Bulk Texture Research Articles

Bulk and local textures of pure magnesium processed by rotary swaging

Rotary swaging processing on commercial as-cast pure Mg has been carried out. Bulk texture variation with the processing passes was investigated using large gauge volume by neutron diffraction, of which results showed a combination of different components such as {00.2} basal fibre and two weak {10.0} and {11.0} fibres. Asymmetric distribution of the basal fibre around swaging direction was observed and being related to the processing parameters. Texture gradient analysis by synchrotron radiation demonstrates a non-uniform deformation of the RS processed pure Mg from surface to the centre.

Magnetic properties and crystallographic textures of Fe 2.6% Si after 90% cold rolling plus different annealing

The effect of rolling and annealing on the crystallographic texture and the magnetic properties of Fe-2.6% Si non-oriented electric steel during 90% cold rolling and different annealing temperature at (600°C, 700°C, 900°C and 1100°C) for 60min and 20min was analyzed. The 97% hot rolled as received material shows development of alpha and gamma fiber texture affecting on the magnetic properties at rolling and transverse direction. 90% cold rolling with moderate annealing temperature (up to 700°C) and 60min annealing time leads to better textures and improved magnetic properties. Due to coarse grained microstructure after annealing, neutron diffractions is an efficient tool for the analysis of Bulk texture of polycrystalline materials, well known for sufficient grain statistics and bulk texture measurement.

Experimental and computational studies of ultrasound wave propagation in hexagonal close-packed polycrystals for texture detection

Texture in hexagonal close-packed (hcp) polycrystalline metals, often developed during thermomechanical processing, affects ultrasonic wave velocity. In this study, the relationship between bulk texture and ultrasonic wave velocity in aggregates of (predominantly) hcp grains is investigated using theoretical, numerical and experimental methods. A representative volume element methodology is presented, enabling the effects of texture on ultrasonic wave speed to be investigated in two-phase polycrystals, and is employed to examine the ultrasonic response of random polycrystals, textured polycrystals and macro-zones often observed in titanium alloys. Numerical results show that ultrasonic wave speed varies progressively with changing texture, over a range of ∼200ms−1, within bounds set by the two extreme single-crystal orientations. Experimental ultrasound studies and full electron backscatter diffraction (EBSD) characterization are conducted on unidirectionally rolled and cross-rolled Ti–6Al–4V samples in three orthogonal directions. In addition, the EBSD-determined textures are incorporated within the polycrystal model and predicted ultrasonic velocities compared directly with ultrasonic experiments. Good quantitative agreement is obtained and both the experimental and computed results demonstrate that ultrasonic velocity profiles exist for random, unidirectionally rolled and cross-rolled textures. The combined results indicate the possibility of the development of a methodology for bulk texture determination within Ti polycrystal components using ultrasound.

Response of tillage and in situ moisture conservation on alteration of soil and morpho-physiological differences in maize under Eastern Himalayan region of India

Better root growth helps the plant for more uptakes of nutrient and water and positively influence the growth and yield attributes. Tillage alters the physicochemical and biological properties of soil and provides the congenial condition for better growth of maize. Four different till system, viz., conventional tillage (CT), zero tillage (ZT), raised bed (RB) and ridge and furrow (RF) were tried with two mulch viz. no mulch (NM) and paddy straw mulch (PSM at 4.0tha−1). RF recorded 18.0% higher seed yield followed by RB (14.5%) and CT (7.5%) over ZT. However, stover yield was 10.1, 8.6 and 5.1% respectively higher for RF, RB and CT over ZT. Mulches also favoured the soil against degradative force and conserved the soil moisture and maintained the soil temperature. Grain and stover yield were 11.1 and 6.5% respectively higher with PSM over NM. Root length, root dry weight and root volume were higher on RF followed by RB over ZT. However, root numbers was higher on ZT but comparable to CT. Root density did not differ with different types of tillage. Similarly, PSM recorded all the root attributes better than NM. Maximum water holding capacity (MWHC), water filled pore space (WFPS) and water content at field capacity and permanent wilting point were higher on RF followed by RB over ZT. Similarly, bulk density of soil at different soil depths were lower in RF followed by RB. Soil temperature was maintained on PSM and it was relatively hotter at early morning (8.00h) and relatively cooler during mid day (12.00h) and evening (16.00h) over NM. Soil organic carbon (SOC) changed with tillage and higher SOC was recorded on ZT at top 0–10 and 10–20cm soil depths but below 20cm there was no significant difference. Consequently, all the physical and chemical parameters were better with PSM over NM. The measured growth and yield attributes of maize depended on soil properties like bulk density, porosity, water potential, texture, aggregation and soil organic carbon.

