Effect of Heat Treatments on Microstructure of Rapidly Solidified TiCo Ribbons

2004 ◽  
Vol 842 ◽  
Author(s):  
Kyosuke Yoshimi ◽  
Akira Yamauchi ◽  
Ryusuke Nakamura ◽  
Sadahiro Tsurekawa ◽  
Shuji Hanada
Keyword(s):  
Crystal Structure ◽  
Dislocation Density ◽  
Grain Growth ◽  
Heat Treatments ◽  
Grain Structure ◽  
Second Phase ◽  
Burgers Vector ◽  
Rapidly Solidified ◽  
Equiaxed Grain ◽  
Observation Results

ABSTRACTThe effect of heat treatments (aging or annealing) on microstructure was investigated for rapidly solidified ribbons of near-stoichiometric TiCo. In as-spun ribbons, it was observed by TEM that an equiaxed grain structure was developed and its crystal structure had been already B2-ordered, while a small amount of a second phase, Ti2Co, finely disperses in grains and along grain boundaries. Some grains were dislocation-free but others contained curved or helical dislocations and prismatic loops having a Burgers vector parallel to <100> directions. By annealing the as-spun ribbons at 700°C for 24h, the dislocation density was obviously increased compared with that of the as-spun ribbons, while grain growth appears to occur slightly. The increase of the dislocation density in the annealed ribbons is believed to result from the condensation and/or absorption of supersaturated vacancies. Therefore, the TEM observation results indicate that a large amount of supersaturated thermal vacancies were retained in the TiCo ribbons by the rapid solidification.

Substructure Development in Rapidly Solidified B2-Type TiCo Ribbons

2005 ◽  
Vol 475-479 ◽  
pp. 849-852 ◽  
Author(s):  
Kyosuke Yoshimi ◽  
Minseok Sung ◽  
Sadahiro Tsurekawa ◽  
Akira Yamauchi ◽  
Ryusuke Nakamura ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Dislocation Density ◽  
Rapid Solidification ◽  
Melt Spinning ◽  
Grain Structure ◽  
Second Phase ◽  
Rapidly Solidified ◽  
Equiaxed Grain

Substructure development through aging and annealing treatments was studied for rapidly solidified TiCo ribbons using TEM. In as-spun ribbons, equiaxed grain structure was developed and its crystal structure was B2-ordered immediately after melt-spinning, while a small amount of fine precipitates existed as second phase. Some grains were dislocation-free but others contained a certain amount of curved or helical dislocations and loops. The dislocation density in the ribbons annealed at 700 °C for 24 h was obviously higher than those in the as-spun ribbons and the ribbons aged at 200 °C for 100 h. The increase of the dislocation density in the annealed ribbons would result from the absorption of excess vacancies. Therefore, the obtained results indicated that a large amount of supersaturated thermal vacancies were retained in TiCo as-spun ribbons by the rapid solidification.

Recrystallization and Grain Growth during Alloy 718 Processing

2007 ◽  
Vol 539-543 ◽  
pp. 3094-3099
Author(s):  
Nho Kwang Park ◽  
Jeoung Han Kim ◽  
Jong Taek Yeom
Keyword(s):  
Grain Size ◽  
Grain Growth ◽  
Heat Treatments ◽  
Grain Structure ◽  
Alloy 718 ◽  
Compression Tests ◽  
Δ Phase ◽  
Grain Boundary Characteristics ◽  
The Difference ◽  
Boundary Characteristics

In Alloy 718 ingot cogging process, dynamic and metadynamic recrystallizations, and static grain growth occur, and also the presence of δ phase plays a key role in controlling the grain size. In this study, the evolution of grain structure in VIM/VAR-processed Alloy 718 ingots during post-cogging heat treatments is dealt with. Compression tests were made on VIM/VAR-processed Alloy 718 ingot at temperatures between 900oC ~ 1150oC. Heat treatments were made on the compression-tested specimens, and the variation of grain size was evaluated. Constitutive equations for the grain growth are established to represent the evolution of microstructures. Special attention is paid to the evolution of grain structure under the condition of dynamic and metadynamic recrystallizations, and grain growth. The grain growth rate depends mainly on the presence of δ-phase below the δ-solvus temperature, and on the difference in the grain boundary characteristics above it.

