Mg2Sn Phase Research Articles

Study on microstructure and properties of Mg2(Si,Sn) compound phase in Mg-Sn-Si magnesium alloy

Microstructure, characteristic and metamorphism of Mg2(Si,Sn) compound phase are studied in as-cast Mg-Sn-Si alloy. The results indicate that Sn atom can replace the partial Si of Mg2Si then form Mg2(Si,Sn) compound phase, and structure of the ternary compound is the same as Mg2Si and Mg2Sn, all belong to face-centered cubic. The element content of Mg2(Si,Sn) phase is not invariable, the Mg2(Si,Sn) phase with high Si content is in Si enrichment region, while it with low Si content is in Si poverty region. The property of Mg2(Si,Sn) phase with high Si content is close to Mg2Si phase, the property of the phase with high Sn content is close to Mg2Sn phase. In experiments, the nano-hardness, elastic modulus, vickers hardness and other physical properties of Mg2(Si,Sn) phase are between Mg2Si phase and Mg2Sn phase, in the metamorphism process of Chinese-script-like Mg2Si phase, Mg2(Si,Sn) compound phase plays a role as a bridge.

Effects of Sn on Mechanical Properties of Magnesium Alloy AZ61

The effects of Sn on the mechanical properties of magnesium alloy AZ61 have been investigated. The results show that the addition of 0.5wt.% Sn can refine the grain size, improve the morphology of β-Mg17Al12 phase, and cause the formation of Mg2Sn phase. The improved microstructure results in the enhanced mechanical properties of magnesium alloy AZ61 at room temperature and 150°C.

Role of icosahedral phase in enhancing the strength of Mg–Sn–Zn–Al alloy

The effect of the selection of the secondary solidification phase on the mechanical properties of the Mg–Sn–Zn and Mg–Sn–Zn–Al alloy rolled sheets has been investigated in the present study. The as-cast microstructure of Mg–7Sn–2Zn (in wt.%) alloy consists of α-Mg dendrite and interdendritic Mg2Sn and MgZn2 phases, while that of Mg–7Sn–5Zn–2Al alloy consists of α-Mg dendrite and interdendritic Mg2Sn and icosahedral (I-) phases. The micron scale interdendritic I-phase in the as-cast Mg–7Sn–5Zn–2Al alloy dissolves into the matrix during homogenizing treatment, and appears again in the α-Mg matrix as 0.1–0.5μm size fine spherical precipitates after rolling process. As a result, the Mg–7Sn–5Zn–2Al alloy exhibits high yield strength of 318MPa in as-rolled state. The high level of strength is attributed to the presence of finely distributed Mg2Sn and I-phase particles embedded in the α-Mg matrix.

Preparation of ternary Mg-Li-Sn alloys from molten salt by electrolysis

Electrochemical behavior of Mg, Li and Sn on tungsten electrodes in LiCl-KCl-MgCl2SnCl2 melts at 873 K was investigated. Cyclic voltammograms (CVs) showed that the underpotential deposition (UPD) of magnesium on pre{deposited tin leads to the formation of a Mg-Sn alloy, and the succeeding underpotential deposition of lithium on pre-deposited Mg-Sn alloy leads to the formation of a Mg-Li-Sn alloy. Chronopotentiometric measurements indicated that the codepositon of Mg, Li and Sn occurs at current densities more negative than {1.16 A¢cm i2 . X-ray difiraction (XRD) indicated that Mg2Sn phase is formed via galvanostatic electrolysis. The element Mg

Microstructure and properties of Mg–3Sn–1Mn (wt%) alloy processed by a novel continuous shearing and rolling and heat treatment

A novel semisolid continuous shearing and rolling process for producing Mg–3Sn–1Mn (wt%) alloy strip was proposed, microstructure and properties of Mg–3Sn–1Mn (wt%) alloy strip processed by the proposed process and heat treatment was investigated. For each condition, at least three tensile tests were performed. Under strong cooling and shearing actions caused by the rotating roll and the fixed shoe, eruptive nucleation, direct globular grain growth and dendrite arm breakage took place in the roll-shoe gap, which causes the formation of fine spherical or rosette primary grains. When the casting temperature was 690°C, and the roll speed was 0.052ms−1, Mg–3Sn–1Mn (wt%) alloy strip was produced. The microstructures of the strip are mainly composed of fine spherical or rosette grains. After deep rolling, the grains of the strip were elongated, the textures were formed in the deep-rolled strip. The ultimate tensile strength (UTS) of the deep-rolled strip is 276±3MPa, and the elongation (EL) is 6.3±0.1% in the rolling direction (RD). After solution treatment at 480°C for 13h and aging at 300°C for 12h, the Mg2Sn phase distributes homogeneously in matrix microstructure and strengthens the mechanical properties, the UTS and EL of the deep-rolled strip reach 305±3.3MPa and 7.8±0.12% in the RD.

