Grain Size Dependence of the Flow Stress of TWIP Steel

2010 ◽  
Vol 654-656 ◽  
pp. 294-297 ◽  
Author(s):  
Ghasem Dini ◽  
Rintaro Ueji ◽  
Abbas Najafizadeh
Keyword(s):  
Grain Size ◽  
Flow Stress ◽  
Twip Steel ◽  
Strengthening Mechanism ◽  
Mechanical Twinning ◽  
Coarse Grained ◽  
Strengthening Effect ◽  
Fine Grained ◽  
Hardening Behavior ◽  
Grain Sizes

The effect of grain size on the flow stress in TWinning Induced Plasticity (TWIP) steel was investigated via the X-ray diffraction (XRD) measurements of dislocation density. The results indicated that the hardening behavior of fine grained samples (mean grain sizes in the range of 2.1-3.8μm) can be described as typical dislocation interactions. However in coarse grained samples (mean grain sizes in the range of 4.7-38.5μm) where extensive mechanical twinning occurs, another strengthening mechanism is required. Consequently, the effect of grain size on the flow stress parameters of the proposed equation was considered and it was found that in the fine grained samples, the Holloman analysis can describe the hardening behavior. However, in coarse grained samples, a second hardening term due to the strengthening effect of mechanical twin boundaries needs to be added to the Holloman equation.

Low-Cycle Fatigue Behavior of TWIP Steel - Effect of Grain Size

2014 ◽  
Vol 891-892 ◽  
pp. 1603-1608 ◽  
Author(s):  
Christian Johannes Rüsing ◽  
Thomas Niendorf ◽  
Andreas Frehn ◽  
Hans Jurgen Maier
Keyword(s):  
Grain Size ◽  
Twip Steel ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Coarse Grained ◽  
Dislocation Slip ◽  
Cycle Fatigue ◽  
Fine Grained ◽  
Grain Sizes ◽  
Before And After

The effect of different grain sizes on the fatigue performance of high manganese TWIP steel (Twinning-Induced Plasticity) in the low-cycle fatigue regime was investigated. The average grain sizes in the fine grained condition were 2 5 μm and after heat treatment in the coarse grained condition about 80 μm were obtained. Pronounced twin-dislocation interactions especially in small grains strengthen the steel during monotonic deformation. Twin boundaries act as obstacles for dislocation slip, and thus, further reduce the effective grain size, which affects the fatigue response as well. The samples were monotonically and cyclically deformed at room temperature. The results reveal that the grain size has a significant influence on the mechanical as well as on the cyclic performance. Especially under cyclic loading differences in the resulting stress levels and cyclic stability can be observed. To clarify the microstructure evolution before and after fatigue with different constant strain amplitudes the samples were analyzed by means of transmission electron microscopy (TEM).

Studies with the intraruminal selenium pellet. 2. The effect of grain size of selenium on the functional life of pellets in sheep

1981 ◽  
Vol 32 (6) ◽  
pp. 935 ◽  
Author(s):  
DR Hudson ◽  
RA Hunter ◽  
DW Peter
Keyword(s):  
Grain Size ◽  
Progressive Increase ◽  
Coarse Grained ◽  
Elemental Selenium ◽  
Average Composition ◽  
Plasma Selenium ◽  
Iron Selenide ◽  
Fine Grained ◽  
Grain Sizes

