Increase Of Mg Content Research Articles

Microstructure and tensile properties of microalloyed Zn-xMg alloys

Zn-xMg alloys with different Mg contents were prepared by adding the Mg element to pure Zn. The effects of different Mg contents on the microstructure and tensile properties of Zn-xMg alloys were studied by scanning electron microscopy, XRD ray diffractometer, and tensile test. The results show that the microstructure of pure Zn and Zn-xMg alloys is composed of coarse grains, and there are twins in the microstructure morphology. The diffraction peak of pure Zn is mainly β-Zn. After adding the Mg element, α-Mg, and Zn2Mg11, diffraction peaks appear in the XRD diffraction pattern. With the increase of Mg content in the alloy, the number of Zn2Mg11 diffraction peaks increases. It is found that the strength and plasticity of the alloy increase with the increase of Mg content. The tensile fracture morphology of the alloy is mainly rock with or without the Mg element and has obvious brittle fracture characteristics.

Effects of Mg content on microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(

In this paper, the effects of the Mg content on the microstructure, mechanical properties and fracture behavior of wrought Al–8Si–(<0.01–1.32)Mg (mass fraction, %) alloy sheets in T6 temper were systematically studied by OM, SEM/EDS, EBSD, LSCM, DSC, TEM and tensile tests. The results show that the size of Si particles decreased slightly with the increase of Mg content, and the recrystallized grain size of experimental alloy sheets was refined from about 16 µm to about 11 µm. The size of β" phases did not change obviously, but its volume fraction increased gradually and then became stable. When Mg content was 1.32%, there were many associated aggregation areas of Mg2Si particles and Si particles in alloy sheet. In addition, the strength of experimental alloy sheets showed an initial increase followed by a slight decrease as the Mg content increased, while the elongation gradually decreased. The finite element model accurately predicted the yield strength of Al–8Si–(<0.01–1.32)Mg alloy sheets in T6 temper, and the model was able to quantify the contribution of various strengthening mechanisms to the yield strength of the alloy sheets. The predicted results were in good agreement with the actual measured results. The tensile fracture mode of Al–8Si alloy sheet was ductile fracture. When Mg content was greater than 0.51%, the fracture pattern of the sheets comprised a combination of ductile and brittle fractures. With the increase of Mg content, the number of dimples in experimental alloy sheets increased slightly, the depth gradually became shallow and the size slightly decreased. Meanwhile, most secondary cracks on the surface of the Al–8Si alloy sheets after tensile fracture bypassed the Si particles and a few sheared the Si particles. With the Mg content gradually increasing to 0.78%, the number of Si particles sheared by secondary cracks gradually increased. However, When Mg content was 1.32%, the intergranular fracture phenomenon of Al–8Si–1.32Mg in T6 temper was weakened or even disappeared. There were multiple particles embedded in the same dimples in the tensile fracture. The particles in the associated aggregation areas were more easily broken.

Effect of Mg and Si contents on hot-dip 55Al-Zn plating: Experimental and molecular dynamics simulation

This paper combines experiments and molecular dynamics simulations to investigate the effects and mechanisms of different Mg and Si contents in hot-dip 55Al-Zn plating on the microstructure. Non-equilibrium molecular dynamics was used to simulate the diffusion process between plating and substrate. The structure and composition of the plated layers were analyzed by electron probe and transmission. Both experimental and simulation results show that Mg and Si elements tend to be enriched at the substrate interface and form the Mg2Si phase. The Fe-Al intermetallic compound layer can be divided into two parts, Fe4Al13(Si, Zn), which is far from the substrate, and Fe4Al13, which is close to the substrate, and grows along the direction perpendicular to the substrate interface. When the Mg content in the plating is 0, Si is enriched near the substrate and exists in the form of Si particles. When the Mg content in the plating is high, Si is present mainly in two forms: diffused in the Fe-Al intermetallic compound layer and formation of Mg2Si. The increase of Mg content in the plating promotes the breaking of Fe atomic bonds, but the aggregation of Mg elements hinders the diffusion of Fe. The Si dispersed in the intermetallic compound layer hinders the diffusion of Fe atoms and makes the intermetallic compound layer thinner. The above results explore the microscopic mechanism of the effect of Mg and Si elements on the plating layer at the atomic level and provide new ideas for the study of conventional hot-dip galvanized steel.

Effects of Magnesium on Transcriptome and Physicochemical Index of Tea Leaves.

