A newly designed composition of non-equiatomic Fe
40
Cr
25
Ni
15
Al
15
Co
5
medium-entropy alloy (MEA) was produced by induction melting (IM). The as-cast alloy was found to consist of a two-phase ...microstructure of BCC (2.87 ± 0.01 Å) and ordered B2 (2.88 ± 0.02 Å) type phases. The structures of these phases were confirmed through X-ray diffraction (XRD) and transmission electron microscopy (TEM) techniques. It was observed that the Ni-Al-enriched ordered B2 phase of cuboidal shapes (~ 100 to 200 nm) is homogeneously distributed in Fe-Cr-rich BCC matrix with a cube-on-cube orientation relationship. The formation of the columnar dendrites (width 50 to 100
μ
m) was identified through optical microscopy (OM). The structural and microstructural stability of the alloy was investigated by heat-treating the alloy through different schedules. Heat-treated samples at different temperatures (< 1273 K) exhibit a similar type of two-phase microstructure with columnar dendrites. However, compositional rearrangement takes place during long time exposure to develop polymorphically related phases. The alloy was observed to possess a high compressive yield strength and hardness,
i.e.
, ~ 1047 MPa and 391 ± 9 HV, respectively, at room temperature. Heat-treated samples at 600 °C and 900 °C (873 K and 1173 K) showed an increase in yield strength and ultimate strength with a significant increase in plasticity due to the increase in volume fraction of B2 phase and softening of the BCC matrix phase. The thermal stability and high strength of this alloy may open new avenues for high-temperature applications.
Rice-based multiple cropping systems are predominant in the Indo-Gangetic Plains of Indian subcontinent. A decline in yield of such systems has been observed and ascribed to quantitative and ...qualitative variations of soil organic matter (SOM). We evaluated the impact of the annual rotation: rice (Oryza sativa L.), wheat (Triticum aestivum L.), jute (Corchorus olitorius L.), with and without fertilizer treatments (control, N, N-P, N-P-K, and N-P-K plus farmyard manure FYM) on SOM and aggregate properties. At 0- to 15-cm soil depth, microbial biomass C and N, hot water-soluble C and N and hydrolyzable carbohydrates, and particulate organic matter C (POMC) and N (POMN) were found in the order N-P-K plus FYM > N-P-K > N-P > N > control. Over the course of the experiment, application of N alone decreased total organic C (TOC) by 20.4%, whereas N-P-K with or without FYM addition either maintained or enhanced compared to initial. Total soil N and mineralizable N declined in all the treatments except N-P-K plus FYM. Irrespective of treatments, microaggregates (53-250 micrometer) dominated with 43.9 to 51.3% of total soil aggregate size distribution, followed by macroaggregates (250-2000 micrometer with 34.6 to 40.1%). The C and N mineralization rate was greater in macroaggregates than in microaggregates, and correlated significantly with POMC (r = 0.67, P less than or equal to 0.01) and POMN (r = 0.88, P less than or equal to 0.01). Nitrogen-phosphorus-potassium plus FYM also improved overall soil aggregation as compared to other treatments. Therefore, the results suggest that the gradual depletion of nutrients and structural degradation may have collectively contributed to the crop yield declines in the rice-wheat-jute rotation and that the integrated use of N-P-K and FYM is an important nutrient management option for sustaining this cropping system.
