Effect Of Mg Content Research Articles

High temperature tensile properties of centrifugally cast in-situ Al-Mg2Si functionally graded composites for automotive cylinder block liners

The effect of Mg content (2.5 and 7.5 wt%) on the development of centrifugally cast in-situ A356-Mg2Si composite functionally graded material (FGM) has been investigated. The secondary dendrite arm spacing (SDAS) has the effect on size and volume% of Mg2Si particles. FGMs are characterized by optical and scanning electron microscopy, X-ray diffraction analysis, measurement of hardness and room and elevated temperature tensile properties (UTS). The microstructural features are correlated with room temperature and high temperature tensile properties at 150 °C and 300 °C. Since the population of Mg2Si particles are maximum at inner zones, the tensile strengths at these zones are maximum among the three zones. The room temperature tensile strength of FGM with 7.5 wt% Mg shows maximum value however it decreases at higher temperatures. The peak UTS of both FG composites in all three zones are attained at around 150 °C. Maximum peak UTS of 178 MPa is obtained with A356–2.5%Mg at this temperature. As the test temperature is increased, the fracture mode is changed from mixed mode to ductile mode. Particle cracking and decohesion of particles from the softer matrix are responsible for these two modes respectively.

Effect of Mg Addition on the Foaming Behaviour of AlSi7 Based Alloy Prepared by Powder Metallurgy Method

Abstract The effects of high Mg addition (2 wt%, 4 wt% and 6 wt%) on the foaming behavior of AlSi7 based alloys were researched. The results show that Mg can react with Al2O3 phase and Si element, and then the produced MgAl2O4 phase which has a good wettability with Al melt and Mg2Si phase are formed. Both of them can uniformly distribute in the alloy and induce a particle based stabilization mechanism, which can significantly reduce the negative impact of gravity drainage and capillarity. High Mg content can also change the pores formation in early stage, as a result, the pores grow and nucleate in a pool of liquid in a fairly spherical way. Therefore, a high expansion rate and good pore structures can be obtained. The disadvantage of high Mg content is the decrease of surface tension which makes pores easy to bust. A good trade-off between the beneficial and adverse effects of Mg content is 4 wt% for AlSi7 based alloy

Effect of Mg content on the thermal stability and mechanical behaviour of PLLA/Mg composites processed by hot extrusion

In the field of bioabsorbable composites for biomedical applications, extrusion has been employed as a method to prepare homogeneous blends of polymeric matrices with bioactive ceramic fillers. In this work, the suitability of processing poly-l-lactic acid/Magnesium (PLLA/Mg) composites by hot extrusion has been assessed by a systematic characterization of PLLA/Mg composites containing different amounts of Mg particles up to 7wt%. The results show that extrusion causes a reduction of almost 20% in the viscosity average molecular weight of PLLA, which further decreases with increasing Mg content. Extrusion gave always rise to a homogeneous distribution of Mg particles within the PLLA matrix. This composite processing was not compromised by the degradation of the polymeric matrix because the processing temperature was always below the onset degradation temperature. In the processing conditions employed in the present work, degradation of the composite slightly increases as more Mg is added up to 5wt%, but is very high at 7wt%. This was also evident from the mechanical behaviour, so that Mg particles improved the stiffness and compression strength of neat PLLA until 5wt% of Mg content, which dropped drastically when the material had 7wt% of Mg. The filler strengthening factor decreases with the increment in Mg content. In order to obtain an optimised contribution of Mg particles, a balance between thermal degradation and mechanical resistance of PLLA must be achieved.

Direct dissimilar joining of aluminium alloys and polyamide 6 by friction lap joining

Direct dissimilar joining of various Al alloy (A1050, A3004, A5052 and A5083) plates and a polyamide 6 plate was performed using friction lap joining (FLJ) with the Al alloy plate as a top and the polyamide 6 plate as a bottom. The effect of Mg content in Al alloys on the joining strength was investigated. TEM analysis made clear that the polyamide 6 and Al alloys were joined via oxide layer consisting of Al2O3 and MgO. The results of XPS analysis indicated that MgO was formed by the heating during FLJ, and the quantity of MgO was increased with increasing Mg content in Al alloys. The tensile shear strengths of A3004, A5052 and A5083 joints were saturated to about 2 kN because of the tensile fracture at the polyamide 6 plate outside the tool-passed zone, which were higher than that of the A1050 joint fractured at the joint interface. The peel strength of the joint was increased with increasing Mg content in Al alloys, and the fracture occurred both at the joint interface and at the polyamide 6 plate on the joint area. The fraction of polyamide 6 plate fracture was also increased with increasing Mg content in Al alloys.