Grain size of elemental selenium is a major factor controlling the long-term effectiveness of intraruminal selenium pellets. Microscope studies of polished sections of new and used selenium pellets showed that two commercially manufactured pellets contained selenium with average grain sizes about 4 and 40 �m respectively. Plasma selenium concentrations in sheep treated with pellets containing the coarse-grained selenium were maintained at higher levels over longer periods of time than those measured for sheep treated with pellets with fine-grained selenium. Pellets removed from sheep after 2, 4, 8, 16 and 28 days showed a progressive increase in the degree of alteration of selenium to a compound of average composition (g/100 g) iron, 33.7; selenium, 51.3 ; oxygen, 15.0. After 28 days only a small percentage of elemental selenium remained in pellets with fine-grained selenium, whereas about 50% remained in pellets with coarse-grained selenium. CSIRO prototype pellets, for which long-term effectiveness had been established, also contained coarse-grained selenium, and remnants of selenium were found in pellets that had been in sheep for periods up to 3 years. Selenium, administered in gelatin capsules or as sachets containing glass-selenium mixtures, was stable under the pH-Eh conditions of the rumen, but was rendered unstable in selenium pellets or iron-selenium mixtures by the presence of iron. It is probable that the most rapid release of selenium to the sheep occurs as a result of a chemical reaction involving the oxidation of iron and concomitant alteration of elemental selenium to iron selenide.

Effect of Grain Size on Mechanical Properties of Dual Phase Steels Composed of Ferrite and Martensite

MRS Advances ◽  
2016 ◽  
Vol 1 (12) ◽  
pp. 811-816 ◽  
Author(s):  
Myeong-heom Park ◽  
Akinobu Shibata ◽  
Nobuhiro Tsuji
Keyword(s):  
Mechanical Properties ◽  
Heat Treatment ◽  
Grain Size ◽  
Tensile Test ◽  
Coarse Grained ◽  
Dual Phase ◽  
Fine Grained ◽  
Grain Sizes ◽  
Dp Structure ◽  
Dp Steels

ABSTRACTIt is well-known that dual phase (DP) steels composed of ferrite and martensite have good ductility and plasticity as well as high strength. Due to their excellent mechanical properties, DP steels are widely used in the industrial field. The mechanical properties of DP steels strongly depend on several factors such as fraction, distribution and grain size of each phase. In this study, the grain size effect on mechanical properties of DP steels was investigated. In order to obtain DP structures with different grain sizes, intercritical heat treatment in ferrite + austenite two-phase region was carried out for ferrite-pearlite structures having coarse and fine ferrite grain sizes. These ferrite-pearlite structures with coarse and fine grains were fabricated by two types of heat treatments; austenitizing heat treatment and repetitive heat treatment. Ferrite grain sizes of the specimens heat-treated by austenitizing and repetitive heat treatment were 47.5 µm (coarse grain) and 4.5 µm (fine grain), respectively. The ferrite grain sizes in the final DP structures fabricated from the coarse-grained and fine-grained ferrite-pearlite structures were 58.3 µm and 4.1µm, respectively. The mechanical behavior of the DP structures with different grain sizes was evaluated by an uniaxial tensile test at room temperature. The local strain distribution in the specimens during tensile test was obtained by a digital image correlation (DIC) technique. Results of the tensile test showed that the fine-grained DP structure had higher strength and larger elongation than the coarse-grained DP structure. It was found by the DIC analysis that the fine-grained DP structure showed homogeneous deformation compared with the coarse-grained DP structure.

Effect of Grain Size and Grain Boundary on Mechanical Yielding Behavior of Fully Stabilized Zirconia

2006 ◽  
Author(s):  
Jie Lian ◽  
Javier Garay ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Grain Size ◽  
Grain Boundary ◽  
Boundary Effect ◽  
Coarse Grained ◽  
Stabilized Zirconia ◽  
Fine Grained ◽  
Grain Sizes ◽  
Reduced Modulus ◽  
Grain Boundary Effect

Mechanical properties of fully yttria stabilized zirconia (F-YSZ) with different grain sizes were investigated using instrumented indentation. While the grain size effect on the yield strength was performed on both the coarse-grained and fine-grained F-YSZ, the grain boundary effect was studied on the coarse-grained F-YSZ by performing nanoindentation within the grains and on/near the grain boundaries. Little variations were observed on mechanical properties such as hardness and reduced modulus, interesting results were obtained on the grain boundary effect on the yielding load for the course-grained F-YSZ.

