Microstructural evolution and corrosion behaviour of friction stir-processed QE22 magnesium alloy

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ankur Kumar ◽  
F. Khan MD ◽  
Sushanta Kumar Panigrahi ◽  
Gajanan P. Chaudhari
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behaviour ◽  
Galvanic Corrosion ◽  
Point Of View ◽  
Second Phase ◽  
Friction Stir ◽  
Ultrafine Grained ◽  
Second Phase Particles ◽  
Before And After ◽  
The Matrix

Abstract Effect of microstructural changes after friction stir processing (FSP) on the corrosion behaviour of rare earth containing QE22 magnesium alloy is studied. FSP produced ultrafine-grained α-Mg matrix and refined the Mg12Nd precipitates whereas Mg12Nd2Ag precipitates got dissolved in the matrix. Although its hardness increased from 76 to 90 VHN, the FSPed alloy displayed inferior corrosion resistance in 3.5 wt% NaCl solution. This is attributed mainly to the iron contamination from FSP and presence of refined second phase particles which work as active cathodic sites. The role of distributed Mg12Nd precipitates before and after FSP is analysed from micro galvanic corrosion point of view.

Microstructure of Friction Stir Processed Mg-Y-Zn Alloy

2007 ◽  
Vol 558-559 ◽  
pp. 777-780 ◽  
Author(s):  
Taiki Morishige ◽  
Masato Tsujikawa ◽  
Sung Wook Chung ◽  
Sachio Oki ◽  
Kenji Higashi
Keyword(s):  
Equal Channel Angular Extrusion ◽  
Second Phase ◽  
Ingot Metallurgy ◽  
Friction Stir ◽  
Fine Grained ◽  
Probe Diameter ◽  
Fine Grain ◽  
Second Phase Particles ◽  
The Matrix ◽  
Zn Alloy

Friction stir processing (FSP) is the effective method of the grain refinement for light metals. The aim of this study is to acquire the fine grained bulk Mg-Y-Zn alloy by ingot metallurgy route much lower in cost. Such bulk alloy can be formed by the superplastic forging. The microstructure of as-cast Mg-Y-Zn alloy was dendrite. The dendrite arm spacing was 72.5 [(m], and there are the lamellar structures in it. FSP was conducted on allover the plate of Mg-Y-Zn alloy for both surfaces by the rotational tool with FSW machine. The stirring passes were shifted half of the probe diameter every execution. The dendrite structures disappeared after FSP, but the lamellar structure could be observed by TEM. The matrix became recrystallized fine grain, and interdendritic second phase particles were dispersed in the grain boundaries. By using FSP, cast Mg-Y-Zn alloy could have fine-grained. This result compared to this material produced by equal channel angular extrusion (ECAE) or rapid-solidified powder metallurgy (RS P/M). As the result, as-FSPed material has the higher hardness than materials produced by the other processes at the similar grain size.

Assessment of Microstructure and Wear Resistance of Friction Stir Processed Cast Mg-Al-Zn Magnesium Alloy

2015 ◽  
Vol 787 ◽  
pp. 442-447 ◽  
Author(s):  
R. Jayaraman ◽  
T. Balusamy ◽  
A.K. Lakshminarayanan
Keyword(s):  
Wear Resistance ◽  
Magnesium Alloy ◽  
Base Metal ◽  
Second Phase ◽  
Micro Hardness ◽  
Friction Stir ◽  
Second Phase Particles ◽  
Metal Wear ◽  
Pin On Disc ◽  
Cast Magnesium

Microstructure, micro hardness and wear resistance of friction stir processed cast magnesium alloy are investigated in this work. Image analysis is used to differentiate the amount of phases present in the base metal and friction stir processed regions. Hardness mapping indicates that the frictions stir processed region has 64 % increase in microhardness compared to the base metal. Wear resistance was evaluated using pin-on-disc testing and it is found that the friction stir processed region has superior wear resistance compared to the base metal. Fine grains with uniformly distributed second phase particles are the reasons for improved microhardness and wear resistance of friction stir processed region.

A COMPARATIVE STUDY TO EVALUATE THE CORROSION PERFORMANCE OF FRICTION STIR WELDED AZ31B MAGNESIUM ALLOY UNDER IMMERSION, SALT FOG, PITTING AND GALVANIC CORROSION TESTS UNDER NACL ENVIRONMENT

2019 ◽  
Vol 14 (1) ◽  
Author(s):  
Ashok Kumar M ◽  
Thirumalaikumarasamy D ◽  
Paventhan R ◽  
Thirumal P
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Behaviour ◽  
Galvanic Corrosion ◽  
Salt Spray ◽  
Welding Process ◽  
Ion Concentration ◽  
Az31b Magnesium Alloy ◽  
Corrosion Tests ◽  
Friction Stir ◽  
Corrosion Rates

