Zone Hardness Research Articles

Estimation of fatigue crack growth rate in different zones of friction stir welded AA7039

The present research aims to study the fatigue crack propagation and fracture toughness behavior of different zones of friction stir welds of AA7039 alloy, as different zones had varying microstructural and mechanical properties. Compact tension specimens with an initial notch in distinct weld zones parallel to the welding direction were machined using welded plates. Friction stir welding altered the base metal grain structure momentously, refined the grain structure in the weld nugget zone, and coarsen the same in the heat-affected zone. No correlation was observed between grain size and weld zone(s) hardness. Weld tensile properties were slightly inferior to base metal despite significantly higher hardness and alternation of grain structure. The fatigue life was dominated by the cycles consumed in crack propagation than crack initiation. The heat-affected zone had higher quasi-static fracture toughness, energy release rate, and resistance toward fatigue crack growth than other zones, because coarse grains and precipitates acted as effective impediments and slowed crack propagation. The heat-affected zone had a mixed-mode fracture, but the weld nugget zone and thermo-mechanically affected zone had an I mode fracture. On fracture surfaces, fracture characteristics such as microvoid coalescence were apparent.

Effect of Post-Fabricated Aging on Microstructure and Mechanical Properties in Underwater Friction Stir Additive Manufacturing of Al-Zn-Mg-Cu Alloy.

The fabricated Al–Zn–Mg–Cu alloy build has low mechanical properties due to the dissolution of strengthening precipitates back into the matrix during friction stir additive manufacturing (FSAM). Post-fabricated aging was considered an effective approach to improve the mechanical performance of the build. In this study, various post-fabricated aging treatments were applied in the underwater FSAM of Al–7.5 Zn–1.85 Mg–1.3 Cu–0.135 Zr alloy. The effect of the post-fabricated aging on the microstructure, microhardness, and local tensile properties of the build was investigated. The results indicated that over-aging occurred in the low hardness zone (LHZ) of the build after artificial aging at 120 °C for 24 h as the high density of grain boundaries, subgrain boundaries, dislocations, and Al3Zr particles facilitated the precipitation. Low-temperature aging treatment can effectively avoid the over-aging problem. After aging at 100 °C for 48 h, the average microhardness value of the build reached 178 HV; the yield strength of the LHZ and high hardness zone (HHZ) was 453 MPa and 463 MPa, respectively; and the ultimate tensile strength of the LHZ and HHZ increased to 504 MPa and 523 MPa, respectively.

Wear Resistance Comparison Research of High-Alloy Protective Coatings for Power Industry Prepared by Means of CMT Cladding

In this study, four protective coating materials: Inconel 718, Inconel 625, Alloy 33 and Stellite 6 were deposited on 16Mo3 steel tubes by means of CMT (Cold Metal Transfer), as an advanced version of MAG (Metal Active Gas) welding method. In the next step, the surface of the deposited coating was remelted by means of TIG (Tungsten Inert Gas) welding method. SEM microstructure of coatings–substrate has been reported, and an EDX-researched chemical composition of the coatings was compared to the nominal chemical composition. The hardness distribution in the cross-section was performed, which revealed that among investigated coatings, Stellite 6 layer is the hardest, at about 500 HV0.2. Other materials such as Inconel 625, Inconel 718 and Alloy 33 represented a cladded zone hardness about 250 HV0.2. Stellite 6 layer had the lowest wear resistance in the dry sand/rubber wheel test, and Stellite 6 layer had the highest wear resistance in the erosive blasting test. This proved the existence of different wear mechanisms in the two test methods used. In the dry sand/rubber wheel test, the Alloy 33 and Inconel 718 only represented higher wear resistance than substrate 16Mo3 steel. In abrasive blasting tests all coatings had higher wear resistance than 16Mo3 steel; however, Stellite 6 coatings represented an approximately 5 times higher durability than other investigated (Inconel 625, Inconel 718, and Alloy 33) coatings.

