Cast Magnesium Alloy Research Articles

Calorimetric analysis of Mg–Li ultra light magnesium alloy

The Thermal-Derivative Analysis, or Computer-Aided Cooling Curve Analysis, is a commonly used method for determining the solidification parameters of metals and alloys. Knowledge of the enthalpy, kinetics and broad characteristics of the transformations taking place during the cooling of an alloy can be obtained with the proper configuration of analytical equipment and arrangement of test techniques. This work practically analyses the changes occurring in the Mg–4.5Li–1.5Al alloy as a result of the modification of the structure by the addition of TiB and Sr. The results indicate that adding grain refinements significantly affects the microstructure and thermal parameters of Mg–4.5Li–1.5Al alloy. The nucleation temperature and solidus temperature decrease with the addition of chemical reagents. Compressive strength improved due to the refinement of grain size. The results confirmed that thermal-derivative analysis is suitable for analysing changes in cast magnesium alloys.

Effects of aging treatment processes on microstructures and mechanical properties of AZ63 casting magnesium alloy

Effects of aging treatment processes on microstructures and mechanical properties of AZ63 casting magnesium alloy

Effect of Surface Strain to Hydroxide Layer Formation on High-Pressure Die Casting Magnesium Alloy

Magnesium hydroxide layer improve corrosion resistance of magnesium alloys. Nonuniform strain on magnesium alloys surface was reported that affected to layer formation and corrosion resistance properties. Hydroxide layer formed to high pressure die cast ASTM AZ91D magnesium alloy, then investigated to correlation between hydroxide layer formation and residual stress and strain distribution on alloy surface which were measured by X-ray. Strain distribution was evaluated by full width half maximum (FWHM) value. Formed hydroxide layer was well compatible with FWHM distribution in as cast specimen. Heat treated for homogenization was carried out to inspection for correlation FWHM. FWHM was significantly lowering by heat treatment. Hydroxide layer tends to thin where FWHM value was low, therefore correlation between nonuniform strain and hydroxide layer formation was found out.

Microstructures and electrochemical behaviors of casting magnesium alloys with enhanced compression strengths and decomposition rates

New-type magnesium alloy with prominent solubility and mechanical property lays foundation for preparing fracturing part in petroleum extraction. Herein, Mg-xZn-Zr-SiC alloy is prepared with casting strategy. Electrochemical and compression tests are conducted to assess the feasibility as decomposable material. Morphology, composition, phase and distribution are characterized to investigate decomposition mechanism. Results indicate that floccule, substrate component and reticulate secondary phase are formed on as-prepared surface. Sample also acts out enhanced compression strength to maintain pressure and guarantee stability in dissolution process. Furthermore, as decomposition time and zinc content increase, couple corrosion intensifies, resulting in gradually enhanced decomposition rate. Rapid sample decomposition is mainly due to basal anode dissolution, micro particle exfoliation and poor decomposition resistance of corroding product. Such work shows profound significance in preparing new-type accessible alloy to ensure rapid dissolution of fracturing part and guarantee stable compression strength in oil-gas reservoir exploitation.

AM20, AJ21 ve AS21 Magnezyum Alaşımlarının Aşınma ve İşlenebilirlik Davranışları Üzerine Karşılaştırmalı Bir Çalışma

This paper is a comparative study on mechanical properties, wear resistance and machinability behaviors of AM20, AJ21 and AS21 (Mg-2Al-X) cast magnesium alloys. The effects of the changing in third alloy component (x:0.5 Mn, 1 Sr and 1 Si, and constant 2 Al, wt.%) in these alloys on microstructure (intermetallic phases), mechanical and wear properties and machinability (cutting force, surface roughness, FBU and also chip formation) were comparatively analyzed. The highest mechanical properties and wear resistance were in AS21 (i.e. 49.2 hardness and 181.5 MPa UTS) alloy and the highest machinability were in AM20 (cutting force 35.6N) alloy. The machinability of the alloys were increase with increasing cutting speed.