Late-Holocene and recent hydroclimatic variability in the central Kenya Rift Valley: The sediment record of hypersaline lakes Bogoria, Nakuru and Elementeita

The sedimentology, salt mineralogy and stable oxygen- and carbon-isotope signatures of a mid-lake sediment sequence from hypersaline Lake Bogoria in Kenya reveal marked climate-driven changes in water-column mixing regime and salinity over the past 1700years. Combined with sedimentological data on short sediment sequences from nearby lakes Nakuru and Elementeita, this results in a preliminary reconstruction of hydroclimatic variability in the central Kenya Rift Valley since ca. 300 AD. Stratigraphic analyses of bulk sediment composition, texture and magnetic susceptibility of all three cores; and smear slide, XRD and stable-isotope analyses on carbonate minerals in the Bogoria sequence allowed to define a succession of sedimentary units, corresponding to distinct phases in lake history. In the lowermost unit, four characteristic trona layers (Na3(HCO3)(CO3)·2H2O) are attributed to predominantly dry conditions during the second half of the first millennium AD and the period equivalent to the Medieval Climate Anomaly, until the first half of the 12th century AD. Lake Bogoria was probably polymictic at that time, its surface level standing significantly lower than today. The second unit displays uniform deposition of nahcolite (NaHCO3), indicative of a strongly stratified lake where a layer of less saline surface water (near-)permanently covers a hypersaline water mass with high pCO2. We propose that this depositional phase reflects the rising lake level related to the transition from dry to more humid climate conditions at the onset of the Little Ice Age, as previously documented for other parts of equatorial East Africa. The third, uppermost Bogoria unit contains only sporadic depositions of magadiite (Na2Si14O29(OH)3·11H2O) and various sodium carbonate minerals. This, together with low magnetic susceptibility, is interpreted to indicate humid Little Ice Age conditions, with highest lake level and reduced salinity around the late-15th to early-16th century AD. From the late-18th to early-19th century and again in the 1870's, the region experienced two episodes of drought more severe than any recorded in historical time. Tentative evidence for these events in the Bogoria record is not well constrained in time, but dated desiccation surfaces in the Nakuru and Elementeita records confirm their widespread nature across eastern equatorial Africa.

Expansion of Eucalyptus Woodlots in the Fertile Soils of the Highlands of Ethiopia: Could It Be a Treat on Future Cropland Use?

A study was conducted to assess the effect of land use change from eucalyptus to cropland on soil physico-chemical properties and perceptions of farmers in Koga irrigation area, Amhara Region. Soil samples were taken from 4 sites of three land uses (eucalyptus woodlots, cropland, and eucalyptus land use changed to cropping) and at 0-20, 20-40 and 40-60 cm depths. The three depths were used for analysis of soil chemical properties, whereas the first two depths for physical properties. Furthermore, randomly selected 15 farmers were interviewed for their perception on the state of soil fertility and crop yield conditions on lands that were recently changed from eucalyptus to cropland. The result showed that except for available P, sampled plots that were changed from eucalyptus to cropland were found better in soil chemical properties (pH, N, CEC) and SOM contents as compared to croplands. As compared to the other two land uses, total N was found larger at eucalyptus woodlots. Regarding soil physical properties (bulk density and texture), little or no difference was recorded among the different land use types. On top of that, farmers perceived that plots that were under eucalyptus have better fertility, require less nitrogen fertilizer and crops perform well compared to plots that are contineously under cropping. Thus, results of this study confirmed that changing land use from eucalyptus to cropland is possible without detrimental effect on soil properties and without affecting productivity of lands to raise crops.

