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.

Corrosion Behaviors of Fluoride Treated Cast Magnesium Alloy in Hank’s Solution

2016 ◽  
Vol 852 ◽  
pp. 113-119
Author(s):  
Chun Yan Zhang ◽  
Ming Bo Yang ◽  
Cheng Long Liu
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloy ◽  
Az31 Alloy ◽  
Second Phase ◽  
Magnesium Alloy Az31 ◽  
Corrosion Behaviors ◽  
Second Phases ◽  
Cast Magnesium Alloy ◽  
Cast Magnesium ◽  
Hank’S Solution

Fluoride conversion films were synthesized on cast magnesium alloy AZ31 by immersion in hydrofluoric acid for different days to improve the corrosion resistance of Mg alloys as degradable implant material. The effects of the films on the corrosion behavior of the mg substrates were investigated by immersion tests. The results showed the fluoride conversion film was affected by the distribution of the chemical component of cast AZ31 alloy and the film on the second phases has more pores and micro-crack, but the bottoms of the pores were also covered by the conversion film and the substrate was not exposed through the pores. The fluoride conversion coatings significantly improved the corrosion resistance of cast AZ31 alloy. The film on the second phase with more pores is the first to dissolve. The most improved corrosion protection was achieved by 15 days treatment with the thickest film in terms of hydrogen evolution rate and damage morphology.

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.

The Room Temperature and Elevated Temperature Fracture Toughness Response of Alloy A-286

1978 ◽  
Vol 100 (2) ◽  
pp. 195-199 ◽  
Author(s):  
W. J. Mills
Keyword(s):  
Fracture Toughness ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Second Phase ◽  
Surface Micromorphology ◽  
Second Phase Particles ◽  
The Matrix ◽  
Temperature Fracture ◽  
Increasing Temperature ◽  
Base Superalloy

The elastic-plastic fracture toughness (JIc) response of precipitation strengthened Alloy A-286 has been evaluated by the multi-specimen R-curve technique at room temperature, 700 K (800°F) and 811 K (1000°F). The fracture toughness of this iron-base superalloy was found to decrease with increasing temperature. This phenomenon was attributed to a reduction in the materials’s strength and ductility at elevated temperatures. Electron fractographic examination revealed that the overall fracture surface micromorphology, a duplex dimple structure coupled with stringer troughs, was independent of test temperature. In addition, the fracture resistance of Alloy A-286 was found to be weakened by the presence of a nonuniform distribution of second phase particles throughout the matrix.

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.

Effect of Ce Addition on Microstructure and Mechanical Properties of ZM21 Magnesium Alloys

2014 ◽  
Vol 788 ◽  
pp. 58-63 ◽  
Author(s):  
Shi Bo Fan ◽  
Jian Peng ◽  
Ming Zhou ◽  
Kai Cui ◽  
Quan Li
Keyword(s):  
Mechanical Properties ◽  
Magnesium Alloy ◽  
Room Temperature ◽  
Matrix Alloy ◽  
Second Phase ◽  
Microstructure And Mechanical Properties ◽  
The Matrix ◽  
Second Phases ◽  
Zm21 Magnesium Alloy ◽  
Ce Content

In this paper, the effects of Ce addition on the microstructure and mechanical properties of the cast and extruded ZM21 magnesium alloy were investigated by OM, XRD, SEM and tensile test at room temperature. It was found that with increase of Ce content, the Mg-Ce and Mg-Zn phases which gather in dendritic gap as second phases increase gradually, and form a network structure finally, which becomes thicker due to serious segregation. Meanwhile, Most of Ce in the extruded ZM21 magnesium alloy is in the forms of second phases, and is broken and dispersed in the matrix alloy during the plastic deformation. With the increase of Ce content, the quantity of the second phase increases, and both the tensile strength and the elongation of ZM21 alloys decrease firstly and then increase. When the content of Ce is 0.57%, the elongation barely reaches the level of ZM21 magnesium alloy. After extrusion, both the tensile and yield strength have been greatly improved.

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.

