Nonfluvial Control of Bimodal Grain-Size Distributions in River-Bed Gravels

1988 ◽  
Vol Vol. 58 ◽  
Author(s):  
John Wolcott
Keyword(s):  
Grain Size ◽  
Size Distributions ◽  
River Bed ◽  
Grain Size Distributions ◽  
Bimodal Grain Size

scholarly journals Three-Dimensional in situ Reconstructions of Microstructures with Bimodal Grain Size Distributions

2019 ◽  
Vol 25 (S2) ◽  
pp. 370-371
Author(s):  
Ashley Bucsek ◽  
Lee Casalena ◽  
Darren C. Pagan ◽  
Partha P. Paul ◽  
Yuriy Chumlyakov ◽  
...  
Keyword(s):  
Grain Size ◽  
Three Dimensional ◽  
Size Distributions ◽  
Grain Size Distributions ◽  
Bimodal Grain Size

scholarly journals Grain Growth after Intercritical Rolling

2004 ◽  
Vol 467-470 ◽  
pp. 305-310 ◽  
Author(s):  
Roumen H. Petrov ◽  
Leo Kestens ◽  
Kim Verbeken ◽  
Yvan Houbaert
Keyword(s):  
Grain Size ◽  
Size Distributions ◽  
Orientation Microscopy ◽  
Final Rolling Temperature ◽  
Responsible Mechanism ◽  
Grain Size Distributions ◽  
Intercritical Region ◽  
Final Rolling ◽  
Parent Austenite ◽  
Bimodal Grain Size

The distribution of the characteristic texture components between the ferrite grains of different size classes has been studied in a steel with 0.082%C, 1.54% Mn, 0.35% Si, 0.055%Nb and 0.078%V after different rolling schedules with a final rolling temperature above or below Ar3. Microstructures and textures were characterized by means of optical microscopy and orientation microscopy. A strong grain refining effect together with a bimodal grain size distribution was observed in the steel both after final rolling in the intercritical region or in the austenite region, close to the Ar3 d temperature. The differences in grain size were interpreted on the basis of three potentially acting mechanisms: (i) transformation- induced recrystallization, (ii) increased mobility of specific grain boundaries and (iii) fast nucleation of ferrite grains on specific sites of the parent austenite microstructure. The experimental data clearly favoured the third of these assumptions as the responsible mechanism for the observed bimodal grain size distributions.

scholarly journals Uniform grain-size distribution in the active layer of a shallow, gravel-bed, braided river (the Urumqi River, China) and implications for paleo-hydrology

2018 ◽  
Author(s):  
Laure Guerit ◽  
Laurie Barrier ◽  
Youcun Liu ◽  
Clément Narteau ◽  
Eric Lajeunesse ◽  
...  
Keyword(s):  
Grain Size ◽  
Size Distribution ◽  
Grain Size Distribution ◽  
Active Layer ◽  
Size Distributions ◽  
Gravel Bed ◽  
Surface Samples ◽  
River Bed ◽  
Braided Stream ◽  
Grain Size Distributions

Abstract. The grain-size distribution of ancient alluvial systems is commonly determined from surface samples of vertically exposed sections of gravel deposits. This method relies on the hypothesis that the grain-size distribution obtained from a vertical cross-section is equivalent to that of the river bed. We report a field test of this hypothesis on samples collected on an active, gravel-bed, braided stream: the Urumqi River in China. We compare data from volumetric samples of a trench excavated in an active thread and surface counts performed on the trench vertical faces. We show that the grain-size distributions obtained from all samples are similar and that the deposit is uniform at the scale of the river active layer, a layer extending from the surface to a depth of approximately ten times the size of the largest clasts.

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