AM Series Magnesium Research Articles

Thermal Properties of AM Series Magnesium Alloys

This paper presents experimental investigation on thermal properties (thermal diffusivity and thermal conductivity) of AM series cast magnesium alloys. The effects of the changing in Al content (from 2 to 9 Al and constantly 0.5 Mn, wt. %) in the alloys on thermal properties, density and hardness were comparatively analyzed. It was observed that intermetallic phases (Mg17Al12 ve Al8Mn5) found in the microstructure of the alloys have an effect on thermal diffusivity, thermal conductivity, density and also hardness. The thermal properties of the alloys were decrease with increasing Al content in the alloy. The thermal properties of the alloys were increase with increasing temperature (the temperature range from 25°C to 400°C). The highest thermal diffusivity was measured on AM20 alloy and the lowest thermal diffusivity were observed on AM90 alloy.

Optimization of cutting forces and surface roughness in dry turning of AM magnesium alloy using Taguchi method

This study aimed to analyze the feed force, cutting force, and surface roughness deviations through CNC lathe turning operation of AM series magnesium alloy. Machining operations were performed using Tungsten Carbide insert with nose radius of 0.8 mm and by varying the basic cutting parameters like feed, cutting speed, and depth of cut. Throughout the experiments, the geometry of the tool was not changed and the cutting fluids are not used in turning operation. The investigation is performed only on the tungsten carbide inserts, and these were changed continuously to prevent the tool wear. The experiments are carried out as per Taguchi’s L27 orthogonal array for cutting force, feed force, and surface roughness under dry cutting conditions. The results prove that the depth of cut and feed mainly influences the Cutting force and feed force. For Surface roughness, the feed and depth of cut are perceived as the influencing controlling factors. Finally, the optimum results are verified by the experimentation.

Casting of High Aluminum Content AM Series Magnesium Alloys by Using a Horizontal Twin Roll Caster

In this paper, twin roll casting of magnesium alloys with high aluminum content such as, Mg-11 mass%Al-0.2 mass%Mn, Mg-12 mass%Al-0.2 mass%Mn, Mg-13 mass%Al-0.2 mass% have been performed for the purpose of use as an original material for hot forging. Also the mechanical properties of the cast materials were examined. A 10 miri-meters thick strip was cast by the use of a horizontal twin roll caster. The microscopic observation was conducted to investigate into the precipitation of the metal compounds such as Mg17Al12, and the Vickers hardness of the cast strips test were performed. From the result of the roll casting experiments, a 10 mm thick strip was continuously cast at a roll speed of 3.1 m/min. The average grain size of the casting strips was about 46 micron meters. When the aluminum content was 13%, the hardness of the twin roll cast (TRC) strips became 1.7 times higher than that of extruded AZ 31. Also, a uniaxial compression test at elevated temperature was conducted to obtain a true strain-true stress curve for examining possibility of direct hot forging (DHF) of TRC magnesium alloys with high aluminum content.

Compressive Creep Behavior of High-Pressure Die-Cast Aluminum-Containing Magnesium Alloys Developed for Elevated Temperature Applications

In addition to AZ- and AM-series magnesium alloys, which are mainly used at ambient temperature, there are also die-cast magnesium alloys developed for use at elevated temperatures. This paper examines the compressive creep resistance of several aluminium-containing magnesium high-pressure die-cast alloys, including the commercially available AE42, AE44-2, AE44-4, MRI230D alloys and newly developed DieMag series, i.e. DieMag211, DieMag422 and DieMag633. Compressive creep is the common load case for automotive powertrain components such as transmission housings, engine blocks or oil pans, which are typically mounted with steel or aluminium bolts that have lower thermal expansion than magnesium alloys. When the components heat up, there is a compressive load in the area around the bolt. The compressive creep experiments are accompanied by microstructure investigations. It is shown that MRI230D and the two high-concentrated DieMag alloys have the best creep resistance at 200°C. Similar results are also observed in the tensile tests at room temperature and 150°C, with DieMag633 showing outstanding strength.