Microstructure and mechanical properties of conventional cast and rheocast Mg–Sn based alloys

In the present study, microstructure and mechanical properties of conventional cast and rheocast Mg–Sn alloy systems were investigated. The microstructure of conventional cast Mg-5%Sn and Mg-8%Sn alloys showed different phases, such as primary α-Mg, β-Mg2Sn phase that precipitates at the grain boundary, and eutectic α-Mg, a dark area surrounding the precipitate phase. With the addition of misch metal in Mg-5%Sn alloy the refinement of microstructure was observed and also the interdendritic second phase changed from rod/irregular shaped to rod and feathery shaped. In Mg-8%Sn-3%Al-1%Si alloy, α-Mg, Mg2Sn, Mg17Al12 and Mg2Si phases were observed. With the addition of Al–Sc master alloy in Mg-8%Sn alloy the matrix grain size became finer. The rheocast microstructures showed that the primary α-Mg phase is non-dendritic and globular shaped. Solution heat treatment at 520°C for 48–72h leads to complete dissolution of Mg2Sn intermetallic in Mg–Sn alloys. During ageing at 200°C discontinuous precipitates were formed at the grain boundaries in the initial stage and later continuous precipitates were occurred in the remaining regions. Hardness values were significantly improved after 100h of aging for all the alloys compared to as-cast alloys. The tensile properties of rheocast alloys were significantly higher than the conventional cast alloys.

Doping Effects on Thermoelectric Properties in the Mg2Sn System

A weak point of Mg2X thermoelectrics is the absence of a p-type composition, which motivates research into the Mg2Sn system. Mg2Sn thermoelectrics were fabricated by a vacuum melting method and a spark plasma sintering process. As a result, Mg2Sn single phases were acquired in a wide range of Mg-to-Sn atomic ratios (67:33 to 71:29), showing slightly different thermoelectric characteristics. However, the thermoelectric properties of the undoped system were not sufficient for application in commercial production. To maximize the p-type characteristics, many atoms [Ni (VIIIA), Cu (IB), Ag (IB), Zn (IIB), and In (IIIB)] were doped into the Mg2Sn phase. Among them, the power factor values increased only in the Ag-doped case. Ag-doping resulted in a power factor that was more than 10 times larger than the value in the undoped case. This result could be important for developing p-type polycrystalline thermoelectrics in the Mg2X (X = Si, Sn) system. However, other atoms [Ni (VIIIA), Cu (IB), Zn (IIB), and In (IIIB)] were not determined to act as acceptor atoms. The maximum ZT value for the Ag-doped Mg2Sn thermoelectric was more than 0.18, which is comparable to the value for the n-type Mg2Si system.

Magnesium Alloy Development for Automotive Applications

This paper summarizes the development of new cast and wrought magnesium alloys using computational thermodynamics tools and experimental approach. The Mg-Al-Ca alloys show excellent creep resistance due to the formation of high-temperature (Mg,Al)2Ca phase. The Mg-Al-Sn alloys are designed for mechanical properties and corrosion resistance through the optimization of Mg17Al12 and Mg2Sn phases in the microstructure. In the Mg-Zn-Ce system, Zn provides strength through solid solution strengthening while Ce increases the ductility via improved texture. Mg-Nd-Zn is a heat-treatable alloy system based on the precipitation hardening of Mg12Nd phase.

Effect of Sr Addition on Microstructures of as-Cast Mg-5Sn-5Zn Alloy

The microstructures and phase constituent of as-cast Mg-5Sn-5Zn-xSr (x=0, 0.5, 1, 2) alloys were analyzed by the optical microscopy (OM), the scanning electron microscope (SEM) and the X-ray diffraction (XRD). The results indicate that an addition of 0.5%-2% (mass fraction) Sr to the Mg-5Zn-5Sn alloy not only refines the dendrite arm spacing of -Mg but also results in the formation of MgSnSr phases. Furthermore, it was found that the increase of Sr results in Mg2Sn phase decreasing and MgSnSr phase increasing. While the MgZn phase which is attached with Mg2Sn phase exists in the form of -Mg+MgZn eutectic structure.

Effect of tin addition on microstructure and electrochemical properties of rolled AZ61-Sn magnesium anodic materials

Microstructure characterization, corrosion behavior, and electrochemical properties of magnesium anode materials containing 1–3 wt.% Sn in AZ61 alloy were studied by optical microscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy-dispersive spectroscopy (EDS), constant current method, potential polarization, and drainage. The results showed that amount of Mg2Sn phase increased, and recrystallization ratio of Sn-contained Mg alloys during rolling process was improved with increasing of Sn content. This resulted in uniform and refined grains. The results also demonstrated that discharge potential was improved and hydrogen release rate was reduced with the addition of Sn. As the current density increased, the release hydrogen rate was rising, owing to negative variance effect of magnesium alloys. The current efficiency gets to 87% at 20 mA/cm2. The main components of the corrosion products are easy-to-peel-off MgO and Al2O3 that can lead to more negative and stable work potential and accelerate battery reaction continuously.

