-ray spectrometry, X-ray photoelectron spectroscopy, time-offlight secondary ion mass spectrometry, focus ion beam microscopy and transmission electron microscopy. The coating had a trilayer structure with a thickness of 200 nm in the proximity of intermetallic particles and 30 nm far from intermetallic particles at the coating matrix. Electrochemical measurements showed that the corrosion resistance of ZrCC on AA3005 was improving during immersion in NaCl solution, i.e., impedance value at low frequency increased with immersion time reaching the average value 8.5 · 106 O·cm2 at 3 mHz after 10 days immersion. Microstructural and compositional characterization showed that this behavior is related to the change in composition and structure of conversion coating including a transformation of ZrF4/ZrOxFy to ZrO2 · 2H2O(s) and formation of Al(OH)3 in the top layer of ZrCC, respectively, accompanied by the change in thickness of individual layers within the coating. [ABSTRACT FROM AUTHOR]

Highlights • The pure τ phase MnAl was obtained by tuning the copper roller speed of 5 m/s. • A high magnetization of 118.2 emu/g was achieved in the as-spun MnAl ribbon. • The phase transformation and magnetic performances were tailored by the copper roller speed. Abstract In this work, the microstructure, phase transformation and magnetic properties of MnAl permanent magnetic alloys prepared by the melt-spinning technique were systematically investigated by tuning the cooling rate. It was shown that the MnAl microstructure, phase transformation and magnetic properties can be tailored by the copper roller speed. With increasing of the roller speed, the phase transformation from the γ 2 , β phases to the ε phase was observed. In addition, the variation of magnetic properties was attributed to the phase content and microstructure of the ferromagnetic τ phase in the MnAl alloys, being controlled by the cooling rate. As a result, the high-purity τ phase MnAl was obtained at a copper roller speed of 5 m/s, which exhibited a high magnetization of 118.2 emu/g. Therefore, this work can provide a method for the direct fabrication of the high-purity ferromagnetic τ phase MnAl alloy. [ABSTRACT FROM AUTHOR]

Two series of Co2MnAl (CMA) and Co2MnAlO (CMAO) thin films deposited on Si (100) coated with thermo-SiO2 by using two CoMnAl targets were studied. One target is oxygen-free and the other one contains 0.8% oxygen. The properties of the two series CMA (O) films strongly depend on deposition conditions and seed layers. The oxygen impurity is a key factor to influence the properties. It would obviously increase the thickness of magnetic dead layer, weaken the magnetic anisotropy, and significantly decrease the spin polarization in CMA film. The magnetoresistance ratios of IrMn pinned top-type magnetic tunnel junctions by utilizing CMAO/CMA as the bottom ferromagnetic electrode were 19% and 68%, respectively. [ABSTRACT FROM AUTHOR]

Abstract High-voltage LiNi 0.5 Mn 1.5 O 4 nanorods were prepared through a low-cost and environment-friendly strategy with MnO 2 nanorods as manganese source. The resulting LiNi 0.5 Mn 1.5 O 4 nanorods showed satisfactory rod-like morphology and obvious characteristic diffraction peaks of LiNi 0.5 Mn 1.5 O 4. According to the research results of electrochemical properties, the obtained LiNi 0.5 Mn 1.5 O 4 nanorods showed excellent cycling stability. When cycled at 1.0 C, this sample exhibited 125.2 mAh g−1 at the first cycle in the voltage range of 3.4–5.0 V. After 200 cycles, the satisfactory capacity of 119.8 mAh g−1 could be obtained with outstanding retention of 95.7%, which was far more advantageous than that of the LiNi 0.5 Mn 1.5 O 4 particles (78.1%). Moreover, the LiNi 0.5 Mn 1.5 O 4 nanorods could show a superior capacity of 93.4 mAh g−1 at 10 C, whiles the LiNi 0.5 Mn 1.5 O 4 particles only exhibited 58.5 mAh g−1. These results indicated that the obtained LiNi 0.5 Mn 1.5 O 4 nanorods possessed great potential and application prospect to be a promising 5.0 V cathode material. [ABSTRACT FROM AUTHOR]