scholarly journals Submarine lava deltas of the 2018 eruption of Kīlauea volcano

2021 ◽  
Vol 83 (4) ◽  
Author(s):  
S. Adam Soule ◽  
Michael Zoeller ◽  
Carolyn Parcheta
Keyword(s):  
Grain Size ◽  
Pore Pressure ◽  
Mechanistic Model ◽  
Large Fraction ◽  
Volcanic Hazards ◽  
Lava Flows ◽  
Coarse Grained ◽  
Fine Grained ◽  
Fine Grain ◽  
Delta Formation

AbstractHawaiian and other ocean island lava flows that reach the coastline can deposit significant volumes of lava in submarine deltas. The catastrophic collapse of these deltas represents one of the most significant, but least predictable, volcanic hazards at ocean islands. The volume of lava deposited below sea level in delta-forming eruptions and the mechanisms of delta construction and destruction are rarely documented. Here, we report on bathymetric surveys and ROV observations following the Kīlauea 2018 eruption that, along with a comparison to the deltas formed at Pu‘u ‘Ō‘ō over the past decade, provide new insight into delta formation. Bathymetric differencing reveals that the 2018 deltas contain more than half of the total volume of lava erupted. In addition, we find that the 2018 deltas are comprised largely of coarse-grained volcanic breccias and intact lava flows, which contrast with those at Pu‘u ‘Ō‘ō that contain a large fraction of fine-grained hyaloclastite. We attribute this difference to less efficient fragmentation of the 2018 ‘a‘ā flows leading to fragmentation by collapse rather than hydrovolcanic explosion. We suggest a mechanistic model where the characteristic grain size influences the form and stability of the delta with fine grain size deltas (Pu‘u ‘Ō‘ō) experiencing larger landslides with greater run-out supported by increased pore pressure and with coarse grain size deltas (Kīlauea 2018) experiencing smaller landslides that quickly stop as the pore pressure rapidly dissipates. This difference, if validated for other lava deltas, would provide a means to assess potential delta stability in future eruptions.

Deformation Size Effects Due to Specimen and Grain Size in Microbending

2010 ◽  
Vol 132 (1) ◽  
Author(s):  
Sunal Ahmet Parasiz ◽  
Reid VanBenthysen ◽  
Brad L. Kinsey
Keyword(s):  
Grain Size ◽  
Sheet Thickness ◽  
Specimen Size ◽  
Coarse Grained ◽  
Thick Sheet ◽  
Hardness Profile ◽  
Localized Deformation ◽  
Fine Grained ◽  
Deformation Distribution ◽  
Deformation Area

Sheet metal forming often consists of bending processes in which gradients of deformation exists through the thickness of the workpiece in a localized deformation area. In microscale bending, these deformation gradients become much steeper, as the changes in the deformation occur over short distances (in the order of micrometers). In addition, with miniaturization, the number of grains that are present through the thickness decreases significantly. In this research, the effect of grain size and specimen size on the deformation distribution through the thickness of microbent sheet specimens was investigated via microhardness evaluations. It was found that the deformation distribution, i.e., hardness profile, is not affected significantly by the grain size when the sheet thickness is large (for 1.625 mm specimens) or by miniaturization of the specimen size when the grain size is fine. However, the deformation distribution of the coarse grained specimens deviates from the fine grained ones and from the 1.625 mm thick sheet specimens when the specimen size is miniaturized.

scholarly journals Sintering of a fine-grained BaCeO3 powder obtained from a co-precipitation method

2018 ◽  
Author(s):  
Roberto Köferstein
Keyword(s):  
Precursor Powder ◽  
Coarse Grained ◽  
Precipitation Method ◽  
Fine Grained ◽  
Grain Sizes ◽  
Three Phase ◽  
Sintering Behaviour ◽  
Co Precipitation ◽  
Precursor Powders ◽  
Powder Compacts