Low carbon steel (LCS) workpieces have been deformed by equal-channel angular pressing (ECAP) at a large equivalent strain of 16.8 at room temperature. The mechanisms of microstructural refinement, ...strengthening, hardening, and fracture behavior are investigated. LCS becomes refined by a sequence of mechanisms of elongation of grains, splitting of elongated grains to bands at low strain, subdivision of bands to cells at intermediate strain, elongation of bands to ribbon grains, and breaking of ribbons to near-equiaxed grains at a high strain level. ECAP of LCS at
ε
vm
= 16.8 refines the material to near-equiaxed grains of size 0.2
µ
m having a high-angle grain boundary fraction of 82.4 pct and average misorientation angle of 40.8 deg. The ultrafine-grained (UFG) LCS contains a dislocation density of 1.7 × 10
15
m
2
. In the initial passes of ECAP, the yield and tensile strengths increase rapidly due to rapid grain refinement, reduction in domain size, and increase in dislocation density. At high strain levels, strengthening can be attributed to a combination of grain refinement, dissolution of cementite in the ferrite matrix, and increase in misorientation angle. At
ε
vm
= 16.8, the ultimate tensile strength (UTS) reaches >1000 MPa with a consequent drop in ductility to ≈10.6 pct. Reduction in ductility is found to be due to high dislocation density, high stored energy in the matrix, and occurrence of nonequilibrium grain boundaries. The LCS at low equivalent strain fails by ductile fracture. The dimple size and its volume fraction decrease, but their number density and stored energy increase with increasing equivalent strain. Beyond a critical equivalent strain of 9, the material fails by ductile-brittle fracture. At
ε
vm
= 16.8, equal-channel angular pressed UFG LCS fails mainly by cleavage fracture.
The low-carbon steel workpieces are deformed by equal-channel angular pressing at 293 K (20 °C) up to an equivalent strain of ~12 using route
B
c
, which results in the bulk ultrafine-grained (UFG) ...structure with high dislocation density and partial dissolution of cementite. The yield strength (YS) is enhanced from 208 (as-received) to 872 MPa and the tensile strength is increased from 362 to 996 MPa, but the material loses total elongation (TE) from 36.2 to 2.9 pct. Cold rolling of equal-channel angular pressed steel produces the refined structure of grain size 0.11
μ
m. The YS increases further to 924 MPa with a marginal gain in ductility due to the reappearance of the
γ
fiber component. Flash annealing the samples, which were equal-channel angular pressed followed by cold rolling, at 873 K (600 °C) results in 27 pct of micron-sized (9
µ
m) ferrite grains in submicron-sized (<1
µ
m) matrix with a reduced defect density and small amount of precipitation of cementite. TE increases from 2.9 to 23.3 pct. The material retains a YS of 484 MPa and tensile strength of 517 MPa, which are higher than those of the as-received material. The UFG grains are failed by cleavage, but the micron-sized grains display ductile fracture. The ductility of the flash-annealed material is recovered significantly due to bimodal grain size distribution in ferrite and the development of a good amount of
γ
fiber texture components. The major contribution toward recovery of ductility comes from the bimodal grain size distribution in ferrite rather the precipitation of cementite.
In the present investigation, γ-Cu
5Zn
8 intermetallic compound having an electron to atom ratio of about 21:13 and being structurally one of the most complex Hume–Rothery phases was selected for ...mechanical milling/alloying. The detailed characterization was carried out by X-ray diffraction and transmission electron microscopy to study the microstructural evolution and stability during the synthesis and processing. Attempts have been made to explore the possibility of the formation of nano-structured and amorphous phases by mechanical milling and to provide a thermodynamic explanation based on an existing semi-empirical model. It was found that γ-phase is quite stable and there was a decrease in crystallite size up to ∼20
nm with an increase in milling/alloying duration up to 40
h. However, amorphization could not be achieved even after 40
h of milling. Detailed Miedema calculation showed that amorphization of the present compound would be possible if the crystallite size can be made below a certain critical value.
High dose rate (HDR) intracavitary brachytherapy (ICBT) is an integral element in the treatment of carcinoma uterine cervix. The main objective of brachytherapy in carcinoma cervix is to deliver a ...lethal dose to tumor cells without inducing unacceptable damage to the surrounding normal tissue. Because the absorbed dose falls off rapidly, higher doses can be safely delivered to the targeted tissue over a short time. The quest for optimum dose and fractionation schedule in HDR ICBT is still ongoing, and there is no uniform consensus. This study aimed to assess the acute dose-related toxicities of HDR brachytherapy schedule of 7 Gy x 3 fractions over 6 Gy x 4 fractions in the treatment of cervical cancer.
The aim of this study was to study the acute treatment-related gastrointestinal (GI) and genitourinary (GU) toxicities between two HDR brachytherapy regimens.