The Effect of Mg Content on Intergranular Corrosion of Al-Mg-Mn Alloys after Annealing

The Intergranular Corrosion (IGC) properties of Al-xMg-0.6Mn (x=3, 4, 5, 6 and 7) wt.% alloys were studied using the mass loss test. The mass loss test results of the alloys annealed at 100-300 ̊C for 1h indicated that the alloys with 3 and 4% Mg were resistant to IGC. While the mass loss values of the 6 and 7% Mg alloys were increased to IGC severe sensitive region, and then abruptly fallen to the IGC-resistant region with the increasing temperature. The mass loss-temperature curve of 5% Mg alloy was actually located between them. After isothermal annealing, the mass loss results indicated a stabilization temperature of the alloys with 5, 6 and 7% Mg appeared at the temperature beyond 220 ̊C, 250 ̊C and 270 ̊C, respectively. Furthermore, below the stabilization temperature 10-20 ̊C, it was observed a type of “special mass loss curve ” in so-called transition region that was showed a quick mass loss increasing to sensitization region and then a decrease to the IGC resistant region with a prolonged annealing time. To explore the “special curve” in transition region, the TEM observation of Al-7Mg alloy annealing at 250 ̊C was conducted, which indicated the sensitization resulted from the continuity of β phase, while the descending to the IGC might to be attributed to the spheroidization of β phase.

Effects of Mg content on pore structure and electrochemical corrosion behaviors of porous Al-Mg alloys

Porous Al-Mg alloys with different nominal compositions were successfully fabricated via elemental powder reactive synthesis, and the phase composition, pore structure, and corrosion resistance were characterized with X-ray diffractometer, scanning electron microscope and electrochemical analyzer. The volume expansion ratio, open porosity and corrosion resistance in 3.5% (mass fraction) NaCl aqueous solution of the alloys increase at first and then decrease with the increase of Mg content. The maxima of volume expansion ratio and open porosity are 18.3% and 28.1% for the porous Al-56%Mg (mass fraction) alloy, while there is the best corrosion resistance for the porous Al-37.5% Mg (mass fraction) alloy. The pore formation mechanism can be explained by Kirkendall effect, and the corrosion resistance can be mainly affected by the phase composition for the porous Al-Mg alloys. They would be of the potential application for filtration in the chloride environment.

Effect of cooling rate and Mg addition on the structural evaluation of rapidly solidified Al-20wt%Cu-12wt%Fe alloy

The present work examines the effect of Mg contents and cooling rate on the morphology and mechanical properties of Al20Cu12Fe quasicrystalline alloy. The microstructure of the alloys was analyzed by scanning electron microscopy and the phase composition was identified by X-ray diffractometry. The melting characteristics were studied by differential thermal analysis under an Ar atmosphere. The mechanical features of the melt-spun and conventionally solidified alloys were tested by tensile-strength test and Vickers micro-hardness test. It was found that the final microstructure of the Al20Cu12Fe samples mainly depends on the cooling rate and Mg contents, which suggests that different cooling rates and Mg contents produce different microstructures and properties. The average grain sizes of the melt spun samples were about 100–300nm at 35m/s. The nanosize, dispersed, different shaped quasicrystal particles possessed a remarkable effect to the mechanical characteristics of the rapidly solidified ribbons. The microhardness values of the melt spun samples were approximately 18% higher than those of the conventionally counterparts.

Effects of magnesium and cooling rate on titanium phase transformation for production of TiO2

X-ray diffraction (XRD) and crystal structure analysis were used to study the effects of Mg content and cooling rate on the titanium phase transformation of three types of titanium slag. The results indicate that in the rapid cooling process, the titanium phase is anosovite, whose chemical formula is MgnTi3–nO5 (0<n<1). In the slow cooling process, when the Mg content is high, anosovite transforms into karrooite MgTi2O5 structure; when the Mg content is low, karrooite MgTi2O5 and rutile TiO2 both exist. The stability of karrooite MgTi2O5 is better than that of anosovite MgnTi3–nO5. Slow cooling contributes to the doping of Mg into the anosovite crystal and stabilises the anosovite crystal structure.