Abnormal Grain Growth in Metals

2007 ◽  
Vol 558-559 ◽  
pp. 717-722 ◽  
Author(s):  
J. Dennis ◽  
Pete S. Bate ◽  
John F. Humphreys
Keyword(s):  
Grain Growth ◽  
Volume Fraction ◽  
Abnormal Grain Growth ◽  
Grain Structure ◽  
Second Phase ◽  
Boundary Misorientation ◽  
Phase Volume Fraction ◽  
Abnormal Growth ◽  
Grain Boundary Misorientation ◽  
Dominant Characteristic

Grain growth may occur in two forms, normal grain growth, characterized by a constant grain size distribution during growth, and abnormal grain growth, where one or more abnormally large grains may form in the microstructure. The presence of abnormally large grains in an otherwise uniform microstructure may be detrimental to the mechanical properties of a polycrystalline structure. Little is understood of the exact cause of abnormal grain growth. The annealing conditions leading to the onset of abnormal grain growth have been investigated via a series of grain growth experiments carried out on an Al-4wt%Cu alloy. The structure of which consisted of equiaxed grains (<8μ) pinned by a fine dispersion of sub-micron second phase particles, which may dissolve upon annealing. Minority texture components may experience accelerated growth due to a higher energy and mobility compared to the surrounding grain structure. The combination of these two events may result in the abnormal growth of some grains. SEM imaging and EBSD data has then made it possible to characterize the influence of particle dissolution and grain boundary misorientation on the onset of abnormal grain growth. The stability of ‘island grains’ found to exist internally in abnormally large grains has also been investigated in relation to the misorientation relationship and localized second phase volume fraction found there. There was only weak evidence of special misorientation relationships between the island grains and the abnormally large grains in which they exist, and although there was evidence of an enhanced fraction of pinning particles at island grain boundaries, this was also true of boundaries in general. The larger size of island grains is their dominant characteristic, and grains which become island grains may have been incipient abnormal grains.

Synthesis and Properties of Bulk Amorphous/Nanocrystalline Aluminum Alloy Composites

2006 ◽  
Vol 510-511 ◽  
pp. 830-833 ◽  
Author(s):  
Si Joon Noh ◽  
Taek Kyun Jung ◽  
Dong Suk Lee ◽  
Mok Soon Kim ◽  
Sung Yi
Keyword(s):  
Volume Fraction ◽  
Grain Structure ◽  
Full Density ◽  
Mixing Ratio ◽  
Forging Process ◽  
High Maximum ◽  
Nanocrystalline Aluminum ◽  
Maximum Compressive Strength ◽  
Rapidly Solidified ◽  
Equiaxed Grain

The rod-shaped bulk composites consisting of Al-10Ni-6Ce and Al-4Fe-0.6Mo-1.1V- 0.3Zr alloy (mixing ratio; 0.7:0.3, 0.5:0.5 and 0.3:0.7) and corresponding monolithic alloys were produced to a full density via powder forging process. The process involved pre-compaction of rapidly solidified alloy powders and subsequent isothermal forging at 673K. The forged Al-10Ni- 6Ce alloy exhibited nano-scaled crystalline particles, such as fcc-Al, Al3Ni, Al4Ce and Al11Ce3 phase, coexisting with an amorphous phase. In the case of the forged Al-4Fe-0.6Mo-1.1V-0.3Zr alloy, an equiaxed grain structure was observed to exist with uniformly distributed nano-scaled Al- Fe based intermetallics. The monolithic Al-10Ni-6Ce alloy had a considerably high maximum compressive strength (MCS) of 1.35 GPa without showing any compressive plastic strain (CPS). In contrast, the monolithic Al-4Fe-0.6Mo-1.1V-0.3Zr alloy possessed noticeably high CPS of 25% with the MCS of 0.71GPa. The composites acquired the CPS varying from 1 to 5.8 % and the MCS from 1.26 to 0.74 GPa, with increment of the volume fraction of Al-4Fe-0.6Mo-1.1V-0.3Zr alloy from 0.3 to 0.7.

