Mn Alloy Research Articles

A criterion of dimensional design to improve flame spread resistance of magnesium alloy components

A criterion for predicting the flame spread time of stick-shaped Mg alloy samples was proposed based on the law of energy conservation. It is indicated that the flame spread time is mainly affected by the material and sample dimension. The initial temperature and ignition temperature of the control volume and the S/lc ratio (the cross-sectional area/cross-sectional circumference) of the sample are decisive for the flame spread time. The flame spread time is proportional to the ΔH (the energy required to heat a unit mass of sample from initial temperature to ignition temperature) and the S/lc ratio, which is confirmed in three Mg alloys of Mg–8.5Al–0.5Zn–0.2Mn, Mg–2.7Nd– 0.4Zn–0.6Zr and Mg–4.0Y–3.3Nd–0.5Zr. For samples with the same dimension, the Mg–8.5Al–0.5Zn–0.2Mn alloy sample possesses the largest ΔH and the longest flame spread time. For samples with constant length and cross-sectional area, the sample with circular cross-section has the largest S/lc ratio and the best flame spread resistance in the same alloy.

Effect of laser welding on the structure and mechanical properties of hot-rolled Al – 3 Ca – 0.5 Cu – 0.5 Mn alloy

Effect of laser welding on the structure and mechanical properties of hot-rolled Al – 3 Ca – 0.5 Cu – 0.5 Mn alloy

Hot deformation behavior and extrusion temperature-dependent microstructure, texture and mechanical properties of Mg–1Mn alloy

Mg–1Mn alloy, extruded at a low temperature in our published protocol, contributed to the intensified basal texture and extremely refined microstructure with spheroidal nanoscale precipitates dispersing throughout the matrix and along the grain boundaries, consequently resulting in the excellent mechanical properties where the alloy exhibited a tensile yield strength of 204.3 MPa and a ductility of 38.8% at room temperature. Therefore, Mg–1Mn alloy was recommended as one of the potential materials for structural applications. In the present investigation, hot deformation behavior through constitutive analysis and extrusion temperature-dependent microstructure, texture and mechanical properties of as-extruded Mg–1Mn alloy were investigated, aiming at revealing how extrusion temperature affected microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. X-ray diffraction patterns demonstrated that phase components of the experimental alloys consisted of the α-Mg matrix and Mn precipitates. Optical microscopy images indicated a significant increase in average grain size of the alloys as the extrusion temperature increasing from 250 °C to 400 °C. Scanning electron microscopy graphics revealed that coarsened particles identified as Mn precipitates by EDS were observed within the matrix when extrusion temperature reached 400 °C. Inverse pole figure maps of the experimental samples subjected to different extrusion temperatures in the present work exhibited the typical basal texture, suggesting that basal slip was activated hardly during the tensile stress applied along the extrusion direction. Consequently, extrusion temperature displayed the significant impact on microstructure, texture, and mechanical properties of as-extruded Mg–1Mn alloy. The alloy extruded at both 250 °C and 300 °C exhibited the strong basal texture and refined microstructure with spheroidal nanoscale precipitates dispersing within the matrix and along the grain boundaries, which contributed to their excellent comprehensive mechanical properties. The alloy extruded at 400 °C possessed the typical basal texture and coarsened microstructure, leading to the extremely poor mechanical properties. Simultaneously, the constitutive model of the Arrhenius equation based on Zener-Hollomon parameters was also established in the present investigation. Therefore, optimizing the extrusion temperature to regulate the microstructure, grain orientation distribution, and morphology of precipitates was considered as one of the effective approaches for achieving the excellent mechanical properties of Mg alloys.

Enhanced thermal conductivity and mechanical properties of extruded Mg-4La-2Al-0.3Mn alloy via hot forging

The Mg-4La-2Al-0.3Mn (LA42) alloy, known for its remarkable thermal conductivity of 110 W/(m⋅K), faces limitations owing to its inherently low strength. In this study, a composite deformation process, involving hot forging and extrusion, was investigated to enhance both the thermal conductivity and mechanical properties of the LA42 alloy. The findings revealed that the composite deformation process effectively precipitated an increased number of solute atoms from the matrix, thereby mitigating the lattice distortion effect and resulting in a superior thermal conductivity of 148.2 W/(m⋅K). Additionally, the combination of hot forging and extrusion proved to be efficient in achieving more pronounced grain refinement with increased dislocation density. Consequently, the yield strength of LA42 alloy was substantially enhanced while maintaining a high elongation, reaching values of 211.1 MPa and 12.5 %, respectively. These exceptional overall properties establish a competitive edge when compared to other state-of-the-art magnesium alloys reported previously.