Microstructure and second-phase particles in low- and high-pressure die-cast magnesium alloy AM50

2005 ◽  
Vol 36 (8) ◽  
pp. 1989-1997 ◽  
Author(s):  
Val Y. Gertsman ◽  
Jian Li ◽  
Su Xu ◽  
James P. Thomson ◽  
Mahi Sahoo
Keyword(s):  
High Pressure ◽  
Magnesium Alloy ◽  
Second Phase ◽  
Die Cast ◽  
Second Phase Particles ◽  
Cast Magnesium Alloy ◽  
Alloy Am50 ◽  
Cast Magnesium

scholarly journals Microstructure and Corrosion of Cast Magnesium Alloy ZK60 in NaCl Solution

Materials ◽  
2020 ◽  
Vol 13 (17) ◽  
pp. 3833
Author(s):  
Zhen Li ◽  
Zeyin Peng ◽  
Kai Qi ◽  
Hui Li ◽  
Yubing Qiu ◽  
...  
Keyword(s):  
Magnesium Alloy ◽  
Corrosion Rate ◽  
Electrochemical Techniques ◽  
Second Phase ◽  
Corrosion Mechanism ◽  
Schematic Model ◽  
General Corrosion ◽  
Second Phase Particles ◽  
Cast Magnesium Alloy ◽  
Cast Magnesium

In this work, the effects of the microstructure and phase constitution of cast magnesium alloy ZK60 (Mg-5.8Zn-0.57Zr, element concentration in wt.%) on the corrosion behavior in aqueous NaCl (0.1 mol dm−3) were investigated by weight-loss measurements, hydrogen evolution tests, and electrochemical techniques. The alloy was found to be composed of α-Mg matrix, with large second-phase particles of MgZn2 deposited along grain boundaries and a Zr-rich region in the central area of the grains. The large second-phase particles and the Zr-rich regions were more stable than the Mg matrix, resulting in a strong micro-galvanic effect. A filiform corrosion was found. It originated from the second-phase particles in the grain boundary regions in the early corrosion period. The filaments gradually occupied most areas of the alloy surface, and the general corrosion rate decreased significantly. Corrosion pits were developed under filaments. The pit growth rate decreased over time; however, it was about eight times larger than the general corrosion rate. A schematic model is presented to illustrate the corrosion mechanism.

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.

Recrystallization in Ultra-Fine Grain Structures of AA3104 Alloy Processed by ECAP and HPT

2012 ◽  
Vol 715-716 ◽  
pp. 346-353
Author(s):  
H. Paul ◽  
T. Baudin ◽  
K. Kudłacz ◽  
A. Morawiec
Keyword(s):  
High Pressure Torsion ◽  
Deformation Mode ◽  
Second Phase ◽  
Orientation Measurement ◽  
Angular Pressing ◽  
Second Phase Particles ◽  
Average Grain Size ◽  
The Matrix ◽  
Electron Microscopes ◽  
Different Strains

The objective of this study was to determine the effect of deformation mode on recrystallization behavior of severely deformed material. Commercial purity AA3104 aluminum alloy was deformed via high pressure torsion and equal channel angular pressing to different strains and then annealed to obtain the state of partial recrystallization. The microstructure and the crystallographic texture were analysed using scanning and transmission electron microscopes equipped with orientation measurement facilities. The nucleation of new grains was observed in bulk recrystallized samples and during in-situ recrystallization in the transmission microscope. Irrespective of the applied deformation mode, a large non-deformable second phase particles strongly influenced strengthening of the matrix through deformation zones around them. It is known that relatively high stored energy stimulates the nucleation of new grains during the recrystalization. In most of the observed cases, the growth of recrystallized grains occurred by the coalescence of neighboring subcells. This process usually led to nearly homogeneous equiaxed grains of similar size. The diameter of grains in the vicinity of large second phase particles was only occasionally significantly larger than the average grain size. Large grains were most often observed in places far from the particles. TEM orientation mapping from highly deformed zones around particles showed that orientations of new grains were not random and only strictly defined groups of orientations were observed.

Sign in / Sign up

Export Citation Format

Share Document