Grain Growth Behavior of a Rapidly Solidified Fe-10Cr-8A1 Alloy

1986 ◽  
Vol 80 ◽  
Author(s):  
M. J. Maloney ◽  
A. J. Garratt-Reed ◽  
G. J. Yurek
Keyword(s):  
Grain Growth ◽  
Hot Isostatic Pressing ◽  
Primary Recrystallization ◽  
Second Phase ◽  
Gas Atomization ◽  
Second Phase Particles ◽  
Cold Rolled ◽  
Grain Growth Behavior ◽  
Rapidly Solidified ◽  
Twin Roll

AbstractA rapidly solidified Fe-10Cr-8Al alloy that contained a dispersion of very fine MnS and Al203 particles was produced by a gas atomization/twin-roll quenching technique. The RS particulates were consolidated by hot isostatic pressing, and the consolidated alloy was hot forged, and then hot and cold rolled. Grain growth took place during primary recrystallization of the alloy; however, once primary recrystallization was complete, the dispersion of second phase particles was effective in pinning alloy grain boundaries.

scholarly journals Effects of Postprocess Hot Isostatic Pressing Treatments on the Mechanical Performance of EBM Fabricated TI-6Al-2Sn-4Zr-2Mo

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2604 ◽  
Author(s):  
Miguel Lopez ◽  
Christina Pickett ◽  
Edel Arrieta ◽  
Lawrence E. Murr ◽  
Ryan B. Wicker ◽  
...  
Keyword(s):  
Grain Growth ◽  
Electron Emission ◽  
Mechanical Performance ◽  
Hot Isostatic Pressing ◽  
Alpha Phase ◽  
Grain Structure ◽  
Isostatic Pressing ◽  
Post Process ◽  
Equiaxed Grain ◽  
Thermionic Electron Emission

An essentially fully acicular alpha-prime martensite within an equiaxed grain structure was produced in an Electron Beam Melting (EBM)-fabricated Ti-6Al-2Sn-4Zr-2Mo (Ti6242) alloy using two different Arcam EBM machines: An A2X system employing tungsten filament thermionic electron emission, and a Q20 system employing LaB6 thermionic electron emission. Post-process Hot Isostatic Pressing (HIP) treatment for 2 h at 850, 950, and 1050 °C resulted in grain refinement and equiaxed grain growth along with alpha-prime martensite decomposition to form an intragranular mixture of acicular martensite and alpha at 850 °C, and acicular alpha phase at 950 and 150 °C, often exhibiting a Widmanstätten (basketweave) structure. The corresponding tensile yield stress and ultimate tensile strength (UTS) associated with the grain growth and acicular alpha evolution decreased from ~1 and ~1.1 GPa, respectively, for the as-fabricated Ti6242 alloy to ~0.8 and 0.9 GPa, respectively, for HIP at 1050 °C. The optimum elongation of ~15–16% occurred for HIP at 850 °C; for both EBM systems. Because of the interactive role played by equiaxed grain growth and the intragrain, acicular alpha microstructures, the hardness varied only by ~7% between 41 and 38 HRC.

