Solid Solution Of Mg Research Articles

Enhanced mechanical properties of LPSOp/Mg composites using super high pressure treatment

The super high pressure (SHP) technique was employed to fabricate the magnesium matrix composites (MMCs) reinforced with long-period stacking order structure powder (LPSOp) by cubic-anvil large-volume press with six rams. The LPSOp was optimized through high energy ball milling (HEBM) with a chemical composition of Mg85Zn6Y9 (at%). The microstructure and mechanical properties of LPSOp/Mg composite was characterized by X-ray diffraction (XRD), scanning electron microscopy/transmission electron microscopy (SEM/EDS), transmission electron microscopy (TEM), microhardness and compressive tests. The microhardness of LPSOp exhibits a notable increase after HEBM, and the thermal stability of LPSOp is affirmed through elevated annealing. The SHPed LPSOp/Mg consists of Mg and LPSO phase. Upon annealing at 400 °C for 1 h, the LPSO phase precipitates from solid solution of Mg and W phase is also identified. The strength of composites by SHP treatment and subsequently annealing is significantly improved compared with the pure Mg without LPSOp, which demonstrates the maximum compression yield strength (CYS) of 250 MPa and ultimate compression strength (UCS) of 375 MPa with satisfactory ductility. The enhanced mechanical properties are attributed to the synergistic reinforcement effects of the dispersed and 3D skeletal structure of LPSOp with excellent interfacial bonding, the coexistence of nano-scale LPSO and W phase and partial solid solution strengthening.

Microstructure and properties of metal inert gas welded joints in a novel Al–Mg–Zn–Er–Zr alloy

Metal inert gas (MIG) welding of a novel Al-5.82Mg-0.61Zn-0.14Er-0.11Zr alloy was performed using ER5E61 and ER5B71 filler wires. The effect of the two filler wires on microstructures and mechanical properties of MIG welded joints was investigated. The study shows that fully penetrated joints are obtained by MIG welding process filled with ER5E61 and ER5B71 wires. Compared with ER5B71, the weld metal (WM) with ER5E61 exhibits a coarse structure and high solid solution of Mg and Mn elements. After the tensile test, the WM with ER5E61 and ER5B71 wires is composed of elongated coarse grains with a higher proportion of low angle grain boundaries (LAGBs). In addition, the lattice rotation occurring within the grains, indicating that single grain has an unevenly plastic deformation after the tensile test. The average microhardness of the WM is 83.4 HV and 82.9 HV for ER5E61 and ER5B71 wire, which is the lowest microhardness in the MIG welded joint. The average ultimate tensile strength (UTS) and elongation index (EI) of the MIG joints are 327.7 MPa and 8.5% for ER5E61 wire, and 314.3 MPa and 8.2% for ER5B71 wire, suggesting the MIG welded joint with ER5E61 wire achieves a good combination of strength and ductility. Quantitative assessments of the effects of different strengthening mechanisms on the strength reveal that dislocation strengthening and solid solute strengthening are the main factors to obtain a higher strength of welded joints with ER5E61.

Simultaneously improving mechanical properties and electrical conductivity of Al-1.9Mn alloys with different Mg and Si addition

A simultaneous achievement of high strength and toughness, as well as high conductivity in traditional Al-1.9Mn cast aluminum alloy used in the manufacture of water-cooled radiator shells has proven to be challenging. The addition of Mg and Si elements was implemented in the cast aluminum alloy for a modified treatment to solve the problem. The results showed that the inclusion of Si facilitated the transformation of the plate-like Mn-rich phase (Al6Mn) in the initial Al-1.9Mn alloy into a Chinese-script phase (Al15Mn3Si2) in the new Al-1.9Mn alloy. A higher Si content resulted in an increased volume fraction of Al15Mn3Si2 and a decreased solid solution of Mn in the matrix. Furthermore, a high content of Mg (0.9 wt%) in the Si modified Al-1.9Mn alloy resulted in a notable property reduction, not only in its elongation, but also in its electrical conductivity. It can be attributed to the formation of Mg2Si and the increased solid solution of Mg in the matrix. Through the optimization of the Mg and Si contents, new Al-1.9Mn alloys with superior mechanical properties and excellent electrical conductivity were successfully developed. With the addition of 0.45 wt% magnesium and 0.75 wt% silicon, the new Al-1.9Mn alloy increased its tensile strength to 170 MPa and yield strength to 88 MPa while maintaining 10 % elongation. At the same time, its electrical conductivity increased by 10.7 % compared to the original Al-1.9Mn alloy. The addition of magnesium and silicon elements can achieve a simultaneous enhancement of both the strength and electrical conductivity of the Al-1.9Mn alloy. This holds the potential to meet the usage requirements for cast aluminum alloys used in water-cooled radiator shells.