Wear and machinability of AM series magnesium alloys

Abstract This study deals with the effect of different quantities of aluminum (Al) on the wear resistance and machinability in AM series cast magnesium alloys. Changes in the quantity of Al in these alloys (containing 0.5 wt.-% Mn) and their effect on hardness, wear resistance and machinability with respect to cutting force were analyzed. To this purpose, AM series cast magnesium alloys (AM20, AM40, AM60, and AM90) in varying amounts of Al from 2 to 9 wt.-% were used. It was observed that the intermetallic phases Mg17Al12 and Al8Mn5 found in the microstructure had an effect on their wear resistance, hardness and machinability (with respect to cutting force), flank build-up, chip formation and surface roughness. AM90 alloy manifested the highest values in terms of hardness, wear resistance and surface quality among these alloys. On the other hand, AM90 alloy had the lowest machinability properties.

Influence of Al content on machinability of AM series magnesium alloys

Influence of Al content on machinability of AM series magnesium alloys

The Influence of Al Content and Thickness on the Microstructure and Tensile Properties in High-Pressure Die Cast Magnesium Alloys

The influence of Al content and section thickness on the microstructural features and tensile properties of high-pressure die cast AM series magnesium alloys is quantified in order to better understand the relationship between microstructure and tensile properties. It is found that with increasing aluminum content, the yield strength increases and the ductility decreases. Increasing the plate thickness results in a decrease in both the yield strength and ductility. The grain size, β-Mg17Al12 phase volume fraction, and solute content are all quantified through the thickness of the plates. It is found that the plates have a skin with increased hardness, due to a fine grain structure. The primary factors affecting strengthening in these alloys, including microstructural variations through the thickness, are accounted for using a linear superposition model. We conclude that yield strength is dominated by grain boundary strengthening and solid solution strengthening effects. The through-thickness grain size and solute concentration were quantified and these variations were found to play an important role in controlling the yield strength of these alloys.

Investigation of Microstructure and Mechanical Properties of ECAP-Processed AM Series Magnesium Alloy

Magnesium alloy Mg-Al-Mn (AM70) was processed by equal channel angular pressing (ECAP) at 275 °C for up to 4 passes in order to produce ultrafine-grained microstructure and improve its mechanical properties. ECAP-processed samples were characterized for microstructural analysis using optical microscopy, scanning electron microscopy, and transmission electron microscopy. Microstructural analysis showed that, with an increase in the number of ECAP passes, grains refined and grain size reduced from an average of 45 to 1 µm. Electron backscatter diffraction analysis showed the transition from low angle grain boundaries to high angle grain boundaries in ECAP 4 pass sample as compared to as-cast sample. The strength and hardness values an showed increasing trend for the initial 2 passes of ECAP processing and then started decreasing with further increase in the number of ECAP passes, even though the grain size continued to decrease in all the successive ECAP passes. However, the strength and hardness values still remained quite high when compared to the initial condition. This behavior was found to be correlated with texture modification in the material as a result of ECAP processing.

Influence of aluminum content on the texture and sheet formability of AM series magnesium alloys

The fabrication of magnesium (Mg) alloy sheets with both high mechanical strength and superior cold formability was sought by optimizing the aluminum (Al) content of the alloy sheets. We investigated the influence of varying Al content from 3wt% to 8wt% on the texture, mechanical properties, and stretch formability of AM series Mg alloys, processed by high-temperature rolling. The ultimate tensile strength improved steadily from 247MPa to 303MPa with an increase in Al, due to solid solution strengthening. The basal texture intensity decreased with increasing Al content, reached a minimum value at 6wt% Al, and then increased as more Al was added. The weakest basal texture led to the smallest Lankford value and the largest strain hardening exponent in the AM60 (6wt% Al) alloy. The alloys with lower Al contents of 3–5wt% exhibited a high fracture elongation of 27%, which continuously decreased to 23% as the Al content increased to 8wt%. The AM50 alloy exhibited excellent stretch formability with the largest Erichsen value of 9.1, while the AM30 and AM80 alloys showed much smaller Erichsen values of 5.6 and 6.0, respectively. This can be attributed to a good balance among the decreased r-value, increased n-value, and enhanced tensile ductility in the AM50 alloy, despite its basal texture being slightly stronger than that of the AM60 alloy.

