Mg-Mn Alloy Research Articles

Anelasticity of Mg-Mn and Mg-Gd alloys

Anelastic relaxation at sub-resonance frequency (from 0.01 to 100 Hz), temperature (from 0 to 450°C) and amplitude (ε0 from 5×10−5 to 10−3) range in binary Mg-0.8 wt%Mn (0.36 at%) and Mg-2 wt%Gd (0.31 at%) in as-extruded and annealed states was experimentally studied and analyzed, to characterize acting thermally activated and structural relaxation effects. Activation parameters for thermally activated anelastic effect and structural studies suggest that it is the grain boundary relaxation with dominating large angle boundaries, while the high-temperature background is mainly controlled by dislocations sliding. Pseudo peak at ∼290 °C (Mg-Mn) and ∼410 °C (Mg-Gd) is the result of the recrystallization process in the as-extruded samples, which indicates that the addition of Gd restricts the recrystallization of Mg compared with the addition of Mn. Analysis of amplitude dependencies of internal friction in the frames of Granato and Lücke approach suggests higher density of movable dislocations in as-extruded Mg-Mn alloy.

Simultaneous improvement of strength and damping capacity of Mg-Mn alloy by tailoring bimodal grain structure

A high damping capacity and a high strength is paradox in magnesium alloys needed to be addressed immediately. In this work, adding Mn into Mg matrix, and combined with low extruded temperature, alloys with bimodal grain structure that is made up of fine recrystallized grains and coarse unrecrystallized grains were obtained. The fine recrystallized grains are conducive to the activation of grain boundary slip, leading to alloy exhibits good plasticity. A large number of parallel dislocations exist in unrecrystallized grains, due to the dislocation recovery and dynamic recrystallization rate are evidently suppressed at low extruded temperature and the Mn precipitates impede the movement of dislocations, which cause a high work hardening rate in bimodal grain structure. This phenomenon not only brings about a high yield strength, but also improves damping capacity of Mg-Mn alloys at room temperature. Because the unrecrystallized grains initial to recrystallize at high temperature, the P2 internal friction peak rises and moves toward the low temperature. When the extruded temperature is 220 °C, the comprehensive properties of the Mg-1Mn alloy outperform the high-damping Mg-0.6Zr alloy, and the yield strength, plasticity and damping capacity at ε = 1 × 10−3 are 169 MPa, 32.5% and 0.042, respectively. Tailoring bimodal grain structure is an effective strategy to ensure strength, plasticity and damping capacity of the Mg alloy at the same time.

Effects of Induction Quenching on the Recrystallization Behavior of a Twin-Structured Mg-Mn Alloy

Effects of Induction Quenching on the Recrystallization Behavior of a Twin-Structured Mg-Mn Alloy

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

Effects of Ca and Nd addition on plastic instability in extruded Mg-Mn alloy deformed under various conditions

Superior ductility Mg-Mn extrusion alloys at room temperature obtained by controlling Mn content

The effect of Mn content (0.4, 0.8, 1.2 wt. %) on microstructure and mechanical properties of as-extruded dilute binary Mg-Mn alloys was studied. With the increase of Mn content from 0.4 wt. % to 1.2 wt. %, the volume fraction of dynamically recrystallized (DRXed) grains decreases from 89% to 40%, while the DRXed grain size decreases from 3.2 μm to 1.9 μm. The segregation of Mn atoms and nano α-Mn dynamical precipitates are observed at the grain boundaries of the extruded Mg-0.8Mn alloys and the amount of dynamically precipitates is increased with increasing Mn content. Tensile tests show that the Mn content significantly affects mechanical properties at room temperature (RT). The Mg-0.8 wt. % Mn alloy shows the excellent ductility of 81 % at room temperature in a strain rate of 1 · 10−3 s−1, the ductility decreases if the Mn content is lower or higher than 0.8 wt. %. The yield strength (YS) and ultimate tensile strength (UTS) increase with increasing Mn content. The large value of strain rate sensitivity exponent (m-value) and small activation volume (V*) of the as-extruded Mg-0.8Mn alloy suggest that grain boundary sliding (GBS) plays an important role in tensile plastic deformation. High volume fraction of the un-DRXed region leads to the reduced contribution of GBS to plastic deformation, decreases ductility at RT. The Atomic force microscopy (AFM) analysis indicates that the contribution of GBS to the total plastic deformation is 2.7 %, 55.1 % and 12.8 % for Mg-0.4Mn, Mg-0.8Mn and Mg-1.2Mn alloys, respectively.

