Effect of Processing Temperature on Microstructure Development during ECAP of Al-Mg-Sc Alloy

2008 ◽  
Vol 584-586 ◽  
pp. 481-486 ◽  
Author(s):  
Oleg Sitdikov ◽  
Elena Avtokratova ◽  
Taku Sakai ◽  
Kaneaki Tsuzaki ◽  
Rustam Kaibyshev ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Grain Structure ◽  
Coarse Grained ◽  
Microstructural Development ◽  
Al Alloy ◽  
Processing Temperature ◽  
Fine Grained ◽  
Grain Boundary Mobility ◽  
Angular Pressing

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy in a temperature interval 200- 450oC (~0.5-0.8 Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. Uniform fine-grained microstructures with the average grain sizes of 0.7 and 2.5 0m, are almost fully evolved at high ECAP strains at 250oC and 450oC, respectively, while ECAP at 300oC (~0.6 Tm) leads to the formation of bimodal grain structure with fine grains of around 1 µm and relatively coarse grains of around 8 µm. The latter are developed due to the occurrence of static recrystallization during “keeping” time in the ECAP channel and/or reheating between ECAP passes. The microstructural development under warm-to-hot ECAP conditions is discussed in terms of the large potential for grain boundary migration resulted from an overlapping of accelerated grain boundary mobility at high pressing temperatures and enhanced driving force for recrystallization, which is caused by a strong inhibition of dynamic recovery in a heavily-alloyed Al alloy.

scholarly journals The Effect of Initial Grain Size on Formability of AZ31B Magnesium Alloy during I-ECAP

2014 ◽  
Vol 611-612 ◽  
pp. 573-580 ◽  
Author(s):  
Michal Gzyl ◽  
Andrzej Rosochowski ◽  
Lech Olejnik ◽  
Aleksey Reshetov
Keyword(s):  
Grain Size ◽  
Magnesium Alloy ◽  
Strong Influence ◽  
Coarse Grained ◽  
Rolled Plate ◽  
Processing Temperature ◽  
Az31b Magnesium Alloy ◽  
Fine Grained ◽  
Angular Pressing ◽  
Logarithmic Equation

The goal of this work was to investigate formability of AZ31B magnesium alloy during incremental equal channel angular pressing (I-ECAP). Square billets were processed using different routes of I-ECAP at temperatures varying from 125 °C to 250 °C. The billets were obtained from commercially available coarse-grained, hot-extruded rod and fine-grained, hot-rolled plate. A strong influence of the initial microstructure on processing temperature was reported. Fine-grained samples were successfully processed at 200 °C, while coarse-grained ones must have been heated up to 250 °C to avoid fracture. A gradual temperature decrease with subsequent passes allowed successful pressing at 150 °C. Processing using various routes of I-ECAP showed that a billet rotation before the last pass had strong influence on mechanical properties. The results of experiments were plotted on the diagram of allowable processing temperature for AZ31B. It was found that the relation between the minimum temperature in I-ECAP and the initial grain size could be described by a logarithmic equation.

Fabric and origin of gneissic layers in anorthositic rocks of the St. Charles sill, Ontario

1981 ◽  
Vol 18 (11) ◽  
pp. 1681-1693 ◽  
Author(s):  
D. H. Rousell
Keyword(s):  
Grain Size ◽  
Grain Boundary ◽  
Strain Rate ◽  
Boundary Diffusion ◽  
Boundary Migration ◽  
Diffusion Mechanism ◽  
Coarse Grained ◽  
Grain Boundary Migration ◽  
Grenville Province ◽  
Fine Grained

The St. Charles sill is located in the Grenville Province and consists of rocks of the anorthosite suite. The sill is a northwesterly trending body, 11 km long and as much as 0.8 km wide, and with a steep dip to the northeast. The sill is characterized by interlayered massive and gneissic rocks metamorphosed under conditions of the amphibolite facies. In the massive rocks plagioclase occurs as strongly twinned laths that range in size from fine-grained crystals to megacrysts. Hornblende, biotite, and garnet occur as subophitic masses and apparently replace original pyroxene. In the gneissic rocks the plagioclase ranges in size from fine to coarse grained and the primary grains are partially replaced by elongate, weakly twinned, anhedral plagioclase. The gneissosity is defined by a dimensional preferred orientation of biotite, hornblende, and secondary plagioclase. The formation of the secondary plagioclase is attributed largely to growth by grain boundary diffusion and, to a lesser extent, by replacement of primary plagioclase by grain boundary migration. In the diffusion mechanism strain rate is inversely proportional to grain size and it is interpreted that the tectonic fabric developed in the finer grained layers of the sill while the coarser grained layers remained essentially undeformed.