Laser cladding of aluminum alloys with concurrent cryogenic quenching for improved microstructure and hardness

In this study, a method to deposit quench-sensitive age-hardening aluminum alloy clads is presented, which produces a hardness similar to the T6 temper without the requirement of solution heat treatment. A high-powered diode laser is scanned across the workpiece surface and material feedstock is delivered and melted via off-axis powder injection. The cladding process is immediately followed by quenching with liquid nitrogen, which improves the cooling rate of the quench-sensitive material and increases the hardness response to subsequent precipitation heat treatment. The method was demonstrated on the laser cladding of aluminum alloy 6061 powder on 6061-T6511 extruded bar substrates of 12.7 mm thickness. Single-track single-layer clads were deposited at a laser power of 3746 W, scan speed of 5 mm/s, and powder feed rate of 18 g/min. The in-situ liquid nitrogen quenching improved the clad hardness by 15.7% from 73.1 HV to 84.6 HV and the heat-affected zone hardness by 19.3% from 87.1 HV to 103.9 HV. Extending the process to multi-track multi-layer cladding further increased the clad hardness to 89.3 HV, close to the T6 temper hardness of 90 HV. Transmission electron microscopy revealed the increased precipitate density in the liquid nitrogen quenched clads were responsible for the higher hardness.

Effect of Surface Hardness and Hydrogen Sulfide Partial Pressure on Sulfide Stress Cracking Behavior in Low Alloy Linepipe Steel

TMCP (thermo-mechanical controlled process) linepipes have long been used in severe sour environments, but recently sulfide stress cracking (SSC) caused by local hard zones has become a concern. In order to clarify the hardness threshold that leads to SSC, four-point bend (4PB) SSC tests as specified in NACE TM0316 were conducted under several H2S partial pressure conditions. At H2S partial pressures of 1 bar and higher, the surface hardness threshold (at 0.25 mm from the surface) observed in 4PB SSC specimens without SSC cracking was approximately correlated to a maximum acceptable hardness level of 250 HV0.1. A stable low surface hardness of 250 or less HV0.1 was achieved by suppressing hard lath bainite (LB) and obtaining a soft granular bainite (GB) microstructure, resulting in a superior SSC-resistant property. It was found that a SSC crack propagated when the surface hardness increased due to an increasing volume fraction of the LB microstructure. Under a 16 bar H2S partial pressure condition, the crack growth rate increased in the sour environment, and hydrogen embrittlement by H2S was promoted. However, in the 4PB SSC test at 16 bar, the stress concentration and the transition to a crack were suppressed because the shape of localized corrosion was semicircular due to low localized corrosivity. This can be the reason why the SSC susceptibility was similar to 1 bar condition, especially in the 4PB SSC test using the samples with lower surface hardness level of 250 or less HV0.1.

In-vitro study of effect of incorporation of antifungal drugs upon growth of candida and surface hardness in permanent soft liners

Introduction: - Long term soft liners (acrylic and silicone based) are used to prevent damage to the abused mucosa, but they have the disadvantage of becoming porous with time leading to a suitable environment for opportunistic infections. This study was aimed to examine the inhibitory effect of incorporation of antifungal drug clotrimazole into long term denture soft liners on the growth of Candida albicans in vitro and evaluate the change in the surface hardness of soft liners.Materials and Method: The present study was done for two different long term soft liners, acrylic based (Permasoft) and silicone-based (Mollosil), by addition of clotrimazole drug in their minimum inhibitory concentration. The properties –zone of inhibition and surface hardness(Shore A) were evaluated at time intervals of 1,7,14,21,35 and 42days. A total of 224 samples were prepared. The properties were analyzed and inter group and intra group data was analyzed statistically by using One way ANOVA, Tukey post hoc-test and Paired t test.Result: The results showed significant creation of zone of inhibition for samples containing clotrimazole with the zone of inhibition decreasing with time. The surface hardness of all the samples increases with time.

Effect of beam wobbling on microstructure and hardness during laser welding of X70 pipeline steel

Laser welding with beam wobbling was employed to weld X70 pipeline steel. The influence of beam wobbling on weld surface morphology, fusion zone microstructure, and microhardness was investigated. The formation of spatter was suppressed by beam wobbling using a beam with higher energy density. At a welding speed of 1.0 m min−1, the weld metal produced with a circular laser wobble pattern contained more martensite but less ferrite, compared to that of static spot welded joint. The presence of more martensite led to the increase in fusion zone hardness. A softened region was found in the inter-critical heat-affected zone. The hardness of the softened region could be improved by increasing the welding speed (from 1.0 to 1.5 m min−1).

