Grain Structure and Precipitates in Squeeze Casting Al-Li-Mg-Zr Alloy

2014 ◽  
Vol 887-888 ◽  
pp. 329-332
Author(s):  
Li Fan ◽  
Zhong Wei Chen ◽  
Qi Tang Hao
Keyword(s):  
Grain Boundaries ◽  
Squeeze Casting ◽  
Grain Structure ◽  
Fine Grained ◽  
Fine Grain ◽  
The Matrix ◽  
Fine Grained Structure ◽  
Heat Treated Condition ◽  
Micrometer Size ◽  
Zr Alloy

Grain structure and precipitates in squeeze casting Al-Li-Mg-Zr alloy for aircraft industry were investigated in heat treated condition, using X-ray diffraction, optical microscopy and transmission electron microscopy. An ultra fine grained structure in sub-micrometer size was obtained, having fine nanograins in it with polycrystalline diffraction rings that are different from the single-crystal patterns in the matrix. Ultra fine grain areas are generally located on the grain boundaries and sub-grain boundaries. In addition, TEM observations indicates the presence of lenticular δ' (Al3Li) phases that symmetrical distributed around the GP zones. The alloy also contains spherical β' (Al3Zr) dispersoids, and S1 (Al2MgLi) phases.

Grain Refinement of 6061 Al Alloy by the Modified Strain-Induced Melt- Activated(SIMA) Process for Semi-Solid Processing

2007 ◽  
Vol 119 ◽  
pp. 311-314 ◽  
Author(s):  
Young Buem Song ◽  
Chun Pyo Hong
Keyword(s):  
Grain Refinement ◽  
Grain Structure ◽  
Al Alloy ◽  
Fine Grained ◽  
Fine Grain ◽  
Fine Grained Structure ◽  
Size Uniformity ◽  
Sima Process ◽  
Semi Solid ◽  
6061 Al Alloy

The dynamic process of fine grain evolution of 6061 aluminum alloy during modified strain-induced, melt-activated (SIMA) process was studied. The modified SIMA process employed casting, two stage homogenization, warm multi-forging, and recrystallization and partial melting (RAP). Multi-forging was carried out at a strain rate of 9x10-3 s-1 to accumulate high strains, with decreasing temperature from 250 to 200 °C. The alloy multi-forged with the accumulated strain of about 12 and RAP at 640 °C for 10 min exhibited the uniform equiaxed recrystallized grain structure. Accordingly, it was evident that multi-forging was very effective on grain refinement and grain size uniformity. The present modified SIMA process was discussed as an alternative thermo-mechanical processing for preparing the alloys with fine grained structure for semi solid processing.

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.

Influence of cooling media in achieving grain refinement of AA2014 alloy using friction stir processing

2020 ◽  
Vol 234 (22) ◽  
pp. 4520-4534
Author(s):  
MVNV Satyanarayana ◽  
Adepu Kumar
Keyword(s):  
Grain Boundaries ◽  
Friction Stir Processing ◽  
Heat Dissipation ◽  
Electron Backscattered Diffraction ◽  
Friction Stir ◽  
Fine Grained ◽  
Fine Grained Structure ◽  
Cooling Media ◽  
Processing Zone ◽  
Friction Stir Processing Sample

The present paper studies the influence of different cooling media (water and cryogenic media) on microstructure, mechanical, and corrosion behavior of friction stir processing of AA2014. From the electron backscattered diffraction results, it was observed that the grain size in stir zone of air-cooled friction stir processing, dry ice-cooled friction stir processing, and underwater friction stir processing are 4.9 µm, 3.5 µm, and 0.9 µm respectively, and the fraction of high angle grain boundaries are more in underwater friction stir processing sample compared to other conditions. The ultra-fine grained structure (0.9 µm) was achieved in underwater friction stir processing due to uniform heat dissipation from the processing zone to the water. Mechanical properties such as hardness and strength were improved in underwater friction stir processing compared to other conditions. The fine precipitates formed in the underwater friction stir processing sample were distributed randomly at grain boundaries, and hence corrosion resistance was improved in underwater friction stir processing sample compared to other conditions.

scholarly journals Texture Evolution in AA6082-T6 BFSW Welds: Optical Microscopy and EBSD Characterisation

Materials ◽  
2019 ◽  
Vol 12 (19) ◽  
pp. 3215 ◽  
Author(s):  
Abbas Tamadon ◽  
Dirk J. Pons ◽  
Don Clucas ◽  
Kamil Sued
Keyword(s):  
Grain Boundary ◽  
Grain Boundaries ◽  
Optical Microscopy ◽  
Electron Backscatter Diffraction ◽  
Texture Evolution ◽  
Grain Structure ◽  
Friction Stir ◽  
Fine Grain ◽  
Grain Structures ◽  
Dynamic Recrystallisation

One of the difficulties with bobbin friction stir welding (BFSW) has been the visualisation of microstructure, particularly grain boundaries, and this is especially problematic for materials with fine grain structure, such as AA6082-T6 aluminium as here. Welds of this material were examined using optical microscopy (OM) and electron backscatter diffraction (EBSD). Results show that the grain structures that form depend on a complex set of factors. The motion of the pin and shoulder features transports material around the weld, which induces shear. The shear deformation around the pin is non-uniform with a thermal and strain gradient across the weld, and hence the dynamic recrystallisation (DRX) processes are also variable, giving a range of observed polycrystalline and grain boundary structures. Partial DRX was observed at both hourglass boundaries, and full DRX at mid-stirring zone. The grain boundary mapping showed the formation of low-angle grain boundaries (LAGBs) at regions of high shear as a consequence of thermomechanical nature of the process.