Magnesium (Mg) is one of the essential elements for the growth of tea tree and is extremely important for its development. In this study, we investigated the effect of Mg on the transcriptome and physicochemical indexes of tea leaves, and the results showed that Mg could significantly affect the gene expression of tea leaves. The results of Orthogonal Partial Least-Squares Discriminant Analysis (OPLS-DA) model analysis showed that a total of 300 key genes (Variable Importance for the Projection, VIP > 1) were screened under different concentrations of Mg treatment, among which 140 genes were up-regulated and 160 genes were down-regulated. The bubble map was used to screen the characteristic genes from the above key genes, and a total of 121 representative characteristic genes were obtained, mainly involving 9 metabolic pathways. Among them, gene expression of three metabolic pathways, including porphyrin metabolism, alpha-linolenic acid metabolism and photosynthesis, showed an increasing trend with the increase of Mg concentration, while gene expression of four metabolic pathways, including biosynthesis of secondary metabolites, anthocyanin biosynthesis, ABC transporters, pentose and glucuronate interconversions, showed a decreasing trend. The results of physiological index analysis showed that with the increase of Mg concentration, the photosynthetic physiological index, theanine and soluble sugar content of tea leaves showed an increasing trend, while the content of tea polyphenol, flavone and caffeine showed a decreasing trend. The results of TOPSIS analysis showed that the physiological indexes of tea trees most affected by Mg were chlorophyll, tea polyphenols and flavonoids, while the metabolic pathways most affected by Mg on gene expression were the metabolic pathways and biosynthesis of secondary metabolites. It can be seen that the effects of Mg on tea tree were mainly related to photosynthesis and synthesis of secondary metabolites, and Mg was beneficial for improving the photosynthetic capacity of tea tree, enhancing the accumulation of primary metabolites, and thus increasing tea yield. However, Mg was not conducive to the synthesis of secondary metabolites of tea tree and the accumulation of main quality indexes of tea leaves.

Formation of intermetallic compounds during reaction between Ti and Al–Mg alloys with various Mg contents

The reactions between Ti and Al–Mg alloys were systematically investigated by heating the Ti/Al–Mg alloy powder mixture compacts with Mg contents ranging from 5.09 to 40.36 wt.% at 660 °C. Mg element in the Al–Mg alloys contributed to the breakage of the oxide films on the surfaces of the Ti and Al–Mg alloy powders, thus, promoting the reactions. In the samples with Mg contents varying from 5.09 wt.% to 25.93 wt.%, the first-formed intermetallic compound was Al18Ti2Mg3, and then Al3Ti generated at the Al18Ti2Mg3/Ti interface. Since the Mg content in the Al–Mg melts decreased during the subsequent heating process, the previously formed Al18Ti2Mg3 in the Ti/Al–5.09Mg sample transformed into Al3Ti accompanied by the reaction of Al with Ti to newly form Al3Ti, generating a single Al3Ti phase. In contrast, the new formation of Al3Ti and its transformation to Al18Ti2Mg3 proceeded continuously in the Ti/Al–13.54Mg and Ti/Al–25.94Mg samples, resulting in a mixture of Al18Ti2Mg3 and a little Al3Ti residue. In the Ti/Al–40.54Mg sample, Al3Ti was the unique reaction product throughout the heating process. The final Al3Ti particles in the Ti/Al–5.09Mg sample were in a blocky shape, while they were in a plate-like form in the Ti/Al–40.54Mg sample, which was caused by the enhanced growth anisotropy due to the decreased interfacial energy between Al3Ti particles and Al–Mg melts with the increase of Mg content. A twin plane re-entrant mechanism was suggested for the growth of Al18Ti2Mg3 particles, weakening the anisotropic growth caused by the directional supply of Ti atoms, and contributing to the blocky morphology of Al18Ti2Mg3 particles. In addition, the volume difference between the formed Al18Ti2Mg3 and consumed Ti was greater than that between the Al3Ti and Ti, and the Al18Ti2Mg3 has worse plasticity than the Al3Ti, resulting in the Al18Ti2Mg3 reaction product fracturing more easily during thickening, thus forming a petal-like structure, but the Al3Ti product being in an almost continuous layer.

