Magnesium Side Research Articles

Effect of welding speed on microstructure, nano-mechanical and nano-tribological characteristics of dissimilar friction stir welded AA6061-T6 and AZ31 alloy

The microstructural, tribological, and mechanical performance of friction-stir welded AA6061-T6 and AZ31 alloys were investigated using electron back scattered diffraction, scanning electron microscope, X-ray diffraction, and electron dispersed spectroscopy methods. The non-destructive X-ray microcomputed tomography test was used to analyse weld porosity. The distribution of volumetric and surface flaws (pores) was found to be confined across the weldment. Using a novel atomic force microscopy method, the nano-tribological characteristics of the base metal and localized regions of welded sample were studied for the first time. The significant difference in wear and friction behaviour was observed in all weld zones and base metal of magnesium side, which was correlated with the hardness of these regions. AFM results showed strong variation in tribological properties in correlation with the hardness trends of different weld zones, i.e. higher hardness leads to low wear. In weldments, intermetallic compounds such as Al12Mg17 and Al3Mg2 were produced, resulting in nanohardness differences as measured by the nanoindentation test. The joint efficiency of 65%, 84%, and 91% were obtained at welding speeds of 16 mm/min, 20 mm/min, and 25 mm/min, respectively.

Microstructure and Mechanical Properties of Laser Welded Magnesium Alloy/Steel Joint Using Cu-Si Composite Interlayer

In this study, Cu-Si composite powder was used as the interlayer to carry out laser lap deep penetration welding of AZ31B magnesium alloy and DP590 dual-phase steel. The effects of Cu-Si composite powder on the weld formation, microstructure, and mechanical properties of magnesium alloy and steel joint were studied. The results show that the addition of Si can improve the laser absorption rate of the interlayer and increase the melting depth at the magnesium side. In addition, the Cu-Si composite interlayer hindered the diffusion of Al, and reduced the thickness of reactive layer at the magnesium alloy and the steel interface. After adding Si into the interlayer, the reactive layer changed from Fe3Al+α-Mg to Fe-(Al, Si) +α-Mg and the content of intermetallic compounds in the reactive layer decreased, which improved the plastic deformation capacity and the ductility of the reactive layer. As a result, the tensile shear force firstly increased and then decreased with the Si increase. The maximum tensile shear force of 86.2 N/mm was achieved when the Si content was 5%, which was 20.4% higher than that of the Cu interlayer. Plus, the fracture location changed from near the steel side to near the magnesium side weld.

Formability of laser welded steel/magnesium dissimilar metal with Sn powder-adhesive interlayer

Abstract The exploratory experiments of laser fusion welding with Sn powder and the automotive adhesive addition were conducted for DP590 dual-phase steel and AZ31B magnesium alloy in an overlap steel-on-magnesium configuration. The characteristics of metal vapor/plasma were analyzed by collecting and analyzing plasma shape and welding spectra. The microstructure of the welded was characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), energy dispersive X-ray spectrometer (EDS). The temperature field distribution of the joint was simulated by COMSOL finite-element software. The results showed that the transfer of heat from steel to the magnesium alloy is hindered by the adhesive layer, which is conducive to the simultaneous melting of steel and magnesium with large differences in melting and boiling points. In addition, the width of the molten pool increases, but the depth is shallow on the magnesium side. Meanwhile, the recoil pressure induced by the splashing of the molten pool reduces, and the surface quality of the weld is improved. Some intermetallic compounds (IMCs), such as FeSn, Fe1.3Sn, and Fe3Sn, are formed inside the molten pool, while columnar dendrite Mg2Sn phase is also produced. The presence of these phases helps realize the bidirectional metallurgical bonding of steel/magnesium dissimilar metals.

Dissimilar metals TIG welding-brazing of AZ31 magnesium alloy to 304 stainless steel

Abstract TIG welding-brazing of dissimilar metals magnesium alloy to stainless steel was investigated, and the wettability and spreadability of magnesium based filler metal on the stainless steel surface were analyzed. The microstructures of welded samples were observed using optical microscope and scanning electron microscopy (SEM). The microhardness at the weld interfaces found to be higher than the substrates owing to the presence of MgAl2 and MgO intermetallic compounds. The maximum tensile strength of the weld joints was about 69 MPa, and the tensile fracture occurred at heat affected zone on weak material of the magnesium side and/or at stainless steel/weld seam interface along intermetallic layer. The fracture surface was analysed by using SEM analysis. The ductile mode of fracture was observed with the formation of voids.

