Al-Mn Alloys Research Articles

Enhancement of perpendicularly magnetized τ-phase in Mn/Al bilayer thin films by swift heavy ion irradiation

This paper reports the swift heavy ion irradiation-induced tailoring of the structural and magnetic properties of the Mn/Al bilayer thin films. Mn/Al bilayer thin films were deposited on Si substrates by the evaporation technique, and as-deposited films were irradiated by a 100 MeV Ag ion beam with two distinct fluences. The molar fraction of τ- phase was enhanced at higher irradiation fluence, as revealed by the XRD and magnetic results. The average crystallite size was increased with the increase in irradiation fluence and obtained in a range of 11 to 14 nm. The magnetic hysteresis curves measured at 300 K confirmed the improvement in the ferromagnetic properties and the perpendicular magnetic anisotropy in these films. The enriched ferromagnetic properties were obtained in the perpendicular direction for the film irradiated at higher fluence, with the saturation magnetization ∼ 44 emu/cc, and coercivity ∼ 1590 Oe measured at the low temperature (5 K). These modified magnetic properties in Mn-Al alloy thin films are advantageous for their applications in spintronics and high-density magnetic memory devices.

Hardness and corrosion behavior of an Al-2Mn alloy with both microstructural and chemical gradients

An Al–2Mn binary alloy with gradient microstructure and chemistry near its surface was fabricated by combining surface mechanical treatment and post-ageing treatment. TEM results indicate that the minimum grain size of the topmost surface layer is below 100 nm. As revealed by SIMS results, Mn is depleted in the surface layer with ~2 μm in thickness, which is due to the “short-circuit” diffusion along grain boundaries and dislocation pipes. Microhardness and corrosion testing results revealed that both hardness and corrosion resistance increase substantially with this gradient design. XPS and Mott–Schottky results demonstrate that the oxide film of the gradient Al–Mn alloy is thinner and denser than that of the coarse-grained sample. Our design method of obtaining gradient distribution both in microstructure and chemistry near metal surface lights a pathway for overcoming the trade-off between properties such as strength and corrosion in 3000 series Al alloys.

Thermally stable and corrosion resistant nanolaminated Al-Mn alloy with low angle boundary structures

Metals with nanometer-sized grains are strong but often suffer from poor thermal stability. Herein, nanolaminated (NL) structure with an average thickness of 110 nm and a low angle grain boundaries (LAGBs) fraction of 80% was obtained in an Al-1Mn (in wt%) alloy produced by high strain rate deformation at cryogenic temperature. The NL structures are thermally stable up to 523 K, which can effectively suppress GB precipitation during aging, thus improving the pitting corrosion resistance in 0.6 M NaCl solution. The high thermal stability of NL structures can be mainly attributed to the formation of a large fraction (80%) of LAGBs.

Microstructure evolution and enhanced mechanical properties in Al-Mn alloy reinforced by B-doped TiC particles

In this work, novel TiC particles doped by trace amounts of B, referred to as TiCB, were introduced to an Al-Mn alloy with the Al-TCB master alloy. The effects of the TiCB particles on the solidification microstructure, extrusion behavior, and mechanical properties of the Al-Mn alloy were systematically studied. The results showed that TiCB particles could significantly refine α-Al grains by providing heterogeneous nucleation substrates and hindering the growth of α-grains. For example, when the amount of added TiCB particles was 0.5 wt%, average α-Al grain size could be refined to a minimum of 40.2 μm from 410.1 μm when no particles were added. After hot extrusion, TiCB particles and fractured α-Al(Fe, Mn)Si formed streamlines along the extrusion direction. More importantly, TiCB particles could inhibit the dynamic recrystallization process during hot extrusion and retain numerous geometrically necessary dislocations. Consequently, the mechanical properties of the Al-Mn alloy at room temperature (25 °C) and elevated temperature (350 °C) were significantly improved after adding TiCB particles. When the amount of added TiCB particles was 1.5 wt%, the ultimate tensile strengths at 25 °C and 350 °C were increased by 25.6% and 32.4%. This work sheds light on the grain refinement and strengthening of non-heat-treatable wrought Al-Mn alloys.