Solidification, α-Al morphologies, and tensile properties of low-Sc modified Al-Mg alloys

Al alloys are very attractive in engineering applications that require a combination of low density and mechanical strength, such as in aeronautical and aerospace industry devices. Therefore, the search for alloys with higher specific strength is justified from environmental and economic points of view. This work aims to study the influence of cooling rates on the phase morphology and tensile properties of ternary Al-Mg-Sc alloys, whose composition covers the spectrum of low-Sc Al-Mg-Sc alloys. The ternary Al-3, −5, and − 10 wt% Mg-0.1 wt% Sc alloys were processed by transient directional solidification. This process induces a wide range of cooling rates which causes the formation of a microstructural variety along the longitudinal cooling direction and, consequently, different tensile properties. Several characterization methods were employed, including: thermal analysis, x-ray diffraction (XRD) structural analysis, SEM-EDS, optical microscopy, CALPHAD, tensile tests, and fractography. Two major findings should be noted after fully characterizing the microstructures, the formed phases, and the tensile properties. Solidification evolution revealed that more Mg added resulted in higher solidification rates due to higher fluidity with more Mg. Furthermore, cell growth was mapped in the three alloy compositions while competing with dendrites. Solidification scaling relationships between dendritic or cellular spacing and cooling rate for all alloys were examined. Although the Al-10 wt% Mg-Sc alloy had more Mg in solid solution, the Al-5 wt% Mg-Sc alloy showed superior tensile strength due to the predominance of cells and thinner primary dendrites trunks forming its microstructure.

High-Throughput Printability Screening of AlMgSi Alloys for Powder Bed Fusion

The importance of both recycling and additive manufacturing (AM) is increasing; however, there has been a limited focus on the development of AM alloys that are compatible in terms of recyclability with the larger scrap loops of wrought 5xxx, 6xxx and cast 3xx aluminium alloys. In this work, the powder bed fusion (PBF) printability of AlMgSi alloys in the interval of 0–30 wt% Mg and 0–4 wt% Si is screened experimentally with a high-throughput method. This method produces PBF-mimicked material by PVD co-sputtering, followed by laser remelting. Strong evidence was found for AlMgSi alloys being printable within two different composition ranges: Si + Mg < 0.7 wt% or for Si + 2/3 Mg > 4 wt% when Mg < 3 wt% and Si > 3 wt%. Increasing the amount of Mg and Si influences the grain structure by introducing fine columnar grains at the melt pool boundary, although the melt pool interior was unaffected. Hardness in an as-built state increased with both Mg and Si, although Si had a neglectable effect at low levels of Mg. Both the evaporative loss of Mg and the amount of Mg in solid solution increased linearly with the amount of Mg.

Suppressing hydrogen blistering in a magnesium-rich healable laser powder bed fusion aluminum alloy analyzed by in-situ high resolution techniques

Hydrogen blistering, i.e. precipitation of supersaturated hydrogen at elevated temperatures, increases porosity during heat treatments in 4xxx series Al alloys manufactured by laser powder bed fusion (LPBF), as demonstrated by 3D X-ray nano-imaging in AlSi12. This paper proposes the design of a healable Al alloy to suppress hydrogen blistering and improve the damage management. The strategy consists of solute atoms diffusing towards nano-voids and precipitating on their surface, thereby filling the damage sites. A new healable Al alloy was thus developed and successfully manufactured by LPBF. 3D X-ray nano-imaging evidenced that the addition of Mg in 4xxx series Al alloys suppresses the hydrogen blistering. This is expectedly due to Mg in solid solution which increases the hydrogen solubility in the Al matrix and due to the healing of these hydrogen pores. Moreover, a significant healing of voids smaller than 500 nm diameter is observed. In-situ heating inside transmission electron microscopy pointed out that Al matrix diffuses inside the fractured Mg2Si particles, thereby demonstrating the healing ability of the new alloy. This has opened the doors to development of new healable Al alloys manufactured by LPBF as well as to new post-treatments to tailor mechanical properties and microstructure without hydrogen blistering.