Oral magnesium supplementation for leg cramps in pregnancy-An observational controlled trial.

Oral magnesium for leg cramps treatment in pregnancy is a controversial issue according to recent Cochrane systematic review. This study aims to evaluate the efficacy of Mg++ supplementation in leg cramps treatment in pregnancy. This observational clinical trial studied 132 pregnant women with leg cramps in the first trimester of pregnancy. At baseline, 74 (56.3%) had two leg cramps episodes per week, 28 (21.1%) three episodes, 13 (9.8%) four episodes and 9 (6.8%) five or more episodes. They were randomized 1:1 to 300 mg/day of oral Mg++ citrate (n = 66) or placebo (n = 66). The primary outcome was the frequency of leg cramps episodes per week reported by pregnant women. Secondary outcomes were the ocurrence of leg cramps and oral magnesium side effects. 130 pregnant women completed the study and the two groups were comparable according to some sociodemographic and clinical characteristics. After 4 weeks of intervention it was observed a 28.4% (39/132) (CI 95%: 20.9-37.0) reduction of leg cramps in all participants and no difference between the two groups was found; reduction of 27.2% (18/66) (CI 95%: 17.0-39.6) in Mg++ group and 32.8% (21/66) (CI 95%: 21.6-45.7) in the placebo group. The OR of leg cramps was 1.3 (CI 95%: 0.6-2.9), p = 0.527, taking the placebo group as reference. Among pregnant women who remained with leg cramps the mean of leg cramps episodes per week showed no significance difference between the Mg++ and placebo groups; t-student test: p = 0.408. Four pregnant women showed gastrointestinal side effects; 2 in each group had nauseas and diarrhoea. Oral magnesium supplementation during pregnancy did not reduce the ocurrence and frequency of episodes of leg cramps.

Cold metal transfer process – A review

The welded joints of dissimilar metals find numerous applications in the field of automobiles, marine, nuclear energy, construction, aerospace. The dissimilar metal welding has lower weld efficiency until the emergence of the Cold Metal Transfer (CMT) process. The process is termed as cold since the heat input is low when compared to the conventional MIG process. This process uses a principle called ‘short-circuiting,’ where the feed wire is retracted when the liquid droplet falls from the welding wire to the substrate. The retraction is done by the electronic regulators of the robot arm of the process, and the arc is reignited when the liquid droplet is fully transferred to the substrate. This paper is based on the different characteristics, microstructure and mechanical properties exhibited by the dissimilar metal welded joints joined by using the CMT process. Discussions were limited to titanium, stainless steel, aluminium, copper and magnesium joints. Welding was performed with optimum parameters of CMT and the results were analysed. Due to the super low heat input of the CMT welding process, rapid heating and cooling was realized. Titanium and stainless steel joint fetched a maximum tensile strength of 318 MPa with the ductility of 8.5%. Magnesium with Aluminium joints produced a max strength of 230 MPa and was high towards the magnesium side and lowered towards the aluminium side. Minimum diffusion layer and changes in the diffusion zones of Al-HAZ and Mg interfaces are observed. The diffusion of the Al matrix was found to be high.

Ultrasonic Welding of Magnesium\u2013Titanium Dissimilar Metals: A Study on Thermo-mechanical Analyses of Welding Process by Experimentation and Finite Element Method

Ultrasonic welding is an effective ways to achieve a non-reactive/immiscible heterogeneous metal connection, such as the connection of magnesium alloy and titanium alloy. But the thermal mechanism of magnesium alloy/titanium alloy ultrasonic welding has not been defined clearly. In this paper, the experimental and the finite element analysis were adopted to study the thermal mechanism during welding. Through the test, the temperature variation law during the welding process is obtained, and the accuracy of the finite element model is verified. The microscopic analysis indicates that at the welding time of 0.5 s, the magnesium alloy in the center of the solder joint is partially melted and generates the liquid phase. Through the finite element analysis, the friction coefficient of the magnesium–titanium ultrasonic welding interface can be considered as an average constant value of 0.28. The maximum temperature at the interface can exceed 600 °C to reach the melting point temperature of the magnesium alloy. The plastic deformation begins after 0.35 s and occurs at the magnesium side at the center of the interface.