An Al-Mn alloy with additions of copper, magnesium, and silicon was prepared and cast into a copper mold. It contains in situ-formed icosahedral quasicrystals (iQCs), as confirmed by electron backscatter diffraction. The aim of this work is to present the mechanical and corrosion properties of this alloy and compare its properties with some conventional commercial materials. The compressive strength and compressive yield strength were 751 MPa and 377 MPa, while the compressive fracture strain was 19%. It was observed that intensive shearing caused the final fracture of the specimens and the fractured iQC dendrites still showed cohesion with the α-Al matrix. The polarization resistance and corrosion rate of the artificially aged alloy were 7.30 kΩ and 1.2 μm/year. The evaluated properties are comparable to conventional, discontinuously reinforced aluminum metal-matrix composites and structural wrought aluminum alloys. [ABSTRACT FROM AUTHOR]

Two TiAl-based alloys, Ti48Al2Mn2Nb1B and Ti50Al2Mn2Nb1B, were prepared via conventional ingot melting and unidirectional solidification (Bridgman process) to investigate their solidification behaviour and the effect of boron addition on grain refinement. Both of them are found to be α solidifying alloys. Their microstructures are refined, featuring fine and randomly oriented lamellar colonies about 150 μm in size, in conventional ingots but the unidirectionally solidified alloys still have columnar microstructures. The entirely different grain refinement behaviour in ingots and Bridgman samples gave rise to the notion that the enhanced α nucleation from the liquid is the key to grain refinement in the two α solidifying alloys although the specific mechanisms are yet to identify. [ABSTRACT FROM AUTHOR]

Abstract: The formation and microstructure of quasicrystals in suction cast Al‐6 wt.% Mn‐2 wt.% TM (TM = Ni, Fe) alloys were investigated by transmission electron microscopy, scanning electron microscopy, energy dispersive spectrometry, and X‐ray diffraction. The suction cast Al‐6 wt.% Mn‐2 wt.% Ni alloy consists of a single decagonal phase of Al56Mn11Ni2, whereas the Al‐6 wt.% Mn alloy with 2 wt.% iron addition comprises a primitive icosahedral phase and a decagonal phase of Al40Mn7Fe2. Thus, the addition of nickel or iron favors quasicrystal formation in the suction cast Al‐6 wt.% Mn alloys. Based on a 4 : 1 matching ratio of aluminum atoms to heavier atoms, the approximate electron to atom ratio is 1.85 in two decagonal phases of Al56Mn11Ni2 and Al40Mn7Fe2. Various morphologies of quasicrystals with a size of more than 5 μm were observed in the microstructure of suction cast Al‐6 wt.% Mn‐2 wt.% TM (TM = Ni, Fe) alloys. The decagonal Al40Mn7Fe2 phase nucleates epitaxially and grows on the icosahedral phase. [ABSTRACT FROM AUTHOR]

Mn 55 Al 45 , Mn 55 Al 44 C 1 , Mn 52.2 Al 45.8 C 2 and Mn 54.2 Al 43.8 C 2 were synthesized by the mechanical alloying method. It was the first time that a high purity τ phase up to 99% of weight percentage was obtained in Mn 54.2 Al 43.8 C 2 , which gave the highest saturation magnetization M s  = 570 kAm −1 ever reported by mechanical alloying up to date. The crystallite size of the τ phase of MnAl(C) alloy decreased with increasing carbon doping, varying from 79 to 159 nm. Additionally, the coercivity (H c ) was found to be inversely proportional to the crystallite size of τ phase. Effect of doping carbon and its position in the τ phase of MnAl(C) alloy were also investigated for the first time by first-principle calculations. It was found that by inserting carbon at the interstitial site in the tetragonal structure, a strong stabilization effect and an expansion of unit cell were observed, which are in good agreement with the experimental results. Moreover, our results indicate that carbon doping reduces the magnetic moment of Mn. [ABSTRACT FROM AUTHOR]

In the present work, two-step heat treatments with preheating at different temperatures (175 °C, 250 °C, and 330 °C) as the first step followed by the peak precipitation treatment (375 °C/48 h) as the second step were performed in Al-Mn-Mg 3004 alloys to study their effects on the formation of dispersoids and the evolution of the elevated-temperature strength and creep resistance. During the two-step heat treatments, the microhardness is gradually increased with increasing time to a plateau after 24 hours when first treated at 250 °C and 330 °C, while there is a minor decrease with time when first treated at 175 °C. Results show that both the yield strength (YS) and creep resistance at 300 °C reach the peak values after the two-step treatment of 250 °C/24 h + 375 °C/48 h. The formation of dispersoids is greatly related to the type and size of pre-existing Mg2Si precipitated during the preheating treatments. It was found that coarse rodlike β′-Mg2Si strongly promotes the nucleation of dispersoids, while fine needle like β″-Mg2Si has less influence. Under optimized two-step heat treatment and modified alloying elements, the YS at 300 °C can reach as high as 97 MPa with the minimum creep rate of 2.2 × 10−9 s−1 at 300 °C in Al-Mn-Mg 3004 alloys, enabling them as one of the most promising candidates in lightweight aluminum alloys for elevated-temperature applications. [ABSTRACT FROM AUTHOR]

