Friction stir processing of newly-designed Mg-5Al-3.5Ca-1Mn (AXM541) alloy: Microstructure evolution and mechanical properties (original) (raw)
Related papers
Ultrafine-Grained Al-Mg-Sc Alloy via Friction-Stir Processing
Metallurgical and Materials Transactions A, 2013
Friction-stir processing (FSP) of twin-roll cast (TRC) Al-Mg-Sc alloy resulted into ultrafinegrained microstructure. The alloy was processed in as-received and aged (563 K [290°C], 22 hours) conditions and at three different tool rotation rates: 800, 400, and 325 rpm. The microstructural features were characterized using electron backscattered diffraction (EBSD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The grain size varied from 0.89 lm to 0.39 lm depending on the processing and initial thermo-mechanical conditions of the alloy. The TRC alloy processed at 325 rpm in aged condition had all the grains less than 1 lm, and 95 pct of grains had high-angle grain boundaries (HAGBs). In all the cases, the fraction of HAGBs were more than 80 pct. The variation of misorientation angle distribution was similar to the theoretical MacKenzie distribution for cubic crystal materials. Grain size analysis at different sections and locations on the transverse section of the dynamically recrystallized zone showed a homogeneous and equiaxed microstructure. The average dispersoid (Al 3 (Sc,Zr)) size was~8.0 nm in diameter obtained using high-resolution TEM. Grain size reduction was observed with increase in Zener-Hollomon parameter. It was shown that under the current microstructural and deformation conditions, dynamic recrystallization via particlestimulated nucleation might not be possible during FSP.
Metallurgical and Materials Transactions B, 2012
The main aim of the current study is the analysis of friction stir processing (FSP) of Mg-based alloys as a possible tool for nanocomposites production. The study reports microstructural changes taking place in a Mg-based alloy (AE42) subjected to FSP under different cooling conditions. The FSP process was carried out with single as well as multipass options. The friction stir processed samples were characterized by scanning electron microscopy (SEM), energy-dispersive spectroscopy (EDS), transmission electron microscopy (TEM), focused ion beam (FIB)-scanning ion microscopy (SIM), and X-ray diffraction (XRD). It was observed that FSP tends to fragment the elongated precipitates and produces near homogeneous distribution of fine particles. The smallest particle size was observed to be produced by double-pass FSP supplemented by rapid cooling, thereby generating in situ nanocomposites. Vickers microhardness testing was done along the thickness (transverse direction) of the specimen to study and understand the variation of hardness with thickness. Nearly a two-times increase in the microhardness of AE42 was observed in the case of double-pass, FSP AE42 with cooling at temperature of approximately 253 K (-20°C). To confirm these observations, another magnesium alloy AM50 was also friction stir processed under similar conditions. The fine submicron grain structure produced in AE42 alloy contributed immensely toward grain boundary strengthening and Orowan strengthening had only marginal influence. Subgrain boundary pinning by in situ nanoparticles contributed significantly in the strengthening process.
Microstructure-Property Relationship for Friction Stir Processed Magnesium Alloy
Advanced Engineering Materials, 2014
Friction stir processing (FSP) of Mg based AE42 alloy was performed under single pass as well as double pass conditions. The evolution of microstructure was investigated using electron back scatter diffraction (EBSD) analysis. EBSD revealed that the grain size and texture varies within the nugget zone of friction stir processed region. The variation of mechanical properties across the nugget region was evaluated using nanoindentation. Hardness and Young's modulus was found to increase along the depth of the friction stir processed specimen. This was attributed to a finer grain structure with increasing depth. The friction stir processed specimen showed higher tendency toward strain hardening compared to as-cast alloy. Understanding microstructure-property relationship paves the way for optimization of FSP conditions and development of advanced functional Mg alloys.