Effect of extrusion ratio on microstructures, mechanical properties, and high cycle fatigue behavior of Mg–5Zn–1Mn alloy

The effects of extrusion ratio (ER) on the microstructures, static mechanical properties, and tension-compression high cycle fatigue (HCF) behavior of the as-extruded Mg–5Zn–1Mn (ZM51) alloy was investigated systematically, and the HCF mechanism was discussed. The results show that texture weakening and grain refinement caused by increasing the ER can effectively enhance the static mechanical properties and alleviate the tensile-compressive asymmetry of the alloy. The fatigue strength at 107 cycles is 124 ± 5, 138 ± 4, and 142 ± 5 MPa for ER8, ER11.5, and ER23, respectively, and the corresponding fatigue ratio is approximately 0.45, 0.49, and 0.50, which means that the as-extruded ZM51 alloy possesses outstanding fatigue resistance. The failure analysis and microstructure evolution of post-fatigued samples demonstrated that the stress amplitudes and microstructure characteristics strongly influence the HCF mechanism of the alloy. At high-stress load, close to the tensile yield strength 160–180 MPa, abundant {101‾2} residual twin bands were observed near the fracture surface. Twinning/detwinning deformation is the dominant fatigue mechanism due to the plastic deformation incompatibility between the matrix and the residual twins. At low-stress load, close to the fatigue strength 125–145 MPa, the fatigue crack initiation mechanism transits from twinning/detwinning to dislocation slip. Grain refinement and texture weakening inhibit the activation of {101‾2} twins, alleviate the twin-dislocation interaction, and promote dislocation slip to dominate the fatigue deformation, thereby enhancing the fatigue life of the alloy. This work provides new insight into the design and development for enhancing the fatigue resistance of wrought Mg alloy to ensure the long-term service safety of structural materials.

Toward high strength and large strain hardening Zn alloys via a novel multiscale-heterostructure strategy

Zn alloy has attracted much attention as a biodegradable material for biomedical applications. However, due to the significant strain softening of Zn alloys, how to break the bottleneck of synergistic yield strength and uniform elongation is an urgent problem to be solved. In this work, a Zn-2.3Cu-0.8Mn (wt.%) alloy was fabricated via low-temperature extrusion and annealing at 330 °C for 1 h to attain dual heterostructures with bimodal grains and multi-scale second phases, focusing on the effect of heterostructure on the mechanical properties. Uniaxial tensile test and loading-unloading-reloading test were applied to reveal the mechanical properties of the Zn-2.3Cu-0.8Mn alloy, while scanning electron microscope, electron backscatter diffraction, and transmission electron microscope were used to characterize its microstructure. Compared with the as-extruded alloy with uniform and fine grains, 330–1 alloy achieves a better combination of strength and uniform elongation (yield strength: 287.8 ± 8.5 MPa, ultimate tensile strength: 321.4 ± 6.8 MPa, and uniform elongation: 14.2 ± 1.8%). The high strength was primarily attributed to the coordination of grain boundary strengthening, hetero-deformation induced strengthening, Orowan strengthening, and dislocation strengthening. Besides, the coarse grains, twinning, as well as the suppression of grain boundary sliding and phase boundary sliding promoted dislocation proliferation and storage capacity, thereby improving work hardening capacity. The large strain hardening capacity was responsible for excellent plasticity. This study provides a feasible strategy for the design of Zn-based alloys with an excellent combination of high strength and strain hardening capacity.

Modeling of Cu Precipitation in Fe–Cu and Fe–Cu–Mn Alloys Under Neutron and Electron Irradiation

Modeling of Cu Precipitation in Fe–Cu and Fe–Cu–Mn Alloys Under Neutron and Electron Irradiation

Irradiation microstructures and hardening in commercial nuclear reactor pressure vessel steels at high extended life fluence

Nuclear reactor lifetimes up to and beyond 80 years may be limited by nano-scale Cu-Mn-Ni-Si precipitates (CRPs and MNSPs) that form under neutron irradiation in pressure vessel (RPV) steels, resulting in hardening and ductile to brittle transition temperature increases, or embrittlement. Here, Atom Probe Tomography (APT) is used to characterize precipitation in nine actual RPV steels, irradiated in the ATR-2 test reactor, to a high fluence 1.38 × 1020 n/cm2 at 292 °C and 3.68 × 1012 n/cm2 s. APT quantifies the relation between a wide range surveillance alloy Cu, Ni, Mn, and Si contents and the corresponding precipitate volume fractions, number densities, sizes, and compositions. The precipitate volume fraction (fp) is dominated by the dissolved steel Cu and Ni contents. Irradiation hardening shows the expected dependence on the √fp. The APT results also provide an opportunity to evaluate flux effects by direct comparisons with corresponding archival data from low flux surveillance irradiations. Most notably, this work establishes a strong microstructural and mechanistic foundation for the new data-driven Odette, Wells, Almirall, and Yamamoto (OWAY) model to predict high fluence RPV steel embrittlement.