The dispersoid precipitation behavior during the solutionizing and aging of Al-xwt.%Cu-1.0 wt.% Mn alloys (x = 2.0, 4.5, and 7.5) and contribution to mechanical properties were investigated using tensile testing and microstructural characterization. A shell-core structure of primary α-Al dendrites is found in Al-Cu-Mn alloys, in which the Cu content in the shell is higher than that in the core. The area of shell zone (Cu-rich) increases with an increase in Cu content in the alloy. Large amounts of fine dispersoid Al-Cu-Mn particles precipitate in solution. An alloy with low Cu content results in only the TMn (Al20Cu2Mn3) particles being precipitated. However, in an alloy with high Cu content, AlCu3Mn2 particles are first found to precipitate beside TMn. However, this precipitation behavior is uneven. The precipitation zones in the solution microstructure are consistent with the Cu-rich regions in the as-cast microstructure. A number of fine particles (dozens nanometer in size) are first found to precipitate on the rod-like TMn particles during the aging phase. The redissolution and granulation of the eutectic CuAl2 phase during the solutionizing process result in the formation of particle-free bands between the precipitation zones. The tension test at 300°C demonstrates that the increase in high temperature strength is due to the dispersoid precipitation during solutionizing, and the precipitation behavior in the aging phase has little or no effect, however, largely improves the tensile strength at room temperature. High temperature strength is significantly increased with an increase in Cu content, which correlates to an increase in number and decrease in size of TMn and AlCu3Mn2 particles. [ABSTRACT FROM AUTHOR]

In this work, the effect of carbon addition on the L1 0 τ-phase stability in (Mn 0.54 Al 0.46 ) 100- x C x ( x  = 0–5) magnetic alloys are investigated. By microstructural analysis, single-phase and dual-phase microstructure are confirmed in 0 ≤  x  ≤ 3 and x  > 3 alloys, respectively. The solubility limit of carbon atoms in τ-phase of about 3 at.% is also determined by the characterization of the intrinsic magnetic properties and the crystal structure. The solid solution of carbon can significantly stabilize the thermodynamically metastable τ-phase, reflecting by the reversible τ→ε transformation path, and suppressing of the τ-phase decomposition effectively at high temperatures. The stabilized τ-phase by carbon doping exhibits higher magnetization in the as-milling state, with the highest magnetization for x  = 3. After annealing at high temperature, the carbon-doped τ-phase is also more stable, resulting in the obvious improvement in magnetization. The magnetization of 86.7 emu/g under 30 kOe and the coercivity of 3.26 kOe are approached in the as-annealed x  = 3 powders. These results clarify the effect of doping carbon on τ-phase stability in MnAl alloys and highlight the guidance and routine for high performance MnAl permanent magnets. [ABSTRACT FROM AUTHOR]

Friction stir processing (FSP) of a new rare earth-free Mg-5Al-3.5Ca-1Mn (AXM541) alloy resulted in significant microstructural refinement and mechanical properties comparable to existing AXM series Mg alloys. Severe refinement of the Al-Ca (C36) phase during FSP led to uniform dispersion throughout the microstructure. The synergistic effect of high heat input and the presence of these 1–4 µm size particles resulted in dynamic recrystallization via particle stimulated nucleation (PSN), with an average grain size of 4.5 µm after FSP. Further, improved mechanical properties of the AXM541 alloy along the processing direction produced a tensile yield strength (TYS) of 322 ± 14 MPa and a total elongation of 16 ± 3%. The increase in strength was also attributed to the dispersion strengthening effect associated with Al-Ca and Al-Mn (D810) particles. Moreover, the AXM541 alloy showed a better mechanical response compared with other AXM alloys irrespective of high Ca/Al ratio, due to the effective refinement and redistribution of Al-Ca phases resulting from FSP. However, strain hardening ability and TYS of the AXM541 alloy could be further improved if the Mn/Al ratio could be tailored, as Al-Mn particles do not break down during FSP. [ABSTRACT FROM AUTHOR]