Interfacial microstructure and mechanical behavior of Mg/Cu bimetal composites fabricated by compound casting process

Abstract Mg/Cu bimetal composites were prepared by compound casting method, and the microstructure evolution, phase constitution and bonding strength at the interface were investigated. It is found that a good metallurgical bonding can be achieved at the interface of Mg and Cu, which consists of two sub-layers, i.e., layer I with 30 μm on the copper side composed of Mg2Cu matrix phase, on which a small amount of dendritic MgCu2 phase was randomly distributed; layer II with 140 μm on the magnesium side made up of the lamellar nano-eutectic network Mg2Cu+(Mg) and a small amount of detached Mg2Cu phase. The average interfacial shear strength of the bimetal composite is measured to be 13 MPa. This study provides a new fabrication process for the application of Mg/Cu bimetal composites as the hydrogen storage materials.

Effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for dual phase steel and magnesium alloy

The aim of present research was investigating the effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for DP600 dual phase steel and AZ31 magnesium alloy in an overlap steel-on-magnesium configuration. Results showed that when Sn-foil was added as interlayer, some defects, such as surface pit, spatter and softening in heat affected zone, can be avoided,oxide and porosity are also no obvious in the weld. A good weld surface with continuous and uniform fish scale welding line is obtained. Fe–Sn phases, such as FeSn, Fe1.3Sn, and Fe3Sn, are formed in steel side, while Mg2Sn is found in magnesium side. These new phases are favorable for realizing the steel/magnesium metallurgical connection, and adding Sn-foil laser welding is an effective way in joining steel to magnesium alloy. However, mechanical property for steel/magnesium joint is closely connected with the brittleness of Mg2Sn phase, how to regulate its brittleness is the key in order to improve the joint properties.

Dissimilar Friction Stir Welding of Immiscible Titanium and Magnesium

The dissimilar friction stir welding of the immiscible combination (i. e., titanium and magnesium) was performed. The thin foil aluminum was inserted between pure titanium and pure magnesium in order to react the two immiscible materials. The welding parameters (i.e., aluminum foil thickness, probe offset and welding speed) were optimized to acquire a sound joint. Also, the influence of the welding conditions on the formation of reaction layer at the interface, aluminum distributions in the magnesium matrix and tensile strength of the joints was systematically examined. With the increasing thickness of the aluminum filler material, the size and amount of the welding defects generated inside the magnesium stir zone (SZ) increased due to the poor material flow. The dissimilar joint between titanium and magnesium fabricated with a thin aluminum filler material and with the optimized probe offset and welding speed shows a high tensile strength because of the properly thin intermetallic compound layer formed at the weld interface and inhibition of the brittle intermetallic compounds formation inside the SZ on the magnesium side during the FSW. The tensile property results indicated that the highest tensile strength of approximately 150 MPa, which is ~88% of the joint strength of pure magnesium can be obtained in the optimized dissimilar titanium and magnesium joint, and it fractured at the heat affected zone (HAZ) in the magnesium.

Numerical and Experimental Investigations in Laser Welding for Steel and Magnesium Alloy

The experiments of laser welding for steel and magnesium alloy in an overlap steel-on-magnesium configuration were carried out, the effect of adding Sn- foil on microstructure and mechanical properties of the weld were investigated, and numerical simulations of laser welding with/without Sn-Foil were also finished. A good agreement between the experimental results and numerical simulations for the shape and size of the molten pool can be seen. Heat transfer slows down from steel to magnesium alloy with Sn-foil, which means the thermal insulation effect, thus steel and magnesium are simultaneously melted with the larger difference in melting and boiling point. In addition, the cooling rate of steel side decreases, the diffusion time is prolonged between Fe and Sn elements, which leads to some phases, such as FeSn, Fe1.3Sn, and Fe3Sn, are formed in the transition zone of steel side, while Mg2Sn phase is found in magnesium side. Hence, adding Sn-foil is an effective way in joining steel to magnesium alloy based on the metallurgical reaction.