Effect of Mn content on the microstructure and mechanical properties of as-extruded Zn-0.2Mg-Mn (wt%) alloys

Zn-0.2 Mg-(0.1–0.8)Mn (wt%) alloys were prepared by indirect extrusion at 200 °C. The granular and strip-shaped Mg2Zn11 and MnZn13 distributed along grain boundaries. With the increase of Mn addition, the amount of MnZn13 increased, and the size was in the range from tens of nanometers to tens of microns. Equiaxed grains with average sizes between 2 μm and 5 μm formed during the extrusion. Non-basal texture with 〈0001〉 tilted away from ED (extrusion direction) about 65° ∼ 85° was the major texture component, and the basal texture was the minor texture component. The refined grains and MnZn13 contributed to the linearly increase of tensile yield strength from 247 MPa for Zn-0.2 Mg-0.1Mn alloy to 348 MPa for Zn-0.2 Mg-0.8Mn alloy. The evolution of non-basal texture contributed to the elongation increasing from 23% for Zn-0.2 Mg-0.1Mn alloy to 30% for Zn-0.2 Mg-0.5Mn alloy, but micron-scaled MnZn13 contributed to the elongation decreasing to 21% for Zn-0.2 Mg-0.8Mn alloy. Thus, with Mn addition between 0.1 wt% and 0.5 wt%, both the yield strength and elongation improved simultaneously.

On the effect of trace Si on accelerating the corrosion of Mg-Mn alloys

The influence of trace Si on the microstructure and corrosion behavior of as-cast Mg-0.4Mn-xSi (x = 0, 0.02–0.3) alloys is studied. With the presence of trace Si in Mg-0.4Mn alloy, MnSi, Mn5Si3 and Mn3Si phases form. The MnxSiy phase significantly increases the corrosion rate of Mg-Mn-Si alloys due to strong micro-galvanic corrosion between MnxSiy phases and Mg matrix. During corrosion, the rod-like MnxSiy precipitates can lead to stronger cathodic activation behavior than the block-like MnxSiy precipitates since the rod-like MnxSiy phase is more difficult to detach from Mg matrix, which results in the more exposed area of cathodic sites. Data AvailabilityThe raw/processed data required to reproduce these findings cannot be shared at this time, because the data also forms part of an ongoing study.

On the Effect of Traces Si on Accelerating the Corrosion of Mg-Mn Alloys

On the Effect of Traces Si on Accelerating the Corrosion of Mg-Mn Alloys

Mechanism of Mn on inhibiting Fe-caused magnesium corrosion

In the present study, to understand the mechanism of Mn on inhibiting Fe-caused Mg corrosion, the corrosion behaviour of commercial pure Mg and Mg-6Mn alloy in 0.6 M NaCl solution is investigated. It is found that in Mg-6Mn alloy, Fe impurity is incorporated into Mn to form Mn (Fe) phase with Fe as solid solute. The initial galvanic corrosion cannot be reduced through converting Fe-rich phase to Mn (Fe) phase, since Mn (Fe) phase also has relatively strong cathodic activity and has much larger volume fraction than Fe-rich phase. However, the cathodic activation behaviour of pure Mg is inhibited. The cathodic activity even decreases for Mg-Mn alloy with increased exposure time, due to the reduced cathodic HER at the Mn (Fe) particles. Mn can be oxidized at the OCP of Mg-6Mn alloy, resulting in relatively dense Mn-rich corrosion film on particle surface, which separates the particle from the electrolyte and, consequently, inhibits HER.

