Grain Size Measurements Research Articles

Determination of the average WC grain size of cemented carbides for hardness and coercivity

Accurate measurements of WC grain size are required to underpin the development of models to predict the mechanical properties of cemented carbides. Some new stereology methods for calculating the average WC grain size are derived based on the observations that the hardness and coercivity were inversely proportional to the content of coarse WC powders. These average WC grain sizes can be calculated by the linear intercepts or equivalent circle diameters determined on polished 2D cross-sections and it is not required to assume intercepts (one-dimension) or equivalent circle diameters (two-dimension) as the three-dimensional grain size. The average linear intercept l[1,0.5] and average cross section diameters d[2,1.5] are proposed to be used as the average graine size associated with hardness. Mathematically, the average l[1,0.5] is the square of ∑p=1tlp/∑p=1tlp12 and the average d[2,1.5] is the square of ∑p=1tdp2/∑p=1tdp32. The average linear intercept l[1,0] and average cross section diameters d[2,1] are proposed to be used as the average graine size associated with coercivity. The average linear l[1,0] is the arithmetic average intercept and the average cross section diameters d[2,1] is surface/length average equivalent circle diameter. These average WC grain sizes result in a better description of the relation between physical properties and grain size, especially for cemented carbides with broad distribution of WC grains.

Reverse Austenite Transformation and Grain Growth in a Low-Carbon Steel

The mechanisms controlling the reverse austenite transformation and the subsequent grain growth are examined in a low-carbon steel during slow continuous heating. The ex-situ metallographic analysis of quenched samples is complemented by in-situ dilatometry of the phase transformation and real-time laser ultrasonic measurements of the austenite grain size. Although the initial state of the microstructure (bainite or martensite) has only limited impact on the austenite transformation temperature, it has significant influence on the mean austenite grain size and the rate of grain growth. The coarsening of austenite islands during reverse transformation occurring from the martensitic microstructure is responsible for a large austenite grain structure at the completion of the austenite formation. On the other hand, a much finer austenite grain size is obtained when the austenite transforms from the bainite microstructure. Upon further heating, the rate of austenite grain growth is limited by the presence of nanometric precipitates present in the bainite microstructure leading to a significantly finer austenite grain size. These results give important guidance for the design of thermomechanical-controlled processing of heavy-gage steel plates.

A novel recycling system for nano-magnetic molecular imprinting immobilised cellulases: Synergistic recovery of anthocyanin from fruit and vegetable waste

Fruit and vegetable waste (FVW) is become a serious problem in developing countries. Enzymolysis is a potentially useful method for the treatment of FVW. In the present study, novel recycled magnetic molecular imprinting immobilised cellulases were prepared based on magnetic modified chitosan (MCTS) and Fe3O4. The properties of obtained were characterised by IR and grain-size measurements. Evaluation of a single factor affecting the loading efficiency of supports and the mixed immobilised enzymes showed better capacity than single immobilised, or free, enzymes. The immobilisation process could improve cellulase stability and repeatability of the method. Meanwhile, the kinetic parameters were also verified. The immobilised enzymes retained most of their capacity after 60days’ storage while free enzymes lost it within 30days. Tests showed that the immobilised enzymes developed excellent capacity and five anthocyanins were collected.

Automatic vision-based grain optimization and analysis of multi-crystalline solar wafers using hierarchical region growing

ABSTRACTSolar power has become an attractive alternative source of energy. The multi-crystalline solar cell has been widely accepted in the market because it has a relatively low manufacturing cost. Multi-crystalline solar wafers with larger grain sizes and fewer grain boundaries are higher quality and convert energy more efficiently than mono-crystalline solar cells. In this article, a new image processing method is proposed for assessing the wafer quality. An adaptive segmentation algorithm based on region growing is developed to separate the closed regions of individual grains. Using the proposed method, the shape and size of each grain in the wafer image can be precisely evaluated. Two measures of average grain size are taken from the literature and modified to estimate the average grain size. The resulting average grain size estimate dictates the quality of the crystalline solar wafers and can be considered a viable quantitative indicator of conversion efficiency.