Effect of Al–5Ti–1B grain refiner on microstructure and properties of arc-additive-manufactured Al–Mg alloy

In this study, a strip-shaped Al–5Ti–1B grain refiner was employed to produce Al–Mg alloy using cold metal transfer arc additive manufacturing. The microstructure and mechanical properties of the straight-wall samples (SWSs) were analyzed. The results indicated that the Al3Ti phase occurred in SWS with Al–5Ti–1B, and acted as heterogeneous nucleation sites during solidification. Formation of Al3Ti particles led to the transformation of the columnar grains between the layers into equiaxed grains and refined the grains at the center of the layers. Furthermore, the Al3Ti particles increased the fraction of low-angle grain boundaries by 8.2%. In addition, the anisotropy in mechanical properties (i.e. tensile strength and elongation) was reduced significantly. Also, the low hardness zone between the layers was eliminated. Thereby, improving the mechanical properties of the additive-manufactured Al–Mg alloy samples.

Effects of annealing process parameters on microstructural evolution and strength-ductility combination of CoCrFeMnNi high-entropy alloy

Microstructures and mechanical properties of the CoCrFeMnNi high-entropy alloys (HEAs) treated by various annealing temperatures and times are investigated in this paper. Typical heterogeneous structure which composed of the ultrafine grains in nano/submicron scale and coarse grains can be obtained by annealing at 873∼923 K. The heterogeneity of grain size contributes to the hetero-deformation induced (HDI) strengthening and hardening, as well as the activation of hierarchical nanotwins, leading to the superior tensile property of the CoCrFeMnNi HEA that evades the strength-ductility trade-off. Meanwhile, the rapid multiplication of geometrically necessary dislocations and hierarchical nanotwins induced by the heterogeneous structure are the main factors to facilitate the upturn of strain hardening rate after yielding. The excessive annealing time reduces the content of ultrafine grains and narrows the mechanical incompatibility between the soft and hard zones, which reduces the effect of HDI strengthening and hardening. Consequently, the optimal annealing temperature for the cold-rolled CoCrFeMnNi HEAs with the reduction ratio of ∼96.7% is approximately 873∼923 K, and the holding time should be controlled to retain more ultrafine grains in the heterogeneous structure for superior strength-ductility combination.

Resistance spot welding of advanced high strength steel for fabrication of thin-walled automotive structural frames

This investigation presents the process parameter optimization of resistance spot welded (RSW) advanced high strength steel (AHSS) joints using response surface methodology (RSM) for fabrication of thin-walled automotive structural frames. Resistance spot welding (RSW) is used to minimize solidification cracking, heat affected zone (HAZ) softening and distortion related problems in joining of thin advanced high strength steel (AHSS) sheets. The three factor – five level central composite design (3 × 5 - CCD) matrix pertaining to the minimum number of experiments was chosen for designing the experimental matrix. The polynomial regression analysis was employed to develop the empirical relationships between RSW parameters and performance characteristics of AHSS joints. The 3-dimensional (3D) response surfaces were developed using RSM which shows the optimal process window to enhance the strength of spot joints. The RSW joints made using welding current of 5.0 kA, electrode pressure of 4.0 MPa, and welding time of 1.50 s displayed maximum lap tensile shear fracture load (LAP-TSFL) of 21.7 kN, cross tensile shear fracture load (CROSS-TSFL) of 17.65 kN, and nugget zone hardness (NZH) of 589 HV0.5 respectively. The results of ANOVA indicates that welding current, electrode pressure and welding time significantly influences the LAP-TSFL, CROSS-TSFL and NZH of joints respectively. The superior TSFL and NZH of joints made using optimized RSW parameters is attributed to the evolution of needle/lath martensite in nugget zone .