Crystallographic Orientation Relationship between Discontinuous Precipitates and the Matrix in AM-Series Alloys

Magnesium alloys have received considerable attention because of their lightweight and recyclability. AM-series and AZ-series Mg-Al alloys have been used for industrial products widely, particularly for AM-series alloys because of better toughness and impact absorption properties than AZ-series alloys. The Mg17Al12intermetallic compound is the only precipitate formed during ageing after the solution heart treatment. Discontinuous precipitates exist in grain boundary randomly, and continuous precipitates exist in the matrix. However, there is few report about the orientation relationship between the discontinuous precipitates and the matrix. The purpose of this study is to investigate the orientation relationship between the discontinuous precipitates and the matrix of AM-series magnesium alloys. Hardness measurement, SEM observation, the electron backscattered diffraction (EBSD) techniques were preformed in order to understand the relationship between the discontinuous precipitate and crystallographic orientation of grains in AM-series magnesium alloy. TEM samples with discontinuous precipitates were prepared using the focused ion beam (FIB). And TEM observation was performed to investigate the discontinuous precipitates and crystallographic orientation in the matrix.

Effect of Al and Mn Contents on Microstructure in AM-Series Magnesium Alloys

Magnesium alloys containing aluminum have been used for industrial materials due to their lightweight and recyclability. And the Mg-Al based alloys are usually used for the industrial production. The Mg17Al12 phase is reported as the precipitate formed in the Mg-Al alloys during aging after the solution heat treatment, which is the discontinuous precipitate in the grain boundary and continuous precipitate in the matrix. The Mg-Al alloys are divided into AZ-series alloys with the addition of Zn, and AM-series alloys with the addition of Mn, respectively. AM-series and AZ-series Mg-Al alloys have been used for industrial products widely, particularly for AM-series alloys because of better toughness and impact absorption properties than AZ-series alloys. However, there is few report about the effect of Al and Mn contents on age-hardening behavior and microstructure of AM-series alloys. The propose of this study is to investigate the difference of the age-hardening behavior and microstructures of AM-series alloys using hardness test and scanning electron microscopy (SEM) observation.

Recycling of high grade die casting AM series magnesium scrap with the melt conditioned high pressure die casting (MC-HPDC) process

Strict government regulations and environmental concerns are the driving forces behind the increased use of magnesium alloys aimed at weight reductions. This however inevitably leads to increased magnesium alloy scrap and calls for effective recycling processes. In this paper, the melt conditioned high pressure die casting (MC-HPDC) process has been investigated as a physical approach for the recycling of AM series magnesium alloy die casting scrap. Process optimization was required to eliminate hot cracking phenomena. The experimental results showed that intensive melt shearing alters the size and morphology of MgO present in the scrap melt, leading to an effective grain refinement that was reflected in the mechanical properties of the recycled alloy. The MC-HPDC process showed excellent potential as a physical recycling approach for Mg alloy scrap, producing casting with properties comparable to those of fresh Mg alloys.

Resorbable Metallic Implant: Findings from an Animal Model

Resorbable metallic implant of magnesium and its alloys had been studied since the 1900s. However, the excessive gas production resulted in its unpopularity after CoCr alloys and stainless steel were developed. With the advancement of alloying technologies, its use as a resorbable implant has re-emerged recently. Foreign researchers focused on the use of AZ-series and magnesium-rare earth metal alloys. However, the corrosion property of AZ-series alloys is unsatisfactory, and the effect of rare-earth metals on human is poorly studied. Therefore, we have investigated on the feasibility of using commercially available AM-series magnesium alloys. Previous researchers avoided this alloy series presumably because of the potential health effect of manganese, however our toxicological risk assessment revealed that the exposure level would be lower than the NOAEL (No Observable Adverse Effect Level), thus it is unlikely to cause any observable health effect on healthy individuals. Subcutaneous implantation of AM-series magnesium alloys into a mouse model for six months confirmed that, while all alloys tested showed slow corrosion and no observable in vivo toxicity, pitting corrosion did not occur for AM-series alloys but was frequent for AZ91D. This suggests that AM-series magnesium alloys are good candidates of resorbable metallic implants.