Microstructural Evolution in a Commercial Al-Mg-Sc Alloy during ECAP at 300°C

2007 ◽  
Vol 558-559 ◽  
pp. 569-574 ◽  
Author(s):  
Oleg Sitdikov ◽  
Taku Sakai ◽  
Elena Avtokratova ◽  
Rustam Kaibyshev ◽  
Kaneaki Tsuzaki ◽  
...  
Keyword(s):  
Microstructural Evolution ◽  
Driving Force ◽  
Static Recrystallization ◽  
Grain Structure ◽  
Coarse Grained ◽  
Microstructural Development ◽  
Continuous Dynamic Recrystallization ◽  
Grain Sizes ◽  
Angular Pressing ◽  
Continuous Dynamic

Microstructural evolution taking place during equal channel angular pressing (ECAP) was studied in a commercial coarse-grained Al-6%Mg-0.4%Mn-0.3%Sc alloy at a temperature of 300oC (~0.6Tm). Samples were pressed using route A to a total strain of 12 and quenched in water after each ECAP pass. ECAP at moderate-to-high strains leads to the formation of a bimodal grain structure with grain sizes of around 1 and 8 μm and volume fractions of 0.3 and 0.6, respectively. The development of new-grained regions has been shown to result from a concurrent operation of continuous dynamic recrystallization that occurs during deformation and static recrystallization that occurs during each ECAP cycle by the exposure of the as-deformed material in the die kept at 300oC for around 1.5 minutes. The microstructural development during warm-to-hot ECAP is discussed in terms of the enhanced driving force for recrystallization, resulting from the evolution of high-density dislocation substructures due to the localization of plastic flow and inhibition of recovery in the present alloy.

Tensile Ductility of Ultra-Fine Grained Copper at High Strain Rate

2010 ◽  
Vol 160-162 ◽  
pp. 260-266 ◽  
Author(s):  
Tao Suo ◽  
Kui Xie ◽  
Yu Long Li ◽  
Feng Zhao ◽  
Qiong Deng
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Testing Machine ◽  
Coarse Grained ◽  
Dislocation Dynamic ◽  
Pressing Method ◽  
Fine Grained ◽  
Angular Pressing ◽  
Split Hopkinson

In this paper, ultra-fine grained copper fabricated by equal channel angular pressing method and annealed coarse grained copper were tensioned under both quasi-static and dynamic loading conditions using an electronic universal testing machine and the split Hopkinson tension bar respectively. The rapture surface of specimen was also observed via a Scanning Electron Microscope (SEM). The experimental results show that the ductility of polycrystalline copper decreases remarkably due to the grain refinement. However, with the increase of applied strain rate, ductility of the UFG-Cu is enhanced. The fracture morphologies also give the evidence of enhanced ductility of UFG-Cu at high strain rate. It is believed the enhanced ductility of UFG materials at high strain rate can be attributed to the restrained dislocation dynamic recovery.

scholarly journals Development of microstructure in the high-temperature deformation of ice

1996 ◽  
Vol 23 ◽  
pp. 293-302 ◽  
Author(s):  
Christopher J. L. Wilson ◽  
Yanhua Zhang
Keyword(s):  
Grain Boundary ◽  
Boundary Migration ◽  
Time Lapse ◽  
Grain Structure ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Grain Boundary Migration ◽  
Crystallographic Slip ◽  
Polycrystalline Ice ◽  
Time Lapse Photography

Microstructural changes in three sets of experiments involving crystallographic slip in anisotropic polycrystalline ice are described and interpreted with the aid of computer models. The development of microstructure was followed using time-lapse photography and transmitted light observations with deformation undertaken in plane strain and at a temperature of approximately –1°C. The deformation within a grain aggregate that accompanies axial shortening is always heterogeneous on a grainscale. The extent of inhomogeneity varies depending on the pre-existing grain structure and the way it can accommodate intragranular slip. Grain interactions are extremely important in determining the bulk deformation and the degree of grain-boundary migration. A consequence of shortening of the aggregate is the formation of high stresses between neighbouring grains and under the appropriate conditions there may be either grain-boundary migration or melting at these sites. Where a sample undergoes translation and shear during deformation, anisotropic grains in the appropriate orientation undergo bending. A buckle instability may then develop and much of the strain is accommodated by grains in easy-glide orientations. In such situations, the ice undergoes extensive recrystallization and grain growth that is concentrated in the areas of greatest buckling.

scholarly journals The Influence of Mg-Based Inclusions on the Grain Boundary Mobility of Austenite in SS400 Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 370
Author(s):  
Chih-Ting Lai ◽  
Hsuan-Hao Lai ◽  
Yen-Hao Su ◽  
Fei-Ya Huang ◽  
Chi-Kang Lin ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Grain Growth ◽  
High Temperatures ◽  
Growth Curves ◽  
Solute Drag ◽  
Grain Structure ◽  
Growth Equation ◽  
Boundary Mobility ◽  
Grain Boundary Mobility ◽  
Boundary Velocity