Improved photovoltaic effect in CuO/Zn1−xMgxO heterojunction solar cell by pulsed laser deposition

In this study, the effect of Mg content in CuO/Zn1−xMgxO heterojunction thin films have been systematically investigated. This heterojunction was fabricated by Pulsed laser deposition on indium tin oxide-covered glass substrate for solar application. The structural and optical properties of this heterostructure were analyzed by x-ray diffraction and ultraviolet-visible spectroscopy. The optical measurements reveal a shift in absorption edge and increase in transmittance with Mg content. Tuning of the band gap has been obtained from 3.28 to 3.5eV corresponding to Mg content x varies from 0 to 0.10. An enhancement of open circuit voltage (Voc) from 178 to 326mV and short circuit current density (Jsc) from 2.06 to 2.13mA/cm2 with the increase of Mg content was observed. It may be due to the conduction band of this heterojunction (CuO/Zn1−xMgxO) moving closer to vacuum level with increasing x. The maximum solar power conversion efficiency (ɳ=0.253%) was found with x=0.10. Hence, this improved solar power conversion efficiency in CuO/Zn1−xMgxO heterojunction makes this promising candidate for photovoltaic application.

Microstructural evolution and mechanical properties of thixoformed A319 alloys containing variable amounts of magnesium

The effects of Mg content on the microstructure and tensile properties of thixoformed A319 alloys were studied. The samples were thixoformed at 50% liquid content and some of the thixoformed samples were subjected to the T6 heat treatment. The samples were then examined by optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray (EDX) spectroscopy and X-ray diffraction (XRD) analysis as well as tensile tests. The results showed that magnesium was able to refine the eutectic silicon in the samples. It was also observed that a compact Al9FeMg3Si5 phase was formed when the magnesium content was 1.0% and 1.5%. The results also revealed that as the magnesium content in the alloy increases, the tensile strengths of the thixoformed alloys also increase. The ultimate tensile strength, yield strength and elongation to fracture of the thixoformed A319 heat treated alloy were 298 MPa, 201 MPa and 4.5%, respectively, whereas the values of the thixoformed heat treated alloy with 1.5% Mg content were 325 MPa, 251 MPa and 1.4%, respectively. Thixoformed A319 alloy showed a dimple fracture behaviour, while thixoformed A319 alloys with 1.5% Mg showed a mixed mode fracture behaviour, where dimple and cleavage ruptures were seen on the fracture surface of the samples.

Effect of Mg content on the hot ductility of wrought Fe-36Ni alloy with Ti addition

Austenitic alloys are prone to cracking as a result of their poor hot ductility during continuous casting and hot working processes. In this study, hot tensile tests were performed to study the effect of Mg content on the hot ductility of Fe-36Ni alloy over the temperature range of 700–1200°C at a strain rate of 10−2s−1. The effects of the Mg content on the particle (i.e., inclusion and precipitate) characteristics and the growth of austenite grains were also investigated. The results indicated that the number density of the particles increased significantly while the mean diameter decreased with increasing Mg content in the experimental alloys. The growth of austenite grains was effectively inhibited by pinning particles in the Mg-treated alloys during solution treatment. Both the pinning particle and austenite grain size markedly affected the hot ductility behaviors of the alloys. The hot ductility curves of the studied alloys had different trends in the intermediate temperature range and were controlled by the competition between dynamic recrystallization (DRX) and grain boundary sliding (GBS). Compared with the alloys without Mg addition, an appropriate number of pinning particles in the alloy with 49ppm Mg addition resulted in a smaller grain size during the solution treatment, which significantly improved the hot ductility by accelerating DRX during the subsequent hot tensile process. However, an excessive number of pinning particles at grain boundaries in the alloy with 60ppm Mg addition inhibited DRX and promoted GBS during the hot tensile process, which were detrimental to the hot ductility. In contrast, the alloys exhibited similar hot ductility troughs at higher temperatures, indicating that Mg has only a slight effect on the hot ductility at these temperatures.