Effective Range of FSSW Parameters for High Load-Carrying Capacity of Dissimilar Steel A283M-C/Brass CuZn40 Joints.

In the current study, a 2 mm thick low-carbon steel sheet (A283M—Grade C) was joined with a brass sheet (CuZn40) of 1 mm thickness using friction stir spot welding (FSSW). Different welding parameters including rotational speeds of 1000, 1250, and 1500 rpm, and dwell times of 5, 10, 20, and 30 s were applied to explore the effective range of parameters to have FSSW joints with high load-carrying capacity. The joint quality of the friction stir spot-welded (FSSWed) dissimilar materials was evaluated via visual examination, tensile lap shear test, hardness test, and macro- and microstructural investigation using SEM. Moreover, EDS analysis was applied to examine the mixing at the interfaces of the dissimilar materials. Heat input calculation for the FSSW of steel–brass was found to be linearly proportional with the number of revolutions per spot joint, with maximum heat input obtained of 11 kJ at the number of revolutions of 500. The temperature measurement during FSSW showed agreement with the heat input dependence on the number of revolution. However, at the same revolutions of 500, it was found that the higher rotation speed of 1500 rpm resulted in higher temperature of 583 °C compared to 535 °C at rotation speed of 1000 rpm. This implies the significant effect for the rotation speed in the increase of temperature. The macro investigations of the friction stir spot-welded joints transverse sections showed sound joints at the different investigated parameters with significant joint ligament between the steel and brass. FSSW of steel/brass joints with a number of revolutions ranging between 250 to 500 revolutions per spot at appropriate tool speed range (1000–1500 rpm) produces joints with high load-carrying capacity from 4 kN to 7.5 kN. The hardness showed an increase in the carbon steel (lower sheet) with maximum of 248 HV and an increase of brass hardness at mixed interface between brass and steel with significant reduction in the stir zone hardness. Microstructural investigation of the joint zone showed mechanical mixing between steel and brass with the steel extruded from the lower sheet into the upper brass sheet.

Repeated low-velocity impact responses of SiC particle reinforced Al metal-matrix composites

This study aimed to investigate experimentally the repeated low-velocity impact behaviors of SiC reinforced aluminum 6061 metal-matrix composites for different volume fractions and energy levels. In addition, the hardness variations were measured by the Vickers hardness tests from the impacted and impact-free cross-sections of the particle reinforced metal-matrix composites. Low-velocity impact tests were applied to composite samples manufactured by powder metallurgy (in 10, 20, and 30% volume fractions) at two total energy levels (15 and 60 J as single) and in repetitions equal to the sum of these energy levels (5 + 5 + 5 and 20 + 20 + 20 J as repeated). As a result, in increasing the impact number for all volume fractions, the total contact time was shortened and the peak contact force increased, whereas both the permanent central deflection and the absorbed energies reduced. Hence, these variations obtained under repeated impacts (5 + 5 + 5 and 20 + 20 + 20 J) revealed that metal-matrix composites showed a tougher behavior with an increase in the impact numbers from 1st to 3rd, particularly because of the strain hardening effect. Furthermore, an increase in volume fraction from 10 to 30% resulted in an increase in the impact strength under all repeated and single impacts despite changing deformation and damage mechanisms due to increasing the strain hardening effect and particle fractures. The hardness was affected by the volume fraction and increased as the volume fraction increased in both the impacted and impact-free zones. The repeated impact increased the impacted zone hardness more than the single impact for all volume fractions. Additionally, the hardness of the impacted zone under 20 + 20 + 20 J repeated impact was measured as the highest value in the 30% volume fraction. Therefore, metal-matrix composites can behave harder with the strain hardening effect under repeated impacts.