Evaluation of Bioabsorbable Mg-Mn Alloy with Anodic Oxidation Treatment.

Magnesium alloys as biodegradable materials have been examined that may replace bone screws and plates in recent studies. But the velocity control of magnesium alloy is very difficult. Until now, the magnesium alloys degrade very fast, thus it couldn't maintain the function in clinical field. Thus the purpose of this study is to evaluate the degradability of anodized magnesium alloy for control the velocity. For this experiment, a Mg-xMn (x = 0, 0.5, 1 wt%) binary alloy was cast in argon gas (99.99%) atmosphere. The specimens of the surface treatment group were anodized for 15 minutes at a voltage of 120 V at room temperature using calcium gluconate, sodium hexametaphosphate, and sodium hydroxide electrolyte. For the mechanical test, SEM, roughness test, hardness test were examined. The degradation test was conducted to measure the hydrogen gas formation volume. For biologic test, cell viability were tested. After anodic oxidation treatment, the surface showed the crater formation, the size of craters were about 200~300 nm. Among nonanodized group, the Mg-0.5Mn showed the highest Vickers hardness and cell viability. However for biodegradability test, Mg-1Mn showed the lowest the hydrogen gas formation. For anodic oxidation treatment, anodic oxidation treatment makes rougher surface, higher hardness, good cell response and lower degradation rate. Overall, anodized Mg-1Mn showed the possibility for clinical application in bone screw and bone plate.

Microstructure and mechanical properties of Mg-Mn alloys by friction stir welding

Mg-Mn alloy is welded by friction stir welding technology to manufacture liquid-cooled components in radar equipment. The effect of welding processes on microstructure and mechanical properties of Mg-Mn alloy was analyzed. The results show that the rotation speed has little effect on the microstructure structure when it is above 1200 rpm. The strength is increased by the increase of rotation speed from 900 rpm to 1500 rpm. The highest ultimate tensile strength is about 175 MPa. Most of the welding joints show brittle fracture during tensile test.

Compressive and Corrosion Properties of Lotus-Type Porous Mg-Mn Alloys Fabricated by Unidirectional Solidification

Lotus-type porous Mg-Mn alloys were fabricated by solid-gas eutectic unidirectional solidification (the Gasar process) by controlling and optimizing the process parameters. The microstructures, compressive properties and corrosion properties in a simulated body fluid solution were investigated. Porous pure Mg was prepared with a preferentially oriented (11$$ \bar{2} $$2) plane, whereas the Mg-2 wt pct Mn alloy showed a preferentially oriented (10$$ \bar{1} $$3) plane. Mn addition refined the grains, improved the Mn precipitates, activated the {10$$ \bar{1} $$2} twin at the end of the pores and increased the compressive strength from 64 MPa for pure Mg to 74 MPa for 1 wt pctMn and 80 MPa for 2 wt pct Mn. Electrochemical tests showed that 2 wt pct Mn addition could decrease the corrosion current from 1.84 × 10−3 to 4.22 × 10−4 A cm−2. Immersion tests suggest that 2 wt pct Mn addition reduced the sample mass loss, which indicated a better corrosion performance, and exhibited a smaller decrease in compressive strength compared with that of the porous pure Mg. This work shows that the Gasar technique can be a promising fabrication method to prepare lotus-type porous Mg-Mn alloys which are more attractive for application in degradable biomaterials engineering.