Effects of Mg content on the mechanical properties and corrosion resistance of Al–Cu–Mg–Ag alloy

The effects of Mg content on the mechanical properties, corrosion resistance and the microstructure of Al–Cu–Mg–Ag alloys were investigated by hardness tests, tensile tests, intergranular corrosion tests, electrochemical analysis, optical microscopy (OM) and transmission electron microscopy (TEM). With the increase of Mg content, the aging hardening process of Al–Cu–Mg–Ag alloy was accelerated, and the peak hardness and the tensile strength at room temperature both increased and then decreased slightly, due to the smaller dimension and larger fraction volume of Ω phases, whereas the high temperature tensile strength increased gradually. In addition, the increase of Mg content led to a larger corrosion current density and thus a higher corrosion rate of Al–Cu–Mg–Ag alloy. The poorest corrosion resistance of Al–Cu–Mg–Ag alloy with the highest Mg content (1.2%) may be due to the largest potential difference between the PFZ and the matrix in this alloy. The alloy with higher Mg content consumed more Cu solution atoms to form the precipitations on the grain boundaries, which results in lower potential of the PFZ correspondingly.

Effect of Mg content on the bioactivity and biocompatibility of Mg-substituted fluorapatite nanopowders fabricated via mechanical activation

The aim of this work was preparation, characterization, bioactivity and biocompatibility evaluation of Mg-substituted fluorapatite (Mg-FA) nanopowders. Mg-FA nanopowders with a chemical composition of Ca10−xMgx(PO4)6F2, with x=0, 0.5, 1, and 2 were prepared by mechanically activated method. The in vitro bioactivity was investigated by soaking the powders in simulated body fluid (SBF) for various time periods to analyze the nucleation and growth of bone-like apatite on the surface of the samples. Cell viability and cell attachment were studied by MTT assay. Results indicated that the bioactivity of all of samples with different Mg content was improved compared with the pure FA. However, the mechanism of bioactivity is different and depends on the amount of Mg substitution. Finally, cell culture suggested that the addition of Mg2+ has no adverse effect and Mg-FA samples have good biocompatibility. The Mg-FA material shows potential in satisfying the requirements of biomedical applications.

Study of off-eutectic Zn–xMg high temperature solder alloys

Researchers have been working for some times to develop a Pb-free substitute for high-Pb containing solders in electronics. In this study the effect of Mg content on microstructure, melting behavior, thermal, electrical and mechanical properties of a new high-temperature Pb-free solder based on binary Zn–Mg alloy were investigated. The nominal compositions of Zn–xMg (x = 0.5–6.0) alloys were synthesized by conventional melting and casting route. The microstructures of the solders changed significantly on adding Mg content. Higher Mg containing alloys were found rich in intermetallic phases. The formation of the Mg2Zn11 and metastable MgZn2 intermetallic phases were identified and were also quantified by X-ray diffraction analysis. The presence of higher amount of intermetallic compounds in hypereutectic Zn–Mg systems deteriorated the tensile properties of the binary alloy. The results of electrical resistivity test indicated that the Mg could elevate the resistivity of newly developed Zn–Mg alloys. The melting behavior of the solder alloys studied by differential thermal analysis (DTA) analysis revealed that the melting temperature range of the solder alloys narrowed with Mg addition. Thermal mechanical analysis (TMA) analysis revealed that the co-efficient of thermal expansion (CTE) decreased on increasing Mg content.

Effect of Mg Content on the Microstructure and Toughness of Heat-Affected Zone of Steel Plate after High Heat Input Welding

The effect of Mg content on the microstructure and toughness of the heat-affected zone (HAZ) of steel plates after high heat input welding was investigated by means of welding thermal simulation test and insitu observation through high-temperature laser scanning confocal microscopy. It was found that with the increase of Mg content in the steel, the former austenite grain sizes were greatly decreased and the mainly microstructural constituents in HAZ were changed from the brittle constituents of Widmanstatten ferrite, ferrite side plate and upper bainite to the ductile constituents of intragranular acicular ferrite and polygonal ferrite. The proportion of grain boundary ferrite was decreased greatly with the further addition of Mg from 27 to 99 ppm. As a result, the HAZ toughness after welding with heat input of 400 kJ cm−1 is increased with increasing Mg content in the steel plate.