Sc and Zr were added to Al-Mn-Mg 3004 alloy to form two populations of strengthening particles (50–70 nm-sized α-Al(Mn,Fe)Si dispersoids and 6–8 nm-sized Al 3 (Sc,Zr) precipitates), and their strengthening effects on the mechanical properties and creep resistance at ambient and elevated temperatures were studied. The results showed that the microhardness and yield strength at ambient temperature greatly increased upon the addition of Sc and Zr. The creep resistance at 300 °C significantly improved due to the precipitation of fine Al 3 (Sc,Zr) particles and reduction of the particle-free zone. However, the yield strength at 300 °C remained constant even though the Sc and Zr content increased. The combined effects of α-Al(Mn,Fe)Si dispersoids and Al 3 (Sc,Zr) precipitates on the yield strengths at 25 °C and 300 °C were quantitatively analyzed based on the Orowan bypass and dislocation climb mechanisms. The analytically predicted yield strengths are in good agreement with the experimental data. [ABSTRACT FROM AUTHOR]

By the method of cold rolling, appropriate intermediate annealing and final annealing treatments, the multi-scale lamellar structure of ultrafine grains distributed in ribbons with coarse grains was produced in an Al-1.2Mn alloy, which displayed excellent combination of high strength and good ductility compared to coarse-grained and ultrafine-grained alloys. The high strength of the alloy with multi-scale lamellar structure is attributed to back stress strengthening associated with the formation of geometrically necessary dislocations and the good ductility results from the high strain hardening rate during plastic deformation. Loading-unloading-reloading tests were carried out to measure the back stresses of the alloys. The results show that the back stress of the specimen with multi-scale lamellar structure is much higher than that of the coarse-grained specimen. [ABSTRACT FROM AUTHOR]

Trace amount (0.3 wt%) of scandium is added to Al–5.6Mg–0.7Mn alloy to form uniformly distributed Al3Sc precipitates for producing a fine-grained and stable microstructure at high temperature through cross-channel extrusion process. Superplasticity and hot workability of the Sc-containing Al–5.6Mg–0.7Mn alloy, after extrusion, are also examined. The result indicates that Al–5.6Mg–0.7Mn alloys with and without 0.3 wt% Sc after extrusion of six passes at 300°C, fine-grained structures were observed with grain sizes of 1–2 µm and improvement of mechanical properties. Furthermore, Al3Sc phase can effectively retard recrystallization to increase the thermal stability and remain equiaxed. The elongation of Al–5.6Mg–0.7Mn alloy with Sc addition to failure is extended to 873% maximum at high temperature of 450°C at strain rate of 1 × 10−1 s−1after six passes in the CCEP. [ABSTRACT FROM AUTHOR]

The effects of elemental doping of Si and Fe on the ε→τ phase transformation and the magnetic properties of MnAl were studied. The magnetic powders of Si- and Fe-doped MnAl were prepared by using induction melting followed by water-quenching, annealing, and salt-assisted ball-milling. The Fe-doped MnAl powders are mainly composed of the L10-structured τ-phase, while the Si-doped MnAl are composed of τ-phase and a small fraction of γ2- and β-phases. A unique thin leaves-like morphology with thickness of several tens of nanometers and diameter size up to 500 nm were observed in the Si-doped MnAl powders. The Fe-doped MnAl powders show irregular shape with much larger dimensions in the range from several to 10 μm. The morphology difference of the samples was ascribed to the variation of the mechanical properties affected by different doping elements. The phase transformation temperatures of the ε-phase of the samples were measured. The doping of Fe decreases the onset temperature of the massive phase transformation in MnAl, while the Si-doping increases the massive phase transformation temperature. Both Fe and Si increase the Curie temperature of MnAl. A substantially enhanced coercivity up to 0.45 T and 0.42 T were observed in the ball-milled MnAl powders doped with Si and Fe, respectively. [ABSTRACT FROM AUTHOR]

The use of metallic particles has been shown to be an effective, low-cost method for degradation of many contaminating compounds. In this work, we analyze the efficiency of MnAl metallic powders for degrading azo dyes, which are the class of colorant compounds most utilized by the textile industry. We used different routes to produce the metallic particles obtaining different internal structures as characterized by X-ray diffraction and electronic microscopy. The ability to act as discoloration materials was assessed by decolorization experiments of Reactive Black 5 and Orange II azo dyes aqueous solutions. The degradation reaction of the dye molecules was monitored by ultraviolet–visible (UV) spectrophotometry showing fast kinetics, with reaction times among the shortest found in literature. The effect of the different production methods on their performance as decolorizing materials was studied as function as various parameters such as initial pH, dye concentration and temperature. The electrochemical and corrosion properties of the MnAl compounds seem to be the key factors explaining the high decolorization efficiency of these materials. [ABSTRACT FROM AUTHOR]

