Mg2Si Alloy Research Articles

Structure and strength properties of the cold-deformed Al–Mg2Si-based alloys with additives of transition metals

Using methods of hardness measurements, determination of the tensile strength properties, and microstructure observation, the effect of annealing at various temperatures on structure and change in the strength properties of the cold-deformed Al–Mg2Si alloys alloyed with joint additives of scandium and zirconium is studied. It is shown that the hardness decreases with increasing annealing temperature to minimal values in the interval of 300–500°C and then increases up to 600°C. Such a change in hardness is explained by the recovery process (hardness decrease) and enrichment of the aluminum solid solution in magnesium and silicon followed by its natural aging (hardness increase). Addition of scandium and zirconium to the colddeformed Al–Mg2Si alloys promotes an increase in their strength properties both after aging of these alloys at 170°C for 16 h and after softening annealing at 400°C for 1 h.

Effect of heat treatment on microstructure and mechanical property of Al–10%Mg2Si alloy

After solution treatment at 520 °C for 6 h and subsequent aging at 200 °C for 6 h, eutectic Mg2Si phase in Al–10%Mg2Si alloy transforms from long rod to short fiber-like and spherical morphologies, and a great number of nano-sized β″ particles precipitate in the Al matrix. The fine eutectic Mg2Si phase combined with nano-sized precipitates gives rise to enhanced hardness and high tensile strength of Al–10%Mg2Si alloy (increasing from 186 MPa to 234.6 MPa).

Corrosion behavior of Al–Mg2Si alloys with/without addition of Al–P master alloy

Corrosion resistance is an important fact to be considered in practical engineering application of Al–Mg2Si alloys, besides the mechanical properties. So in the paper, corrosion behavior of Al–20%Mg2Si with/without Al–3%P master alloy in 3.5% NaCl solution was investigated. For the Al–20%Mg2Si alloy, Mg2Si acts as anode and corrosion starts from its surface at the initial stage of corrosion process. As the corrosion proceeds, electrochemical polarity converts between Mg2Si and α(Al), which results in the corrosion of Al matrix with the formation of pits. Moreover, after addition of Al–3%P master alloy, Mg2Si transforms from enormous dendrite to fine and uniformly distributing polyhedron, which inhibits the corrosion pits from propagating in Al matrix and enhances the corrosion resistance of Al–20%Mg2Si.

Influence of Surface Refinement on Microstructure of Al-Si Cast Alloys Processed by Welding Method

In most cases, construction materials are selected so as to attain the optimal technological properties at the lowest possible weight and cost. Studies on the improvement of the properties of casting alloys have been continuously conducted over the recent years. Both the microstructure and properties of alloys may be altered via modification with chemical components, optimization of the crystallization process, heat treatment or a combination of these methods. While searching for alternative methods of improving the engineering surface properties of hypo- and hypereutectic Al-Si alloy, an attempt was made to modify its microstructure with the use one of a heat sources. This paper presents the results of an experiment investigating the microstructure and the hardness of the Al-9%SiMg and Al-20%SiMg alloys processed by TIG welding method.

Joint effect of scandium and zirconium on the structure and the strength properties of Al–Mg2Si–Based alloys

The joint effect of scandium and zirconium on the strength properties and the electrical resistivity of industrial Al–Mg2Si–based alloys has been studied. The additional alloying of Al–Mg2Si alloys with transition metals leads to substantial grain refinement of the aluminum solid-solution and, therefore, an increase in the strength properties of the industrial alloys.

The Age-Precipitations Structure Of Al-Mg-Ge Alloy Aged At 473K

Abstract The Al-Mg-Ge alloy is one of the age-hardening aluminum alloy after solution heat treatment. It has been proposed that the age-precipitation behavior of Al-Mg-Ge alloy is different from that of Al-Mg-Si alloy according to our previous works about the microstructure on Al-Mg-Ge alloy over-aged at 523K. For example, The hardness of peak aged Al-1.0mass%Mg2Ge alloy is higher than that of Al-1.0mass%Mg2Si alloy. The precipitates in the over-aged samples have been classified as some metastable phases, such as the β’-phase and Type-A precipitates and equilibrium phase of β-Mg2Ge by TEM observation. There a few reports about microstructure on Al-Mg-Ge alloys observed by TEM for different aging times. The age-precipitations structure of Al-Mg-Ge alloy has not been became clear. In this work, TEM observation was investigated the microstructure on Al-1.0mass%Mg2Ge alloy for difference aging times aged at 473K.