Effect of microstructural heterogeneity on the balanced-biaxial and tensile behavior of a Zn alloy sheet

A 0.65 mm thick Zn sheet was processed at room temperature by equal channel angular sheet extrusion (ECASE), which allowed for the fabrication of a heterogeneous material. The processed sheet's heterogeneity manifested as larger dislocation clusters and smaller grain sizes on the surface than in the sheet's center, generating as well a 35% increase in yield strength while preserving a fracture elongation of 26%. ECASE processing resulted in a slightly higher deformation limit than that of the as-received material with a weight reduction of 9%. The improvement in the processed sheet's mechanical properties was associated with the formation of twins on the surface, resulting in a smaller grain size and heterogeneity between the twins-free and twinned grains. These two microstructures produced a combination of hard and soft zones. ECASE processing formed twins in particular grains that in turn created a high density of geometrically necessary dislocation (GND) arrays in twin-free neighboring grains. It should be noted that the twinned grains had a low density of geometrically necessary dislocations (GND). In addition to the heterogeneity between twinned and twin free grains, a heterogeneous GND distribution was formed between the surface and the processed sheet's center, with the basal slip system dominating.

Mechanical Properties and Deformation Mechanisms of Heterostructured High-Entropy and Medium-Entropy Alloys: A Review

Recently, heterostructured (HS) materials, consisting of hard and soft zones with dramatically different strengths, have been developed and received extensive attention because they have been reported to exhibit superior mechanical properties over those predicted by the rule of mixtures. Due to the accumulation of geometrically necessary dislocations during plastic deformation, a back stress is developed in the soft zones to increase the yield strength of HS materials, which also induce forward stress in the hard zones, and a global hetero-deformation induced (HDI) hardening to retain ductility. High-entropy alloys (HEAs) and medium-entropy alloys (MEAs) or multicomponent alloys usually contain three or more principal elements in near-equal atomic ratios and have been widely studied in the world. This review paper first introduces concepts of HS materials and HEAs/MEAs, respectively, and then reviewed emphatically the mechanical properties and deformation mechanisms of HS HEAs/MEAs. Finally, we discuss the prospect for industrial applications of the HS HEAs and MEAs.

Sulfide Stress Cracking (SSC) of Low Alloy Linepipe Steels in Low H<sub>2</sub>S Content Sour Environment

Resistance to Sulfide Stress Cracking (SSC) caused by local hard zones of pipe inner surface has been required in low alloy linepipe steel. In this study, using two samples with different surface hardness, the detailed SSC initiation behavior was clarified by four-point bend (4PB) SSC tests in which immersion time and applied stress were changed in a sour environment containing 0.15 bar hydrogen sulfide (H2S) gas. SSC cracks occurred when the applied stress was higher than 90% actual yield strength (AYS) in higher surface hardness samples over 270 HV0.1. From the fracture surface observation of SSC crack sample, it was found that the mechanism gradually shifted from active path corrosion (APC) to hydrogen embrittlement (HE), and that the influence of APC mechanism remained partially in the process of SSC initiation at the tip of corrosion pit or groove. The polarization measurement in the 4PB SSC test showed that the anodic and cathodic reactions (especially cathodic reactions) were activated when the applied stress was 90% AYS or higher. The FEM coupled analysis simulating the stress and strain concentration at the bottom tip of the corrosion groove and the hydrogen diffusion and accumulation was carried out. The principal stress in the tensile direction showed the maximum value at 0.04-0.06 mm away from the tip of the corrosion groove, and the hydrogen accumulation became the maximum. It was analytically found that the SSC crack initiated and propagated with HE mechanism dominated type when the threshold value of about 0.82 ppm is exceeded.

Experimental investigation of tensile properties and microstructure of TIG welded dissimilar joints of Al6061/Al5083 Aluminum alloy

The welding of aluminium alloys especially in dissimilar combination is challenging owing to numerous problems. The present study focuses to optimize processes parameters for dissimilar welding of 6 mm thick dissimilar Al-6061 and Al-5083, using Tungsten Inert Gas welding as well as to investigate the influence of the process parameters on tensile properties and microstructure of developed welds. A single V-butt joint configuration (bevel angle 60 and root gap 2 mm) ̊ of plates was used for welding. Three levels of input parameters viz. voltage, current and welding speed were selected for performing experiments as per L9 orthogonal array. The hardness and tensile strength were taken as output parameters or performance characteristic in the study. The optimum parameter settings for highest heat affected zone hardness and ultimate tensile strength of dissimilar welds have been suggested by using S/N ratio. The result predicted by optimization has an error of 2-3%. Finally, the effects of voltage, current and welding speed on m icro structure, hardness and tensile strength of welds have been investigated. Welding speed and current were the most influencing process parameter for controlling the hardness of HAZ and tensile strength of the welds.