Combustion Synthesis and Phase Formation in the Ti–Al–Mn Alloy

Combustion Synthesis and Phase Formation in the Ti–Al–Mn Alloy

Effect of nicotinic acid additives on the electrodeposition of Al-Mn alloy from AlCl3-based ionic liquids

Effect of nicotinic acid additives on the electrodeposition of Al-Mn alloy from AlCl3-based ionic liquids

On the ε → τ phase transformation and twinning in L10−MnAl alloys

Formation of twins have been recognized as the bottleneck that limit the high-performance of L10-type Mn-Al permanent magnets. Although it is known that twinning occurs as a consequence of ε → τ phase transition, the detailed formation mechanism is still unclear. We studied systematically the phase transformation processes of ε → τ by transmission electron microscopy. The two-step transformation includes first a diffusion-controlled ordering transformation from disordered A3-type ε-phase to ordered B19-type ε’-variants, and second, a shearing transformation from ε’-phase to L10-type τ-phase via the stepwise atomic displacement with the vector of x3<100>ε’. The two τ-variants generated from the same ε’-variant constitute the true twins with included angle of ∼76° The combination of τ-variants which are generated from different ε’-variant produces the order twins and pseudo twins with the included angles of ∼85° and ∼48°, respectively. The effects of true twins and order twins on coercivity are compared by studying the domain structures during demagnetization. The order-twin boundary has a more significantly effect on promoting the nucleation and propagation of the reversal domain, giving rise to a severer degradation effect on coercivity compared with true-twin boundary. The combination of directional solidification and hot-deformation is identified to effectively manipulate the ε → τ phase transition based on the proposed mechanism, as demonstrated by good magnetic properties of ∼400 mT in coercivity and ∼0.67 in remanence ratio in L10−MnAl magnets. Our work explains the mechanism on the formation of various twins in L10−MnAl, and offers guidelines of fabricating high-performance twins-containing MnAl permanent magnets.

Improvement of strength and ductility synergy in a room-temperature stretch-formable Mg-Al-Mn alloy sheet by twin-roll casting and low-temperature annealing

• Twin-roll casting leads to the formation of uniform and fine grain structures. • The microstructure feature is effective to improve strengths-ductility synergy. • In-plane isotropic tensile property and good RT formability have been obtained. Strength and ductility synergy in an Mg-3mass%Al-Mn (AM30) alloy sheet was successfully improved via twin-roll casting and annealing at low-temperature. An AM30 alloy sheet produced by twin-roll casting, homogenization, hot-rolling, and subsequent annealing at 170 °C for 64 h exhibits a good 0.2% proof stress of 170 MPa and a large elongation to failure of 33.1% along the rolling direction. The sheet also shows in-plane isotropic tensile properties, and the 0.2% proof stress and elongation to failure along the transverse direction are 176 MPa and 35.5%, respectively. Though the sheet produced by direct-chill casting also shows moderate strengths if the annealing condition is same, the direct-chill casting leads to the deteriorated elongation to failure of 23.9% and 30.0% for the rolling and transverse directions, respectively. As well as such excellent tensile properties, a high room-temperature stretch formability with an Index Erichsen value of 8.3 mm could be obtained in the twin-roll cast sheet annealed at 170 °C for 64 h. The annealing at a higher temperature further improves the stretch formability; however, this results in the decrease of the tensile properties. Microstructure characterization reveals that the excellent combination of strengths, ductility, and stretch formability in the twin-roll cast sheet annealed at the low-temperature annealing is mainly attributed to the uniform recrystallized microstructure, fine grain size, and circular distribution of (0001) poles away from the normal direction of the sheet.

Liquid metal corrosion resistant LaPO4 coating with metallophobic characteristics fabricated on 316 stainless steel using electrophoretic deposition technique

A liquid metal corrosion (LMC) resistant and metallophobic lanthanum phosphate (LaPO 4 ) coating was prepared on SUS316 stainless steel using electrophoretic deposition (EPD) technique. A specific hierarchical surface structure was created on coating surface by adjusting EPD process parameters. LMC test was performed using three different metal melts, Al–Zn–Mg alloy, Mg–Al–Mn alloy, and pure Zinc. Results indicated that steel bare surface was severely attacked by all three melts. The mechanism of corrosion process was explained in each case. After coating, the LaPO 4 covered steel showed an excellent resistance against all three liquid metals. Besides, wetting of steel surface by liquid metals was strongly decreased by application of LaPO 4 surface coating. This can be attributed to the intrinsic metallophobic characteristic of LaPO 4 as well as the hierarchical surface structure developed on coating surface.