Effect of Impurities on Spinel Precipitation Behavior in Molten Fayalite Slag

The effects of alumina (Al2O3) and magnesia (MgO) impurities on the precipitation of spinels such as magnetite (Fe3O4) due to the oxidation of fayalite (Fe2SiO4) slag in copper smelters were investigated. Molten fayalite slag was oxidized in alumina, magnesia, and quartz sample boats, and spinel precipitation behaviors were compared. The inclusion of Al2O3 and MgO as impurities promoted the precipitation and growth of spinel crystals. It was assumed that this effect was attributed to the rapid formation of hercynite at the interface between the alumina sample boat and slag, growth of spinel due to the substitution of Al and Fe(III) in hercynite, and the solid solution of Mg in spinels. However, as the experiments with quartz sample boats were conducted unavoidably with SiO2 saturated slag, the possibility of suppression of solute diffusion due to increased viscosity and decreased FeO activity in the slag cannot be ignored. Therefore, it is considered that the effects of Al2O3 and MgO on spinel precipitation must be further investigated.

Effects of Minor Gadolinium Addition and T4 Heat Treatment on Microstructure and Properties of Magnesium

Mg–Gd alloys are candidates for degradable implants combining favorable mechanical and corrosion properties. Gd has a high solid solubility in Mg and an acceptable biocompatibility. The influences of different amount of Gd additions and solid solution (T4) treatment on mechanical properties and corrosion in 0.9 wt% NaCl and cell culture medium (CCM) of magnesium are systematically investigated. The effects of Gd are clarified by microstructural characterizations as well as stress and degradation analysis. It is shown that minor Gd additions to pure Mg lead to Gd solid solution in Mg (α) and the formation of Mg5Gd intermetallic particles (IMPs), which increase the hardness, tensile, and compressive strength. The GdH2 phase is found in low‐alloyed Mg–Gd alloys. The corrosion rate (CR) is increased by the addition of more Gd due to the increased kinetics of the cathodic reaction. However, the resistance to degradation is effectively improved by T4 heat treatment due to the dissolution of IMPs. The reduced susceptibility to pitting can be achieved by a minor Gd addition and T4 heat treatment. The Mg–2Gd alloy is a potential candidate for implants due to its good combination of tailorable mechanical properties and low homogeneous in vitro degradation rate (DR).

(Digital Presentation) Micro-Electrochemical Analysis of Initiation Processes of Intergranular Corrosion of Al-Cu and Al-Cu-Mg Alloys

The intergranular corrosion of 2000 series Al alloys is related to the depletion of Cu at and around grain boundaries due to precipitation of Cu-containing intermetallic particles (IMPs) such as Al2Cu. It is also known that the intergranular corrosion resistance is improved by Mg addition. In general, IMPs play an important role in localized corrosion of Al alloys [1-3]. In this study, to clarify the role of IMPs in the initiation of the intergranular corrosion, in situ observations during micro-electrochemical measurements were performed.Al-4.5Cu and Al-4.5Cu-1.5Mg alloys were prepared as specimens. Solution treatment and artificial aging treatment were conducted. After heat-treatment, the specimen surfaces were grinded and polished down to 1 µm using a diamond paste. SEM/EDS analysis indicated that Al2Cu particles were generated in both Al-4.5Cu and Al-4.5Cu-1.5Mg alloys. Furthermore, in the case of Al-4.5Cu-1.5Mg, Al2CuMg was found to be formed in addition to Al2Cu.Immersion test was carried out in 0.1 M NaCl for 5 h, and the number and length of intergranular corrosion damages were analyzed. The results show that Mg accelerates the initiation of intergranular corrosion but prevents the growth of intergranular corrosion. For both alloys, in situ observations indicated that pitting corrosion was generated at IMP before the initiation of intergranular corrosion. Acidic solutions inside the pits are likely to cause intergranular corrosion. For the Al-4.5Cu alloy, partial dissolution of Al2Cu intermetallic particles was observed as the preceding event of pitting. Moreover, the initiation sites of the partial dissolution on Al2Cu particles were found to be Cu2FeAl7.For the Al-4.5Cu-1.5Mg alloy, pitting corrosion was found to be initiated at discolored intermetallic particles. From the results of SEM/EDS analysis of the specimen after short-time immersion tests, Al2CuMg was found to discolor more readily than Al2Cu. The increase in the number of intergranular corrosion damages with Mg addition is determined to be due to the formation of Al2CuMg particles. It is considered that the decrease in the growth rate of intergranular corrosion can be attributed to Mg in solid solution.

