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.

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.

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.

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.

Preparation of Nano Ti3SiC2/MoSi2 Composite by SPS Process

2011 ◽  
Vol 284-286 ◽  
pp. 2414-2419 ◽  
Author(s):  
Jun Cai Zhang ◽  
Cheng Chang Jia
Keyword(s):  
Mechanical Activation ◽  
Particle Diameter ◽  
Second Phase ◽  
Strong Restriction ◽  
Matrix Surface ◽  
Second Phase Particles ◽  
The Matrix ◽  
Strong Repulsion

In this paper, nano-Ti3SiC2/MoSi2 composite, whose second phase was 20-150nm, was in situ prepared by mechanical activation (MA) and SPS process with the quaternary powers of Mo, Si, Ti, and C. The results showed that: (1) matrix MoSi2 has strong repulsion to other elements, which leads to more second-phase particles inside the matrix rather than on the matrix surface; (2) matrix MoSi2 has strong restriction on the growing of the second phase, which makes the particle diameter of the second phase inside the matrix only in 200 nm around, while that over the surface reaches to 800 nm around.

Effect of ECAP Pass on Corrosion Behavior of High-Al Content Magnesium Alloys

2013 ◽  
Vol 747-748 ◽  
pp. 270-275
Author(s):  
Qiang Fan ◽  
Wei Liang ◽  
Li Ping Bian ◽  
Man Qing Cheng
Keyword(s):  
Corrosion Resistance ◽  
Corrosion Behavior ◽  
Performance Test ◽  
Corrosion Current ◽  
Second Phase ◽  
Al Content ◽  
Microstructure Observation ◽  
Angular Pressing ◽  
The Matrix ◽  
High Al Content

In view of low strength and poor corrosion resistance of Mg alloys, a Mg-12Al-0.7Si alloy was designed, fabricated and subjected to equal channel angular pressing (ECAP) in order to refine the microstructure. Microstructure observation and electrochemical performance test were conducted to investigate the influence of the microstructural variation subjected to multi-pass ECAP processing on the corrosion behavior of the alloy. The results showed that both α-Mg matrix and β-Mg17Al12of the alloy were significantly refined after processing for different passes (2,4,6,8) through route BC, and the 4-pass ECAPed alloy in 3.5% NaCl solution presents the lowest weight loss, lower corrosion current and higher corrosion potential in the polarization curves. The reason for high corrosion resistance of 4-pass ECAPed alloy and the effects of grain size of the matrix and the particle size, distribution of second phase and dynamic precipitates on corrosion behavior of the alloy were discussed.

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.

Continuous and Discontinuous Recrystallization of 6013 Aluminum Alloy

2013 ◽  
Vol 753 ◽  
pp. 221-224 ◽  
Author(s):  
Krzysztof Sztwiertnia ◽  
Magdalena Bieda ◽  
Anna Korneva
Keyword(s):  
Aluminum Alloy ◽  
Grain Boundaries ◽  
Second Phase ◽  
Sheet Plane ◽  
Temperature Range ◽  
Orientation Mapping ◽  
Second Phase Particles ◽  
The Matrix ◽  
Continuous Recrystallization

In situ orientation mapping using TEM and calorimetric measurements were carried out to investigate the annealing behavior of cold-rolled 6013 aluminum alloy. The recrystallization of the material can be considered to be a number of processes that correspond to two separate stored energy release peaks. In the temperature range of the peak 1, the deformation zones around the large second-phase particles acted as sites for particle-stimulated nucleation. In the matrix, at the same time, some elongation of grains occurred. The elongated matrix grains appeared because of the reduction of the dislocation density and the annihilation of some low-angle grain boundaries between chains of subgrains lying in layers parallel to the sheet plane. The matrix processes in this temperatures range can be considered forms of continuous recrystallization. The matrix high-angle grain boundaries started to migrate at the temperature range of the peak 2. They moved mostly in the direction normal to the sheet plane. Heating of the sample for an appropriate time at those temperatures resulted in the complete discontinuous recrystallization of the material. The recrystallized microstructure was dominated now by elongated grains, which were a few times thicker than those obtained by annealing at the temperatures of the peak 1.

Effect of Heat Treatments on Microstructure and Properties of Hot Compression Aluminum Alloy 7A04

2011 ◽  
Vol 480-481 ◽  
pp. 433-436
Author(s):  
Mu Meng ◽  
Zhi Min Zhang ◽  
Jian Min Yu ◽  
Xin Kai Li
Keyword(s):  
Heat Treatment ◽  
Aluminum Alloy ◽  
Second Phase ◽  
Transgranular Fracture ◽  
High Deformation ◽  
Microstructure And Properties ◽  
T6 Heat Treatment ◽  
Second Phase Particles ◽  
The Matrix ◽  
Fracture Appearance

Aluminum alloy 7A04 compressed at high deformation temperature and large deformation is applied in two different heat treatment (T5 and T6), then microstructure and properties of the alloy after heat treatment are investigated. The mechanical properties are studied by means of the tensile testing and the hardness testing. The microstructure characteristics and the fractorgraphy analysis are respectively investigated with optical microscopy and SEM. The experimental results indicate that after T6 heat treatment, the second-phase particles dispersed in the matrix, which can efficiently improving the strength of the alloy, but reduced the toughness. After T5 heat treatment, the coarse and discontinuous second-phase is distributed along the grain boundary, which can lead to the low strength and high toughness because of the lack of the strengthening phase in the grains. The fracture appearance is intercrystalline fracture after T6 heat treatment, and dimple transgranular fracture after T5 heat treatment.

Aging and Precipitation Behavior in Supersaturated Al-2%Fe Alloy Produced by High-Pressure Torsion

2014 ◽  
Vol 794-796 ◽  
pp. 766-771 ◽  
Author(s):  
Jorge M. Cubero-Sesin ◽  
Masashi Watanabe ◽  
Makoto Arita ◽  
Zen Ji Horita
Keyword(s):  
High Pressure ◽  
High Pressure Torsion ◽  
Xrd Analysis ◽  
Aged Condition ◽  
Subsequent Aging ◽  
Transmission Electron ◽  
Fe Content ◽  
Average Grain Size ◽  
The Matrix ◽  
Peak Aged

The aging behavior of a cast Al-2 wt.% Fe alloy processed by High-Pressure Torsion (HPT) at room temperature was studied by subsequent aging treatments at 200 °C. Observations by Transmission Electron Microscopy (TEM) revealed that the microstructure after HPT processing reached an ultrafine-grained level with an average grain size in the Al matrix of ~120 nm. The initial eutectic structures were fragmented into particles with sizes of less than 400 nm and partially dissolved in the matrix up to a supersaturated Fe content of ~1% as confirmed by X-Ray Diffraction (XRD) analysis. The peak-age condition was achieved within 0.25 h of aging, which provides the maximum hardness of ~200 HV. Analyses by high-resolution S/TEM show that round particles of Al6Fe with sizes of ~5-10 nm and semi-coherent with the matrix are the dominant precipitates in the peak-aged condition. The hardness increases by aging for 12 h above the as-HPT-processed level of 185 HV. The dominant precipitate phase transforms to Al3Fe in the over-aged condition with a loss of coherency during growth. Enhanced precipitation kinetics was observed because of high density of lattice defects induced by the HPT processing, which were also confirmed by significant recovery in the electrical conductivity of the samples after aging.

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