The formation of BaCeO3 by a co-precipitation method is described herein. The coprecipitationroute leads to an orange (BaCe)-precursor powder (1). To improve the sinteringbehaviour, a small amount of Ge4+ was incorporated, leading to a (BaCe0.95/Ge0.05)-precursor(2). Both precursor powders results in fine-grained preceramic powders (1A, 2A) aftercalcination. The shrinkage and sintering behaviour of resulting powder compacts were studiedin comparison to a coarse-grained mixed-oxide BaCeO3 powder (3). Compacts of 2A reach arelative density of 90 % after sintering at 1350 °C with grain-sizes between 0.9−3.2 μm. Onthe other hand ceramics of 1A and 3 have, after sintering at 1500 °C (10 h), relative densitiesof 85 % and 76 %, respectively. Ceramic bodies of 1A consisted of phase-pure orthorhombicBaCeO3, whereas bodies of 2A show reflections of BaCeO3 and a Ba2GeO4 phase. DTAinvestigations of samples 1A and 2A reveal three phase transitions at 255 °C (1A) and 256 °C (2A) as well as 383 °C (1A) and 380 °C (2A). A very weak one can be obtained in the range880−910 °C

Microhardness Enhancement in Fully Dense Fe-Based Nanophase Metallic Alloys

1995 ◽  
Vol 400 ◽  
Author(s):  
L. He ◽  
E. Ma
Keyword(s):  
Grain Size ◽  
High Energy ◽  
Metallic Alloys ◽  
Full Density ◽  
Strengthening Effect ◽  
Two Phase ◽  
Grain Sizes ◽  
Sinter Forging ◽  
Interphase Boundaries ◽  
Energy Ball

AbstractNano-grained Fe-29Al-2Cr intermetallic and Fe-Cu two-phase composites have been consolidated to full density from powders produced by high-energy ball milling, using a sinter forging procedure developed recently in our laboratory. Grain sizes remained within nanophase range (<100 nm) after consolidation. Microhardness tests of Fe-29Al-2Cr samples consolidated to different density levels indicate a significant strengthening effect due to nanoscale grain size and a monotonic microhardness increase with decreasing residual porosity. Fully dense Fe-Cu composites exhibit enhanced microhardness as compared with rule-of-mixtures predictions, which may be attributable to interface strengthening at fcc-bcc interphase boundaries.

scholarly journals Characterization of glacial silt and clay using automated mineralogy

2019 ◽  
Vol 60 (80) ◽  
pp. 49-65
Author(s):  
Jeff W. Crompton ◽  
Gwenn E. Flowers ◽  
Brendan Dyck
Keyword(s):  
Grain Size ◽  
Size Composition ◽  
Rock Properties ◽  
Fine Grained ◽  
Rock Fragments ◽  
Grain Sizes ◽  
Automated Mineralogy ◽  
Log Normal ◽  
Discrete Populations

AbstractGlacial erosion produces vast quantities of fine-grained sediment that has a far-reaching impact on Earth surface processes. To gain a better understanding of the production of glacial silt and clay, we use automated mineralogy to quantify the microstructure and mineralogy of rock and sediment samples from 20 basins in the St. Elias Mountains, Yukon, Canada. Sediments were collected from proglacial streams, while rock samples were collected from ice marginal outcrops and fragmented using electrical pulse disaggregation. For both rock fragments and sediments, we observe a log-normal distribution of grain sizes and a sub-micrometer terminal grain size. We find that the abrasion of silt and clay results in both rounding and the exploitation of through-going fractures. The abundance of inter- versus intragranular fractures depends on mineralogy and size. Unlike the relatively larger grains, where crushing and abrasion are thought to exploit and produce discrete populations of grain sizes, the comminution of fines leads to a grain size, composition and rounding that is continuously distributed across size, and highly dependent on source-rock properties.

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.

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