An investigation was carried out to quantify and characterize the corrosion behaviour of AZ31B magnesium alloy joints. Extruded Mg alloy plates of 6 mm thick of AZ31B grade were butt welded using a solid state, environmentally cleaner welding process, friction stir welding process. The weld specimens were underwent immersion, salt spray, pitting and galvanic corrosion tests in order to quantify and characterize the corrosion rates of the welds with the influence of different pH values, chloride ion concentration and the corrosion time. The corrosion rates, microstructure, scanning electron microscopy and X-ray diffraction analysis concludes the optimum parameter for the usage of the magnesium alloy welds for the best service applications. Keywords: Keywords: EDM, Alumina and Genetic Algorithm

Corrosion of AZ91 - Influence of the β-Phase Morphology

2009 ◽  
Vol 618-619 ◽  
pp. 473-478 ◽  
Author(s):  
M.C. Zhao ◽  
Peter J. Uggowitzer ◽  
M. Liu ◽  
Patrik Schmutz ◽  
G. Song ◽  
...  
Keyword(s):  
Corrosion Behaviour ◽  
Galvanic Corrosion ◽  
Mg Alloys ◽  
Model Alloy ◽  
Second Phase ◽  
Surface Films ◽  
Β Phase ◽  
The Matrix ◽  
Theoretical Phase Diagram ◽  
Multi Phase

The influence of the microstructure, particularly the morphology of the β phase, on the corrosion of Mg alloys has been studied using AZ91 as a model alloy and compared with the corrosion of pure magnesium, used as a standard for comparison. The concentration of the impurity element Fe was below the limit evaluated from theoretical phase diagram construction. Corrosion was measured using hydrogen evolution measurements and some polarization measurements. Corrosion behaviour was characterized for four different microstructures produced by heat treatment of as-cast AZ91: namely (i) as-cast, (ii) homogenization anneal (for 5h and 10h at 380°C), (iii) solid solution and (iv) solution treated and aged. The influence of microstructure can be understood from the interaction of the following three factors: (i) the surface films, (ii) micro-galvanic corrosion acceleration dependant on the amount and distribution of the second phase (the  phase in AZ91) and (iii) the second phase can act as a corrosion barrier and hinder corrosion propagation in the matrix, if the second phase is in the form of a continuous network. It is expected that these factors are important for all multi-phase Mg alloys because all known second phases have corrosion potentials more positive than that of the -phase. The electrochemical measurements did not give good values for the corrosion rate in agreement with the literature.

Effect of Heat Treatment on Microstructures and Properties of AZ40M Alloy

2016 ◽  
Vol 849 ◽  
pp. 173-180 ◽  
Author(s):  
Lin Lai ◽  
Kui Zhang ◽  
Ming Long Ma ◽  
Guo Liang Shi
Keyword(s):  
Magnesium Alloy ◽  
Second Phase ◽  
X Ray Diffraction ◽  
Homogenization Treatment ◽  
Homogenization Process ◽  
Β Phase ◽  
Before And After ◽  
The Matrix ◽  
Tensile Fractures ◽  
Tensile Experiment

The influence of two-step homogenization on microstructures and properties of AZ40M magnesium alloy were investigated by the scanning electronic microscopy (SEM), X-ray diffraction analysis (XRD) and tensile experiment. Through comparing the microstructure and mechanical properties of the alloy before and after homogenization treatment, a two-step homogenization process of the semi-continuous casting AZ40M magnesium alloy ingot was determined. The result shows that the as-cast AZ40M alloy mainly contained two kinds of second phase, β-Mg17Al12 and Al8Mn5. Treating at temperature of 380 °C for 8 h as the first step homogenization treatment and then treating at temperature of 420 °C for 20 h as the second step homogenization treatment made the eutectic phase (α-Mg/β-Mg17Al12) completely eliminated and the alloying elements such as Al, Zn distributed uniformly. Al8Mn5 is the residual second phase in the homogenized AZ40M alloy. During the homogenization process, the β-phase dissolved which made the content of Al increased in the matrix. The decomposition of β-phase benefits the tensile strength and elongation of the alloy. The tensile fractures of as-cast and homogenization alloys are characteristic of ductile fracture.

Noncombustible Magnesium Alloy Processed by Rotary-Die Equal Channel Angular Pressing Method

2007 ◽  
Vol 544-545 ◽  
pp. 419-422 ◽  
Author(s):  
Akira Watazu ◽  
Ichinori Shigematsu ◽  
Xin Sheng Huang ◽  
Kazutaka Suzuki ◽  
Naobumi Saito
Keyword(s):  
Magnesium Alloy ◽  
Equal Channel Angular Pressing ◽  
Raw Materials ◽  
The Other ◽  
Raw Material ◽  
Second Phase ◽  
Pressing Method ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
The Matrix

Noncombustible Mg-8Al-2Ca rods were processed by RD-ECAP. The magnesium alloy rod had Mg matrix and Al2Ca second phase. Grains with about 20 μm in diameter were observed in the matrix of the raw materials. The grains in matrix had no anisotropy. On the other hand, positions of second phase particles had anisotropy and the second phase particles formed lines. The samples processed by RD-ECAP had no crack and the samples had 20mm diameter. Grains in matrix of the 4 pass RD-ECAP sample had no anisotropy and the grains had under about 5 μm in diameter. The second phase particles had round shapes and were uniformly distributed as compared with the raw material rod. Therefore, the RD-ECAP is useful for forming noncombustible Mg-8Al-2Ca alloy with fine-grains.