Evolution of phases during tempering of P91 steel at 760℃ for varying tempering time and their effect on microstructure and mechanical properties

In the present investigation, a systematic study has been undertaken with regard to the effects of tempering time on room temperature mechanical properties of P91 (X10CrMoVNNB9-1) steel. Samples cut from P91 (X10CrMoVNNB9-1) industrial pipe were normalized at 1040 ℃ for 40 min and then tempered at 760 ℃ for different tempering times starting from 2 h to 8 h. Detailed analysis of microstructure, particle size, inter-particle spacing, and secondary phase carbide particles of the tempered samples was conducted by secondary electron microscopy technique. Optical microscopy was also utilized to characterize the tempered samples and for the measurement of grain size. In order to reveal the various phases formed during tempering of P91 (X10CrMoVNNB9-1) steel, X-ray diffraction was carried out . To study the fracture surface morphology of tensile tested and impact tested specimen field-emission scanning electron microscopy was carried out. The effect of tempering time on the microstructural parameters revealed an increase in grain size up to 4 h of tempering and then decreased because of recrystallization. The coarsening of secondary phase carbide particles M23C6 was revealed with an increase in tempering time. As a consequence, yield strength, hardness, and ultimate tensile strength were observed to decrease with increase in the tempering time. However, a drastic change was observed in the yield strength, ultimate tensile strength, and toughness after tempering for 6 h. From the present study, it was concluded that optimum combination of yield stress, ultimate tensile strength, hardness, and toughness obtained after tempering at 760 ℃ for 6 h.

Long-term weakening of the East Asian summer and winter monsoons during the mid- to late Holocene recorded by aeolian deposits at the eastern edge of the Mu Us Desert

The East Asian summer monsoon (EASM) and East Asian winter monsoon (EAWM) are major drivers of environmental conditions in East Asia. However, due to the lack of high-resolution EAWM records, the phase relationship between the EASM and EAWM during the Holocene epoch is still debated. Here, we use magnetic and grain-size measurements from a sequence of aeolian sediments from the eastern edge of the Mu Us Desert to track the history of the EASM and EAWM from 7.5 to 2.5ka. The results show that both the EASM and EAWM exhibit a similar long-term weakening trend during this interval. In view of the stable glacial boundary conditions and the significantly decreased rates of atmospheric CO2 rise since the mid-Holocene, we suggest that orbitally-induced insolation was the major cause of the weakening of both the EASM and EAWM. Decreasing summer insolation and increasing winter insolation reduced the thermal contrast between the ocean and the Asian continent in both summer and winter time, resulting in the weakening of both monsoon systems during the mid- to late Holocene.

The Agh Band loess-palaeosol sequence – A terrestrial archive for climatic shifts during the last and penultimate glacial–interglacial cycles in a semiarid region in northern Iran

Abstract The Northern Iranian loess profiles host important information on Quaternary climate and palaeoenvironmental changes in the region. They build an important link between the Eurasian loess belt and European and Central Asian archives. Due to a climatic gradient with decreasing precipitation from the west to the east and from the south to the north, loess-palaeosol sequences formed synchronously under different climatic conditions can be studied over short distance in the Iranian Caspian Lowland. The Agh Band profile is located in the so called Iranian “Loess Plateau”, a semi-arid region with 200–350 mm annual precipitation. The loess deposits at Agh Band reach a thickness of >60 m. An about 50 m thick step-profile was prepared and the litho/pedostratigraphy was investigated. Samples for laser-diffractometry grain-size measurements were taken every 2 cm. The magnetic susceptibility was measured in 4 cm intervals and the CaCO3-content in 8 cm intervals. To establish a chronological framework a pIRIR290 luminescence dating approach was applied to the 4–11 μm polymineral fraction. The results show that the Agh Band profile yields a climate archive reaching from MIS 7 to MIS 2. Several chronological hiatuses of some 10 ka show that periods of intense loess accumulation were interrupted by phases of only minor loess sedimentation and/or erosion. The Agh Band profile is subdivided by several shifts in grain-size distribution. The coarsening- and fining up trends correlate with increasing and decreasing wind-velocity, respectively. In the central part of the Agh Band loess sequence a weakly developed palaeosol is preserved which was developed at around 80 ka. Furthermore, the loess deposits formed from about 100 ka to 60 ka ago show banded structures. A pedocomplex including two well-developed palaeosols consisting of Bw(y) horizons and a CB-horizon as well as intercalated loess can be found in the lower part of the sequence also evidenced by the increased values of magnetic susceptibility. The corresponding luminescence age estimates indicate that the palaeosols represent a period of increased humidity and landscape stability during late MIS 7 and MIS 6. Hence, in the Agh Band loess, various changes in the palaeo-sedimentary system, triggered by changes in climate can be observed. This yields important information on the sensitive response of sedimentary systems and landscapes within semi-arid regions to shifts in moisture and possibly temperature.