A Sustainable Process to Produce Manganese and Its Alloys through Hydrogen and Aluminothermic Reduction

Hydrogen and aluminum were used to produce manganese, aluminum–manganese (AlMn) and ferromanganese (FeMn) alloys through experimental work, and mass and energy balances. Oxide pellets were made from Mn oxide and CaO powder, followed by pre-reduction by hydrogen. The reduced MnO pellets were then smelted and reduced at elevated temperatures through CaO flux and Al reductant addition, yielding metallic Mn. Changing the amount of the added Al for the aluminothermic reduction, with or without iron addition led to the production of Mn metal, AlMn alloy and FeMn alloy. Mass and energy balances were carried out for three scenarios to produce these metal products with feasible material flows. An integrated process with three main steps is introduced; a pre-reduction unit to pre-reduce Mn ore, a smelting-aluminothermic reduction unit to produce metals from the pre-reduced ore, and a gas treatment unit to do heat recovery and hydrogen looping from the pre-reduction process gas. It is shown that the process is sustainable regarding the valorization of industrial waste and the energy consumptions for Mn and its alloys production via this process are lower than current commercial processes. Ferromanganese production by this process will prevent the emission of about 1.5 t CO2/t metal.

Microstructural features and mechanical properties of a novel Ti- and Zr-modified Al-Mn alloy processed by laser powder bed fusion

The expansion of the material library for the laser powder bed fusion (LPBF) process is essential for the further establishment of the process in areas such as the aerospace and automotive industries. In this study, we designed a high-strength and low-cost Al-Mn-Ti-Zr alloy specifically tailored to the unique conditions of the LPBF process. Gas-atomized pre-alloyed powder was prepared and used as feedstock to fabricate LPBF specimens for microstructural examination and mechanical testing. By taking advantage of the high solidification rate, unconventionally large amounts of Mn (3.7 ± 0.5 wt%) are metastably frozen within the α-Al matrix, contributing significantly to solid solution hardening (~104 MPa ≙ 37% share of yield strength). The as-built specimens exhibit a yield strength of 284 ± 3 MPa, an ultimate tensile strength of 320 ± 1 MPa, and an elongation at fracture of 16.9 ± 0.2%. This new alloy exhibits a bimodal microstructure consisting of alternately distributed fine equiaxed and coarse columnar grain regions. Further microstructural analyses reveal a high number of primary L12 cubic Al3(Tix Zr1 - x) nanoparticles within the equiaxed α-Al grains near the bottom of the melt pool. A highly coherent interface with the α-Al matrix confirms high efficiency for heterogeneous nucleation during solidification. In addition to the Al3(Tix Zr1 - x) nanoparticles, an AlxMn(Fe, Si) phase with a quasi-crystalline structure is observed along the grain boundaries and interdendritic areas.

Technical basis of using laser direct energy deposition as a high-throughput combinatorial method for DC-cast Al-Mn alloy development

This work evaluated the technical basis of using laser direct energy deposition (DED) additive manufacturing (AM) as a rapid alloy screening method to study the phase transformation of second phase particles and recrystallization behavior of Al-Mn alloy AA3104 throughout the steps of thermomechanical processing. The study focused on assessing the differences between DED and DC-cast AA3104 alloy after homogenization and hot rolling. The fast cooling and repeated in situ thermal cycles during DED AM resulted in different phase transformation behavior compared to conventional DC-cast alloys. DED alloys exhibited a higher fraction of α-Al (Fe,Mn)-Si particles, more uniform particle distribution, and stronger cube texture in the as-fabricated condition. Homogenization promoted Al6(Fe,Mn) to α-Al (Fe,Mn)-Si phase transformation in both DED and DC-cast alloys. After homogenization, DED alloys exhibited two times as many coarse α particles in area fraction as DC-cast alloys but fewer nanoscale dispersoids. These unique material characteristics in DED alloys were responsible for easier recrystallization after hot rolling and annealing. While the differences existed, DED and DC-cast AA3104 alloys demonstrated a similar trend in phase transformation and recrystallization, strongly reinforcing that DED AM can support high-throughput Al alloy development.