Antioxidative Properties of Baltic Sea Keystone Macroalgae (Fucus vesiculosus, Phaeophyceae) under Ocean Warming and Acidification in a Seasonally Varying Environment.

Simple SummaryThe brown seaweed Fucus vesiculosus is the dominant and the most ecologically crucial primary producer and habitat founder in the Baltic Sea. In the shallow coastal zone, F. vesiculosus is particularly exposed to strongly and rapidly changing environmental conditions due to global change. This study examines how single and joint effects of elevated seawater temperature and pCO2 levels influence F. vesiculosus in all four seasons, using benthic mesocosms. The antioxidative properties and the sensitivity of F. vesiculosus photosynthetic performance to oxidative stress under different global change scenarios were assessed. F. vesiculosus tolerated strong hydrogen peroxide stress in all seasons, as reflected in high antioxidative enzyme activities and a low degree of membrane lipid peroxidation. Forecasted warming affected the antioxidative properties of F. vesiculosus stronger than acidification, causing significantly increased lipid peroxidation under elevated temperatures in all seasons. However, pCO2 levels modulated the oxidative stress of F. vesiculosus under warming. Overall, summer heatwaves reaching lethal temperatures in shallow waters will most likely determine the persistence of Baltic F. vesiculosus. The keystone macroalga Fucus vesiculosus (Phaeophyceae), dominating shallow hard bottom zones, encounters a strongly and rapidly changing environment due to anthropogenic change over the last decades in the Baltic Sea. Thus, in four successive benthic mesocosm experiments, the single and joint effects of increased temperature (Δ + 5 °C) and pCO2 (1100 ppm) under ambient irradiances were experimentally tested on the antioxidative properties of western Baltic F. vesiculosus in all seasons. The antioxidative properties (superoxide dismutase activity and lipid peroxidation) as well as the sensitivity of F. vesiculosus photosynthetic performance (i.e., effective quantum yield) to oxidative stress under these global change scenarios were seasonally examined. F. vesiculosus exhibited high and relatively constant photosynthetic performance under artificial hydrogen peroxide (H2O2) stress in all seasons. High activities of superoxide dismutase and a relatively low degree of the biomarker for lipid peroxidation (malondialdehyde concentration) were found in F. vesiculosus. Thus, Baltic F. vesiculosus is equipped with a high antioxidative potential to tolerate strong oxidative stress for at least short periods. Antioxidative properties of F. vesiculosus were more strongly affected by warming than by acidification, resulting in significantly increased malondialdehyde concentrations under elevated temperature levels in all seasons. Oxidative stress was enhanced in F. vesiculosus under warming but seem to be modulated by seasonally varying environmental conditions (e.g., high and low irradiances) and pCO2 levels. However, more frequent summer heatwaves reaching and surpassing lethal temperatures in shallow coastal waters may determine the F. vesiculosus population’s overall persistence in the Baltic Sea.