This is a prospective institutional study carried out from May 2018 to September 2018. In this time period, 66 patients of cervical cancers fulfilling our inclusion criteria were treated with concurrent chemoradiation (CCRT) following brachytherapy. During treatment, patients were randomized to arm A-7 Gy per fraction for three fractions and arm B-6 Gy per fraction for four fractions. Acute GI and GU toxicities were assessed using Common Terminology Criteria for Adverse Events (CTCAE) Version 4.03. All patients were kept for follow-up for 3 months in this study.
There is no statistically significant difference between the two arms for acute GI and GU toxicities, and the results were comparable.
Considering the increased hospital burden of locally advanced cervical cancer patients in the Indian context, the HDR brachytherapy schedule of 7 Gy per fraction is preferable to 6 Gy per fraction for a lesser fractionation schedule.
The pulsatile blood flow through constricted artery generates fluid mechanical forces on internal layer of artery, endothelium. These fluid mechanical factors affect endothelial lining from keeping ...artery healthy. In this paper, a series of numerical simulations of modeled bell shaped stenosed artery have been carried out for investigation of fluid mechanical factors of realistic pulsatile flow at the inlet of modeled stenosis with bell shaped geometry. The governing equations for two-dimensional unsteady laminar flow of incompressible fluid are solved by finite volume method followed by SIMPLER algorithm. The fluid mechanical factors, particularly wall pressure, streamline contour, peak wall shear stress, low wall shear stress and oscillatory shear index, having inferences to the arterial disease, are investigated by simulation results of different percentage of restrictions. All these parameters have a noticeable impact for the plaque deposition. The impacts of Reynolds number and Womersley number for both of mild stenosis and severe stenosis on arterial disease, atherosclerosis are also investigated by evaluating fractional flow reverse and oscillatory shear potential.
Composite powders of pre-alloyed 316 L austenitic stainless steel with yttria (Y
2
O
3
) powder in various compositions (0.3, 1.0, 1.5 and 2 wt%) were synthesized by mechanical alloying using a high ...energy ball mill. The 25-h milled powder has shown no changes other than exhibiting an austenite phase of FCC (
a
= 3.54 Å) structure. Milled powders were found to contain nano-yttria dispersed in the austenitic stainless steel matrix of nano-crystallite size and with high lattice strain. Milled powders were cold pressed and sintered at 1100 °C (1373 K) in a controlled atmosphere. It can be inferred that nano-yttria dispersion restricts grain growth of matrix even during conventional sintering. The present yittria dispersed austenitic alloy showed the low physical density and increase in compressive strength (194–374 MPa) and hardness (477–528 HV). The compressive strength and hardness enhancement can be attributed primarily to the dispersoids of nano-yttria in the austenitic matrix by dispersion strengthening/hardening mechanisms.
The billets of interstitial-free (IF) steel are deformed by equal-channel angular pressing (ECAP) at 298 K (25 °C) adopting the route B
C
up to an equivalent strain (
ε
vm
) of 24. The evolution of ...microstructures and their effects on the mechanical properties are examined. The microstructural refinement involves the elongation of grains, the subdivision of grains to the bands with high dislocation density, and the splitting of bands into the cell blocks and then cell blocks into the cells. The widths of the bands and the size of cells decrease with strain. The degree of reduction in the grain size is highest at the low strain level. However, most of the boundaries at this stage are of low-angle boundaries (at
ε
vm
= 3). Thereafter, the misorientation angle increases by progressive lattice rotation with strain. The coarse bands transform step by step from the lamellar structure to the ribbon-shaped grains and finally to the near-equiaxed grain structures with the subgrains of a saturated low-angle grain boundary fraction of 0.34 at very large strain >15. The as-received coarse-grained microstructure (grain size of 57.6 ± 21
µ
m) has been refined to 257 ± 48 nm at an equivalent strain of 24. The strength increases considerably up to
ε
vm
= 3 due to grain refinement and high dislocation density. However, the strengthening at later stages is mainly due to the increase in misorientation angle and refinement. Initial yield strength of 227 MPa is increased to a record value of 895 MPa on straining up to
ε
vm
= 24 at 298 K (25 °C). Uniform elongation decreases drastically at low equivalent strain but it regains marginally later. The ECAPed sample fails by a ductile fracture at
ε
vm
= 0.6 to 6 but by a mixed mode of ductile–brittle fracture at larger strain of 9 to 24.
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