Theoretical and Experimental Research of Hydrogen Solid Solution in Mg and Mg-Al System.

The study of hydrogen storage properties of Mg-based thin films is of interest due to their unique composition, interface, crystallinity, and high potential for use in hydrogen-storage systems. Alloying Mg with Al leads to the destabilization of the magnesium hydride reducing the heat of reaction, increases the nucleation rate, and decreases the dehydriding temperature. The purpose of our study is to reveal the role of the aluminum atom addition in hydrogen adsorption and accumulation in the Mg-H solid solution. Ab initio calculations of aluminum and hydrogen binding energies in magnesium were carried out in the framework of density functional theory. Hydrogen distribution and accumulation in Mg and Mg-10%Al thin films were experimentally studied by the method of glow-discharge optical emission spectroscopy and using a hydrogen analyzer, respectively. It was found that a hydrogen distribution gradient is observed in the Mg-10%Al coating, with more hydrogen on the surface and less in the bulk. Moreover, the hydrogen concentration in the Mg-10%Al is lower compared to Mg. This can be explained by the lower hydrogen binding energy in the magnesium-aluminum system compared with pure magnesium.

Effect of solidification rate and Al content on solid solution in Mg–Al–Zn alloy

Mg–Al–Zn alloys with different Al content and different cooling conditions were prepared. The solid solution content of Al and Zn in the alloy was determined by electrochemical phase separation. The results show that Al has a large amount of solid solution, while Zn has a very low amount. Al can play a role in solid solution strengthening, while Zn is very small. Al has a repulsive effect on Zn and reduces the solid solubility of Zn. The higher the Al content it has, the larger the Al solid solution and the smaller the Zn solid solution we observe. The higher the solidification cooling rate is, the greater the solid solution amount of Al and Zn is.

Preparation of Fe3O4 particles with unique structures from nickel slag for enhancing microwave absorption properties

Recycling valuable metal elements from metallurgical slags and exploring their functional material applications have attracted more recent attention. In this paper, Fe3O4 particles with unique structures, solid solutions of Mg, Ni, and Co and inlays of silicates in magnetite crystals were extracted from nickel slag by molten oxidation and magnetic separation processes. The microstructure, morphology, magnetic and electromagnetic properties, and microwave absorption performance of the Fe3O4 particles were characterized. The results show that the Fe3O4 crystals oxidized at 1400 °C exhibit granular shapes with a uniform distribution in the silicate matrix, while they change into both dendritic and granular morphology at 1450 °C and finally into dendritic structures at 1500 °C. The Fe3O4 particles prepared at 1400 °C reach an optimal reflection loss value of −29.90 dB under a thickness of 3.5 mm and an effective absorbing frequency band of 3.28 GHz (5.52–8.80 GHz), indicating that their unique structure favours microwave absorption. The joint action of strong magnetic loss and the appropriate dielectric loss were supposed to sustain the absorption mechanism of the Fe3O4 particles.