Spallation-based numerical simulations of ice-induced vibration of structures

A full-scale 3D numerical simulation model of ice-induced vibration of structures has been developed (using LS-Dyna™) and applied to the Molikpaq facility for an ice-encroachment event similar to that which occurred on May 12, 1986 in the Beaufort Sea. The bulk ice sheet used for the simulations had elastic properties, and its dimensions were 6 km × 6 km × 2.5 m. Where ice crushing occurred at the structure-ice interface the ice model used was a crushable foam that incorporated regular spallation events. Typical characteristics of ice-crushing in the brittle regime were manifested by the model. That is, a narrow horizontal hard zone (relatively-intact high-interface-pressure ice) was present in the mid-height region of the ice-edge contact area. Soft-zone material (shattered spall debris from the hard zone) was also represented. Evolution of the hard-zone contact area involved rapid reductions in size during spallation events, immediately followed by fast growth during consequent elastic surging of the near-field ice sheet and structure towards each other, and then some slower growth (due to the bulk ice-sheet velocity) until the next spalling event. The specified ‘thickness’ of the spalls was 5.4 cm, as previously determined from Molikpaq records of the frequency of the spalling events as a function of ice-sheet speed. Spallation (and associated rapid drops in load) occurred at regular intervals whenever a critical amount of hard-zone stress was reached at the ice-structure interface. The amplitude of the Molikpaq repetitive movements in response to the sawtooth loading from the spalling events depended on whether the resonant frequency of the structure/ice system was higher (for a strong response) or lower (for a weak response) than the spalling frequency, where the spalling frequency is directly proportional to the ice-sheet speed. The continuously variable resonant frequency of the structure/ice system had a maximal limiting value (~ 2.1 Hz), designated as the At-Spallation-Resonant-Frequency (ASRF), that was essentially determined by the time duration of load drops at spallation events. The simulations inherently accounted for the variable effective mass and effective spring constant of the ice sheet.

Fruit development, structure and histology inNelumbo(Nelumbonaceae: Proteales)

AbstractNelumbonaceae, along with Proteaceae and Platanaceae, comprise a sister clade to the family Sabiaceae in the order Proteales, although these families were previously not considered to be related. In this work, we investigated fruitlet development in Nelumbo with a special focus on the principal events of fruitlet ontogenesis and its pericarp histogenesis, aiming to determine whether fruit structure and histology can provide characters supporting current systematic positions and affinities of these families and reveal potential synapomorphies for the order. We demonstrated for the first time that each carpel comprises a biseriate outer and inner epidermis and thick mesophyll with numerous air canals, which differentiate after pollination into a pericarp with a biseriate palisade exocarp and undifferentiated endocarp. The mesocarp differentiated into a protective hard peripheral zone and a soft inner zone. We propose the following additional autapomorphies for Nelumbonaceae: (1) the development of a specific zone of palisade cells of the subdermal layer of the exocarp with U-shaped cell walls thickening to form a light line around the locule, and potentially preventing apoplastic water transport; (2) the presence of a soft inner parenchymatous zone of the pericarp comprising numerous air cavities, channels and layers of spongy parenchyma, which can function as a seed cushion; (3) simultaneous growth of pollinated and unpollinated fruiting carpels up until the middle developmental stages; and (4) intensive development of the embryo and the seed at the late developmental stage in both Nelumbo spp., which has not been reported in any other member of Proteales. The presence of numerous vascular bundles in the fruitlets of Nelumbonaceae, Platanaceae and some Proteaceae is a synapomorphy for these three families forming a well-supported clade in Proteales.

A Further Application of Coefficient of Anisotropy and Reflection Coefficient as Indices in Delineating Groundwater Potential in Basement Complex of Ado Ekiti, Southwestern Nigeria

One index might not be enough in geophysical investigation of underground water potentials in basement terrain, there is a need to look into other indices for an improved investigation, the combination of some indices will lead credence to the result hence this work is a further application of coefficient of anisotropy, reflection coefficient and fracture coefficient on spatial distribution of underground water in Ado Ekiti basement complex. This work examined the thickness of aquifer, its resistivity spread and other hydro geological parameters such as total longitudinal conductance, total transverse resistances, coefficient of Anisotropy, reflection coefficient and fracture contract to determine water potentials in the study area. Resistivity and thickness are linearly related for high productive Aquifer formation, thus these indices generated from thickness and resistivity have been examined in other to determine the porosity and permeability and hence transmissivity of the aquiferous zone in the study area. Aquifer resistivity ranges from 7.7Ωm to 545Ωm in weather zone and between 9.5Ωm to 1902.6Ωm in fracture zone these values are within productive range in basement complex environment. Shallow basement of less water potential have been found in part of North west and north east of the study area, total transverse resistance also discovered low porosity at Aiyedun quarters, Elemi housing Estate and Ita Eku these are hard rock zone, this area has also been identified through their coefficient of anisotropy as low or none productive zone the coefficient of anisotropy is higher than 1.5. Area of promising water bearing zone are with the North west, west, south west and south east of the study area.