Degradation mechanism of MgO–MgAl2O4 dual-phase refractory in contact with the automobile gear steel SCr420H with Si–Mn, Al and Ce–Al deoxidation

The current research, the degradation mechanism of MgO–MgAl2O4 dual-phase crucibles in contact with steel SCr420H with Si–Mn, Al, and Ce–Al deoxidation was investigated using a laboratory steelmaking experiment at 1873 K. The refractory interface in contact with the steel and inclusions was analysed using SEM and EPMA. In the case of Si–Mn deoxidation, the refractory's MgO phase was initially attacked by the dissolved Si, resulting in its transformation into the 2MgO–SiO2 phase, as confirmed by thermodynamic calculations. In the case of Al deoxidation, the reaction between the dissolved Al and the refractory had a significant effect on the increase in Mg concentration and MgAl2O4 inclusions. Refractory degradation was suppressed because the MgAl2O4 phase was an equilibrium phase based on thermodynamic consideration. The distribution of the MgAl2O4 phase in the refractory hindered the degradation reaction. The primary degradation mechanism in the case of Al deoxidation was steel penetration. In Ce–Al deoxidation, both Ce and Al were involved in refractory degradation. During this process, the MgO phase reacted with the dissolved Al, leading to its transformation into the MgAl2O4 phase, which was subsequently modified to the Ce–Al–O phase. Additionally, the MgAl2O4 phase was directly denatured into the Ce–Al–O phase.

Improving work temperature span and reversibility of magnetoelastic transition of (Mn,Fe)2(P,Si) alloys by Mg doping

Magnetocaloric materials with wide working temperature span and reversible magnetic transition are beneficial for the magnetic refrigerator. Besides of giant magnetocaloric effect, (Mn,Fe)2(P,Si) alloys exhibit significant thermal/magnetic hysteresis and a narrow working temperature span. In this work, the impact of Mg doping on the phase structure and magnetocaloric effect of Mn1.05Fe0.9P0.5Si0.5-xMgx alloys has been studied. The results show that all samples crystallize into Fe2P-type main phase with little impurity phase. After Mg doping, the lattice parameter a of the main phase increases from 6.027(0) Å to 6.049(0) Å and c decreases from 3.488(6) Å to 3.480(6) Å, which leads to the increase of Curie temperature. Density functional theory calculation results confirm that the Mg atom located on the 2c site can increase the covalent bond length, and then enhance the ferromagnetic coupling between atoms leading to the increase of Curie temperature. Moreover, the first-order magnetic phase transition of Mn1.05Fe0.9P0.5Si0.5-xMgx alloys is inhibited with the increase of Mg content, which results in the decrease of thermal/magnetic hysteresis and the increase of the effective working temperature span. For Mn1.05Fe0.9P0.5Si0.48Mg0.02 alloy, it has a Curie temperature of about room temperature, effective refrigeration capacity of 291.7 J·kg−1, working temperature window of 46 K and magnetic entropy change of 9.4 J·kg−1·K−1. The alloy can be an excellent candidate in room temperature magnetic refrigeration devices with a wide temperature span.

Physical properties of Mg doped ZnS thin films via spray pyrolysis

Chemical spray pyrolysis (CSP) was utilized to create pure Zinc Sulfide (ZnS) and magnesium (Mg) doped thin films on a clean glass substrate at a temperature equal to 400°C. X-ray diffraction test revealed a cubic wurtzite crystal structure with average crystallite sizes of 10.99 and 12.27 nm for ZnS and ZnS: Mg, respectively. XRD analysis of the doped films revealed a polycrystalline structure with a predominant peak along the (220) plane and additional peaks along the (111), (200), and (222) planes. The grain size raised from 10.99 to 12.27 nm as a result of the XRD patterns. The increase in Mg content from 0% to 3%, affect the bandgap that fell from 3.52 to 3.42 eV. As the Mg content increased, the transmittance and refractive index of the films was lowered.

Preparation and analysis of Ag2Se1-xTex thin film structure on the physical properties at various temperatures by thermal evaporation

Chemical spray pyrolysis (CSP) was utilized to create pure Zinc Sulfide (ZnS) and magnesium (Mg) doped thin films on a clean glass substrate at a temperature equal to 400°C. X-ray diffraction test revealed a cubic wurtzite crystal structure with average crystallite sizes of 10.99 and 12.27 nm for ZnS and ZnS: Mg, respectively. XRD analysis of the doped films revealed a polycrystalline structure with a predominant peak along the (220) plane and additional peaks along the (111), (200), and (222) planes. The grain size raised from 10.99 to 12.27 nm as a result of the XRD patterns. The increase in Mg content from 0% to 3%, affect the bandgap that fell from 3.52 to 3.42 eV. As the Mg content increased, the transmittance and refractive index of the films was lowered.