Interfacial Segregation of Sn during the Continuous Annealing and Selective Oxidation of Fe-Mn-Sn Alloys.

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0-10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks.

High-throughput synthesis of binary Al–Mn alloys by directed energy deposition with improved accuracy of composition adjustment

High-throughput synthesis of binary Al–Mn alloys by directed energy deposition with improved accuracy of composition adjustment

Multiscale modelling of damage occurrence of eutectic phase in Al–Ni–Mn alloy

Aluminum-nickel binary alloys exhibit good thermal stability. However, by adding Mn microstructures of the alloy are largely changed and resulting mechanical properties could be significantly affected. A microstructure based approach coupled with damage criteria was proposed for investigating local stress, strain developments and damage mechanisms on the micro-scale of Al–4Ni–1Mn with Sc and Zr alloy. For the model, flow curves of each constituent phase were determined using both experiments and dislocation theory. Tensile test results of the alloy showed that damage mostly initiated within α-Al matrix and afterwards propagated to eutectic phase region. Therefore, the Hosford-Coulomb ductile damage model was employed for describing failure evolution of the Al matrix. The representative volume element (RVE) model fairly demonstrated microstructure deformation of a mini-tensile sample. Then, effects of different phase morphologies on local damage onset of the examined alloy were analyzed. It was found that eutectic particles with aspect ratio higher than 7 and oriented in parallel to loading direction were the most critical sites of cracking. This result was in accordance with experimental fracture analyses.

Microstructures evolution and mechanical properties of dilute Mg-Y-Al-Ca-Mn alloy during uniaxial compression deformation at different strain levels

The isothermal compression tests of dilute as-extruded Mg-2Y–1Al (wt%) alloy, Mg-2Y–1Al-0.3Ca-0.7Mn (wt%) alloy and Mg-2Y–1Al-0.7Ca-0.3Mn (wt%) alloy were systematically carried out. The experimental temperature (T) was 200 °C, the strain rate (ε̇) was 0.001 s−1 and the strain levels ranged from 0.1 to 0.3. Tests results demonstrated that compressive strength and yield strength clearly increased after adding Ca and Mn, just as Mg-2Y–1Al-0.3Ca-0.7Mn alloy and Mg-2Y–1Al-0.7Ca-0.3Mn alloy had displayed. It was worth mentioning that peak stress of Mg-2Y–1Al-0.7Ca-0.3Mn alloy was 100 MPa higher than that of Mg-2Y–1Al alloy under the strain count of 0.3. The main reason was that adding Ca and Mn into Mg-2Y–1Al caused existence of more second phases which made microstructure finer. Furthermore, microstructures evolution and deformation mechanisms of three alloys were investigated by electron backscatter diffraction (EBSD). Based on EBSD results, what could be found was there existed plenty of twins which could be determined to be {10−12} extension twin when strain count is 0.1. And because of more second phases, Mg-2Y–1Al-0.3Ca-0.7Mn alloy and Mg-2Y–1Al-0.7Ca-0.3Mn alloy activated more extension twins than Mg-2Y–1Al alloy. When strain count was 0.3, it could be seen that three alloys all occurred dynamic recrystallization (DRX) and the main DRX mechanism was strongly believed to be discontinue dynamic recrystallization (DDRX). According to dislocation slip analysis results of three alloys, much pyramidal <c+a> slip and little prismatic <a> slip was activated during compression and dominated deformation.