Particle-Stimulated Nucleation of Dynamic Recrystallization in AZ31 Alloy at Elevated Temperatures

2005 ◽  
Vol 488-489 ◽  
pp. 261-264 ◽  
Author(s):  
Lan Jiang ◽  
Guang Jie Huang ◽  
Stéphane Godet ◽  
John J. Jonas ◽  
Alan A. Luo
Keyword(s):  
Magnesium Alloy ◽  
Elevated Temperatures ◽  
Az31 Alloy ◽  
Coarse Grained ◽  
Second Phase ◽  
Compression Tests ◽  
Second Phase Particles ◽  
The Matrix ◽  
Second Phases ◽  
Cast Magnesium

Particle-stimulated nucleation (PSN) was investigated in magnesium alloy AZ31 to study the effect of the evolution of second-phases during extrusion and other metal forming processes. Compression tests were carried out on samples taken from coarse-grained as-cast magnesium alloy billets containing a lamellar Mg17All2 eutectic phase and (Al, Mn) particles. These revealed that particle-stimulated DRX nucleation (PSN) was taking place during hot deformation and that this is facilitated by the fragmentation of the Mg17All2. When Mg17All2 dissolves into the matrix at about 350°C, the (Al, Mn) particles remain effective in producing PSN at temperatures up to at least 400°C. This suggests that alloy design leading to a suitable distribution of second-phase particles can improve the properties and formability of wrought magnesium alloys.

Friction Stir Processing to Increase the Application Temperature of Rare Earth Magnesium Alloy AE42

2012 ◽  
Vol 622-623 ◽  
pp. 515-519
Author(s):  
M. Govindaraju ◽  
K. Rao Prasad ◽  
Uday Chakkingal ◽  
K. Balasubramanian ◽  
Ravi Ravindran
Keyword(s):  
Rare Earth ◽  
Magnesium Alloy ◽  
Thermal Cycling ◽  
Friction Stir Processing ◽  
Processing Parameters ◽  
Stir Zone ◽  
Second Phase ◽  
Parent Metal ◽  
Friction Stir ◽  
The Matrix

AE 42 is rare earth containing magnesium alloy which was developed for creep resistance and automobile applications. This alloy was subjected to friction stir processing and the effect of processing parameters on the properties was studied in detail. Mechanical and metallurgical properties of stir zone were evaluated and compared with parent metal. Thermal cycling of stir zone was carried out to study the stability of it at high temperature. Due to processing, stir zone microstructure was refined to 5 micron. The second phase inter-metallic particles Mg17Al12, Al11Ce3 and Al2Ce were refined to tiny pieces of 1-2 micron and evenly distributed in the matrix. The stir zone was stable up to 250°C during thermal cycling. Mechanical properties of friction stir zone were superior to parent metal.

Composites Fabrication via Friction Stir Processing

2011 ◽  
Vol 690 ◽  
pp. 125-128 ◽  
Author(s):  
Ning Sun ◽  
Diran Apelian
Keyword(s):  
Friction Stir Processing ◽  
Al Alloy ◽  
Second Phase ◽  
Alloy Matrix ◽  
Friction Stir ◽  
Surface Composites ◽  
Second Phase Particles ◽  
The Matrix ◽  
High Level ◽  
Advanced Tool

Friction stir processing (FSP) is a post-processing method that locally manipulates the microstructure by imparting a high level of energy in the solid state giving rise to improved mechanical properties. Additionally, FSP has emerged as an advanced tool to produce surface composites and synthesize the second phase into the matrix. In the current study, FSP was investigated for the manufacture of localized zones of composite materials made by the emplacement of a second phase into cast A206 Al alloy matrix. Both the discontinuously reinforced aluminum (DRA) and some encapsulated powders (nano-sized SiC or Ta) were used for the second phase emplacement. Through SEM and EDS mapping, the morphology and distribution of second phase particles have been studied. The work shows that friction stir processing is a viable means of producing localized composite zones in Al components.

Polishing process effect on the image of dispersed precipitates

1984 ◽  
Vol 42 ◽  
pp. 534-535
Author(s):  
C.T. Hu ◽  
C.W. Allen
Keyword(s):  
Matrix Material ◽  
Specimen Preparation ◽  
Second Phase ◽  
Precipitate Particle ◽  
Polishing Process ◽  
Second Phase Particles ◽  
The Matrix ◽  
Surface Profiles ◽  
Thinning Process

One important problem in determination of precipitate particle size is the effect of preferential thinning during TEM specimen preparation. Figure 1a schematically represents the original polydispersed Ni3Al precipitates in the Ni rich matrix. The three possible type surface profiles of TEM specimens, which result after electrolytic thinning process are illustrated in Figure 1b. c. & d. These various surface profiles could be produced by using different polishing electrolytes and conditions (i.e. temperature and electric current). The matrix-preferential-etching process causes the matrix material to be attacked much more rapidly than the second phase particles. Figure 1b indicated the result. The nonpreferential and precipitate-preferential-etching results are shown in Figures 1c and 1d respectively.

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