Solute-Vacancy Clustering In Al-Mg-Si Alloys Studied By Muon Spin Relaxation Technique

Abstract Zero-field muon spin relaxation experiments were carried out with Al-1.6%Mg2Si, Al-0.5%Mg, and Al-0.5%Si alloys. Observed relaxation spectra were compared with the calculated relaxation functions based on the Monte Carlo simulation to extract the dipolar width (Δ), trapping (νt), and detrapping rates (νd), with the initially trapped muon fraction (P0). The fitting analysis has elucidated that the muon trapping rates depended on the heat treatment and solute concentrations. The dissolved Mg in Al dominated the νt at lower temperatures below 120 K, therefore the similar temperature variations of νt were observed with the samples mixed with Mg. The νt around 200 K remarkably reflected the heat treatment effect on the samples, and the largest νt value was found with the sample annealed at 100°C among Al-1.6%Mg2Si alloys. The as-quenched Al-0.5%Si sample showed significant νt values between 80 and 280 K relating with Si-vacancy clusters, but such clusters disappeared with the natural aged Al-0.5%Si sample.

Joint effect of scandium and zirconium on the recrystallization of aluminum Al–Mg2Si alloys

Metallographic analysis and hardness measurements are used to study the recrystallization processes in aluminum Al–Mg2Si alloys with scandium and combined scandium and zirconium additions that occur during annealing of the cold-deformed alloys at 100–600°C. The temperature of the onset of recrystallization of the Al–Mg2Si alloys with scandium and combined zirconium and scandium additions is shown to be 50°C higher than that of the alloys free from scandium and zirconium. It was noted that the small grain sizes of the alloyed compositions lead to weaker disordering during recovery and recrystallization.

Microstructure of Hypereutectic Mg-Si Alloy with Sn, Al and Mn Additions

In the present study, the microstructure of Mg-5Si alloys with tin, aluminum and manganese was investigated. The microstructure of Mg-5Si alloy consists of the primary coarse Mg2Si phase, α-Mg solid solution and eutectic α-Mg + Mg2Si in which the eutectic Mg2Si phase solidifies in the form of Chinese script particles. The Mg2Sn phase and α-Mg solid solution with tin appear in the microstructure, when 7 wt.% of Sn was added to the Mg-5Si alloy. Aluminum dissolve in the α-Mg matrix and participates in the formation of Al2Sn phase. The addition of manganese promotes the formation of Mn5Si3 compound.

New Semisolid Casting of an Al-25Wt.% Mg<sub>2</sub>Si Composite Using Vibrating Cooling Slope

Al-Mg2Si composites have gained considerable attention because of their attractive properties such as low density, improved wear resistance and good castability. However, when in-situ routes are used for processing of these composites, the formation of coarse Mg2Si particles with sharp cornersis inevitable and is detrimental for the composite properties. This problem is intensified when a hypereutectic composition such as Al-25wt.% Mg2Si alloy is processed. In the present study, an innovative semisolid technique termed as the Vibrating Cooling Slope (VCS) has been applied to produce a sample of in-situ Al-25wt.% Mg2Si composite.This technique combines the conventional cooling slope and vibration casting methods into an integrated one for producing fine and globular structures in the as-cast condition. An inclined plate was prepared from a 10mm thickness copper plate and was coated by boron nitride. This platecould vibrate mechanically in the vertical direction at a predetermined frequency by the aid of four springs and an electric motor. The molten Al-16.5wt.%Mg-9.4%Sialloy with 100oC superheat was poured on the surface of this cooling slope (set at 45° inclined angle)while it was vibrating at the frequency of 40 Hzandamplitude of 400 μm.The semisolid alloy travelled the length of 40 cm on the slope before being poured into a steel mold (60 mm internal diameter and 35 mm in height). Also for the purpose of comparison, gravity casting (GC) and conventionally still cooling slope casting (CS)were carried outboth using the same mold and with the same superheat.The samples were sectioned, polished and subjected to metallographicstudies,porosity and hardness measurements. It was concluded that CS and VCS techniques resulted in a decrease in the size of Mg2Si particles by about 50%and 70% respectively when compared with the gravity casting. However, the increased shape factor of Mg2Si particles in the VCS and CS processed samples was insignificant as compared with GC. Although in comparison with GC, the VCS processed sample showed a higher porosity level, it exhibited a higher hardness value. These results were attributed to the finer and modified microstructure obtained via this newly developed technique.