Effects of Mg-contents and substrate parameters on structure and optical properties of Mg-doped ZnO nanorods fabricated by hydrothermal method

Mg-doped ZnO nanorods with different contents have been fabricated on various substrates by hydrothermal method. The effects of Mg-contents and different substrates on structural and optical properties are analyzed by scanning electron microscopy, X-ray diffraction, photoluminescence (PL) spectra, energy dispersive X-ray spectroscopy and Raman spectroscopy. The results reveal that the Mg-doped ZnO nanorods possess good crystalline quality and morphology when the molar ratio of Mg/Zn is 1. The PL spectra show that the UV emissions have an obvious blue shift with the increase of Mg-content. The results of investigation for the samples grown on different substrates show that the crystal quality and morphology of the samples grown on ZnO layer are perfect, and the UV emission also occurs blue shift owing to the effects of different substrates.

Effect of Mg content on microstructure and corrosion behavior of hot dipped Zn–Al–Mg coatings

In this article, Zn–Al–Mg coatings were prepared by hot dipping method. The surface morphology, cross–section microstructure, microhardness, composition, corrosion behaviour of ZAM coatings were investigated by using X–ray diffraction (XRD), Optical microscope, Environmental scanning electron microscopy equipped with EDS (FESEM–EDS), Microhardness tester and Electrochemical analysis respectively. Corrosion test was also performed in a standard salt fog spray chamber. Microstructure studies indicates that Zn grain size was refined and eutectic areas at Zn grain boundary areas increased with increasing Mg content. ZA5M1.5 and ZA5M2 coatings have two distinct layers. Mg tends to exist in the outer layer while Al is in the inner layer. The inner layer is composed of Al5Fe2Zn0.4 intermetallic, which may to contribute to the microhardness. The outer layer is Zn grains surrounded by Zn–Mg etutectics, which may improve the corrosion resistance. The microhardness is more than 700 HV50g for Al-rich layer and around 151 HV25g for Mg-rich layer. The improved corrosion resistance of Zn–5%Al-1.5%Mg coating comes from the corrosion product of flocculent type simonkolleite, which prolongs the micro-path and impedes the movement of O2 and H2O, ultimately retards the overall corrosion process.

Novel self-gelling, injectable composites for bone regeneration based on gellan gum hydrogel and calcium and magnesium carbonate microparticles

Event Abstract Back to Event Novel self-gelling, injectable composites for bone regeneration based on gellan gum hydrogel and calcium and magnesium carbonate microparticles Timothy Douglas1, Agata Lapa2, Katarzyna Reczynska2, Malgorzata Krok-Borkowicz2, Krzysztof Pietryga2, Sangram K. Samal3, 4, David Schaubroeck5, Marijn Boone6, Pascal Van Der Voort7, Karel De Schamphelaere8, Christian V. Stevens9, Veerle Cnudde6, Elzbieta Pamula2 and Andre G. Skirtach1, 4 1 Ghent University, Molecular Biotechnology, Belgium 2 AGH University of Science and Technology, Biomaterials, Poland 3 Ghent University, General Biochemistry and Physical Pharmacy, Belgium 4 Ghent University, Centre for Nano- and Biophotonics,, Belgium 5 Ghent University, Center for Microsystems Technology (CMST), Belgium 6 Ghent University, Geology and Soil Science, Belgium 7 Ghent University, Inorganic Chemistry, Belgium 8 Ghent University, Laboratory for Environmental and Aquatic Ecology, Environmental Toxicology Unit (GhEnToxLab), Belgium 9 Ghent University, Sustainable Organic Chemistry and Technology, Belgium Introduction: Hydrogels are becoming more popular biomaterials for bone regeneration due to their injectability and the ease of incorporation of inorganic particles, e.g. calcium phosphate (CaP)[1]. Carbonates, e.g. CaCO3 have been successfully applied as bone regeneration materials and are more soluble than CaP. Carbonate particles could potentially serve as delivery vehicles for slow release of calcium (Ca) or magnesium (Mg) ions to crosslink anionic polysaccharides such as gellan gum (GG) to form homogeneous hydrogels. Carbonate microparticles containing Ca and/or Mg can be formed easily by mixing Ca2+ and Mg2+ and CO32- ions in varying concentrations. In this study, carbonate microparticles containing different amounts of Ca and Mg were added to a GG solution. Ca2+ and Mg2+ released from microparticles crosslinked GG to yield hydrogel-microparticle composites. The effect of Mg content on gelation, cytocompatibility and cell growth was studied. Methods: Ca2+/Mg2+ solutions of different Ca:Mg elemental ratios and CO32- solution were prepared. Particles were separated off by centrifugation, dried and autoclaved and subjected to physiochemical characterization using FTIR, XRD, SEM, Raman, AAS and DLS. To generate self-gelling GG-microparticle composites, microparticles were resuspended in ddH2O and mixed with autoclaved GG solution at 37º C. Final microparticle and GG concentrations were 2.5% and 0.66%, respectively (w/v). Gelation speed, microparticle distribution and cytocompatibility were investigated by rheometry, Micro-CT and MG-63 osteoblast-like cell culture in eluate from composites and directly on composites, respectively. Results: In the absence of Mg, calcite with some vatertie was formed. At low Mg content, magnesian calcite was formed. Increasing Mg content further increased general amorphicity. Microparticles of calcite, vaterite and magnesium calcite did not induce hydrogel formation. Addition of Mg-richer microparticles induced gelation within 25 min. Microparticle dispersion in hydrogels was homogeneous. All composites were cytocompatible. Cell growth after 7 d was highest on composites containing particles with an equimolar Ca:Mg ratio. Discussion: Increasing Mg content in the microparticles increased their amorphicity, in turn increasing their solubility, resulting in enhanced ion release and GG crosslinking and, in turn, hydrogel formation. Other studies have reported a beneficial effect of Mg as a component of CaP on cell proliferation[2], as observed in this study. Conclusion: Carbonate microparticles containing a sufficient amount of Mg induce GG hydrogel formation, resulting in injectable, cytocompatible hydrogel-microparticle composites. FWO, Belgium