Soil water repellency in Mediterranean rangelands under contrasted climatic, slope and patch conditions in southern Spain

Abstract This study evaluates the spatial and temporal variability in soil water repellency (SWR) in two Mediterranean rangelands (with similar tree and shrub species) and its relationships to different eco-geomorphologic variables (climate, aspect, soil cover and some soil properties). Every month from October 2008 to May 2009 (rainy season), soil moisture and SWR was measured in field conditions by means of gravimetric method and Water Drop Penetration Test, respectively. Also, disturbed and undisturbed soil samples were taken to analyze some soil properties: bulk density, texture, organic matter, pH and electrical conductivity. The entire tests were performed in north and south aspect hillslopes and beneath shrub and bare soil in every of them. The results indicated that: i) climatic conditions seem to be more transcendent than the vegetal species for explaining the variability in SWR; ii) thus, SWR appears to be controlled by the antecedent rainfall and soil moisture; iii) more severe SWR were observed in patches characterized by sandier soils and/or higher organic matter contents; and iv) the factor ‘hillslope aspect’ was not found so crucial as it was expected.

Inherited Fabric in an Omphacite Symplectite: Reconstruction of Plastic Deformation under Ultra-High Pressure Conditions

We investigated an eclogitic gneiss from the Western Gneiss Region in Norway, which underwent subduction as part of Baltica lithosphere beneath Laurentia during the Scandian orogeny. Petrologic data indicate that the eclogite was deformed plastically at about 4 GPa and 800°C producing a strong macroscopic foliation and lineation. Whereas garnet remained largely stable during the retrograde uplift, omphacite was transformed statically into a symplectite consisting of lamellar diopside and plagioclase with more equant grains of hornblende and orthopyroxene. Measurements of the crystallographic preferred orientation with electron backscatter diffraction show that diopside and hornblende, as well as orthopyroxene, have a systematic orientation relationship with the macroscopic fabric, as well as the (presumed) orientation of the host omphacite. The orientation relationship between the chain silicates is very sharp with the crystallographic forms {100}, {010}, and <001> being parallel. Their bulk texture shows a maximum of <001> parallel to the lineation and girdles of {010} and {110} perpendicular to the lineation with maxima subparallel to the foliation corresponding to an L-type texture of the original omphacite and indicating constrictional strain with an additional component of pure shear/simple shear component.

The effect of strontium in plasticity of magnesium alloys

The objective of this article is to quantify relationships between microstructural changes and the room temperature mechanical behavior of novel extruded Mg–Al–Zn–Sr alloys. To this aim, targeted mechanical testing coupled with full-field strain measurements and simultaneous acoustic emission recordings is further combined with grain-scale observations. To date, the precise effect of alloying elements on the plasticity of Mg alloys is still largely unknown. Strontium in wrought Mg alloys has already been shown to reduce grain size and texture anisotropy, as well as improve their creep resistance, replicating the effects of rare earth elements. To further investigate the effects of Sr on the mechanical properties and plasticity of Mg alloys compression tests were performed and were coupled with nondestructive measurements provided by digital image correlation and acoustic emission monitoring. The results presented herein demonstrate the effect of the extrusion temperature and provide direct correlations between Sr content and bulk mechanical properties, overall plasticity and texture evolution in these novel alloys. Furthermore, the addition of Sr was found to be related to distinct strain localizations near yielding, which were linked to twinning activity, providing in this way a route for quantitative control of their microstructural design.

Influence of pre- and post-extrusion heat treatments on microstructure and anisotropy of mechanical properties in a Mg–Al–Zn alloy

The pre-extrusion homogenization treatment at 400°C effectively dissolves the eutectic phase and the liberated Al contributes in solid solution strengthening. After extrusion with prior homogenization, an abnormal grain growth occurs at the region favored by the local degree of dynamic recrystallization (DRX) and texture. This weakens the bulk texture, reduces the directional anisotropy in yield Stress and eliminates the strength differential effect without any loss of yield stress. The secondary recrystallization during post-extrusion annealing at 400°C leads to pronounced grain growth, the texture is profoundly weakened and the yield stress becomes isotropic but is reduced by 33%.