Archives of Metallurgy and Materials, 2016
The samples of the as-cast AM60 magnesium alloy were subjected to Friction Stir Processing (FSP). The effect of FSP on the microstructure of AM60 magnesium alloy was analyzed using optical microscopy and X-ray analysis. Besides, the investigation of selected properties, i.e. hardness and resistance to abrasion wear, were carried out. The carried out investigations showed that FSP leads to more homogeneous microstructure and significant grain refinement. The average grain size in the stirred zone (SZ) was about 6-9 μm. in the thermomechanically affected zone (TMAZ), the elongated and deformed grains distributed along flow line were observed. The structural changes caused by FSP lead to an increase in microhardness and wear resistance of AM60 alloy in comparison to their non-treated equivalents. Preliminary results show that friction stir processing is a promising and an effective grain refinement technique.
Consolidation and Mechanical Properties of Mechanically Alloyed Al-Mg Powders
Nanostructured Al-Mg bulk samples with compositions in the range of 10 – 40 at.% Mg have been produced by consolidation of mechanical alloyed powders. Powders with composition Al90Mg10 and Al80Mg20 were consolidated into highly dense specimens by hot extrusion. Room temperature compression tests for the Al90Mg10 specimen reveal interesting mechanical properties, namely, a high strength of 630 MPa combined with a plastic strain of about 4 %. The increase of the Mg content to 20 at.% increases the strength by about 100 MPa but it suppresses plastic deformation. The Al60Mg40 powder was consolidated at different temperatures by spark plasma sintering and the effect of the sintering temperature on microstructure, density and hardness have been studied. The results reveal that both density and hardness of the consolidated samples increase with increasing sintering temperature, while retaining a nanocrystalline structure. These results indicate that powder metallurgy is a suitable processing route for the production of nanocrystalline Al-Mg alloys with promising mechanical properties.
Microstructural modification of as-cast Al-Si-Mg alloy by friction stir processing
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2006
Friction stir processing (FSP) has been applied to cast aluminum alloy A356 plates to enhance the mechanical properties through microstructural refinement and homogenization. The effect of tool geometry and FSP parameters on resultant microstructure and mechanical properties was investigated. The FSP broke up and dispersed the coarse acicular Si particles creating a uniform distribution of Si particles in the aluminum matrix with significant microstructural refinement. Further, FSP healed the casting porosity. These microstructural changes led to a significant improvement in both strength and ductility. Higher tool rotation rate was the most effective parameter to refine coarse Si particles, heal the casting porosity, and consequently increase strength. The effect of tool geometry was complicated and no systematic trend was observed. For a standard pin design, maximum strength was achieved at a tool rotation rate of 900 rpm and traverse speed of 203 mm/min. Post-FSP aging increased strength for materials processed at higher tool rotation rates of 700 to 1100 rpm, but exerted only a marginal effect on samples prepared at the lower rotation rate of 300 rpm. Two-pass FSP with 100 pct overlapping passes resulted in higher strength for both as-FSP and post-FSP aged conditions.
Friction stir processing of cast magnesium alloys
2007
This thesis investigates the feasibility and benefits of using friction stir processing as a thermo-mechanical microstructural modification tool for local property enhancement or casting repair of magnesium alloys, specifically high strength EV31A and WE43. Castings often have usage limitations due to the inherent microstructural inhomogeneity from solidification; in addition magnesium cast alloys generally suffer from poor ductility and relatively low strength, yet the low density of magnesium is very attractive for weight critical applications. Friction stir processing (FSP) is a proven tool for enhancement of aluminum alloys, imparting a fine-grained, homogeneous microstructure. The alloys in this study are designed for elevated temperature service in the aerospace and high performance automotive industries and are suitable in applications were lightweight and exceptional strength are desired. WE43 has excellent temperature resistance up to 300°C, and EV31A is a more industry cost-effective alternative to WE43 and has excellent strength retention up to 200°C. Results from the present work showed that both alloys are easily adapted to the use of FSP, and significant strength and ductility gains were achieved in both alloys over their respective as-cast peak strengthened states. v ACKNOWLEDGMENTS I thank first and foremost my advisor; Dr. Rajiv Mishra, for his patience, guidance and support throughout my undergraduate and graduate studies. Dr. Mishra's dedication to the group and his students has demonstrated that kindness fosters diligence. His generosity and mentorship have made my stay at UMR not only possible in many ways, but also enjoyable.