Effective Mg Incorporation in CdMgO Alloy on Quartz Substrate Grown by Plasma-Assisted MBE

The development of CdMgO ternary alloy with a single cubic phase is challenging but meaningful work for technological advancement. In this work, we have grown a series of Cd1-xMgxO ternary random alloys with various Mg concentrations (x = 0, 30, 32, 45, and 55%) on quartz substrate by plasma-assisted molecular beam epitaxy (PA-MBE) technique. The structural investigations of alloys were performed using the X-ray diffraction (XRD) technique. The decreases in average crystallite size and lattice parameters were observed with an increase in Mg content in the alloys. XRD analysis confirms a single cubic phase is obtained for alloy compositions. The elemental and morphological studies were carried out using energy dispersive x-ray (EDX) spectroscopy and atomic force microscope (AFM) technique, respectively. The optical investigation was carried out using UV-Vis spectroscopy. The optical bandgaps were estimated using the Tauc relation and it was varied from 2.34 eV to 3.47 eV by varying the Mg content from zero to 55% in the alloys. The Urbach energy increases from 112 meV to 350 meV which suggests a more disordered localized state with an increase in Mg incorporation in the alloys.

Influence of the Mg content on the microstructure and mechanical properties of Al-xMg-2.0Si-0.6Mn alloy

In this study, the effect of Mg content on the microstructure and mechanical properties of the Al-xMg-2.0Si-0.6Mn alloy was investigated. The study aimed to investigate the optimal addition of Mg elements to improve the comprehensive performance of the alloy. The microstructure, phase composition and fracture morphology of the alloy were determined through OM, SEM, TEM and XRD analysis. With the increase of Mg content, the number of strengthening phases increases, which improves the comprehensive properties of the alloy. When the Mg content in an alloy exceeds 5%, the solubility of the Mg2Si phase in the matrix is reduced, and the development of the coarse Mg2Si phase limits the alloy's elongation. The performance is excellent when the content of Mg is 5%. The alloy has maximum tensile strength, yield strength, and elongation of 227.22 MPa, 136.55 MPa, and 7.24%, respectively. Furthermore, we discovered that the point-like Mg2Si phase exists in the alloy and coexists with the point-like α-Al15(Fe, Mn)3Si2. TEM investigation revealed the incoherent relationship between the two point-like phases, and the phase diagram suggested α-Al15(Fe, Mn)3Si2 as a probable substrate for the nucleation of the Mg2Si phase.

Effect of Mg content on the microstructure and magnetic properties of rare-earth-free MnBi alloys

The low-temperature phase MnBi (LTP-MnBi) has become one of the most promising rare-earth-free permanent magnetic alloys owing to its unique positive temperature coefficient of coercivity. However, so far, the maximum energy product of MnBi alloys is still lower than its theoretical value. In this study, Mn55Bi45-xMgx (x = 0, 1, 2, 3, and 4) alloys were prepared by induction melting followed by an annealing process. The effects of Mg content on the microstructure and magnetic properties of MnBi alloys were investigated. The results showed that the partial substitution of Mg for Bi inhibited the formation of LTP-MnBi. With the increase of Mg content, the coercivity increases from 8.1 kOe for x = 0 to 10.0 kOe for x = 4, but the saturation magnetization decreased from 71.7 emu/g for x = 0 to 61.3 emu/g for x = 4. Finally, the calculated maximum energy product of 11.1 MGOe was obtained in the annealed Mn55Bi43Mg2 powder.

Co-precipitation of Mg-doped Ni0.8Co0.1Mn0.1(OH)2: effect of magnesium doping and washing on the battery cell performance.

Co-precipitation of Ni0.8Co0.1Mn0.1(OH)2 (NCM811) and Mg-doped (0.25 wt% and 0.5 wt%) NCM811 precursors is carried out from concentrated metal sulphate solutions. In this paper, the aim is to study the role of magnesium dopant in the co-precipitation step of NCM811, the cathode active material and further the Li-ion battery cell performance. Based on the results, magnesium was fully co-precipitated in the NCM811 precursors, as expected from thermodynamic calculations. The presence of magnesium in these precursors was also confirmed by several characterization methods and magnesium was evenly distributed in the sample. It was observed that tapped density decreased and surface area increased with an expected increase in Mg content. Surprisingly, Mg doping did not improve the cyclability of coin cells, due to the stable crystal structure of NCM811. However, a slight improvement in cyclability was seen in pouch cells after 1000 cycles. A washing effect was clearly seen in lattice parameters and washing also decreased the capacity retention after 62 cycles for all samples.