On the evolution of heterogeneous microstructure and microtexture in impacted aluminum–lithium alloy

Abstract The microstructure and texture evolution in an aluminum–lithium alloy showing adiabatic shear band after dynamic deformation has been carried out using electron backscatter diffraction and bulk texture measurement using X-ray diffraction. The uniquely heterogeneous microstructure is characterized by fine sub-micron grains of the matrix phase and small spherical precipitates while the region away from the shear band shows deformed elongated grains and plate shaped precipitates. The interface between the shear band and rest of the sample shows unique deformation features indicating the existence of both continuous as well as geometric dynamic recrystallization in the impacted sample. It is inferred that the coarse grain size accompanied with heterogeneous deformation conditions during dynamic loading leads to the coexistence of competing recrystallization mechanisms in aluminum–lithium alloy.

Texture and Microstructure Evolution of a Zirconium Alloy During Uniaxial Compression at 500°C

The texture and microstructure evolution during uniaxial compression of Zircaloy-4 at 500C has been studied. X-ray diffraction was used to measure the bulk texture compressive after strains of 20% and 50%. Early stages of texture evolution involve the strengthening of the fibre through the action of prismatic slip. With further deformation, the basal poles move toward the rolling direction from the normal direction as a result of a non-prismatic slip system. A detailed EBSD study in a small region showed that the grains of the fibre are more stable than those of the fibre. The latter rotates further during deformation and shows a greater spread of grain average misorientation (GAM). This could be due to a greater accommodation of plastic strain in these grains and/or a difference in recovery rates between the two fibres.

Exploring the interacting effect of soil texture and bulk density on root system development in tomato (Solanum lycopersicum L.)

Knowledge of the responses of root systems in horizoned heterogeneous soil is vital to optimise uptake of water and nutrients to maximise crop productivity. We explored the interacting effects of soil bulk density and texture on the development of root systems in tomato.Two main techniques were employed, X-ray micro-Computed Tomography (μCT), to provide non-destructive, three-dimensional (3D) images of root systems in situ and destructive root washing followed by WinRHIZO® scanning. Solanum lycopersicum L. cv. Ailsa Craig plants were grown in soil columns for 10 days to measure the effect of soil compaction on selected root traits. Treatments included bulk density (1.2–1.6Mgm−3), soil texture (loamy sand and clay loam) and the effects of layering.The effect of bulk density on root growth was greatest 3 days after transplanting (DAT) in both soil types. The effect of soil texture was not apparent at this stage, but was significant at 10 DAT for most root and shoot variables. The influence of bulk density differed between soil types as increasing compaction promoted plant growth in clay loam but retarded root growth in loamy sand.We observed that at 3 DAT root growth is primarily influenced by bulk density but by 10 DAT a switch in the processes regulating root growth occurs and the texture of the soil becomes very influential. Future investigations of root growth must consider soil physical properties individually and at specific time points, as their importance changes as the root system becomes established. Here we have demonstrated both positive and negative impacts across a wide range of bulk density treatments in different soil textures on root growth. This illustrates the importance of understanding the complex nature of root–soil interactions, especially for agricultural practices such as seedbed preparation.

Distribution of Soil Density at a Bottomland Hardwood Forest Wetland Restoration, Chicot County, Arkansas

Bottomland hardwood forest (BLHF) soils provide a myriad of ecosystem services, yet much information is lacking with respect to how soil physical properties influence biogeochemical cycling along topographic gradients. Current patterns of vegetation at a 149ha wetland restoration site in Chicot County, Arkansas, suggest the presence of ecologically significant variation in soil properties within the Perry Clay soil series. A study was initiated in the Lower Mississippi Alluvial Valley (LMAV) to map soil bulk density and texture as well as to identify the interrelationships between soil physical properties, soil organic carbon, and total nitrogen. A random grid was used to extract 132 fixed-volume soil cores to a depth of 90cm for bulk density and texture determination. Bulk density was mapped for three depth increments: 0-30cm, 30- 60cm, and 60-90cm, using ordinary kriging. Bulk density differed significantly (α=0.05) by depth with mean densities and 95% CI of 1.37 ± 0.19 Mg m-3 , 1.46 ± 0.22 Mg m-3, and 1.52 ± 0.25 Mg m-3 , respectively. The coefficient of variation at each depth was 7.0%, 7.5%, and 8.5%. Increasing variation with depth can be attributed to surface homogenization during crop production as well as differential accumulation of parent material during pedogenesis in the LMAV. These results presented provide a benchmark and will be used for further quantification of soil nutrient pools during the progression of afforestation of the forested wetland.