The mechanical behavior of polymer-metal structure (PMCS) made by Friction Assisted Joining is investigated. Al-Mg Alloy and polyetheretherketone (PEEK) were adopted. Laser texturing was performed on the aluminum substrate to enhance the strength of the joints. A campaign of experimental tests was conducted by varying the energy supplied during the joining process. During the heating and the cooling phases, the thermal history and temperature gradients were monitored by means of an IR camera. Single lap shear tests were conducted to determine the mechanical behavior of the joints. Morphological analysis and fracture surface analysis were performed by means of Optical Microscopy and Scanning Electron Microscopy to evaluate the material flow produced under different processing conditions as well as the mean features of the joints. The highest strength joints were achieved after a heating time of 25 s to which corresponded an supplied energy of 3.5 kJ, which led to a maximum and average temperature (reached by the upper aluminum surface during the joining process) of 390 °C and 350 °C, respectively. Under such conditions, the maximum shear force of 6.9 kN and an average shear strength of 47 MPa were achieved corresponding to a joint efficiency of 83%. [ABSTRACT FROM AUTHOR]

We grow MnAl films on different underlayers by molecular beam epitaxy (MBE), and investigate their structural and magnetic properties. L 1 0 -ordered MnAl films were successfully grown both on an MgO(0 0 1) single-crystalline substrate and on an Mn 4 N(0 0 1) buffer layer formed on MgO(0 0 1) and SrTiO 3 (0 0 1) substrates. For the MgO substrate, post rapid thermal annealing (RTA) drastically improved the crystalline quality and the degree of L 1 0 -ordering, whereas no improvement in the crystallinity was achieved by altering the substrate temperature ( T S ) during MBE growth. However, high-quality L 1 0 -MnAl films were formed on the Mn 4 N buffer layer by simply varying T S . Structural analysis using X-ray diffraction showed MnAl on an MgO substrate had a cubic structure whereas MnAl on the Mn 4 N buffer had a tetragonal structure. This difference in crystal structure affected the magnetic properties of the MnAl films. The uniaxial magnetic anisotropy constant ( K u ) was drastically improved by inserting an Mn 4 N buffer layer. We achieved a perpendicular magnetic anisotropy of K u  = 5.0 ± 0.7 Merg/cm 3 for MnAl/Mn 4 N film on MgO and 6.0 ± 0.2 Merg/cm 3 on STO. These results suggest that Mn 4 N has potential as an underlayer for L 1 0 -MnAl. [ABSTRACT FROM AUTHOR]

The structural stability of nanocrystalline aluminum-manganese (Al-6.5 at.% Mn) alloys is studied in the temperature range of 200-400 °C. Transmission electron microscopy shows that grain growth in this alloy is subdued by the presence of Mn, such that 100 nm or finer grain sizes can be retained at 200 and 300 °C even after 1 month of annealing. In contrast, the principal mode of instability in the alloy is the precipitation of the equilibrium AlMn phase, which was observed to form at much shorter timescales and is present at 300 and 400 °C after just 30 min. Differential scanning calorimetry was used to study the kinetics of the AlMn reaction using Johnson-Mehl-Avrami-Kolmogorov analysis and construct a time-temperature-transformation (TTT) diagram for this process. It is found that this Al-Mn single-phase nanostructured alloy can be stable against forming the AlMn phase and against grain growth for several months below 200 °C and for short thermal excursions up to 300 °C. [ABSTRACT FROM AUTHOR]

Applying inter-layer rolling to the wire+arc additively manufacturing (WAAM) process with increasing loads of 15 kN, 30 kN and 45 kN, achieves excellent mechanical properties for 5087 (Al-Mg4.5-Mn) alloys. Compared with the as-deposited alloy, the average micro hardness, yield stress and ultimate tensile strength of 45 kN rolled alloys reached to 107.2 HV, 240 MPa and 344 MPa, which were enhanced by 40%, 69% and 18.2%, respectively. Primary coarse grain structures were found to become greatly refined with an evident rolling texture after deformation. The strengthening mechanisms mainly are deformation strengthening, grain refinement, and solution strengthening. Meanwhile, the elongation of rolled alloys stays over 20%. The plasticity was not obviously diminished compared with the as-deposited alloy. This is two times greater than the commercial wrought Al-Mg alloy with similar composition. The excellent plasticity may be chiefly due to grain refinement, pores closure and reduction, and grain recrystallization during the WAAM re-heating process. The combination process of rolling deformation with WAAM deposition is an effective technique in refining microstructure and improving mechanical properties for AM aluminum alloys. [ABSTRACT FROM AUTHOR]