Identification of a late Quaternary alluvial–aeolian sedimentary sequence in the Sichuan Basin, China

The late Quaternary sedimentary sequence in the northwestern part of the Sichuan Basin consists of five lithological units and with increasing depth include the: Chengdu Clay; Brown Clay; Red Clay; Sandy Silt; and basal Muddy Gravel. The genesis, provenance and age of the sediments, as well as the possible presence of hiatuses within this sequence are debated. Measurements of grain-size, magnetic susceptibility, quartz content, quartz δ18O values, element composition, and Sr–Nd isotopic concentrations of samples from a typical sedimentary sequence in the area provides new insights into the genesis and history of the sequence. The new data confirm that the sediments in study site are alluvial–aeolian in origin, with basal alluvial deposits overlain by aeolian deposits. Like the uppermost Chengdu Clay, the underlying Brown Clay and Red Clay are aeolian in origin. In contrast, the Silty Sand, like the basal Muddy Gravel, is an alluvial deposit and not an aeolian deposit as previously thought. Moreover, the succession of the aeolian deposits very likely contains two significant sedimentary hiatuses. Sedimentological analysis demonstrates that the source materials for the aeolian deposits in the northwestern part of the Sichuan Basin and those on the eastern Tibetan Plateau are different. Furthermore, the loess deposits on the eastern Tibetan Plateau are derived from heterogeneous local sources.

Automated Riverbed Sediment Classification Using Low-Cost Sidescan Sonar

AbstractThe use of low-cost, low-profile, and highly portable sidescan sonar is on the ascendancy for imaging shallow riverine benthic sediments. A new automated, spatially explicit, and physically-based method for calculating lengthscales of bed texture elements in sidescan echograms (a 2D plot of acoustic intensity as a function of slant range and distance) is suggested. It uses spectral analysis based on the wavelet transform of short sequences of echograms. The recursive application of the transform over small overlapping windows of the echogram provides a robust measure of lengthscales of alternating patterns of strong and weak echoes. This textural lengthscale is not a direct measure of grain size. Rather, it is a statistical representation that integrates over many attributes of bed texture, of which grain size is the most important. The technique is a physically-based means to identify regions of texture within a sidescan echogram, and could provide a basis for objective, automated riverbed sedime...

Factors controlling mud accumulation in the Heuksan mud belt off southwestern Korea

The Heuksan mud belt (hereafter HMB) is 20~50 km wide, ~200 km long, and ~50 m thick, having accumulated in the course of the Holocene transgression on the tide-dominated epicontinental shelf southwest of Korea. The internal architecture of the HMB is characterized by offshore prograding clinoforms. Of particular interest are the depositional processes responsible for this anomalously thick mud accumulation within a relatively short period of time. Tidal currents are important in the dispersal of mud in the HMB, although these alone cannot explain such an enormous mud deposit. In order to understand the formative processes of the HMB, a detailed sedimentary facies analysis, including high-resolution grain-size measurements, has been conducted on more than 30 short cores and three long drill cores recovered from the mud belt. Five major mud facies were identified. Of these, mud sequences showing a thickening–thinning trend of alternating silt and clay laminae suggestive of a tidal origin occur dominantly at inner to mid shelf locations. By contrast, internally structureless muds with sharp bases and no bioturbation, which are interpreted of representing fluid-mud deposits, are widespread at mid to outer shelf locations. Wave-generated mud ripples and storm beds on the inner shelf suggest that storm waves in winter resuspend previously deposited mud to form near-bed fluid-mud suspensions with resulting gravity-driven mud transport across the low-gradient outer shelf. This previously not recognized process is probably a major factor controlling depositional processes on the giant mud belt, enabling rapid accumulation and offshore progradation even during transgression, i.e., at times of sea-level rise.