Densification, microstructure and properties of Sc and Zr modified Al-Mn alloy prepared by selective laser melting

In this work, the selective laser melting (SLM) of Sc and Zr modified Al-Mn alloy was systematically investigated, with a particular emphasis on the density behavior, microstructure and mechanical properties. The process parameters were significantly impact on the relative density and the maximum relative density of SLM-processed Al-Mn-Sc-Zr specimens reached 99.8% at the optimized process parameters. With the reduction of energy density, the melting mode of melting pool changed from keyhole mode to conduction mode. At the high energy density, near-spherical pores were generated because of the evaporation of low melting alloy constituents. With the decreasing of energy density, irregular pores were generated, which was mainly caused by the insufficient energy input. The SLM processed Al--Mn-Sc-Zr showed a duplex grain microstructure consisting of regions of columnar grains and equiaxed grains. Good mechanical properties were reached in as-fabricated condition: tensile strength ≥ 426 MPa and elongation to fracture ≥ 18%. Besides, no significant anisotropy was found in the stress–strain behavior between horizontal and vertical building direction.

Novel laminated multi-layer graphene/Cu–Al–Mn composites with ultrahigh damping capacity and superior tensile mechanical properties

Laminated multi-layer graphene/Cu–Al–Mn composites were prepared via packaged hot roll bonding process for the first time. Microscopic observation shows that the grains in the Cu–Al–Mn layers are remarkably refined. Multi-layer graphene films intermittently disperse at the interfaces between Cu–Al–Mn layers. Some small fragments of multi-layer graphene films are squeezed into the Cu–Al–Mn layer, and around them, due to the formation of in-situ Al2O3 phase and nano-twins, multi-stage and multi-phase structures are formed. Performance tests show that the composites have ultrahigh damping capacity. Within a wide temperature range of 25–300 °C, the value of damping plateau is up to 0.1 (about 10 times that of the original Cu–Al–Mn alloy). The composites also have superior tensile mechanical properties. Their tensile strength and elongation are up to 913.3 MPa and 13.4% respectively (2.5 times and 4.1 times that of the original Cu–Al–Mn alloy). Microstructural origins of the excellent comprehensive properties were discussed in detail.

Surface characterization of Fe–10Al–25Mn alloy for biomaterial applications

The austenitic stainless-steel biomaterial, AISI 316L stainless steel, is one of the most widely used for orthopedic or prosthetic implant devices because it is easy to manufacture at a relatively low cost. However, corrosion is a challenging issue related to major alloying compounds with body fluids and wear. Therefore, this study aimed to develop a biomaterial of Fe–Al–Mn alloys by minimizing chromium (Cr) and nickel (Ni) contents. In the research, an attempt has been made to increase the corrosion resistance of Fe–10Al–25Mn alloy using plasma nitriding, which was considered one of the most cost-effective surface treatments. The processes were carried out at various treatment temperatures between 350 and 550 °C, with a pressure of 1.8 mbar in 3 h. Several tests were performed, such as chemical compositions, scanning electron microscopy (SEM) combined with energy dispersive spectroscopy (EDS), hardness, and corrosion. The results indicated that the treatment of plasma nitriding at temperatures up to 500 °C significantly enhances the corrosion resistance and increases the hardness of the alloy. At 500 °C, the percentage of nitrogen atoms reaches a peak and then decreases. It means that the nitride formation process on the alloy surface occurs more massively. The amount of nitrogen deposited on the surface of the Fe–10Al–25Mn alloy, as well as a thin layer of iron nitride, is noticeable in the SEM-EDS test. Furthermore, the formation of phases due to the nitriding temperature significantly impacts the alloy properties.

Effect of the heat treatment on the electrical resistivity and magnetization reversal behavior of MnAl alloys