Friction stir processing of magnesium alloys used in automobile and aerospace applications
A new microstructural modifications technique was developed by the Welding Institute (TWI) of United Kingdom in 1991 is known as friction stir processing (FSP). The FSP is a newer technique used for refining and homogenizing the grain structure of metal sheet. Friction stir processing is a great potential in the field of super-plasticity and metal matrix composites. Many investigators observed that the FSP greatly enhances super plasticity in many Al alloys. It is a solid-state processing technique based on friction stir welding technique in which a specially designed rotating cylindrical tool that comprises of a probe and shoulder. The probe of the tool is inserted into the sheet material while rotating and the shoulder moves over the surface of the sheet, and then traverses in the desired direction. The contact between the rotating probe and the sheet material generate heat due to friction which softens the material and the mechanical stirring caused by the probe, the material within the processed zone undergoes intense plastic deformation yielding a dynamically-recrystallized fine grain microstructure. This paper mainly deals with friction stir processing of magnesium alloys with different reinforcement and different input parameters. The study consist of the effect of different reinforcement addition methods that i.e. groove method and drill hole method on tribological and mechanical properties. The result shows that the addition of reinforcements improves the ultimate tensile strength, strain rate and wear resistance.
Friction stir processing of magnesium alloys used in automobile and aerospace applications-A Review
A new microstructural modifications technique was developed by the Welding Institute (TWI) of United Kingdom in 1991 is known as Friction stir processing (FSP). The FSP is a newer technique used for refining and homogenizing the grain structure of metal sheet. Friction stir processing is a great potential in the field of super plasticity and metal matrix composites. Many investigators observed that the FSP greatly enhances super plasticity in many Al alloys. It is a is a solid-state processing technique based on friction stir welding technique in which a specially designed rotating cylindrical tool that comprises of a probe and shoulder. The probe of the tool is inserted into the sheet material while rotating and the shoulder moves over the surface of the sheet, and then traverses in the desired direction. The contact between the rotating probe and the sheet material generate heat due to friction which softens the material and the mechanical stirring caused by the probe, the material within the processed zone undergoes intense plastic deformation yielding a dynamically-recrystallized fine grain microstructure. This paper mainly deals with friction stir processing of magnesium alloys with different reinforcement and different input parameters. The study consist of the effect of different reinforcement addition methods that i.e. groove method and drill hole method on tribological and mechanical properties. The result shows that the addition of reinforcements improves the ultimate tensile strength, strain rate and wear resistance.
Morphological Evolution of Mg-Al-La-Ca Alloy Induced by a Mechanical Stirring Process
Journal of Materials Engineering and Performance, 2019
This paper aims to evaluate the morphological evolution of a magnesium-aluminum alloy (Mg-6Al-3La-1Ca) processed by a mechanical stirring process (MSP) with different stirring times. An apparatus for semisolid metal alloy processing was used to melt and obtain rheocast material. Transformation temperatures were determined at a slow cooling rate using computer-aided cooling curve thermal analysis (CA-CCTA) and differential scanning calorimetry (DSC). Isothermal mechanical stirring (605°C), at 950 rpm, was carried out with a solid fraction of 0.29 and stirring times of 0, 1, 2, 4, 8 and 10 min, followed by fast cooling in water. The results showed that the microstructure after conventional casting (0 min-no stirring) is composed of an a-Mg dendritic matrix, Al 11 La 3 , (Al,Mg) 2 Ca and Mg 2 Ca compounds. With the 1-min stirring time, it was not possible to obtain globular structures. For stirring times longer than 2 min, a primary a-Mg globular morphology was obtained. Microstructures with 2 min of stirring time showed better globularization than those obtained under the other conditions. Morphological changes were observed for Al 11 La 3 and (Al,Mg) 2 Ca after the MSP followed by fast cooling.