Coastal erosion problem, modelling and protection

Goksu Delta, located in the south of Silifke County of Mersin on the coastal plain formed by Goksu River, is one of the Specially Protected Areas in Turkey. Along the coastal area of the Delta, coastline changes at significant rates are observed, concentrating especially at four regions; headland of Incekum, coast of Paradeniz Lagoon, river mouth of Goksu and coast of Altinkum. The coast of Paradeniz Lagoon is suffering significantly from erosion and the consequent coastal retreating problem. Therefore, the narrow barrier beach which separates Paradeniz Lagoon from the Mediterranean Sea is getting narrower, creating a risk of uniting with the sea, thus causing the disappearance of the Lagoon. The aim of this study was to understand the coastal transport processes along the coastal area of Goksu Delta to determine the coastal sediment transport rates, and accordingly, to propose solutions to prevent the loss of coastal lands in the Delta. To this end, field measurements of currents and sediment grain sizes were carried out, and wind climate, wave climate, circulation patterns and longshore sediment transport rates were numerically modeled by HYDROTAM-3D, which is a three dimensional hydrodynamic transport model. Finally, considering its special importance as an environmentally protected region, some coastal structures of gabions were proposed as solutions against the coastal erosion problems of the Delta. The effects of proposed structures on future coastline changes were also modeled, and the coastlines predicted for the year 2017 are presented and discussed in the paper.

Advances in grain-size, mineral, and pore-scale characterization of lithic and clay-rich reservoirs

Clay- and lithic-rich sandstones are difficult to characterize through uncored well sections in terms of their grain size, porosity, and mineralogy, all of which are required for assessing reservoir quality and production performance. This paper presents results from a study through one such interval and shows how a combination of different techniques can be used to better understand rock properties of complex reservoirs, thereby helping to reduce reservoir uncertainty. In this study, mean data from laser grain-size analysis are comparable to point-counted grain size, and both are considered as viable analytical methods. Automated quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN®) provides a further useful and consistent grain-size measurement that can be applied to both core and cuttings samples. The QEMSCAN has also proved to be a valuable technique in the mineralogical analysis of sandstones that are lithic, clay- and feldspar-rich, eliminating the subjective nature that is inherent with optical analysis. Results from the studied interval show that porosity measured by conventional core analysis (CA) and mercury injection capillary pressure (MICP) analysis are generally comparable with log-derived total porosity. Porosity measured from point-counting and QEMSCAN techniques is significantly lower than total porosity, with the QEMSCAN porosity locally equivalent to log-derived effective porosity. Both point-count and QEMSCAN porosities show better correlations with permeability ( and 0.94, respectively) than total porosity values ( and 0.60 CA and MICP, respectively), suggesting that they might provide a measure of effective porosity in high-quality reservoir rocks.

Comparative Grain-Size Measurements for Validating Sampling and Pretreatment Techniques in Terms of Solifluction Landforms, Southern Carpathians, Romania

Abstract Grain-size distribution has become in the last years an important indicator in the analysis of periglacial processes and landforms. However, as they exhibit a complex sedimentology, careful sampling is required to draw meaningful conclusions. The aim of the present study was therefore to validate the sampling procedure carried out on solifluction forms and to evaluate the effect of sampling pretreatment during grain size analysis. A comparison between multiple measurements of grain size distribution using the laser diffraction method (LDM) was performed on 54 sediment samples collected from different solifluction landforms at different depths in the alpine area of the Southern Carpathians. The results of parallel measurements were compared using textural and statistical indicators. The received distributions reinforced the properness of field sampling procedure in most of the cases. The results of textural classification and fractional composition showed a high consistency between the two parallel measurements made on untreated and pretreated samples. An overall fining as a matter of etching was identified. Relative deviation increased and correlation decreased as pretreatment advanced. HCl etching resulted a greater deviation and variability in case of the sand fraction, H2O2 rather affected the silt fraction. The greatest deviations were experienced in case of landforms developed on crystalline limestone. Pretreatment of samples introduced a major uncertainty to further comparison and interpretation. Thus, multiple LD measurements on a representative group of samples from the entire sample set were suggested before the geomorphological or environmental interpretation of results to decrease the uncertainties and to validate the processes

An evaluation of different measures of dynamically recrystallized grain size for paleopiezometry or paleowattometry studies