Jadeite–K-feldspar rocks and jadeitites from northwest Turkey

1997 ◽  
Vol 61 (409) ◽  
pp. 835-843 ◽  
Author(s):  
Aral I. Okay
Keyword(s):  
Grain Size ◽  
Debris Flows ◽  
Bulk Rock ◽  
Rock Composition ◽  
Bulk Rock Composition ◽  
Fine Grained ◽  
Fine Grain ◽  
The Matrix ◽  
Mineral Pair

AbstractBlueschist-facies rocks with jadeite-K-feldspar-lawsonite paragenesis occur as exotic blocks in Miocene debris flows in the blueschist belt of northwest Turkey. The jadeite-K-feldspar rocks have a very fine grain size and although recrystallized locally retain a relict porphyritic volcanic texture. The former nepheline microphenocrysts, recognized from their characteristic shapes, are pseudomorphed by jadeite and K-feldspar, while the relict magmatic aegirine has rims of jadeite. The matrix of the rock consists of very fine-grained aggregates of jadeite, K-feldspar and lawsonite. In some blocks, jadeite makes up >60% of the mode. Jadeite, K-feldspar and lawsonite in the blocks are essentially pure end-member in composition. P-T estimates for these rocks are 8 ± 2 kbar and 300 ± 50°C. The preserved volcanic texture, relict aegirine and the bulk rock composition indicate that these rocks represent metamorphosed phonolites. The paragenesis in these rocks shows that jadeite-K-feldspar is a stable mineral pair in blueschist-facies P-T conditions.

Thermoelectric properties of germanium telluride with fine-grained structure

2020 ◽  
Vol 11 ◽  
pp. 15-25
Author(s):  
L. D. Ivanova ◽  
◽  
Yu. V. Granatkina ◽  
I. Yu. Nikhezina ◽  
A. G. Malchev ◽  
...  
Keyword(s):  
Thermoelectric Properties ◽  
Melt Spinning ◽  
High Energy ◽  
Grain Structure ◽  
Thermoelectric Efficiency ◽  
Fine Grained ◽  
Germanium Telluride ◽  
Fine Grained Structure ◽  
Properties Of Materials ◽  
P Type

The microstructure and thermoelectric properties of materials based on germanium telluride p-type conductivity doped with copper and bismuth obtained by hot pressing of three types powders prepared by grinding an ingot to a size of hundreds microns (0.315  mm) to hundreds of nanometers (mechanical activation) in planetary high-energy mill and melt spinning were investigated. The microstructure of the samples were analyzed by optical and electron scanning microscopies. The nanoscale grain structure of these samples was established. The thermoelectric characteristics of the materials: Seebeck coefficient, electrical and thermal conductivities, were measured both at room temperature and in the temperature range of 100 – 800 K. The slopes of these dependencies are estimated. The coefficient of thermoelectric figure of merit is calculated. The higher thermoelectric efficiency (ZT = 1.5 at 600 K) was received for the samples hot-pressed from granules, prepared by melt spinning.

Development of Ultra-Fine Grained Structure in an Al-5.4%Mg-0.5%Mn Alloy Processed by ECAP

2010 ◽  
Vol 667-669 ◽  
pp. 487-492
Author(s):  
Alla Kipelova ◽  
Ilya Nikulin ◽  
Sergey Malopheyev ◽  
Rustam Kaibyshev
Keyword(s):  
Plastic Deformation ◽  
Structure Formation ◽  
Equal Channel Angular Pressing ◽  
Microstructural Evolution ◽  
Coarse Grained ◽  
High Angle ◽  
Fine Grained ◽  
Angular Pressing ◽  
Fine Grained Structure ◽  
Zr Alloy

Microstructural changes during equal channel angular pressing (ECAP) at the temperatures of 250 and 300°C to the strains ~4, ~8 and ~12 were studied in a coarse-grained Al-5.4%Mg-0.5%Mn-0.1%Zr alloy. At a strain of ~4, the microstructural evolution is mainly characterized by the development of well-defined subgrains within interiors of initial grains and the formation of fine grains along original boundaries. Further straining leads to increase in the average misorientation angle, the fraction of high-angle grain boundaries and the fraction of new grains. However, only at 300°C, the plastic deformation to a strain of ~12 leads to the formation of almost uniform submicrocrystalline (SMC) grained structure with an average crystallites size of ~ 0.5 m. At 250°C, the microstructure remains non-uniform and consists of subgrains and new recrystallized grains. The mechanism of new SMC structure formation after ECAP is discussed.