Forty Years of Soil Formation in a South Georgia, USA Borrow Pit

This study investigated soil properties in a sand borrow pit in southern Georgia, USA that was used in 1961 and then abandoned with no efforts at reclamation and compares those developing soils to natural soils surrounding the pit. There are distinct vegetative zones within the pit; three are included in this study. Soil samples were collected and described using standard techniques and analyzed for bulk density, C content, texture, pH, and penetration resistance. Piezometers and thermometers were installed to track water levels and soil temperature. Rates of leaf litter accumulation and pit revegetation were determined, and a detailed topographic map of the pit was prepared. Although soil formation over only 41 yr is slight, there are distinct differences in the soils between the vegetative zones that were studied. Soil differences are attributed to differences in topographically controlled access to water and bulk density/penetration resistance, which infl uence vegetative growth and litter accumulation. Study of surrounding developed soils reveals that soils within the pit still have a signifi cant amount of development remaining before they reach equilibrium with the natural environment. Peer Reviewed Papers

Indicadores de qualidade do solo em sistemas agroflorestais

The use of agroforestry systems ( AFS) to enable food production is currently considered a feasible and effective alternative to ensure sustainability , providing improvement in aspects related to conservation of natural resources . In this sense , the present study aimed to evaluate physical , microbiological attributes and content of organic carbon in two agroforestry systems management ( SAF SAF A and B ) , compared to other production systems ( Herbal Farming in silvicultural system and with soy) well as an area under natural vegetation ( forest ) as reference of the original soil condition . The experimental design was completely randomized with five replications . The evaluated parameters were : bulk density, macroporosity , microporosity , total porosity and texture . Still evaluated carbon from the soil microbial biomass , microbial activity , and microbial metabolic quotients . Among the systems evaluated, the SAF was presented the quality index closest to the area of native vegetation ( forest ) soil. The crop area was the most affected as the quality of the soil environment , indicating trends of environmental degradation with continued use of monoculture . On the other hand , diversification of species in agroforestry systems allowed more favorable conditions for improving soil quality , when compared to systems under monoculture .

Land use effects on soil carbon in the Argentine Pampas

Our objective was to establish the pattern of variation of soil organic (SOC) and inorganic (SIC) carbon stored in surface and deep soil layers of the Argentine Pampas as affected by environmental conditions and land use. Eighty two farms, widespread over the region, were used for the study. At each farm paired treatments were sampled representing common land uses: trees, uncropped controls, seeded pastures, cropped fields and periodically flooded areas. Bulk density, SOC, SIC, texture, pH and electrical conductivity were determined to 1m depth. Rainfall and temperature were obtained from climatic records. Significant differences were detected between treatments in SOC contents. Average SOC stocks to 1m were: 131tha−1 under trees>101tha−1 in uncropped control>90tha−1 in pastures=86tha−1 in cropped field>and 70tha−1 in flooded sites. Compared with uncropped controls, SOC was significantly different in all soil layers under trees, to 75cm depth in flooded sites and to 50cm in pastures and cropped soils. Agriculture determined a reduction of 16% of SOC to 50cm in sampled sites. In the 50–100cm depth a decrease of 9% was observed, though not significant. The stratification pattern of SOC in depth was not affected by the treatments; implying that land use impacted the SOC sequestered in soil, but not its allocation in depth. SIC accounted for one third of total soil carbon, average SIC stock was 50tCha−1 to 1m. Both, its stock and distribution in the profile were not affected by the treatments; with greater SIC stocks founded in deep soil layers. An artificial neural network model was developed that allowed the estimation of SOC (R2=0.64) based on climate, soil properties and land use. The model, linked to information from satellite image classification, was used for the estimation of present SOC stock of pampean soils, which accounted for 4.22±0.14Gt in an area of 48.2Mha. Using soil surveys performed during the 1960–1980 period we estimated a SOC stock of 3.96±0.22Gt. Consequently, no change of total SOC stock seems to be produced in the last decades in the region. At smaller scale, counties with SOC content greater than 95tha−1 to 1m depth lost carbon; increases prevailed below this threshold. Apparently, SIC reservoirs seem have not change during the last decades.