Solid solution strengthening mechanism in high pressure die casting Al–Ce–Mg alloys

A series of Al-xCe (x = 2, 4, 6, 8, 10 wt%) and Al–8Ce-yMg (y = 0, 0.10, 0.25, 0.50, 0.75 wt%) alloys were prepared by high-pressure die casting. The introduced cerium element promoted the nucleation of α-Al grains. Al11Ce3 phase served as the heterogeneous nucleation substrate of α-Al due to the small lattice mismatch of 6.72%. According to the results calculated by Nelson-Riley extrapolation function, the lattice constant of α-Al increased from 4.0511 Å to 4.0540 Å with the increasing of Mg content from 0 wt% to 0.75 wt%. Due to the solid solution strengthening effect of Mg atoms, the yield strength of Al–8Ce-yMg alloys and the hardness of α-Al matrix in the Al–8Ce-yMg alloys showed a parabolically increasing tendency, from 92 MPa to 115 MPa and 0.502 GPa–0.575 GPa, respectively. The work hardening capacity of Al–8Ce-yMg alloys was improved by the solid solution of Mg with the work hardening exponent increasing from 0.21 to 0.27. The solid solution of Mg atoms reduced the stacking fault energy of Al–8Ce-yMg alloys and suppressed the dynamic recovery process of the alloys during deformation process, which promoted the formation of dislocation tangles and dislocation networks in the α-Al matrix.

Experimental investigation of phase equilibria in the Mg-rich corner of Mg-Nd-Sc system

Phase equilibria in the Mg-rich corner of Mg–Nd–Sc ternary system was studied by using the equilibrated alloys method. The partial isothermal sections at 500 °C, 530 °C, and 550 °C were constructed by analyzing the phase constitution and the chemical compositions of the present phases in 19 alloy samples. The Mg3(Mg, Nd, Sc) phase exhibited noticeable ternary solubility introduced by the solid solution of Mg and Sc in the Mg3Nd lattice. (Mg_hcp) showed a narrow homogeneity range paralleling to Mg–Sc binary boundary, whereas Mg41Nd5 showed negligible ternary solubility at all three temperatures. The three-phase equilibrium region of (Mg_hcp) + Mg41Nd5 + Mg3(Mg, Nd, Sc) dominated the Mg-rich corner and was surrounded by three two-phase equilibrium regions constituted by any two of above three phases. The primary crystals and the solidification pathways of alloys in the Mg-rich corner were analyzed via the as-cast microstructure. The matrix phases of (MgSc_bcc) and/or (Mg_hcp) together with the precipitations of Mg3(Mg, Nd, Sc) and other ordering structures could provide additional space to optimize microstructure and properties of Sc-alloyed Mg–Nd alloys.

Ultrafine-grained Al-Mg-Zr alloy processed by shear-assisted extrusion with high thermal stability

Shear-assisted processing and extrusion (ShAPE) is used to consolidate Al-4.2Mg-1.6Zr-0.25Si-0.1Fe (wt.%) powders. The extruded alloy exhibits: (i) near-zero porosity; (ii) an attractive combination of tensile yield strength (~220 MPa), ultimate strength (330 MPa) and elongation (>20%); and (iii) excellent thermal stability at 400 °C. The ultra-fine grain size in the gas-atomized powders – created and stabilized by primary L12-Al3Zr submicron precipitates - is maintained after consolidation and subsequent exposure at 400 °C, contributing twice as much to strength as Mg in solid-solution. Electron microscopy reveals the microstructure of the L12-Al3Zr precipitates, and other precipitates (Mg2Si and Al3Fe) and dispersoids (oxides).

Aging- and creep-resistance of a cast hypoeutectic Al-6.9Ce-9.3Mg (wt.%) alloy

A ternary Al-6.9Ce-9.3Mg (wt.%) hypoeutectic alloy, consisting of equal amounts of α-Al(Mg) solid-solution regions and Al(Mg)-Al11Ce3 eutectic colonies, is investigated in terms of its aging and creep resistance. The eutectic regions exhibit a microhardness of 1230 MPa, which is thrice the value of Al-Al11Ce3 eutectic regions in a binary Al-12.5Ce (wt.%) near-eutectic alloy, demonstrating that Mg in solid-solution enhances the strengthening provided by the micron-scale highly-branched Al11Ce3 phase. X-ray diffraction measurements during ambient-temperature tensile testing reveal that load is being transferred from the Al(Mg) matrix to the Al11Ce3 phase, confirming that the fine eutectic microstructure displays composite strengthening in addition to the expected precipitation- and solid-solution strengthening. The hardness remains effectively unchanged after aging at 450 °C for up to 8 weeks, indicating excellent coarsening resistance of the Al11Ce3 phase. The ternary alloy exhibits creep resistance at 300 °C slightly inferior to the near-fully eutectic binary Al-12.5Ce (wt.%) alloy, consistent with the presence of large regions of fast-creeping primary Al(Mg) solid-solution matrix between the strong Al(Mg)-Al11Ce3 eutectic colonies in the hypoeutectic ternary alloy.