In today's additive manufacturing sector, one of the most popular areas is selective laser melting (SLM) due to its capability of producing geometrically complex metal parts directly from CAD model in a few short steps. Many studies have been reported on static mechanical properties of SLM components; however, dynamic properties of SLM components of different materials have not been thoroughly investigated. Only few papers have been published on the dynamic mechanical behavior, especially in the crack resistance of selective laser melted AlSi10Mg alloy. In the present study, the effect of loading rate, dynamic versus quasi static, on the fracture toughness of the as-built alloy (X and Z orientations) has been investigated. The experimental results revealed the inherently anisotropic behavior for loading rates where the Z orientation exhibited lower toughness compared to the x orientation. The dynamic loading by impact, resulted in a significant decrease of the toughness values up to about 50% compared to the quasi-static loading. This mechanical response was attributed to the increase in the yield stress which alters the state stress at the crack tip from the plane-stress to some extent of the mix-mode plane stress/strain. [ABSTRACT FROM AUTHOR]

Prealloyed powders of Mn54Al46 were mechanically milled, and the as-milled powders subsequently annealed at temperatures from 350 to 600 °C to produce the ferromagnetic L10-structured τ phase. It was found that the magnetic properties are strongly dependent on both the fraction of τ phase and the grain size. Due to the nanostructure, a large coercivity, up to 4.8 kOe, was obtained for Mn54Al46 powders annealed at 400 °C for 10 min. Both remanence curves and δM plots showed no exchange coupling between the τ-phase nanograins. The mechanism for the magnetization process was determined to be domain-wall pinning type. [ABSTRACT FROM AUTHOR]

The decomposition of the thermodynamically metastable τ phase in MnAl has been studied using electron backscatter diffraction. The results showed that the nucleation of the equilibrium phase, β-Mn, in mechanically worked and recrystallized τ-Mn 54 Al 46 occurred preferentially at general grain boundaries, while twin-like defects displayed higher resistance against nucleation. Static recrystallization led to a change in the population of types of interface where the content of general grain boundaries is increased greatly. The reduced stability of mechanically worked τ compared to as-transformed τ is therefore attributed to a combination of recrystallization and selective nucleation at general grain boundaries. [ABSTRACT FROM AUTHOR]

New nanocrystalline aluminum alloys have been fabricated by electrodeposition. These are thermodynamically stable alloys of Al-Mn and Al-Zr with grain sizes <100 nm. Al-Mn and Al-Zr alloys are characterized here showing high strength (up to 1350 MPa) and hardness (up to 450 HVN) while maintaining the specific gravity of Al. Smooth and dense deposits plated from ionic liquids, such as EMIM:Cl (1-Ethyl-3-methylimidazolium chloride), can develop to thicknesses of 1 mm or more. [ABSTRACT FROM AUTHOR]

Substitution of conventional honeycomb composite sandwich structures with lighter alternatives has the potential to reduce the mass of future vehicles. Here we demonstrate nanocrystalline aluminum-manganese truss cores that achieve 2-4 times higher strength than aluminum alloy 5056 honeycombs of the same density. The scalable fabrication approach starts with additive manufacturing of polymer templates, followed by electrodeposition of nanocrystalline Al-Mn alloy, removal of the polymer, and facesheet integration. This facilitates curved and net-shaped sandwich structures, as well as co-curing of the facesheets, which eliminates the need for extra adhesive. The nanocrystalline Al-Mn alloy thin-film material exhibits high strength and ductility and can be converted into a three-dimensional hollow truss structure with this approach. Ultra-lightweight sandwich structures are of interest for a range of applications in aerospace, such as fairings, wings, and flaps, as well as for the automotive and sports industries. [ABSTRACT FROM AUTHOR]