Abstract. Paleopiezometry and paleowattometry studies are essential to validate models of lithospheric deformation and therefore increasingly common in structural geology. These studies require a single measure of dynamically recrystallized grain size in natural mylonites to estimate the magnitude of differential paleostress (or the rate of mechanical work). This contribution tests the various measures of grain size used in the literature and proposes the frequency peak of a grain size distribution as the most robust estimator for paleopiezometry or paleowattometry studies. The novelty of the approach resides in the use of the Gaussian kernel density estimator as an alternative to the classical histograms, which improves reproducibility. A free, open-source, easy-to-handle script named GrainSizeTools ( http://www.TEOS-10.org) was developed with the aim of facilitating the adoption of this measure of grain size in paleopiezometry or paleowattometry studies. The major advantage of the script over other programs is that by using the Gaussian kernel density estimator and by avoiding manual steps in the estimation of the frequency peak, the reproducibility of results is improved.

ANALYTICAL MODELING OF THE MICROSTRUCTURE EVOLUTION OF TITANIUM ALLOYS DURING HIGH-SPEED STAMPING OF THE BLADES OF GAS-TURBINE ENGINES

The analysis procedure of the microstructure evolution during intense deforming is developed and approved by an example of high-speed stamping (HSS) of GTE blades made of VT9 titanium alloy based on the analytical model of dynamic recrystallization. Model coefficients were calculated by the results of the measurement of grain sizes during the preliminary experiments on high-speed upsetting of cylindrical samples made of VT9 alloy. The microstructure was investigated experimentally after HSS of the blades made of VT9 alloy using a VSM4 hammer with the motion velocity of falling parts in deformation beginning of 30 m/s. The microstructure evolution of the deformed medium is modeled analytically (by the sizes of the α phase) allowing for the variation in texture along main deformation directions with an error up to 10 %.

Paleohydrology and 3D Facies Architecture of Ancient Point Bars, Ferron Sandstone, Notom Delta, South-Central Utah, U.S.A

Abstract Most outcrops of fluvial deposits consist of a series of cliff exposures, either natural or manmade (e.g., roadcuts). Predictions, and especially observation of plan-form geometry, such as might be made with numerical experiments or from studies of modern rivers, are challenging to test in most ancient outcrops. This study examines ancient exhumed channel belts from the Cretaceous Notom Delta of the Ferron Sandstone Member in south-central Utah. Extensive plan-view exposures with local vertical cliff exposures allowed documentation of channel plan-form, channel-belt dimension, bar migration patterns (translation versus expansion), and cross-sectional facies architecture. Channel-fill thickness and bedding structure, documented from the cliff exposures, were used in paleohydraulic reconstructions. Approximately 270 paleocurrent directions were integrated with grain-size measurements to reconstruct the 3D facies architecture. Paleocurrent measurements are consistent within specific facies architectural units (such as unit bars) and show systematic variation at the channel-belt scale that can be used to infer channel and bar migration patterns. In this example, the migration pattern of the single-thread channel bend was interpreted to change from expansion to translation with a corresponding bend sinuosity that increased from 1.01 to 1.44. Inclined large-scale foresets are interpreted to be indicative of unit bars. Empirical equations result in estimated average channel depths from 1.7 m to 3.6 m with corresponding widths of 23 m to 89 m respectively. These empirical estimates match the dimensions measured in the field. For example, channel widths of around 50 m were measured from abandoned channel fills. Bar thickness, measured from vertical outcrops, ranges from 5.4 m to 6.3 m, which yields a narrower estimate of channel width ranging from 47 to 59 m. Integration of sediment size, bedforms type, and channel depth were used to estimate the discharge of the river, which is on the order of < 400 m3/s. This suggests that the Ferron deltas were characterized by small, steep-gradient “dirty” rivers, which is consistent with the hyperpycnal nature of linked downstream deltaic systems.