Designing and characterizing multicomponent, plant-based bigels of rice bran wax, gums, and monoglycerides

In this study, plant-based, edible water-in-oil biphasic gels (bigels) were developed and characterized. Bigels were composed of a rice bran wax (RBW)/soybean oil oleogel (OG) and a sodium alginate/kappa-carrageenan hydrogel (HG). The addition of monoglycerides (MG, 0–2% w/w) in the OG phase and the effect of OG:HG ratio (0:10, 7:3, 8:2, 10:0) were evaluated through physical, microstructural, thermal, and rheological analyses. All bigels were self-supporting and visually homogeneous, except the 7:3 formulation containing 1 and 2% MG, which showed phase separation. Confocal laser scanning microscopy revealed that MG acted as emulsifiers by reducing the HG particle size. Differential scanning calorimetry measurements showed that RBW and MG crystallized in the OG phase, indicating that both components acted as oleogelators. In line with these results, increasing the MG concentration in the OG phase increased the solid fat content of the bigels. Results from small deformation rheology showed that the rheological properties of the bigels were mainly governed by the OG phase. The mechanical strength (G′) followed the trend 0:10≪8:2–7:3<10:0 and further increased after MG addition. The resistance to permanent deformation followed the opposite trend and increased with the increase in MG concentration. In particular, the 8:2 formulation containing 2% MG best fitted the rheological properties required for commercial semi-solid fats. Consequently, the bigels developed in this study constitute a promising plant-based substitute for semi-solid fats with an improved saturated to unsaturated fatty acid ratio.

Effect of filler materials on the porosity formation of aluminum alloy by laser welding with filler wire

Porosity is a critical defect in aluminum alloys during laser welding. In this study, three filler wires with different Mg content were used to study the effect of Mg on the porosity formation in laser wire filling welding. The increase of Mg content of filler wire leads to the increase of recoil pressure and decrease the surface tension of keyhole wall, which promotes the molten filler wire with more Mg content to transfer to keyhole. The molten droplets flow down the front wall of the keyhole and connect with the protrusion of the rear wall, resulting in the collapse of the keyhole. Therefore, the porosity is more likely to occur in the laser welding with higher Mg content filler wire.

Predicted interfacial thermal conductance and thermal conductivity of graphite flakes/Al composites with different alloy composition

Abstract Graphite flake/Al composites are promising thermal management materials due to their light weight and excellent thermal properties. The interface structure is a key factor that impacts the thermophysical properties. In this work, prediction models based on the acoustic mismatch model (AMM) and the effective medium approach (EMA) were developed to evaluate the effect of the alloying elements on the interfacial thermal conductance (ITC) and thermal conductivity (TC) of graphite flake/Al composites. With the increase in Si content, the ITC for the graphite flakes/Al composites increases clearly. In contrast, the ITC for the graphite flakes/Al composites decreases with the increase in Mg content. The variation range of ITC of graphite flakes/Al–Mg–Si composites is (2.3 × 107–3.1 × 107) W m−1 K−1. The thermal conductivity of the graphite flakes/Al–Mg–Si composites is in the range of (412–476) W m−1 K−1. With the increase in the volume fraction of graphite flake, the thermal conductivity of the graphite flakes/Al composites is significantly improved.

Sustainable alternative cathodes of sodium-ion batteries using hybrid P2/O3 phase Na0.67Fe0.5Mn0.5−xMgxO2

The Na0.67Fe0.5Mn0.5−xMgxO2 compound with x = 0.02, 0.04, 0.06, 0.08, 0.1, 0.15 was synthesized by solid state reaction. The structure of the samples gradually transformed from P2 phase to O3 phase with the increase of Mg content. The hybrid P2/O3 phase transition metal oxides with high performance was prepared to promote the application of sodium-ion batteries. Na0.67Fe0.5Mn0.46Mg0.04O2 exhibited a hybrid P2/O3 phase structure, which showed high electrochemical performance. Due to the synergy of P2 and O3 phase, the conductivity for the migration of Na ions in the experimental cell, exhibited the highest ion diffusivity. Here, Fe and Mn-based transition metal oxide materials as a cathode material can have great application potential for sodium-ion batteries and can be one of the most promising alternatives to the limited lithium-ion battery.