Three-Dimensional Micron-Resolution X-Ray Laue Diffraction Measurement of Thermal Grain-Evolution in Aluminum

2004 ◽  
Vol 467-470 ◽  
pp. 1373-1378 ◽  
Author(s):  
J.D. Budai ◽  
W. Yang ◽  
B.C. Larson ◽  
J.Z. Tischler ◽  
W. Liu ◽  
...  
Keyword(s):  
Grain Growth ◽  
Lattice Structure ◽  
Three Dimensional ◽  
Automated Analysis ◽  
Grain Structure ◽  
Polycrystalline Materials ◽  
Second Phase ◽  
Diffraction Measurement ◽  
X Rays ◽  
X Ray

A new technique for investigating 3D grain growth in polycrystalline materials using white x-ray microdiffraction with micron point-to-point spatial resolution is presented. This technique utilizes focused polychromatic x-rays at the Advanced Photon Source, differential aperture depth-profiling, CCD measurements, and automated analysis of spatially-resolved Laue patterns to measure local lattice structure and orientation. 3D thermal grain growth studies of hotrolled aluminum have been initiated to demonstrate the capabilities of this method. Complete 3D grain orientation maps were obtained from a hot-rolled aluminum polycrystal. The sample was then annealed to induce grain growth, cooled to room temperature, and re-mapped to measure the thermal migration of all grain boundaries within the same volume region. Initial observations reveal significant grain growth above 360°C, involving movement of both low- and high-angle boundaries. Systematic measurements have been obtained of the as-rolled grain structure and of the microstructural evolution after annealing at successively higher temperatures. Small second-phase precipitates have been identified. Such measurements will provide the detailed 3D experimental link needed for testing theories and computer models of 3D grain growth in bulk materials.

Effect of Cr on Grain Refinement and Mechanical Properties of Al-Si-Mg Alloys

2015 ◽  
Vol 789-790 ◽  
pp. 95-99 ◽  
Author(s):  
Aakash Kumar ◽  
Gaurav Sharma ◽  
Chandrabalan Sasikumar ◽  
Shahrukh Shamim ◽  
Himkar Singh
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Growth ◽  
Testing Machine ◽  
Weight Percent ◽  
Stir Casting ◽  
Optical Microscope ◽  
Mg Alloys ◽  
Grain Structure ◽  
Second Phase

Grain growth of Aluminium alloys at high temperature reduces their strength significantly. Therefore it is essential to control the grain growth by suitable techniques. The effect of Cr on refining the grain structure of Al alloys is investigated in the present work. Cr is added into Al-Si-Mg alloy by stir casting techniques. Subsequently the alloys were subjected to annealing at 500oC for 1 hour to study the grain growth behavior of these alloys. An optical microscope is used to analyze the grain size and microstructure. The mechanical properties of these alloys were studied using a universal testing machine. The Cr additions were varied between 0.5 to 4 weight percent. The Cr addition had shown a significant effect in refining the grain size of Al-Si-Mg alloys. The average grain diameter after annealing was found to be about 151 μm in unalloyed samples while, the 2 wt % Cr added samples showed about 92 μm. The second phase particles, Al7Cr found precipitated along the grain boundaries apart from Al2Si and Mg2Si. However Cr additions more than 2% does not show significant role in refining the grain size. Cr also improved the mechanical properties such as yield strength, ultimate tensile strength and fracture toughness moderately.

Grain Refinement in Titanium-Erbium Alloys

1974 ◽  
Vol 32 ◽  
pp. 522-523
Author(s):  
B. B. Rath ◽  
J. E. O'Neal ◽  
R. J. Lederich
Keyword(s):  
Electron Microscopy ◽  
Size Distribution ◽  
Grain Refinement ◽  
Grain Growth ◽  
Volume Fraction ◽  
Pure Titanium ◽  
Systematic Investigation ◽  
Second Phase ◽  
Titanium Matrix ◽  
Average Size

Addition of small amounts of erbium has a profound effect on recrystallization and grain growth in titanium. Erbium, because of its negligible solubility in titanium, precipitates in the titanium matrix as a finely dispersed second phase. The presence of this phase, depending on its average size, distribution, and volume fraction in titanium, strongly inhibits the migration of grain boundaries during recrystallization and grain growth, and thus produces ultimate grains of sub-micrometer dimensions. A systematic investigation has been conducted to study the isothermal grain growth in electrolytically pure titanium and titanium-erbium alloys (Er concentration ranging from 0-0.3 at.%) over the temperature range of 450 to 850°C by electron microscopy.

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