Experimental Investigation and optimization of Process Parameters for Shear Strength of Compound Cast Bimetallic Joints

Joining of A356 alloy and magnesium was carried out by vacuum assisted sand mold compound casting process. Microstructure at the joint interface was studied by using optical microscope, scanning electron microscope, energy dispersive X-ray spectroscopy and X-ray diffractometer. Characterization indicated that a relatively uniform joint interface was obtained. The joint interface was composed of three distinct layers containing Mg2Al3 on aluminum side, Mg17Al12 + δ eutectic structure on magnesium side and Mg17Al12 as middle layer. As a result of interaction between silicon, present in A356 with magnesium, Mg2Si compound was formed. Push out test was conducted on electronics universal testing machine to measure the shear strength across the joint interface. The important process parameters (grit size of sand paper, insert temperature, pouring temperature and vacuum pressure) were optimized to maximize the shear strength. Optimization was carried out by using response surface methodology, desirability analysis and genetic algorithm (GA) techniques. It was observed that the shear strength increased by 14.21, 8.60 and 4.80% with genetic algorithm, desirability analysis and regression model respectively. GA reported the optimal value of shear strength.

Effect of Bonding Temperature on the Microstructure and Strength of the Joint between Magnesium AZ31 and Ti-6Al-4V Alloys Using Copper Coatings and Tin Interlayers

Transient Liquid Phase (TLP) bonding was performed between Mg-AZ31 and Ti-6Al-4V alloys with various bonding temperatures using Cu coatings and Sn interlayers. The bonding parameters such as bonding pressure and bonding time were fixed at 1 MPa and 15 minutes respectively in order to study the effect of bonding temperature on the joint evolution. Bonds made at temperatures of 540, 560, 580 and 600 C showed good bond strength. The obtained bonds were investigated by Electron Probe Micro-analyzer EPMA and showed reaction layers and diffusion zones for all bonds made. The maximum joint shear strength of 78 MPa was obtained for bond made at 580 C. X-ray diffraction XRD and X-ray photoelectron spectroscopy XPS were taken for the fractured surfaces of bond made at 580 C. The analysis of the fractured surfaces found that the reaction layer contains Sn5Ti6 IMC in the titanium side and Mg2Cu IMC in the magnesium side where the fracture occurs at the diffusion zone in the mg side.

Laser offset welding of AZ31B magnesium alloy to 316 stainless steel

In this paper, the feasibility of using a fiber laser to perform a dissimilar metal joining was explored. AZ31B magnesium and 316 stainless steel were autogenously joined in butt configuration. The weldability between different materials is often compromised by a large difference in thermal properties and poor metallurgical compatibility. Thus, the beam was focused onto the top surface of the magnesium plate, at a certain distance from the interfaces (offset), and without using any interlayer or groove preparation. Such a method was called laser offset welding (LOW). Results proved a very good capability. The ultimate tensile strength exceeded the value of 100MPa, since a resistant and thin layer of hard intermetallic compounds is formed within the fusion zone. The rupture was observed within the magnesium side, far from the centerline. The metallurgy of fusion zone indicated the effectiveness of phases coalescence, without mixing at liquid states. LOW was demonstrated to be a promising technique to join dissimilar metal welds, being capable to produce an effective bonding with good tensile strength.

Characteristics of friction welded AZ31B magnesium–commercial pure titanium dissimilar joints

Abstract It is essential to understand the weld interface characteristics and mechanical properties of dissimilar joints to improve its quality. This study is aimed at exploring the properties of friction welded magnesium–titanium dissimilar joint using tensile testing coupled with digital image correlation, optical and scanning electron microscopy, x-ray diffraction and microhardness measurements. Microstructurally different regions such as contact zone, dynamic recrystallized zone, thermo-mechanically affected zone, and partially deformed zone in the magnesium side were observed. No discernible regions were observed in the titanium side, as it had not undergone any significant plastic deformation. Phase analysis indicated that the aluminium from the magnesium side diffused toward the weld interface and formed a thin continuous intermetallic layer by reacting with the titanium. Microhardness mapping showed a steep hardness gradient from the titanium to magnesium side. Critical analysis is done on the tensile characteristics of the specimen and the response of the local regions to the deformation process is mapped.

Dissimilar FSW of immiscible materials: Steel/magnesium

Abstract The dissimilar joint between a light metal and a strong metal such as steel, is necessary for reducing the weight of vehicles. Friction Stir Welding (FSW) is a useful process to obtain several kinds of dissimilar joints and many studies have already been reported. However, the joint between steel and magnesium has not been aggressively studied, because it is an immiscible system. Aluminum is one of the most popular alloying elements for magnesium, and the iron–aluminum system has many intermetallic compounds due to their strong interactions. In this study, the Fe–Al intermetallic compound layer was successfully formed at the joint interface between iron and magnesium using aluminum in the magnesium alloys. The joint strength increased with the increasing aluminum content of the magnesium alloy due to the depletion of aluminum at the magnesium side near the interface.