Influence of hydrogen on crystallization of cast magnesium alloys

It is shown that hydrogen is a demodifying element of the structure of cast magnesium alloys during their crystallization. Hydrogen atoms, adsorbing on elementary nanocrystals in melts, prevent the combination of nanocrystals into the nucleus of crystallization of α‑phase microcrystals. As a result, molds with an unmodified structure are formed. Modifiers reduce the concentration of adsorbed hydrogen in the melts of magnesium alloys. This results in the milling of α‑phase microcrystals in castings as they solidify.

Simulation and analysis of AZ80 magnesium alloy centrifugal casting

Centrifugal casting magnesium alloy pipe has been widely used. Still, because of its poor mechanical properties, it isn’t to meet the needs of the working environment, which limits its development in civil and industrial fields. Therefore, it is necessary to study the centrifugal casting process of magnesium alloy. In this paper, AZ80 magnesium alloy is used as the research material, and the numerical simulation of the centrifugal casting process is carried out by ANSYS Fluent software. The influence of different variable conditions on the solidification rate is analyzed, and a concept of defect ratio is proposed. The post-processing software is used to write an expression for macroscopic analysis of pore defect ratio on the outer surface of the casting, using which the influence of defect ratio under different variables is given. The research aims to guide the centrifugal casting experiment and predict the defects, greatly saving resources and costs.

Investigation of castability, mechanical, corrosion properties and flammability of ML-OPB and EWZ43 magnesium alloys

Magnesium alloys are usually considered as structural materials when the weight reduction is important - in aircraft and space industry for example. In recent years, there has been an increase in the use of new generation ignition-proof high-strength magnesium alloys in the design of aircraft parts. The properties of new ignition-proof casting magnesium alloys ML-OPB (Mg–6.7Y–2.6Zn–0.5Zr–0.35Ce– 0.35Yb; wt.%) and EWZ43 (Mg–3.8Y–4.4Nd–0.6Zr–0.6Zn; wt.%) were investigated and compared with properties of commercial magnesium alloys. The microstructure of investigated alloys in the as-cast condition comprises of a magnesium solid solution and a significant amount of eutectic. Heat treatment according to the T6 mode results in change in the eutectic phase’s morphology and also to their partial dissolution in the magnesium matrix. Long-term high-temperature holding, simulating operating conditions (500 h at 300 °C), leads to the formation of precipitates along the grain boundaries in both alloys, significantly reducing the mechanical properties. During the oxidation of the samples, it was established that the main components that involved into the oxide film and provides the protective properties of the alloys is Y, Nd and Yb. The investigated alloys have a high strength, which is not lower than that of the ML10 alloy. At the same time, the advantage of the ML-OPB alloy is a high elongation at fracture, while the EWZ43 alloy is characterized by high strength. The corrosion rate of the investigated alloys exceeds the corrosion rate of known commercial ML10 and AZ91 alloys, which implies the need for additional protection against corrosion of investigated alloys. At the same time, the castability of ML-OPB and EWZ43 alloys is no lower than that of most commercial magnesium alloys. An oxide film with high Y content and high protective properties is formed when the alloys interact with the sand mold bonded with furan resin. The ignition temperature of the investigated alloys is 100–150 °C higher than that of the ML10 alloy. The flammability test of alloys in the flame of a gas burner, made on cone samples and typical aircraft castings «bracket», showed that ML-OPB and EWZ43 alloys are almost non-flammable under the conditions of experiment.

INVESTIGATION OF THE HEAT TREATMENT MODES EFFECT ON THE STRUCTURE AND PROPERTIES OF A FIREPROOF MAGNESIUM CASTING ALLOY OF THE Mg-REM-Zr SYSTEM

The research results on the development of a new generation Mg-REM-Zr fire-safe magnesium casting alloy system are presented. Serial magnesium alloys do not have both high strength at room temperature and a sufficient level of heat resistance. A unique domestic foundry magnesium alloy has been developed with consistently high specified properties at the same time. In addition, the obtained ignition temperature indicators of the developed alloy allow it to be attributed to the group of fireproof magnesium alloys. The conducted studies of the its heat treatment parameters made it possible to choose the optimal mode that ensures the achievement of high strength characteristics of the alloy.