Effect of Mg Content and Heat Treatment on the Mechanical Properties of Low Pressure Die-Cast 380 Alloy

The present study was carried out on a 380 alloy containing 9.13% Si, 3.22% Cu, 1.01% Fe, 0.06% Mg, 0.16% Mn, and 2.28% Zn. The magnesium level was increased to 0.3 and 0.55%, by adding pure Mg to the melt. Tensile and fatigue samples were produced using low pressure die casting. The results show that the average dendrite arm spacing was about 6 μm. Increasing the amount of Mg from 0.06% to 0.55% increased the volume fraction ofπ-Al8Mg3FeSi6and Q-Al5Cu2Mg8Si6phases from 0.8% to 1.7%. Following solutionizing at 490°C for 8 h, the maximum ultimate tensile strength was obtained from alloys containing 0.3% Mg. Further increases in Mg content resulted in an increase in the amount of insoluble intermetallics and, hence, low tensile strength. Aging at 155°C for times up to 25 h resulted in a linear increase in the alloy strength regardless of the amount of added Mg. Aging at 220°C, however, revealed multiple peaks corresponding to the precipitation of various phases. A good relation between the applied force and the number of cycles prior to failure was established. The alloy containing 0.3% Mg produced the best fatigue resistance. The effect of porosity was more pronounced on the fatigue samples than on the tensile bars.

Dry Reforming of Methane over Mg-Co-Al Mixed-Oxides Catalysts: Effect of Mg Content and Reduction Conditions

Mg-Co-Al mixed oxides were synthesized by the precipitation method and evaluated for dry reforming of methane. The samples were characterized by thermal techniques (TGA/DTA, NH3-TPD, H2-TPR, and TPO), specific surface area, and X-ray diffraction (XRD). Activity runs were conducted at atmospheric pressure, temperatures between 400 and 550°C, a CH4/CO2 molar ratio of 1, and a space velocity of 6000 NmL CH4/g/h. The partial substitution of Co with Mg increased the surface area and thermal stability and changed the reducibility and acid-base properties of the samples. These modifications led to a higher activity for dry reforming of methane for the catalyst with Mg/Co = 0.5, primarily due to its enhanced thermal stability. However, its higher activity was followed by higher amounts of coke. The different activation procedures highlighted Co3O4 as the main active phase rather than the Co-mixed oxides. Therefore, milder activation temperatures are required to properly reduce the Co3O4 phase and avoid sintering.