Holocene aeolian activity and climatic change in Qinghai Lake basin, northeastern Qinghai–Tibetan Plateau

Aeolian deposits in the Qinghai Lake basin on the northeastern Qinghai–Tibetan Plateau (NETP) were studied in order to reconstruct changes in aeolian activity related to climatic changes over the last 12.5 ka. We used 20 optically-stimulated luminescence and conventional radiocarbon dates to construct chronological frameworks for four aeolian sections. The results indicate that aeolian activity occurred episodically at 12.5 ka, 11.2 ka, ~ 9.0 ka, ~ 8.5 ka, 5.5 ka, 2.6 (2.4) ka and 1 (0.9) ka. Paleosols developed mainly during 9.5–4 ka. The field stratigraphy of the sections, together with measurements of grain size, magnetic susceptibility (MS), and total organic carbon (TOC), indicate that aeolian activity was strong during the Last Glacial period. Following the Younger Dryas (YD), Holocene interglacial conditions began to develop in the Qinghai Lake basin at ~ 12 ka. With the strengthened Asian summer monsoon (ASM) and the decrease in insolation, the climate became warm and humid. According to the record of aeolian activity, the early Holocene can be divided into two intervals, before and after ~ 9.5 ka. Aeolian activity remained strong from ~ 12 ka–9.5 ka, although the climate was more humid than that of the Last Glacial period. Between 9.5 ka and 8.5 ka the aeolian activity weakened and the climate became warm and wet, but variable. Following the mid-Holocene Climatic Optimum, the climate became significantly drier at ~ 4 ka and aeolian activity strengthened again. Overall, the ASM dominated aeolian activity in the Qinghai Lake basin during the Holocene, with enhanced aeolian activity corresponding to a weakened ASM. Paleosol development exhibited a lagged response to the strengthened ASM, and therefore aeolian sand layers in the section do not always indicate a cold and dry climate.

Microstructure characterization via stereological relations — A shortcut for beginners

Stereological relations that can be routinely applied for the quantitative characterization of microstructures of heterogeneous single- and two-phase materials via global microstructural descriptors are reviewed. It is shown that in the case of dense, single-phase polycrystalline materials (e.g., transparent yttrium aluminum garnet ceramics) two quantities have to be determined, the interface density (or, equivalently, the mean chord length of the grains) and the mean curvature integral density (or, equivalently, the Jeffries grain size), while for two-phase materials (e.g., highly porous, cellular alumina ceramics), one additional quantity, the volume fraction (porosity), is required. The Delesse–Rosiwal law is recalled and size measures are discussed. It is shown that the Jeffries grain size is based on the triple junction line length density, while the mean chord length of grains is based on the interface density (grain boundary area density). In contrast to widespread belief, however, these two size measures are not alternative, but independent (and thus complementary), measures of grain size. Concomitant with this fact, a clear distinction between linear and planar grain size numbers is proposed. Finally, based on our concept of phase-specific quantities, it is shown that under certain conditions it is possible to define a Jeffries size also for two-phase materials and that the ratio of the mean chord length and the Jeffries size has to be considered as an invariant number for a certain type of microstructure, i.e., a characteristic value that is independent of the absolute size of the microstructural features (e.g., grains, inclusions or pores).

Analytical modeling of the microstructure evolution of titanium alloys during high-speed stamping of the blades of gas-turbine engines

The analysis procedure of the microstructure evolution during intense deformation is developed and approved by the example of high-speed stamping (HSS) of GTE blades made of VT9 titanium alloy based on an analytical model of dynamic recrystallization. Model coefficients were calculated by the results of a measurement of grain sizes during preliminary experiments on the high-speed upsetting of cylindrical samples made of VT9 alloy. The microstructure was investigated experimentally after the HSS of blades made of VT9 alloy using a VSM4 hammer with the motion velocity of falling parts in the beginning of deformation at 30 m/s. The microstructure evolution of the deformed medium is modeled analytically (by the sizes of the α phase), allowing for the variation in texture along main deformation directions with an error reaching 10%.

Grain Size Measurement in Steel by Laser Ultrasonics Based on Time Domain Energy

Laser ultrasonics, a technique based on the generation of ultrasonic waves by a pulsed laser and on their detection by a laser interferometer, can be used to determine grain sizes in steels. The absolute values of the average grain size can be calculated directly from the attenuation measurements of ultrasonic longitudinal bulk waves. The general methods of attenuation measurements are computed based on the amplitude of longitudinal waves. In fact, the amplitude as only one value is infected by the noise. Besides, the attenuation should be considered as the energy reduction. The method of time domain energy is proposed to compute the attenuation. The results indicate that time domain energy can improve the accuracy of the grain size prediction. The laser ultrasonic technique may be incorporated online for direct measurements of grain size during steel production. [doi:10.2320/matertrans.M2014445]