Investigation on the Atomic Mechanism for Grain Refinement of Magnesium Alloys by Mg-Zr Master Alloy.

The valence electron structure, bond energy, and cohesive energy of Mg, Zr, and α-Mg containing Zr, and α-Zr containing Mg crystals were calculated using the empirical electron theory of solids and molecules (EET). The calculation results show that the bond and cohesive energies of Zr were much greater than those of Mg, so Zr particles could precipitate ahead of α-Mg in general magnesium alloy melts or insoluble Zr particles exist when the magnesium melt temperature is relatively low. The bond energy of α-Zr decreases with the increase in Mg content; therefore, at the end of the growth of Zr particles, the remaining Zr atoms in the melt exist in the form of Mg-Zr clusters. In order to reduce the surface energy of Zr particles, the outer surface of Zr particles tends to terminate with a Zr-Mg atomic layer, that is, a stable two-dimensional Zr-Mg atomic layer is formed first on the (0001) crystal surface of the outermost surface of Zr particles. Furthermore, on the basis of the calculated results, a complementary criterion to the edge-to-edge model of heterogeneous nucleation is also proposed. {ure and single Zr particles cannot become the heterogeneous nucleus of α-Mg, but when there is an atomic layer of two-dimensional Zr-Mg on its surface, the nucleation of particles can be activated. Mg atoms in the liquid phase preferentially attach to the Zr-Mg/Mg-Zr atomic layer on the surface of Zr particles to grow and form a stable ordered structure, which lastly transforms Zr particles into efficient heterogeneous cores.

Influences of Mg concentration in ZnMgO film on energy band alignment at CIGSSe/Zn1-xMgxO interface and performances of CIGSSe solar cells

Zn1-xMgxO buffered CdS free CIGSSe solar cell has been believed to be a new simplified structure solar cell with great potential. ZnMgO film plays an important role. To obtain a high quality Zn1-xMgxO thin film becomes a key issue. In this work, Zn1-xMgxO films with different Mg concentrations were prepared by magnetron co-sputtering, and physical performances of Zn1-xMgxO films were investigated. Meanwhile, CdS free CIGSSe solar cells were prepared based on Zn1-xMgxO buffer layers. The effects of Mg concentration in Zn1-xMgxO buffer layers on device performances, energy band alignment, and interface recombination of CIGSSe solar cells were studied. The results show that although the doping of Mg reduces the crystallinity of Zn1-xMgxO films, it increases the band gap by increasing the conduction band minimum. In Zn1-xMgxO buffered CdS free CIGSSe solar cells by all-sputtering process, the photoelectric conversion efficiency increases first and then decreases with the increase of Mg concentration in the x range from 0 to 0.3, which is mainly attributed to the changes of FF and VOC. Meanwhile, the change of Mg concentration affects the energy band alignment at the CIGSSe/Zn1-xMgxO interfaces. The highest efficiency of 15.2 % of Zn0.8Mg0.2O buffered CdS free CIGSSe solar cell with the energy band difference of 0.27 eV was obtained in this work.

Poisson's Ratio Structure Beneath the Nazca Ridge

AbstractThe Nazca Ridge (NR) was formed near the interaction of a hotspot mantle plume and an active spreading center. We use active‐source wide‐angle seismic data to obtain 2‐D Vp and Vs tomographic models, and hence the Poisson's ratio (ν) structure beneath the NR. Results show a ∼2 km thick seismic layer 2A with ν values of 0.25–0.32 in the uppermost crust interpreted as pillow basalts with a low degree of fracturing and/or hydrothermal alteration. The 2A/B boundary layer presents ν values of 0.27–0.29 consistent with pillow basalts/sheeted dykes units. A ∼3 km layer 2B overlies a ∼10 km layer 3 with ν values of 0.24–0.3 at the 2/3 boundary layer. The lowermost layer 3 presents ν values of 0.28 ± 0.02 suggesting an increase in Mg content (≥10% wt). The NR crust (∼15 km thick) requires an increment of the asthenospheric mantle potential temperature in ∼100°C formed by passive adiabatic decompression melting.