Role of B19′ martensite deformation in stabilizing two-way shape memory behavior in NiTi

Deformation of a B19′ martensitic, polycrystalline Ni49.9Ti50.1 (at. %) shape memory alloy and its influence on the magnitude and stability of the ensuing two-way shape memory effect (TWSME) was investigated by combined ex situ mechanical experimentation and in situ neutron diffraction measurements at stress and temperature. The microstructural changes (texture, lattice strains, and phase fractions) during room-temperature deformation and subsequent thermal cycling were captured and compared to the bulk macroscopic response of the alloy. With increasing uniaxial strain, it was observed that B19′ martensite deformed by reorientation and detwinning with preferred selection of the (1¯50)M and (010)M variants, (201¯)B19′ deformation twinning, and dislocation activity. These mechanisms were indicated by changes in bulk texture from the neutron diffraction measurements. Partial reversibility of the reoriented variants and deformation twins was also captured upon load removal and thermal cycling, which after isothermal deformation to strains between 6% and 22% resulted in a strong TWSME. Consequently, TWSME functional parameters including TWSME strain, strain reduction, and transformation temperatures were characterized and it was found that prior martensite deformation to 14% strain provided the optimum condition for the TWSME, resulting in a stable two-way shape memory strain of 2.2%. Thus, isothermal deformation of martensite was found to be a quick and efficient method for creating a strong and stable TWSME in Ni49.9Ti50.1.

Modification of texture and microstructure of magnesium alloy extrusions by particle-stimulated recrystallization

Conventional magnesium alloy Mg–1Zn–0.4Zr and a modified version of the same alloy containing Nd-based rare earth mischmetal and Y were extruded at 400°C to study dynamic recrystallization and its role in the microstructure and texture development. Second phase particles in the modified alloy seemed to generate new orientations other than the deformed orientation. Although this occurred within small volume fraction of the material, the respective recrystallizing grains grew up to considerable sizes consuming larger volumes of the extruded microstructure and dominating the bulk texture. The consequent mechanical behavior tested in plane strain compression at room temperature demonstrated improved strain hardening behavior and enhanced ambient formability relative to the conventional alloy due to well-scattered texture and prolonged activity of basal slip within a large volume of the deformed microstructure.

Microstructural Response During Isothermal and Isobaric Loading of a Precipitation-Strengthened Ni-29.7Ti-20Hf High-Temperature Shape Memory Alloy

A stable Ni-rich Ni-29.7Ti-20Hf (at. pct) shape memory alloy, with relatively high transformation temperatures, was shown to exhibit promising properties at lower raw material cost when compared to typical NiTi-X (X = Pt, Pd, Au) high-temperature shape memory alloys (HTSMAs). The excellent dimensional stability and high work output for this alloy were attributed to a coherent, nanometer size precipitate phase observed using transmission electron microscopy. To establish an understanding of the role of these precipitates on the microstructure and ensuing stability of the NiTiHf alloy, a detailed study of the micromechanical and microstructural behaviors was performed. In-situ neutron diffraction at stress and temperature was used to obtain quantitative information on phase-specific internal strain, texture, and phase volume fractions during both isothermal and isobaric testing of the alloy. During isothermal testing, the alloy exhibited low isothermal strains due to limited detwinning, consistent with direct measurements of the bulk texture through neutron diffraction. This limited detwinning was attributed to the pinning of twin and variant boundaries by the dispersion of fine precipitates. During isobaric thermal cycling at 400 MPa, the high work output and near-perfect dimensional stability was attributed to the presence of the precipitates that act as homogeneous sources for the nucleation of martensite throughout the material, while providing resistance to irrecoverable processes such as plastic deformation.