Conventional and cooling assisted friction stir welding of AA6061 and AZ31B alloys

Conventional and cooling assisted friction stir welded Al–Mg joints were investigated by visual inspection, optical macro plus microscopy, scanning electron micrographs, energy dispersive X-ray spectroscopy, X-ray diffractions, tensile testing and micro hardness indentation. The nugget zone is characterized by onion rings composed of different phases such as Mg in an Al matrix, Al in an Mg matrix as well as intermetallic compounds, Al3Mg2 and Al12Mg17. A diffusion layer was detected on the Al side of the joint between the nugget and thermo-mechanically affected zones identifying a solid solution of Mg in Al. No diffusion layer was observed on the Mg side. The tensile strength of the dissimilar joints is enhanced by cooling assisted welding process due to the reduction in the amount of intermetallic compounds inside the weld bead. Congruently, higher hardness peaks are reported in the nugget zone of conventional FSW joint with respect to the CFSW joint.

Preparation of a single-phase Mg–6Zn alloy via ECAP-stimulated solution treatment

Abstract The solution of the intermetallic phase and the homogenization of composition are important for Mg alloy biomaterials. A single-phase Mg–6Zn alloy with the average grain size of about 20 µm was prepared by ECAP processed for six passes at 320 °C. It indicated that the ECAP could significantly promote the process of solid solution in Mg–Zn alloy. The results showed that complete dissolution of the intermetallic phase improved the corrosion resistance of Mg–6Zn alloy in 0.9% NaCl solution by turning the corrosion behavior into uniform corrosion and increased the hardness in combination with its smaller grain size.

Ab-initio based search for late blooming phase compositions in iron alloys

We present a systematic analysis, based on ab initio calculations, of concentrated solute arrangements and precipitate phases in Fe-based alloys. The input data for our analysis are the calculated formation and interaction energies of point defects in the iron matrix, as well as the energies of ordered compounds that represent end-members in the 4-sublattice compound energy model of a multicomponent solid solution of Mg, Al, Si, P, S, Mn, Ni, and Cu elements and also vacancies in bcc Fe. The list of compounds also includes crystal structures obtained by geometric relaxation of the end-member compounds that in the cubic structure show weak mechanical instabilities (negative elastic constants) and also the G-phase Mn6(Ni,Fe)16(Si,P)7 having a complex cubic structure. A database of calculated thermodynamic properties (crystal structure, molar volume, enthalpy of formation, and elastic constants) of the most stable late-blooming-phase candidates is thus obtained. The results of this ab initio based theoretical analysis compare well with the recent experimental observations and predictions of thermodynamic calculations employing Calphad methodology.

Effect of pre-deformation cooling rate on the age-hardening response of ultrafine grained AA6063

In this article, effect of pre-deformation cooling rate after solution heat treatment on the evolution of microstructure and tensile properties of AA6063 aluminum alloy is investigated. For this purpose, samples of AA6063 are solution heat treated at 550°C for 6h. Followed by this treatment, some samples are furnace cooled (FC), some air cooled (AC) and the rest water quenched (WQ). After 2, 6 and 10 passes equal channel angular pressing (ECAP), significantly finer nanostructure was observed in the WQ samples. This was attributed to the effect of higher concentration of Mg in solid solution. In addition, the WQ samples showed higher initial tensile strength being attributed to the more enriched solid solution and more significant strengthening during severe plastic deformation which was attributed to higher dislocation density generated during deformation. In addition, it was found that the WQ samples in un-deformed and deformed conditions show a more significant response to aging in terms of strengthening. In fact, age hardening was observed for both AC and WQ samples in un-deformed condition and after 2 passes ECAP. Age hardening was as well observed in the WQ samples which were deformed for 6 and 10 passes. However, age softening was observed in the AC samples when the number of ECAP passes was increased to 6 and 10.