The casting Mn51Al47C2 alloy were undergone two distinct heat treatment processes, consisting of the heat treatment at 1000 and 925 °C. The process followed by quenching and annealing at 500 °C for 15 min. The low electrical resistivity for the heat treatment stage at 1000 °C (165* 10-4 Ω.m) can be described by the small fraction of the L10-ordered τ-phase (40 %). But the high resistivity for heat treatment at 925 °C (290.4* 10-4 Ω.m) originates within the large fraction (>95%) of the L10-ordered τ-phase with space inversion symmetry inhibiting the transport process. The magnetic characterization revealed higher Ms, Mr and Hc along with superior (BH)max for Mn51Al47C2 alloy heat-treated at 925 °C. Additionally, the derivative hysteresis loops assign narrow maxima to Mn51Al47C2 alloy when containing less amount of the L10-ordered τ-phase. Also, tracking the magnetization reversal behavior through the Henkel plots display the increasing negative-peak dominated curve for Mn51Al47C2 alloy when moving from the as homogenized sample (100% τ-phase) to those heat-treated at 1000 (40% L10-ordered τ-phase) and 925 °C (>95% L10-ordered τ-phase), respectively. This highlights the deterioration of the exchange coupling interaction between the grains when dominated with a highly ordered L10-τ-phase. The trend is best confirmed by the quantitative results gained from recoil loops for demagnetization, reversible and irreversible magnetization curves, indicative of a low degree of exchange interactions when the L10-ordered τ-phase is dominant. Furthermore, analyzing the nucleation field through the Kondürsky model gives a low value of 0.41 kOe for the alloy in the as homogenized state. This behavior can be attributed to the boosted propagation of the anisotropy field and enhanced magnetic exchange coupling in a structure with dominant regular τ-phase for which the deleterious effects of the interfaces for the L10-ordered τ-phase can be avoided.

Magnetic properties and electronic structure of Mn-Al alloys in the β-Mn structure

In this work, the electronic structure and magnetic properties of the Mn-Al alloys with different Mn and Al concentrations in the β-Mn-type structure have been theoretically investigated. The structural stability of different types of aluminum and manganese atoms occupations of the 12d and 8c site positions are compared. For the Mn3Al with 5Al in the 12d positions we obtained the most energetically preferable arrangement of Mn and Al ions in this alloy. Further occupation of this type of position by the Al atoms might be responsible for the lower effective magnetic moment estimated from the experimental data. Our theoretical calculations demonstrate the complex character of the magnetic properties and electronic structure of the Mn-Al alloys.

Achieving superior combination of yield strength and ductility in Mg–Mn–Al alloys via ultrafine grain structure

Ternary magnesium-based alloys with an aluminum content of 0.5 wt.% and a varying manganese content of x = 1, 2, and 3 wt.% (Mg-xMn-0.5Al) were prepared and characterized. The study focused on the effect of Mn addition on the formation of ultrafine grains (UFGs, average grain size <1 μm) and the mechanical properties of the alloys. After extrusion at a relatively low temperature of 250 °C, the average grain sizes of Mg-2Mn-0.5Al and Mg-3Mn-0.5Al samples were successfully refined to values of 0.9 ± 0.39 μm and 0.8 ± 0.34 μm, respectively, of submicron scale. The Mg-3Mn-0.5Al sample simultaneously demonstrated superior yield stress (YS, 274 MPa) and fracture elongation (FE, 48.9%). The high YS was associated with the UFG structure, residual dislocations, and nanosized precipitates, while the high FE was attributed to the low dislocation storage rate and UFGs with random orientations. The formation of UFGs is mainly caused by a recrystallization process promoted by particle-stimulated nucleation. The grain growth is suppressed by dynamic precipitated α-Mn particles.

An Evaluation of the Tribological Behavior of Cutting Fluid Additives on Aluminum-Manganese Alloys

The introduction of additives enhances the friction and wear reduction properties of cutting fluids (CFs) as well as aids in improving the surface quality of the machined parts. This study examines the tribological behavior of polymer-based and phosphorus-based additives introduced into cutting fluids for the machining of Al-Mn alloys. Ball-on-disc tests were used to evaluate the coefficient of friction (COF) and lubrication failure temperature to study the performance of the additives in the cutting fluids. Surface characterization was performed on the sliding tracks induced on the Al-Mn disc surfaces and used to propose the wear and friction reduction mechanisms. The polymer-based additive possessed a higher temperature at which lubrication failure occurred, displayed comparable COF at a lower temperature under certain conditions, and possessed a steadier tribological behavior. However, the phosphorus-based additive was observed to display lower COF and wear damage from 200 °C till failure. The lower COF values for the phosphorus-based additive at 200 °C corresponded with lower surface damage on the Al-Mn surface. The phosphorus-based additive’s performance at 200 °C could be attributed to the forming of a phosphorus-rich boundary layer within the sliding wear track, resulting in less surface damage on the Al-Mn surface and lower material transfer to the counterface steel ball surface.

Effect of Al content on microstructure, thermal conductivity, and mechanical properties of Mg–La–Al–Mn alloys

Effect of Al content on microstructure, thermal conductivity, and mechanical properties of Mg–La–Al–Mn alloys