In an effort to develop high strength aluminum alloys, a near-AA5083 Al-Mg alloy powder was cryomilled in liquid nitrogen and consolidated by vacuum hot-pressing (VHP). The composition of the Al-Mg alloy was designed to minimize intermetallic particles that often lead to premature fracture especially when flow strength is high. The as-VHP material had poor ductility and therefore was extruded under different conditions to obtain a good combination of tensile strength and ductility. The microstructure of samples were characterized using X-ray diffraction, EBSD, FIB induced secondary electron orientation contrast imaging, and TEM techniques, which together provided unique assessment at multiple length scales. The samples exhibited a wide range of grain sizes that could be binned into three different groups: i) grain sizes of 50–100 nm, (ii) sizes in the 100–300 nm range, and (iii) elongated larger grains with widths in the range 0.5–2 µm. Room temperature tensile tests with cylindrical dog-bone geometry indicated a high ultimate strength of 730–770 MPa and reproducible elongation to failure of about 3–4%. This combination of strength and ductility in the material are some of the best that have been reported for alloys close to the weldable and corrosion resistant AA5083 composition, and likely a result of the multi-scale microstructure resulting from the processing route. [ABSTRACT FROM AUTHOR]

We have measured antiferromagnetic resonance (AFMR) frequency-field dependences for aluminum-manganese garnet MnAlGeO at frequencies from 1 to 125 GHz and fields up to 6 T. There are three AFMR modes for all orientations, their zero field gaps are about 40 and 70 GHz. Andreev-Marchenko hydrodynamic theory [7] well describes experimental frequency-field dependences. We have observed hysteresis of resonance absorption as well as history dependence of resonance absorption near gap frequencies below 10 kOe in all three measured field orientations, which are supposedly due to the sample domain structure. Observation of the AFMR signal at the frequencies from 1 to 5 GHz allows to estimate repulsion of nuclear and electron modes of spin precession in the vicinity of spin-reorientation transition at H || [100]. [ABSTRACT FROM AUTHOR]

This study focuses on the effect of dynamic aging on the thermo-mechanical cyclic stability of Cu 73 Al 16 Mn 11 (at%) shape memory alloy (SMA) during constant stress (isobaric) and stress-free heating-cooling experiments. Isobaric heating-cooling experiments under various tensile stress magnitudes revealed almost no residual strain up to 60 MPa. Subsequently, the cyclic stability of the samples was further investigated via thermal cycles under 60 MPa with increasing upper cycle temperature (UCT) values. The increase in UCT led to the ordering of the parent phase and formation of the bainite and α phases. In addition to the effect of UCT on the formation of bainite, stress had an accelerating effect on the bainitic transformation. The martensitic transformation temperatures increased due to ordering when UCTs were set to 120 °C and 145 °C and then started to decrease due to the formation of the bainite and α phases when the UCTs were set to 175 °C and 205 °C. Consequently, it was determined that the cyclic stability of Cu-Al-Mn SMAs for high temperature applications strongly depends on the UCT. [ABSTRACT FROM AUTHOR]

Gas-atomized Mn 54 Al 46 particles constituted nominally of only ε- and γ 2 -phases, i.e. no content of the ferromagnetic L1 0 -type τ-phase, have been used to study the evolution of phases during short time of high-energy milling and subsequent annealing. Milling for 3 min is sufficient to begin formation of the τ-MnAl phase. A large coercivity of 4.9 kOe has been obtained in milled powder after annealing at 355 °C for 10 min. The large increase in coercivity, by comparison with the lower value of 1.8 kOe obtained for the starting material after the same annealing conditions, is attributed to the combined formation of the τ-MnAl and β-Mn phases and the creation of a very fine microstructure with grain sizes on the order of 20 nm. Correlation between morphology, microstructure and magnetic properties of the rapidly milled MnAl powders constitutes a technological advance to prepare highly coercive MnAl powders. [ABSTRACT FROM AUTHOR]

In the present work, various Mn amounts (up to 2 wt%) have been added into Al-Mn-Mg 3004 alloy to study their effect on the evolution of microstructure and elevated-temperature properties. Results showed that the dominant intermetallics are interdendritical Al6(MnFe) until to 1.5 wt% Mn. With further addition of Mn to 2 wt%, the blocky primary Al6Mn/Al6(MnFe) and high volume of fine Al6(MnFe) intermetallics form in the matrix, leading to the rapid increase on the volume fraction of intermetallics. After the precipitation heat treatment (375 °C/48 h), the precipitation of dispersoids increased with increasing Mn contents and reached the peak condition in the alloy with 1.5 wt% Mn, resulting in the highest yield strength and creep resistance at 300 °C. However, the elevated-temperature properties became worse in the alloy with 2 wt% Mn due to the lowest volume fraction of dispersoids and highest volume of dispersoid free zone. [ABSTRACT FROM AUTHOR]