G–D Map Method for Analyzing Effects of Elements on Size Control of In Situ Formed Mg2Si in Mg Melts

An approach for selecting alloying elements to control the size of an in situ formed phase is proposed based on a G–D map, which is derived from basic thermodynamic and kinetic principles. The G–D map is divided into four zones. Elements in Zone III are potential refiners whereas those in Zone II should be avoided in processing. When applied to the Mg2Si/Mg system, we find that Sr, P, Sb and Sn refine Mg2Si by increasing the nucleation rate and inhibiting the growth rate. Conversely, Ti, Mn, Zr and V contribute to coarse-shaped Mg2Si by postponing nucleation. The content of alloying elements should be matched with the Si content, and the required amount can be pre-estimated from the G–D map. Mg2Si formed in Mg-Al and Mg-Zn alloy is smaller than that in Mg-Si and Mg-Mn alloy, because Al and Zn suppress the diffusion of Si, particularly at high Si contents. The predictions of this approach are consistent with experimental observations. Hence, the G–D map can provide useful guidance for quantitative phase refinement design.

Vpliv deformacije med hladnim valjanjem in temperaturo žarenja na rast zrn zlitine Al-4%Mg-Mn

Vpliv deformacije med hladnim valjanjem in temperaturo žarenja na rast zrn zlitine Al-4%Mg-Mn

Change in dominant deformation mechanism of Mg alloy via grain boundary control

The impact of grain boundary structures on mechanical properties and its deformation behavior was investigated on a wrought processed Mg-0.3 at%Mn binary alloy. The Mg-Mn alloy, which had an average grain size of 1.2 µm and a high density of low-angle grain boundaries, was fabricated via caliber rolling. This alloy exhibited yield strength of more than 300 MPa and had low strain rate dependence in both tension and compression tests at room temperature. The major deformation mechanism was dislocation slip for tension and deformation twinning for compression, respectively, as is well established for conventional wrought processed magnesium alloys. However, an extruded Mg-Mn alloy having an average grain size of 1.8 µm is reported to exhibit a good elongation-to-failure and large strain rate dependence. While the same cast billet was used, the result obtained from caliber rolled alloy is inconsistent with that from the extruded alloy. This is due to the difference in grain boundary structures, i.e., the existence of low-angle grain boundaries in the caliber rolled alloy. Low-angle grain boundaries, which do not have free volume, are difficult for segregation of alloying elements. The mechanical properties and deformation mechanism can be clearly controlled by grain boundary structures through wrought process.

Effect of alloying elements on room temperature stretch formability in Mg alloys

The effect of alloying elements on room temperature stretch formability and its deformation mechanism was investigated using pure magnesium and its binary alloys containing an element of Ag, Al, Ca, Li, Mn, Pb, Sn, Y and Zn, respectively. All of the alloys as well as pure magnesium were produced by extrusion and had a similar average grain size. The alloying elements clearly affected stretch formability as measured by Erichsen testing. The addition of manganese or yttrium element played a role in improving formability; on the other hand, most of the alloying elements did not improve formability, as exhibited by their limited dome height values, which were similar to or lower than that of pure magnesium. This resulted from their differences in deformation mode. An intragranular misorientation axis analysis using electron back-scatter diffraction results revealed that the Mg-Y alloy had a high fraction of grains amenable to non-basal dislocation slips, which is a helpful deformation mode for improving formability. In contrast, pure magnesium and the Mg-Mn alloy, which had a high limited dome height, did not have a high fraction of such grains. Grain boundary sliding compensated for the lack of <c>-component, such as activating non-basal dislocation slips.