Enhanced cyclic durability of low-cost Ti–V–Cr hydrogen storage alloys by elemental alloying

Low-cost low vanadium (low-V) hydrogen storage materials have high reversible capacities (>2.0 wt%) under moderate conditions, however, they suffer from drastic capacity decay during cycling. In this work, a series of TiCr1.1M0.1(V–Fe)0.6 (M = Mn, Mo and Nb) alloys are prepared by elemental alloying on the basis of the low-cost, low-V alloy TiCr1.2(V–Fe)0.6 alloy, and the modification mechanism of the elemental alloying on the cycling durability of the alloy is systematically investigated. In 100 cycles, the results demonstrated that the original alloy TiCr1.2(V–Fe) 0.6 suffered from poor desorption capacity (1.13 wt%) and lowly capacity retention rate (60.43%). Compared to the addition of Mn and Nb, TiCr1.1Mo0.1(V–Fe)0.6 obtained higher cyclic hydrogen storage capacity (1.32 wt%) and capacity retention (68.04%). In addition, it is found that the addition of Mo can inhibit the formation of the secondary phase during the cycling, and the abundance of the C14 Laves phase maintained at only 2.47% after 100 cycles. According to the microstructural analysis of the alloys during cycling, it is found that the decrease in grain size, the accumulation of micro strain and dislocation density, and the degree of particle pulverization seriously affect the cycling durability of the alloys, resulting in a drastic decrease in the dehydrogenation cycling capacity. Finally, it should be noted that although the improvement in cycle durability with Mo alloying is limited, it is still a positive reference for developing low-cost low-V alloys with good cycle durability.

Improved corrosion resistance and mechanical properties of severely deformed ZM31 alloy

The hexagonal close-packed (HCP) crystal structure of Mg alloys lead to poor formability as well as other undesirable mechanical behaviors in an otherwise highly sought-after alloy for commercial use. This study investigates the evolution of microstructure, texture, corrosion and mechanical behaviors in Mg–Zn–Mn (ZM31) alloy after processing using Equal Channel Angular Pressing (ECAP). Dynamic recrystallization was evident in the ECAP-processed samples, correlated with a substantial fiber structure, and resulted in the attainment of notable grain refinement and high lattice strain. Average grain sizes of 2.2 and 2 μm were achieved via 2 and 4-Pass Bc processing, respectively. This significant refinement yielded lower corrosion rates through enhancement of the thickness, coherency, and stability of formed protective oxide layers. The corrosion rate in the NaCl medium was substantially enhanced by 99.5% after four passes via route Bc. The recrystallized fine structure was found to have contributed to yield strength, ultimate strength, and microhardness improvements. Deformation enhanced yield and ultimate strengths by 132% and 64%, respectively. The distinctive grain refinement mechanism exhibited through the current ECAP procedure has potential to pave the way for novel and impactful utilizations of ZM31 in industries that demand exceptional mechanical and corrosion performance.

Impact of scandium and terbium on the mechanical properties, corrosion behavior, and biocompatibility of biodegradable Mg-Zn-Zr-Mn alloys

Magnesium (Mg)-based bone implants degrade rapidly in the physiological environment of the human body which affects their structural integrity and biocompatibility before adequate bone repair. Rare earth elements (REEs) have demonstrated their effectiveness in tailoring the corrosion and mechanical behavior of Mg alloys. This study methodically investigated the impacts of scandium (Sc) and terbium (Tb) in tailoring the corrosion resistance, mechanical properties, and biocompatibility of Mg–0.5Zn–0.35Zr–0.15Mn (MZZM) alloys fabricated via casting and hot extrusion. Results indicate that addition of Sc and Tb improved the strength of MZZM alloys via grain size reduction and solid solution strengthening mechanisms. The extruded MZZM–(1–2)Sc–(1–2)Tb (wt.%) alloys exhibit compressive strengths within the range of 336–405 MPa, surpassing the minimum required strength of 200 MPa for bone implants by a significant margin. Potentiodynamic polarization tests revealed low corrosion rates of as–cast MZZM (0.25 mm/y), MZZM–2Tb (0.45 mm/y), MZZM–1Sc–1Tb (0.18 mm/y), and MZZM–1Sc–2Tb (0.64 mm/y), and extruded MZZM (0.17 mm/y), MZZM–1Sc (0.15 mm/y), MZZM-2Sc (0.45 mm/y), MZZM-1Tb (0.17 mm/y), MZZM-2Tb (0.10 mm/y), MZZM–1Sc-1Tb (0.14 mm/y), MZZM-1Sc-2Tb (0.40 mm/y), and MZZM–2Sc–2Tb (0.51 mm/y) alloys, which were found lower compared to corrosion rate of high-purity Mg (∼1.0 mm/y) reported in the literature. Furthermore, addition of Sc, or Tb, or Sc and Tb to MZZM alloys did not adversely affect the viability of SaOS2 cells, but enhanced their initial cell attachment, proliferation, and spreading shown via polygonal shapes and filipodia. This study emphasizes the benefits of incorporating Sc and Tb elements in MZZM alloys, as they effectively enhance corrosion resistance, mechanical properties, and biocompatibility simultaneously.