Microstructure and properties of biomedical Mg-Zn-Ca alloy at different extrusion temperatures

Due to its good biocompatibility, magnesium alloy has been greatly developed in the application field of absorbable implant metal materials in recent years. At the same time, the disadvantages of magnesium alloy materials are more obvious. Because of the poor mechanical properties of as-cast magnesium alloy, the bearing capacity as an implant is insufficient. In this paper, the self-made cast magnesium alloy was strengthened by extrusion at three extrusion temperatures, and then the grain refinement and phase composition of the extruded magnesium alloy were investigated by optical microscope and X-ray diffractometer. The grain shape, recrystallization volume fraction, grain orientation and microstructure of magnesium alloy at different extrusion temperatures were studied by quasi-in-situ electron backscattering diffraction (EBSD). Through tensile test, the mechanical properties of magnesium alloy under different extrusion parameters were studied. It was found that the lower the extrusion temperature, the higher the tensile strength of the material. This paper aims to improve the mechanical properties of magnesium alloys, and provide theoretical and practical guidance for the preparation, processing and application of high-performance medical magnesium alloys.

Effect of cyclic loading on mechanical properties and microstructure of die cast magnesium alloy AZ91D

Abstract Magnesium alloy materials are often affected by cyclic stress, resulting in fatigue fracture due to changes in mechanical properties. In this study, external cyclic loads were introduced to simulate the loading of AZ91D (Mg-9Al-0.5Zn) parts. Tensile tests under static and external circulation loads were performed on the same specimens, and the effect of loading conditions on the mechanical properties of the specimens (tensile strength, yield strength and elongation) were studied. The internal microstructure of the test specimens was analyzed, and the influence of cyclic loading on the microstructure change of the specimens was discussed. Compared with static load, under the condition of cyclic loading, the tensile strength and yield strength of the specimens are increased by more than 15%, and the elongation rate is increased by 3 times. In addition, the microstructure images showed that many twins and the second phase β-Mg17Al12 were generated inside the AZ91D microstructure under cyclic loading. The former results in specimens crack initiation and it is the root cause of fatigue fracture. And the latter accounts for the strengthening of the mechanical properties of specimens.

Analysis of Solubility Change of Soluble Magnesium Alloy by Melting Treatment in Petroleum Downhole

In order to solve the problem that the material utilization rate of soluble magnesium base alloy rod is less than 30%, the method of magnesium alloy rod casting is adopted to improve the material utilization rate. However, the cooling mode affects the dissolution rate of soluble magnesium alloy after casting. According to the different thermal conductivity of different materials, cylindrical graphite molds and copper molds with diameters of 5mm and 40mm are selected for casting magnesium alloys. In order to ensure the reliability of experimental results, polarization method and weight loss method were used to analyze the dissolution rate of soluble magnesium base alloy under different cooling modes. The test results show that: Magnesium alloy is cooled and solidified by copper mold with a diameter of 5mm, and the dissolution rate is the highest in 1.5% NaCl solution with a speed of 1.2856mm/h. The grain size of magnesium alloy can be refined by increasing cooling rate. After the grain boundary of magnesium-based alloy is refined, the grain boundary between the alloy increases, the number of corrosion galvanic cells increases, and the dissolution rate of magnesium-based alloy gradually increases.

Effect of Heat-Treatment Conditions on the Structure and Properties of a Fireproof Cast Magnesium Alloy of the Mg–REM–Zr System

Effect of Heat-Treatment Conditions on the Structure and Properties of a Fireproof Cast Magnesium Alloy of the Mg–REM–Zr System