Room temperature grain boundary sliding behavior of fine-grained Mg-Mn alloys

The impact of chemical composition, i.e., the manganese element, on room-temperature mechanical properties and its deformation behavior was examined using a series of Mg-Xat% (X = 0.05, 0.1, 0.3, 0.45, 0.6 and 0.8) Mn binary alloys. The average grain size of these alloys was controlled to be 2–3 µm by extrusion temperature. The manganese segregates at grain boundaries, and the fraction of dispersed particles increases with increasing manganese addition. The results obtained from tensile tests reveal that the chemical composition is unlikely to affect the strain rate dependence, which is the major deformation mechanism. The strain rate sensitivity (m-value) is calculated to be ~ 0.1 and ~ 0.2–0.3 in the quasi-static and in the low strain rate regimes, respectively, for all the alloys. This indicates that the contribution of grain boundary sliding on deformation increases at lower strain rates. On the other hand, the elongation-to-failure in tension is clearly influenced by manganese concentration. The chemical composition of 0.3 at% manganese brings about a good ductility of nearly 95% and 145% in the strain rates of 1 × 10−3 and 1 × 10−5 /s, respectively; however, a further manganese addition leads to a decrease in the elongation-to-failure. Deformed microstructural observations show that cavities nucleate at the interface between matrix and particles without any deformation twin formation, and they are the origin of fracture. A high amount of manganese causes formation of the dispersed particles; as a result, it is ineffective to improve the ductility.

Synergistic effects of composition and heat treatment on microstructure and properties of vacuum die cast Al-Si-Mg-Mn alloys

The purpose of this study was to prepare high-quality Al-Si-Mg-Mn alloy with a good combination of strength and ductility employing the vacuum-assisted high-pressure die cast process. An orthogonal study of heat treatments was conducted to design an optimized T6 heat treatment process for both AI-10%Si-0.3%Mg-Mn and AI-11%Si-0.6%Mg-Mn alloys. The results demonstrate that no obvious blisters and warpage were observed in these two alloys with solid solution treatment. After the optimal T6 heat treatment of 530°Cx3h + 165°Cx6h, AI-11%Si-0.6%Mg-Mn alloy has better mechanical properties, of which tensile strength, yield strength and elongation reached 377.3 MPa, 307.8 MPa and 9%, respectively. The improvement of mechanical properties can be attributed to the high density of needle-like β(Mg5Si6) precipitation after aging treatment and the fine and spherical eutectic Si particles uniformly distributed in the α-AI matrix.

Effect of Post-annealing and Strong Deformation Process on the Mechanical and Corrosion Properties of a Mg-Mn alloy for Biomedical Application

In this study, the influence of an annealing treatment and strong deformation process on the mechanical and corrosion properties of a Mg alloy for biomedical applications was investigated. The mechanical and corrosion properties in a Mg-1.6wt% Mn (M1) alloy as functions of the twin density and grain refinement were compared. The value of the corrosion current (Icorr) depended linearly on the area fraction of the twin in a coarse and twinned microstructure. The grain refinement via high-ratio differential speed rolling (HRDSR) processing was rather effective for obtaining remarkable increase in hardness and an improvement in the corrosion characteristic compared to a reduction of the twin density in as cast M1 alloy.

Great room temperature stretch formability of fine-grained Mg-Mn alloy

The effect of grain size and forming speed on room temperature formability was examined using Mg-0.3at%Mn binary alloy with different average grain sizes (2.5 and 18.5µm). Erichsen tests revealed that the limited dome height (LDH) was clearly influenced by these factors. LDHs increased with finer grain sizes and/or lower forming speeds. The highest LDH was obtained to be 8.2, which is superior to that in the conventional aluminum (A5083) alloy (LDH=4.3), in the present Erichsen testing conditions. The results obtained from the tensile tests under strain rate ranges similar to those of the Erichsen tests showed high strain rate sensitivity (m-value, where m=0.06–0.13 for the meso-grained alloy and 0.11–0.22 for the fine-grained alloy, respectively), irrespective of the extrusion direction vs. the tensile direction. Deformed microstructural observations after tensile and Erichsen tests revealed the existence of deformation twinning; however, the area/volume fraction of its microstructural feature was too small to affect the deformation mechanism. Instead of the deformation twinning-related fracture, cavitation due to grain boundary sliding was the origin of fracture during the present Erichsen tests. The further activation of grain boundary sliding was an effective method to improve the room temperature formability of magnesium alloys.