The Impact of Thermomechanical Treatment on Structure, Electrical Resistance and Hardness of Al–4% Cu–3% Mn Alloy Casted in an Electromagnetic Crystallizer

The Impact of Thermomechanical Treatment on Structure, Electrical Resistance and Hardness of Al–4% Cu–3% Mn Alloy Casted in an Electromagnetic Crystallizer

Ductility enhancement by activating non-basal slip in Mg alloys with micro-Mn

The effect of micro-Mn addition on the microstructure and mechanical properties of Mg alloys was analyzed. Electron back scattered diffraction, slip traces analysis, transmission electron microscopy and visco-plastic self-consistent polycrystal constitutive modeling were performed to investigate the deformation mechanisms in the tensile test. The results show that the average grain size of Mg−Mn alloys decreases from 28.30 to 5.10 μm with Mn addition. Furthermore, with the increment of Mn content, the ductility of the as-extruded samples improves from 14.33% to 20.33%, and the yield strength increases from 84 to 180 MPa. The reason for this simultaneous improvement is that the critical resolved shear stress gap between basal slip and non-basal slip decreases from 173 to 115 MPa, which leads to the increase of non-basal slip activity. The adjustment of slip system difference by microalloying elements provides a way to develop Mg alloys with high strength and ductility.

First‐principle screening of corrosion resistant solutes (Al, Zn, Y, Ce, and Mn) in Mg alloys for Integrated Computational Materials Engineering guided stainless Mg design

AbstractMg alloy suffers from its poor corrosion resistance as a result of anodic dissolution of Mg and hydrogen evolution reaction (HER) in humid environments. In this study, the effects of alloying elements (Al, Zn, Y, Ce, and Mn) on both processes in Mg alloys have been quantitatively predicted. Using first‐principle calculations, we first obtained the substitution energies of alloying elements to compare their segregation preference, and then analyzed the influence of solutes at different layers on the stability and hydrogen adsorption properties of Mg(0001) surface by calculating the formation enthalpy, surface energy, vacancy formation energy, work function, Bader charge, deformation charge density, and adsorption free energy of H atom. It has been found that, on the one hand, the interior Mn solute atoms reduce the dissolution of Mg atoms and the transfer of electrons, consequently slowing down the anodic dissolution process. On another hand, the Mn, Y, and Ce elements on the surface inhibit the cathodic HER process by elevating the absolute value of hydrogen adsorption free energy, as a result of those solutes effectively controlling H adsorption behavior on Mg(0001) surface. In contrast, all five elements dissolved inside the Mg grain do not show significant effects on the H adsorption behavior.

Optimization of Mechanical and Thermoelectric Properties of SnTe-Based Semiconductors by Mn Alloying Modulated Precipitation Evolution.

Multiscale defects engineering offers a promising strategy for synergistically enhancing the thermoelectric and mechanical properties of thermoelectric semiconductors. However, the specific impact of individual defects, in particular precipitation, on mechanical properties remains ambiguous. In this work, the mechanical and thermoelectric properties of Sn1.03- xMnxTe (x = 0-0.30) semiconductors are systematically studied. Mn-alloying induces dense dislocations and Mn nano-precipitates, resulting in an enhanced compressive strength with x increased to 0.15. Quantitative calculations are performed to assess the strengthening contributions including grain boundary, solid solution, dislocation, and precipitation strengthening. Due to the dominant contribution of precipitation strengthening, the yield strength of the x = 0.10 sample is improved by ≈74.5% in comparison to the Mn-free Sn1.03Te. For x ≥ 0.15, numerous MnTe precipitates lead to a synergistic enhancement of strength-ductility. In addition, multiscale defects induced by Mn alloying can scatter phonons over a wide frequency spectrum. The peak figure of merit ZT of ≈1.3 and an ultralow lattice thermal conductivity of ≈0.35Wm-1K-1 are obtained at 873 K for x = 0.10 and x = 0.30 samples respectively. This work reveals thaprecipitation evolution optimizes the mechanical and thermoelectric properties of Sn1.03- xMnxTe semiconductors, which may hold potential implications for other thermoelectric systems.

Microstructure Evolution and Strengthening Mechanisms of Cast Al–Cu–Mn Alloy via Ti–Zr-Synergistic Micro-alloying

Microstructure Evolution and Strengthening Mechanisms of Cast Al–Cu–Mn Alloy via Ti–Zr-Synergistic Micro-alloying