Microstructure and Mechanical Properties of Wrought Mg-4.1Li-2.5Al-1.7Zn-1Sn Alloy

An Mg-Li-Al-Zn-Sn alloy was prepared by vacuum melting. The actual content of the elements in the alloy was determined using inductively coupled plasma-atomic emission mass spectrometry (ICP-AEMS). The density of the alloy was detected using Archimedes’ method. Extrusion and rolling deformation were carried out on this alloy. Its microstructures and mechanical properties were then studied with an optical microscope (OM), scanning electronic microscope (SEM), X-ray diffractometer (XRD), energy dispersive spectrometer (EDS), and tensile tester. The extruded alloy was composed of α-Mg and Mg2Sn phases and had good strength and elongation properties as well as a good comprehensive performance. After further rolling deformation, an Al-Li phase appeared due to atomic diffusion during the hot rolling process. Strain-hardening and the strengthening effect of the Al-Li phase further improved the strength of the alloy but decreased its elongation capacity.

Solidification Microstructure and Mechanical Properties of Cast Magnesium-Aluminum-Tin Alloys

The solidification microstructure and mechanical properties of as-cast Mg-Al-Sn alloys have been investigated using computational thermodynamics and experiments. The as-cast microstructure of Mg-Al-Sn alloys consists of α-Mg, Mg17Al12, and Mg2Sn phases. The amount of Mg17Al12 and Mg2Sn phases formed increases with increasing Al and Sn content and shows good agreement between the experimental results and the Scheil solidification calculations. Generally, the yield strength of as-cast alloys increases with Al and Sn content, whereas the ductility decreases. This study has confirmed an early development of Mg-7Al-2Sn alloy for structural applications and has led to a promising new Mg-7Al-5Sn alloy with significantly improved strength and ductility comparable with commercial AZ91 alloy.

Microstructure and Tensile Properties of a Mg-5Sn-4Al Alloy

The microstructure and tensile properties at room temperature of as-cast, solution-treated and aged samples of a Mg-5Sn-4Al (wt%) alloy are investigated. The microstructure of the as-cast sample consists of a-Mg primary, Mg2Sn and Mg17Al12 divorced eutectic, secondary precipitations Mg17Al12 and Mg2Sn. After solution treatment, all the Mg17Al12 particles and the majority of Mg2Sn phases are dissolved into the matrix and the tensile strength and the elongation of the alloy increase obviously. During aging process many fine particles of Mg2Sn precipitate which result in the improvement of the yield strength.

Microstructures and Mechanical Properties of Mg-6Al-1Zn-xSn (x=0.5, 1, 2 and 3.5 Wt%) Alloys during Solution Treatment at 420°C

The effect of solution treatment at 420°C on the microstructures and mechanical properties of the Mg-6Al-Zn+xSn (x=0.5, 1, 2 and 3.5 mass %) alloys have been investigated. The results showed that the Mg2Sn phase was present in both the cast and the heat-treated alloys. The Mg2Sn particles tended to be spherodized during the solution treatment. Amount of Sn increased the tensile strength of the alloys.

Microstructures, mechanical properties and compressive creep behaviors of as-cast Mg-5%Sn-(0–1.0)%Pb alloys

The microstructures, tensile properties and compressive creep behaviors of Mg-5%Sn-(0–1.0)%Pb (mass fraction) alloys were studied. The microstructures of the Mg-Sn-Pb alloys consist of dendritic α-Mg and Mg2Sn phase. The addition of Pb can refine the size of Mg2Sn phase and grain size, reduce the amount of Mg2Sn phase at grain or inter-dendrite boundaries and change the distribution of Mg2Sn phase. Pb exists in the Mg2Sn phase or dissolves in α-Mg matrix. The mechanical properties of the tested alloys at room temperature are improved with the addition of Pb. When the Pb content is over 0.5%, the mechanical properties are decreased gradually. The Mg-5%Sn-0.5%Pb shows the best ultimate tensile strength and elongation, 174 MPa and 14.3%, respectively. However, the compressive creep resistance of the Mg-Sn-Pb alloys is much lower than that of the Mg-Sn binary alloy at 175 °C with applied load of 55 MPa, which means that Pb has negative effects on the compressive creep resistance of the as-cast Mg-Sn alloys.