The electrodeposition process of aluminum and aluminum-manganese alloys was studied in situ, by using an electrochemical quartz crystal microbalance, EQCM, with damping monitoring, in AlCl3 based ionic liquids. Cyclic voltammetry, potentiostatic and galvanostatic deposition were performed at different temperatures, from 25°C up to 100°C. The morphology of the deposits was investigated by SEM and AFM, and their composition by EDX. The stoichiometry of the alloys was calculated from the EQCM data, based on Sauerbrey's equation. We could show that for thin films electrodeposited on gold electrodes, one can tune their morphology, and in the case of the alloys, also their composition, by modifying the deposition current or potential, as well as by modifying the temperature of the electrolyte. The morphology of the deposits changed gradually with increasing the amount of Mn in the electrolyte from a polyhedral like structure for Al films to round granules for the AlMn alloys. The mechanism for electrodeposition and dissolution of Al and AlMn alloys were analyzed and discussed based on the EQCM data. [ABSTRACT FROM AUTHOR]

Two different transformation routes, quenching followed by heat treatment (route 1), and cooling at intermediate rate (route 2), were used to obtain the L1 0 phase in Mn-Al alloys. The resulting materials showed remarkable differences in microstructure and magnetic properties. In addition, fully transformed material was cold-worked and then recovered by heat treatment. The microstructure of both cold-worked and recovered samples appeared similar in backscattered electron images, however, the magnetic properties differed greatly. Large numbers of electron backscatter diffraction (EBSD) patterns were recorded from all the materials and the pattern quality was quantified, yielding a measure of the dislocation density. The results indicated that both the dislocation density and the coercivity of the cold-worked sample were much higher than in the recovered sample. In addition to other microstructural changes, the route 1 sample had higher dislocation density and coercivity compared to the route 2 sample. For the as-transformed materials, the results were supported by EBSD misorientation mapping and strain analysis of x-ray diffraction data. The continuum theory of dislocations was used to show that the local stress fields of dislocations will cause distortions in the crystal structure leading to local changes in the intrinsic magnetic properties. Such features are likely to act as pinning centres for magnetic domain walls and therefore a higher dislocation density implies a higher coercivity. This conclusion was additionally supported by initial magnetisation curves, which showed evidence for an active pinning mechanism in the cold-worked sample but not for the recovered sample. [ABSTRACT FROM AUTHOR]

The galvanic corrosion behavior between pure Al and synthesized bulk Mg2Si in 0.01 M NaCl solution at different pH values has been investigated by the scanning vibrating electrode technique (SVET). At pH 2, bulk Mg2Si actively dissolves and it acts as an anode. With the increase of exposure time, the anodic activity of Mg2Si decreases drastically and eventually anodic activity appears on Al surface. In alkaline solution, Mg2Si phase always acts as the cathode. The preferential dissolution of Mg and enrichment of Si found by energy dispersive X-ray spectroscopy are responsible for the observed anodic activity decay of Mg2Si in acidic solution. At pH 6, the galvanic corrosion current of Al/Mg2Si couple is much less than those at pH 2 and pH 13, and Mg2Si mainly undergoes self-dissolution. These results indicate that the dealloying of binary Mg2Si phase depends on the solution pH value and corrosion time, which subsequently have a great influence on the galvanic corrosion current of Al/Mg2Si couple. [ABSTRACT FROM AUTHOR]

The present manuscript probes the decomposition behaviour of the ferromagnetic binary metastable Heusler alloy in the Al-Mn system. The ferromagnetic ordered tetragonal phase (L1, popularly known as τ phase), which is metastable in nature, was synthesised from the melt through a copper mould chill casting process using 10-mm diameter mould. Isothermal and non-isothermal heat treatments were carried out to understand the decomposition sequence of τ phase at high temperatures. The metastable phase undergoes, on heating, a eutectoid-like decomposition of $$ \tau \to \beta {\text{Mn}} + \gamma_{2} $$ , where $$ \gamma_{2} $$ is the intermetallic phase AlMn. Both the phases are present in the equilibrium diagram. The two phases at higher temperature further transform to a single phase ε having a hexagonal structure. We show through in situ X-ray diffraction studies that $$ \gamma_{2} $$ transforms to a disordered bcc phase ( $$ \gamma_{\text{bcc}} $$ ) prior to the transformation to the ε-phase. The overall sequence of phase decomposition during heating can be given as $$ \tau \to \tau + \beta \to \beta + \gamma_{2} \to \beta + \gamma_{\text{bcc}} \to \varepsilon $$ . The high-temperature $$ \gamma_{\text{bcc}} $$ phase cannot be retained through quenching experiment and its existence can only be established by in situ studies. [ABSTRACT FROM AUTHOR]