Superplastic Deformation of YBa2Cu3O7−x in a Superplastic Metal Matrix

1990 ◽  
Vol 196 ◽  
Author(s):  
J. Emilio Moreno ◽  
G. Torres-Villasefor
Keyword(s):  
Grain Boundaries ◽  
Room Temperature ◽  
Meissner Effect ◽  
Grain Boundary Sliding ◽  
New Class ◽  
Fine Grain ◽  
The Matrix ◽  
High Transition ◽  
Boundary Sliding ◽  
Zn Alloy

ABSTRACTThe new class of high-transition-temperature ceramic superconductors (e.g. Y-Ba-Cu-O) show a fine grain size polycrystalline structure, similar to that shown by the superplastic metals. The material behaves in a brittle manner with a strain to fracture below 0.5 % at room temperature. One of the reasons for this mechanical behavior is that the grain boundaries are easily separated when a stress is applied. It was found in this work that a deformation of the superconductor ceramic (scc) in superplastic metal (spin) matrix reduces the separation of the grain boundaries in such materials so that they can be deformed at room temperature. The spin matrixes used in this work were Zn-Cd, Bi-Sn and Cd-Sn. It was found that the highest the yield point of the matrix the highest the deformation induced in the scc. The Cd-Zn alloy was the most effective in avoiding the separation of the grain boundaries during the deformation of a composite formed by a cylinder of scc embedded in a spin matrix. Meissner effect was observed in the scc, after more than 160 % of plastic deformation. SEM observations show that deformation takes place by grain boundary sliding and some grain refinement was observed.

High Strength Mg-Zn-Y-Ce-Zr Alloy Bars Prepared by RS and Extrusion Technology

2005 ◽  
Vol 488-489 ◽  
pp. 495-498 ◽  
Author(s):  
Xuefeng Guo ◽  
Jacob Kinstler ◽  
Lilia Glazman ◽  
Dan Shechtman
Keyword(s):  
Grain Boundaries ◽  
High Strength ◽  
Submicron Particles ◽  
Commercial Alloy ◽  
X Ray Diffraction ◽  
X Ray ◽  
The Matrix ◽  
Extrusion Technology ◽  
Scanning Electron ◽  
Zr Alloy

Based on the commercial alloy ZK60 which contains 6%Zn, high strength Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr magnesium alloy bars of 10 to 50 mm in diameters were prepared by rapid solidification (RS) and extrusion processes （RSE）. For those RSE solid bars, the ultimate tensile strengths steadily maintain on a level of 490 to 520 MPa, the elongations are between 6 to 10%. The HV50 hardness is between 85 and 90. In order to reveal materials microstructures both RS ribbons and RSE solid bars, the Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr alloy was analyzed with an optical microscopy (OM), a scanning electron microscopy (SEM) equipped with an energy-dispersive X-ray spectrometer (EDS) and an X-ray diffraction apparatus. It was found that the microstructure of the RS ribbon consists of super saturated (Mg) solid solution; thermally stable Mg3Y2Zn3 (W) and Mg7Ce2 intermetallic compound particles which uniformly dispersed interior grains and W and Mg7Ce2 compound networks at grain boundaries. After extrusion, the microstructure of RSE Mg-6.0%Zn-1.0%Y-0.6%Ce-0.6%Zr solid bar consists of the same phases as the RS ribbons. The networks existing at RS ribbon’s grain boundaries were break up into submicron particles and dispersed uniformly on the matrix formed after extrusion.

Surface layer modification by cryogenic burnishing of Al 7050-T7451 alloy with near ultra-fine grained structure

2021 ◽  
pp. 1-22
Author(s):  
Bo Huang ◽  
Yusuf Kaynak ◽  
Ying Sun ◽  
Marwan Khraisheh ◽  
I. S. Jawahir
Keyword(s):  
Surface Integrity ◽  
Surface Hardness ◽  
Grain Structure ◽  
Fine Grained ◽  
Compressive Stresses ◽  
Wear And Corrosion ◽  
Cryogenic Burnishing ◽  
Subsurface Layers ◽  
Fine Grained Structure ◽  
Wear And Corrosion Resistance

Abstract Burnishing has been increasingly utilized to improve the surface integrity of manufactured components. The generation of surface and subsurface layers with ultrafine grains, attributed to severe plastic deformation and dynamic recrystallization, leads to improved surface integrity characteristics including surface and subsurface hardness and reduction in surface roughness. Additionally, due to the generation of compressive stresses within the refined layers, increase in fatigue life and improved wear and corrosion resistance can be achieved. In this study, we apply cryogenic burnishing on Al 7050-T7451 discs and compare the surface integrity characteristics with dry conventional burnishing. A special roller burnishing tool with flexible rotating roller head was designed and used to perform the cryogenic burnishing experiments using liquid nitrogen as the coolant. The results show that cryogenic burnishing can increase the surface hardness by an average of 20-30% within a layer depth of 200 μm compared to only 5-10% increase using dry conventional burnishing. Refined layers with nano grain structure were also generated. During cryogenic burnishing the tangential burnishing forces were higher than those of dry conventional burnishing due to rapid cooling and work hardening of the material.

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