Effect of Tin on Microstructure and Electrochemistrical Properties of Mg-Al-Sn-Zn Magnesium Alloys Anodic Materials

Morphologies, microstructure and composition distribution of the magnesium anodic materials were studied by metallographic microscopy, x-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive spectroscopy (EDS). The corrosion behavior and electrochemical properties of Mg alloy were also investigated by constant current method, potential polarization, collecting gas through drainage. The results show that tin restrained β-Mg17Al12 phase precipitation along the grain boundary. With the content of tin increasing, granular Mg2Sn phase was improved. After uniform heat treatment, most of β-Mg17Al12 phase was dissolved, but most of Mg2Sn was not dissolved. Tin could improve self-corrosion potential and release hydrogen rate. Magnesium alloy anode with 1% tin content had high discharge potential and current efficiency. With the current density increasing, the release hydrogen rate augmented. The current efficiency reached 82 % at 20mA/cm2. The main composition of the corrosion products were MgO and Al2O3 which were easily peeled off. As a result, more negative and stable work potential was produced and the reaction was accelerated continuously.

Influences of the quantity of Mg2Sn phase on the corrosion behavior of Mg–7Sn magnesium alloy

The influence of the quantity of the Mg2Sn phase on the corrosion behavior of different solution temperature treated Mg–7Sn magnesium alloy has been investigated by electrochemical measurements, scanning electron microscope (SEM) observation, X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) analysis. With the increase of solution temperature, the quantity of Mg2Sn phase decreased and the tin concentration of matrix increased. The dissolved tin in Mg matrix took part in the film formation and the constituent of film was magnesium oxide and stannic oxide. The corrosion mode and corrosion rate were associated with the quantity of Mg2Sn phases and tin concentration of the matrix. If most of tin was present as Mg2Sn, the corrosion mode was pitting corrosion and it accelerated the corrosion rate. If most of tin was dissolved in matrix, the corrosion mode was filiform corrosion and it decreased the corrosion rate. The experiment evidences demonstrated that the corrosion resistance can be improved by increasing the tin concentration of matrix and the lowest corrosion rate was observed for sample solution treated at 540°C.

Microstructure and Impression Creep Characteristics of Cast Mg-5Sn-xBi Magnesium Alloys

The microstructure and creep behavior of a cast Mg-5Sn alloy with 1, 2, and 3 wt pct Bi additions were studied by impression tests in the temperature range 423 K to 523 K (150 °C to 250 °C) under punching stresses in the range 125 to 475 MPa for dwell times up to 3600 seconds. The alloy containing 3 wt pct Bi showed the lowest creep rates and, thus, the highest creep resistance among all materials tested. This is attributed to the favorable formation of the more thermally stable Mg3Bi2 intermetallic compound, the reduction in the volume fraction of the less stable Mg2Sn phase, and the dissolution of Bi in the remaining Mg2Sn particles. These particles strengthen both the matrix and grain boundaries during creep deformation of the investigated system. The creep behavior of the Mg-5Sn alloy can be divided into the low- and high-stress regimes, with the respective average stress exponents of 5.5 and 10.5 and activation energies of 98.3 and 163.5 kJ mol−1. This is in contrast to the creep behavior of the Bi-containing alloys, which can be expressed by a single linear relationship over the whole stress and temperature ranges studied, yielding stress exponents in the range 7 to 8 and activation energies of 101.0 to 107.0 kJ mol−1. Based on the obtained stress exponents and activation energies, it is proposed that the dominant creep mechanism in Mg-5Sn is pipe-diffusion controlled dislocation viscous glide the low-stress regime and dislocation climb creep with back stress in the high-stress regime. For the Mg-5Sn-xBi alloys, however, the controlling creep mechanism is dislocation climb with an additional particle strengthening effect, which is characterized by the higher stress exponent of 7 to 8.

Microstructure and Tensile Properties of an Mg-5Sn-5Zn Alloy

The microstructure and tensile properties at room temperature of as-cast, solution-treated and aged samples of a Mg-5Sn-5Zn (wt%) alloy are investigated. The microstructure of the as-cast sample consists of -Mg primary, Mg-MgZn eutectic, divorced eutectic Mg2Sn and secondary precipitation Mg2Sn. After solution treatment, all the MgZn particles and the majority of Mg2Sn phases are dissolved into the matrix and the tensile strength and the elongation of the alloy increase obviously. During aging process many fine particles precipitate which result in the improvement of the yield strength.

Hot-Extruded Microstructure and Mechanical Properties of Mg-Al-Sn Alloys

The microstructure of as-cast Mg-xAl-2Sn alloys consists of an α-Mg matrix, a Mg17Al12 eutectic phase and a Mg2Sn phase. In as-cast alloys, the Mg17Al12 eutectic phase was located at along grain boundaries. The eutectic phase of the extruded alloys was elongated in the extrusion direction and crushed into fine particles because of deformation during hot extrusion, and the grain size was refined with an increased Al content. The maximum values of the yield strength and tensile strength were 240 MPa and 300 MPa at 9 wt.% containing Al element, respectively.