Wear properties of squeeze cast in situ Mg2Si–A380 alloy

In situ composites have been studied mainly to eliminate wettability, porosity and non-uniform distribution of particulate problems in composite materials. Al–Mg2Si alloy are preferred choice of such group of alloys owing to the combination of light weight and improved mechanical properties. The morphology of Mg2Si is one of the key parameters for the wear properties. In this work, squeezed casting method was used to produce samples where porosity was aimed to be reduced and morphology of Mg2Si was altered. In addition, the wear properties of in situ A380–Mg2Si were investigated. It was found that as squeeze pressure was increased, porosity and size of Mg2Si was decreased and wear rate was increased.

Precipitation of metastable phases and its effect on electrical resistivity of Al-0.96Mg2Si alloy during aging

The precipitation behavior and its influence on the electrical resistivity of the Al-0.96Mg2Si alloy during aging were investigated with in-situ resistivity measurement and transmission electron microscopy (TEM). The precipitates of the peak aged alloy include both β″ and β′, but the amount ratio of β″ to β′ varies with the aging temperature and time increasing. The precipitates during aging at 175 °C are dominated by needle-like β″ phases (including pre-β″ phase), the size of which increases with the time prolonging, but does not increase substantially after further aging. The evolution of electrical conductivity is directly related to such microstructural evolution. However, the hardness of the alloy stays at the peak value for a long term. When the alloy is aged at 195 °C, the ratio of β″ to β′ becomes the main factor to influence relative resistivity (Δρ) value. The higher the temperature is, the smaller the ratio is, and the faster the Δρ value decreases. Moreover, the hardness peak drops with the decrease of the ratio. With the size and distribution parameters measured from TEM images, a semi-quantitative relationship between precipitates and the electrical resistivity was established.

Enhancement in Strength and Ductility of Al-Mg-Si Alloy by Cryorolling followed by Warm Rolling

The effect of cryorolling followed by warm rolling (CR+WR) on strength and ductility of Al- Mg-Si alloys has been studied in the present work. Ultrafine grained Al 6063 alloy was developed through cryorolling up to 80% and warm rolling up to 50% at 200°C followed by ageing at 100°C for 22 hr. It is compared with the material processed through cryorolling followed by low temperature ageing. By implementing this new approach, simultaneous improvement in strength (290MPa) and ductility (15%) was achieved in Al 6063 alloys. The microstructure and precipitate evolution were characterized by Optical microscope, Electron back scattered diffraction (EBSD) and Transmission electron microscope (TEM) techniques. The ultrafine grain structure with 150-300nm was observed in CR+WR sample. Mechanical properties were studied by performing hardness and tensile testing at room temperature. Strength and ductility of CR+WR samples are found to be superior to CR sample after peak ageing treatment.

Modification of Mg2Si in Mg-Si alloys with neodymium

The modification effect of neodymium (Nd) on Mg2Si in the hypereutectic Mg-3%Si (mass fraction) alloy was investigated by optical microcopy, scanning electron microscopy and X-ray diffraction. The results indicate that the morphology of the primary Mg2Si transforms from coarse dendrite into fine polygon with increasing Nd content. The average size of the primary Mg2Si significantly decreases to about 10 μm with increasing Nd content up to 1.0%, and then becomes coarser again. The modification and refinement of the primary Mg2Si are mainly attributed to the poisoning effect. The NdMg2 phase in the primary Mg2Si transforms into NdSi and NdSi2 compounds as the Nd content exceeds 3.0%. Therefore, it is reasonable to conclude that the proper Nd (1.0%) addition can effectively modify and refine the primary Mg2Si.

Microstructural evolution and mechanical properties of misch metal added Mg-Si alloys

Effect of misch metal additions (0.3, 0.6, 0.9 and 1.2 wt%) on the refinement of Mg2Si phase in Mg-1.15Si alloy has been studied and compared with the base alloy. MM addition effectively refines the microstructure by breaking the α-Mg halos and lamellar eutectic phase and the maximum refinement is obtained for 0.6 MM addition. For higher MM additions (0.9 and 1.2 wt%), the refinement effect gets reduced and the formation of RE-Si compound is dominated. Improved tensile properties are obtained with the addition of MM and are attributed to the refinement of microstructure and the presence RE-Si compound. The tensile properties obtained are correlated with the microstructure and mirofractomechnisms.