Вплив легування золотом на структуру та властивості магнієвого сплаву NZ30K

In this work, was conducted research to improve the structure and properties of cast magnesium alloy NZ30K by doping with gold, for use in osteosynthesis. Gold is a safe alloying element for the human body. The effect of alloying 0.05%, 0.1% and 0.2% Au of magnesium alloy NZ30K was investigated in this work. A qualitative and quantitative assessment of the structural components of the alloy was carried out. It was shown that gold was part of the complex doped intermetallic phases, which were additional centers of crystallization. It was established that the optimal complex of properties is achieved by introducing 0.1%Au. At the same time, the average grain size is reduced by 52.4% compared to the original alloy. It was found that for the NZ30K+0.1%Au alloy, simultaneous increase in the strength limit by 7.8% and increase in the relative elongation by almost two times was observed. It was investigated the possibility of using a biodegradable magnesium alloy in the manufacture of fixators during osteosynthesis, biocorrosion processes. It was found that the addition of 0.1% Au slows down the biocorrosion processes and contributes to maintaining a high level of strength limit (σB = 200MPa) after exposure for 6 months in a gelofusin solution. Therefore, gold is a promising material for improving the structure and improving the properties of biodegradable magnesium alloy implants. Keywords: NZ30K, gold, biodegradable implants, microstructure, X-ray spectral microanalysis, mechanical properties, biocorrosion.

Influence of Anodizing by Electro-Chemical Oxidation on Fatigue and Wear Resistance of the EV31A-T6 Cast Magnesium Alloy

In the last decades, several anodizing processes for Mg alloys have been proposed to achieve a good wear and corrosion resistance combination. In particular, Electro-Chemical Oxidation (ECO) showed an improved dense and compact anodized layer compared to other anodizing processes carried out above the dielectric breakdown voltage, such as Plasma Electrolytic Oxidation (PEO). However, the influence of the ECO treatment on the tribological behavior and cyclic mechanical performance of Mg alloys has not been investigated yet. This paper reports on the influence of ECO on dry sliding behavior (vs. 100Cr6 bearing steel (block-on-ring contact geometry)) and rotating bending fatigue performance of the rare earth (RE)-containing Mg alloy EV31A-T6, comparing it with both untreated EV31A-T6 and PEO-treated EV31A-T6, used as benchmarks. The ECO-treated alloy showed improved tribological behavior (critical load for coating failure one order of magnitude higher and coefficient of friction 40% lower than for PEO) and fatigue strength (no decrease for ECO-treated samples compared to the untreated alloy, while PEO-treated samples induced a 15% decrease) due to the increased compactness and lower defectivity of the anodized layer, induced by the minimization of destructive arc discharges during coating growth. In addition, the ECO treatment significantly improved wear resistance compared to the untreated alloy, avoiding, at the same time, the decrease in fatigue strength, which typically occurs after PEO. Therefore, the ECO process can be applied to improve wear resistance without decreasing the fatigue strength of high-performance components.

Numerical Simulation and Process Optimization of Magnesium Alloy Vehicle Dashboard Cross Car Beam (CCB) Based on MAGMA

At present, the qualified rate of large thin-walled magnesium alloy castings is low. In this study, the effects of mold structure and process parameters were investigated to improve the production qualification rate of castings. The filling process of die castings was simulated by numerical simulation technology to optimize their structure. On the basis of an optimized mold structure, the process parameters of die castings were optimized using a response surface model, and a group of optimal process combinations were obtained: pouring temperature—660 °C; mold preheating temperature—200 °C; injection speed—6.5 m/s. The rationality of the optimized mold structure and process parameters is verified by die-casting experiments. The results show that the optimized mold structure and process parameters can effectively reduce the internal shrinkage cavity casting defects of automotive CCB castings, and effectively improve the production qualification rate of magnesium alloy CCB castings. This research has important guiding significance for the production of large thin-walled magnesium alloy parts.