In this study, the effects of the addition of Mg to the grain growth of austenite and the magnesium-based inclusions to mobility were investigated in SS400 steel at high temperatures. A high-temperature confocal scanning laser microscope (HT-CSLM) was employed to directly observe, in situ, the grain structure of austenite under 25 torr Ar at high temperatures. The grain size distribution of austenite showed the log-normal distribution. The results of the grain growth curves using 3D surface fitting showed that the n and Q values of the growth equation parameters ranged from 0.2 to 0.26 and from 405 kJ/mole to 752 kJ/mole, respectively, when adding 5.6–22 ppm of Mg. Increasing the temperature from 1150 to 1250 °C for 20 min and increasing the addition of Mg by 5.6, 11, and 22 ppm resulted in increases in the grain boundary velocity. The effects of solute drag and Zener pinning on grain boundary mobility were also calculated in this study.

Cavitation Behavior of Ultra-Fine Grained Ti-6Al-4V Alloy Produced by Equal-Channel Angular Pressing

2007 ◽  
Vol 551-552 ◽  
pp. 621-626
Author(s):  
Young Gun Ko ◽  
Yong Nam Kwon ◽  
Jung Hwan Lee ◽  
Dong Hyuk Shin ◽  
Chong Soo Lee
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Equal Channel Angular Pressing ◽  
Cavity Growth ◽  
Rate Sensitivity ◽  
Theoretical Models ◽  
Coarse Grained ◽  
Fine Grained ◽  
Angular Pressing ◽  
Cavitation Behavior

Cavitation behavior during superplastic flow of ultra-fine grained (UFG) Ti-6Al-4V alloy was established with the variation of grain size and misorientation. After imposing an effective strainup to 8 via equal-channel angular pressing (ECAP) at 873 K, alpha-phase grains were markedly refined from 11 μm to ≈ 0.3 μm, and misorientation angle was increased. Uniaxial-tension tests were conducted for initial coarse grained (CG) and two UFG alloys (ε = 4 and 8) at temperature of 973 K and strain rate of 10-4 s-1. Quantitative measurements of cavitation evidenced that both the average size and the area fraction of cavities significantly decreased with decreasing grain size and/or increasing misorientation. It was also found that, when compared to CG alloy, cavitation as well as diffused necking was less prevalent in UFG alloys, which was presumably due to the higher value of strain-rate sensitivity. Based on the several theoretical models describing the cavity growth behavior, the cavity growth mechanism in UFG alloys was suggested.

Susceptibility to Stress Corrosion Cracking in Ammonia of Nanostructured Cu-10wt%Zn Alloy Produced by Severe Plastic Deformation

2008 ◽  
Vol 584-586 ◽  
pp. 887-892 ◽  
Author(s):  
Hiroyuki Miyamoto ◽  
Alexei Vinogradov ◽  
Satoshi Hashimoto
Keyword(s):  
Grain Boundary ◽  
Applied Stress ◽  
Room Temperature ◽  
Stress Test ◽  
Constant Load ◽  
Coarse Grained ◽  
Ammonia Vapour ◽  
Boundary State ◽  
Angular Pressing ◽  
Zn Alloy

In this study, susceptibility to SCC of nanostructured Cu-10wt%Zn alloys, produced by equal-channel angular pressing (ECAP) was investigated under the constant stress test in ammonia vapour, which has been well-known typical environment for IGSCC of Cu-Zn alloy. Billets having diameter of 20 mm and length of 100 mm were subjected to ECAP for eight passes at room temperature to obtain structure with grain size of about 100 nm. After ECAP, some of the billets were flush-annealed in 473 K for 60 seconds to decrease excessive unequilibrium dislocations at grain boundaries. Coarse grained specimens without ECAP and one-pass specimens were also tested for comparison. The specimens for SCC were tensioned by a constant load in ammonia vapour inside a glass chamber for 24 hours at room temperature. After the SCC tests, maximum length of cracks was evaluated by SEM. Specimen having UFG structure by 8-passes exhibited cracks in lower applied stress ratio, (=σa/σys) compared with 0- and 1-pass samples, where σa is applied stress and σys is yield stress, respectively. Most importantly, the specimen with annealed at 473K for 60s after ECAP cracked in higher applied stress. It became less sensitive to SCC after flush annealing although mechanical properties were not changed considerably. In our previous studies, we reported that the SCC of UFG copper produced by ECAP, and the sensitivity to SCC becomes lower by flush annealing. Results are discussed in terms of grain boundary state with or without extrinsic grain boundary dislocations

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