Refinement of Mg2Si reinforcement in a commercial Al–20%Mg2Si in-situ composite with bismuth, antimony and strontium

Refinement by addition elements of Al–Mg2Si alloys is known to result in a change of primary Mg2Si morphology. In this paper, the effects of Bi, Sb and Sr on the characteristic parameters of Al–20%Mg2Si in-situ composite have been investigated by computer aided cooling curve thermal analysis and microstructural inspection. Size, density and aspect ratio measurements showed that additions of 0.4wt.% Bi, 0.8wt.% Sb and 0.01wt.% Sr refined the Mg2Si reinforcement. Exceeding these concentrations, however, resulted in coarsening of Mg2Si particles with no change in the morphology. The results also showed that addition elements caused a decrease in the nucleation and growth temperatures of Mg2Si particles. The refining effect of Bi, Sb and Sr is likely to be related to the effect of oxide bifilms suspended in the composite melt as favored nucleation substrates for Mg2Si particles.

Effects of Sb and heat treatment on the microstructure of Al-15.5wt%Mg2Si alloy

The modification effects of alloying element Sb and heat treatment on Al-15.5wt%Mg2Si alloy were investigated by Olympus microscopy (OM), scanning electron microscopy and energy disperse spectroscopy (SEM-EDS), and X-ray diffraction (XRD). It is found that Sb plays a significant role in shaping primary Mg2Si phase and eutectic Mg2Si phase in Al-15.5wt%Mg2Si alloy. The Sb addition of about 1.0wt% makes the resultant alloy show the finest primary Mg2Si phase and the eutectic Mg2Si phase with well distribution. But further increasing the Sb content decreases the amount of primary Mg2Si phase, and some segregated phases appear at regions between the grains. In addition, heat treatment can modify the microstructural feature of Sb-modified Al-15.5wt%Mg2Si alloy in terms of obviously shortening the nodulizing time of primary Mg2Si phase and eutectic Mg2Si phase.

Hrtem Observation of the Precipitates in Cu and Ag Added Al-Mg-Si Alloys

It has been known that Cu- and Ag-added Al-1.0mass%Mg2Si alloys (Al-Mg-Si-Cu alloy and Al-Mg-Si-Ag alloy) have higher hardness and elongation than those of Al-1.0mass%Mg2Si alloy. In this study, the aging behaviour of Al-Mg-Si-Cu alloy, Al-Mg-Si-Ag alloy and (Cu+Ag)-addition Al -1.0 mass% Mg2Si alloy has been investigated by hardness test and TEM observation. The Al-Mg-Si-Cu-Ag alloy has the fastest age-hardening rate in the early aging period and the finest microstructure at the peak hardness among three alloys. Therefore the microstructure of the precipitate in Al-Mg-Si-Cu-Ag alloy has been investigated by HRTEM observation to understand the effect of Cu and Ag addition on aging precipitation.

The Microstructure and Mechanical Properties of Al-7%SiMg Alloy Treated with a Exothermic Modifier Contained Na and B

Results of studies on the modification of Al-7%SiMg alloy with an exothermic modifier on base Na2B4O7 are presented in the paper. The alloy was modified in a casting mold. Its structure, tensile strength and percentage elongation were determined. The results of the study indicate that in addition to modifier quantity and the type of reducing agent applied to produce an exothermic reaction, the reaction's thermal effect influences the quality of the modification process, leading to changes in the microstructure and mechanical properties of the alloy.

Influence of Neodymium Addition on the Microstructure, Mechanical and Thermal Properties of Mg-Si Alloys

The present work aims to investigate the influence of neodymium addition on the microstructure, mechanical and thermal properties of Mg-Si alloys. Different proportions of (0.3, 0.6, 0.9 and 1.2 wt.%) Nd has been added to the hypo (Mg-1.15Si) and hypereutectic (Mg-6Si) alloys. The microstructural studies reveal that the Nd additions change the size and mor hology of Mg-halos in the hypoeutectic Mg-Si alloy. In the hypereutectic alloy, the Nd additions considerably reduce the size of the primary Mg2Si phase besides, modifying the Mg2Si morphology from a coarse dendritic to a polyhedral shape. The amount of Nd required for the optimal modification of both alloys is experimentally determined. Increase in mechanical properties obtained with Nd addition is correlated with the microstructural refinement. To understand the microfracture mechanism, the SEM analysis has been carried out.