Effect of lamellar LPSO phase on mechanical properties and damping capacity in cast magnesium alloys

The effect of the lamellar long period stacking order (LPSO) phase on both mechanical properties and damping capacity of magnesium alloys is still vague. After heat treatment at 540 °C for 4 h and 450 °C for 10 h, the Mg-10Gd-2Y–1Zn-0.5Zr-0.2Nd (wt%) alloy with the lamellar LPSO phase is prepared to study the influence of lamellar LPSO phase on damping capacity and mechanical properties. Combined transmission electron microscopy (TEM) and scanning electron microscopy (SEM) equipped with electron back-scattering patterns (EBSD) system, it is surprisingly found that the growth direction of the lamellar LPSO phase on basal plane is nearly parallel to the slip direction of basal dislocations, which is benefit from dislocations movement on basal plane. The dislocations move on basal plane easily, lead to a relative high damping capacity. The alloy with LPSO phases shows higher ultimate tensile strength (UTS) and elongation (EL), increased from 234 MPa to 2.6% to 254 MPa and 4.6%, respectively. The lamellar LPSO phase has an attribution to UTS and EL due to its kink deformation mechanism. Therefore, the lamellar LPSO phase can be used as a functional phase to enhance the damping capacity and mechanical properties at the same time, and providing new ideas about preparing high-strength and high-damping magnesium alloy.

Microstructure and mechanical properties of GTA-based wire arc additive manufactured AZ91D magnesium alloy

Wire arc additive manufacturing offers advantages in producing large metal structures. The current research on GTA-based wire arc additive manufacturing (GTA-WAAM) of magnesium alloys is focused on deformed magnesium alloys, mainly on the Mg-Al alloy system. However, there is little research on GTA-WAAM for casting magnesium alloy. This study investigates the microstructural characteristics and mechanical properties of AZ91D magnesium alloy (AZ91D-Mg) deposited by GTA-WAAM. Single-pass multilayer thin-walled components were successfully fabricated. The results show that equiaxed grains dominate the microstructure of the deposited samples. During the remelting process, the precipitated phases dissolve into the matrix, and they precipitate and grow from the matrix under the thermal effect of the subsequent thermal cycle. The mechanical properties in the vertical and horizontal directions are similar, showing higher overall mechanical properties than the casting parts. The average yield strength is 110.5 MPa, the ultimate tensile strength is 243.6 MPa, and the elongation is 11.7%. The overall hardness distribution in the deposited sample is relatively uniform, and the average microhardness is 59.6 HV0.2.

Effect of Material and Fin Geometry of Effectiveness of 100 CC Small Motorcycle Automobile Cylinder

In the case of design of a small two-wheeler, designing a cylinder and its cooling system is a big deal for engineers and researchers. To have a stable combustion in case of SI engine, the temperature at any point of cylinder can’t be raised to auto ignition temperature of the fuel. Thus, the cooling system of engine must be properly designed. When designing cylinder of two-wheeler, the choice is very limited. The fins can be an important technique for engine cooling. This paper presents a comparative study of magnesium alloy and grey cast iron (GCI) alloy as probable cylinder materials and rectangular, triangular and Trapezoidal shape as fin geometry. The solid geometry of cylinder having different types of extended surface was prepared in Solidworks and imported to ANSYS for further processing. The GCI alloy found to be better than magnesium alloy and the rectangular fin profile gave the least total heat flux.

Microstructure and surface integrity of machined AZ91 magnesium alloy

AZ91 magnesium alloy is one of the most popular materials among all cast magnesium alloys due to its excellent corrosion resistance and good cast-ability. Although AZ91 is categorized as soft materials and easy-to-cut, there are many challenges in the finish machining of AZ91. In this research, a comprehensive as well as novel study on the surface integrity of machined AZ91 magnesium alloy is presented. To this end, AZ91 samples are machined under different cutting conditions and afterward, both surface and subsurface features are analyzed. Assessing the finished surface is conducted by surface 3D topography, roughness measurement, and scanning electron microscope. In terms of subsurface characterization, the effect of machining conditions cutting speed and feed rate on the micro hardness variation, subsurface microstructure changes, plastic deformations, and subsurface defects are studied. Results indicated that when machining AZ91, surface defects mostly are formed around the secondary phases. Moreover, twining and shear bands are the main microstructural changes close to the machined surface. Additionally, finishing machining of AZ91 induced subsurface plastic deformation to the depth of 180 μm as well as micro cracks propagation, in secondary phases, to nearly 100 μm under the machined surface.