Intracellular absorption of transdermal magnesium demonstrated by ESEM-EDS

Magnesium, the second most abundant intracellular cation in human body, plays a fundamental role in intracellular metabolism. As a cofactor in a huge number of key enzimatic reactions, magnesium is especially important for those enzymes that use nucleotides as cofactors or substrates (phosphotransferases, phosphohydrolases, etc.). The majority of magnesium studies were performed by detecting serum magnesium concentration, measure that doesn’t consider the intracellular uptake. In the present study, a different approach has been carried out. By means of an Environmental Scanning Electron Microscope (ESEM) equipped with an Energy Dispersive Spectroscopy (EDS) detector, the intracellular magnesium presence and uptake has been measured in a semiquantitative approach on samples of exfoliating epithelial cells from the oral mucosa [1]. The intracellular magnesium uptake has been experimentally induced by applying, twice a day and for 4 months, on the skin of healthy volunteers, a spray of a magnesium chlorate supersaturated solution. Epithelial cells and blood samples were collected at time zero and every 2 months of treatment. Despite the constant serum concentration of magnesium along the treatment and in absence of any side effect, the EDS analysis reveals a progressive and regular intracellular magnesium increasing of about 100% of the values at each experimental step. Results can confirm the high specificity and, more in general, the high reliability of the EDS analysis about a parameter that can result neglect utilizing only the serum concentration. Moreover, transdermal absorption of magnesium can represent an efficient way of magnesium administration, low dose and side effect free, to be utilize in chronic clinical magnesium deficiency [2].

Mechanical and metallurgical properties of diffusion bonded AA2024 Al and AZ31B Mg

In the present study, diffusion bonding was carried out between AZ31B magnesium and AA2024 aluminium in the temperature range of <TEX>$405^{\circ}C$</TEX> to <TEX>$475^{\circ}C$</TEX> for 15 min to 85 min and 5MPa to 20 MPa uniaxial loads was applied. Interface quality of the joints was assessed by microhardness and shear testing. Also, the bonding interfaces were analyzed by means of optical microscopy, scanning electron microscopy, energy dispersive spectrometer and XRD. The maximum bonding and shear strength was obtained at <TEX>$440^{\circ}C$</TEX>, 12 MPa and 70 min. The maximum hardness values were obtained from the area next to the interface in magnesium side of the joint. The hardness values were found to decrease with increasing distance from the interface in magnesium side while it remained constant in aluminium side. It was seen that the diffusion transition zone near the interface consists of various phases of <TEX>$MgAl_2O_4$</TEX>, <TEX>$Mg_2SiO_4$</TEX> and <TEX>$Al_2SiO_5$</TEX>.

Microstructure and mechanical properties of dissimilar welded Mg–Al joints by ultrasonic spot welding technique

Dissimilar spot welds of magnesium–aluminium alloy were produced via a solid state welding process, i.e. ultrasonic spot welding, and a sound joint was obtained under most of the welding conditions. It was observed that a layer of intermetallic compound (IMC) consisting of Al12M17 formed at the weld centre where the hardness became higher. The lap shear strength and failure energy of the welds first increased and then decreased with increasing welding energy, with the maximum lap shear strength and failure energy occurring at ∼1250 J. This was a consequence of the competition between the increasing diffusion bonding arising from higher temperatures and the deterioration effect of the intermetallic layer of increasing thicknesses. Failure predominantly occurred in between the aluminium alloy and the intermetallic layer, which normally stayed at the magnesium side or from the cracks of the IMCs in the reaction layer.

A Preliminary Investigation on Friction Stir Spot Welding of Steel/Mg

Dissimilar metal of Steel and Magnesium alloy used for friction stir spot welding is studied. Based on using orthogonal test method optimizes the process parameters and gets satisfactory joints , SEM is used to observe the features of joint,XRD is applied to determine the joint phase, and the results show that: the design of rotating tool without pin is reasonable and it can form satisfactory joints without keyhole of spot welding. The performance of spot welding joint depends on the extent of diffusion of Zn and Mg and high weld consistency. There is small existence of intermetallics made of MgZn2,Mg0.97Zn0.03 in welding joint.The properties of joint depends on the intermetallics, Due to this,The microhardness of joint increases gradually from the magnesium side to steel side.