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•Effects of heat treatment on microstructure, mechanical, corrosion properties of SLM 15-5 PH stainless steel are reported.•Aging leads to formation of fine spherical ε-copper ...precipitates of about 15 nm and makes the specimen brittle.•Coarsening of elliptical ε-copper precipitates and increase in reverted austenite make overaged specimens ductile.•Higher aging temperature and longer soaking time does not have significant effect on different mechanical properties.•Application oriented mechanical and corrosion properties can be achieved by selecting proper heat treatment.
With recent advancements in additive manufacturing, Selective Laser Melting (SLM) is emerging as an unconventional manufacturing process of exceptional flexibility capable to fabricating any complex part without requiring expensive fixtures, tooling, mold or any other additional auxiliary with a very short lead time from design conceptualization to fabrication. Very few reports are available on the effect of heat treatment on mechanical and corrosion properties of SLM 15-5 Precipitation Hardening (PH) stainless steel. Herein, micro-structural evolution and its correlation with various mechanical and corrosion properties of heat treated SLM 15-5 PH stainless steel are investigated to widen the application of SLM parts for industrial usages. Results show, standard aging condition (H900) increases yield strength, hardness and corrosion resistance through the formation of fine spherical ε-Cu-rich precipitates (∼15 nm), but makes the specimens brittle resulting in an increase in wear rate and a decrease in impact energy. Combined effects of coarsening of elliptical ε-Cu-rich precipitates and increase in reverted austenite phase in overaging (H1150) make the specimen ductile having relatively low yield strength, hardness, wear rate but high impact energy. Solution annealing was found to reduce anisotropy in mechanical properties through the homogenization of microstructure. Higher aging temperature and longer soaking time doesn’t have significant impact on different mechanical properties but deteriorates the corrosion properties. Solution annealing before aging is recommended for the homogeneity in microstructure. Present findings can be used as a guideline to select proper post heat treatment for SLM 15-5 PH stainless steel to impart application oriented mechanical and corrosion properties.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
An analytical solution for the temperature variation in a semi-infinite workpiece heated by repetitive laser pulses has been derived and the effects of various process parameters, viz. laser power, ...beam diameter, scan speed, pulse duration, repetition frequency and duty cycle on the surface transformation hardening have been investigated. The study shows that the soaking time of the top surface layer at a temperature above the phase transformation temperature, on which the homogeneity of microstructure and the depth of hardening depend, can be increased by repetitive laser pulse heating in comparison to continuous wave laser heating. The depth of hardness increases with the number of incident laser pulses at low frequencies in the range of Hz. This has been demonstrated by comparing the surface hardness characteristics of AISI 1055 steel specimens resulted by the continuous wave and repetitive laser pulse hardening processes.
► An analytical model for temperature in repetitive laser pulse hardening developed. ► Theoretical and experimental study of CW and pulse laser hardening presented. ► Time for homogenization of austenite is relative longer in repetitive pulse heating. ► Depth of hardening increases with number of laser pulses at low pulse frequencies. ► Repetitive pulse heating provides better control of hardening process.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Mild steel substrates were coated with commercially available alumina and chromia powders using the powder flame spraying process. The top layers of the flame sprayed coatings were remelted using a ...2 kW fiber laser. Thermo-cycles of the laser remelting process were monitored on-line using an infrared pyrometer. Cooling rates were varied using different laser scanning speeds. Surface morphology, microstructure and phases of the laser treated and as-sprayed coatings were investigated using optical microscopy, scanning electron microscopy, X-ray diffraction and X-ray tomography. Surface residual stress of the as-sprayed and laser treated coatings was measured using X-ray diffraction. The inherent defects like porosity and inter-lamellar boundary diminish to a great extent upon laser remelting. Surface residual stress of the remelted coatings tends to increase with increase in cooling rate. Surface crack density of the laser treated coating was reduced appreciably when coatings were preheated prior to laser remelting.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Modern agriculture is primarily focused on the massive production of cereals and other food-based crops in a sustainable manner in order to fulfill the food demands of an ever-increasing global ...population. However, intensive agricultural practices, rampant use of agrochemicals, and other environmental factors result in soil fertility degradation, environmental pollution, disruption of soil biodiversity, pest resistance, and a decline in crop yields. Thus, experts are shifting their focus to other eco-friendly and safer methods of fertilization in order to ensure agricultural sustainability. Indeed, the importance of plant growth-promoting microorganisms, also determined as "plant probiotics (PPs)," has gained widespread recognition, and their usage as biofertilizers is being actively promoted as a means of mitigating the harmful effects of agrochemicals. As bio-elicitors, PPs promote plant growth and colonize soil or plant tissues when administered in soil, seeds, or plant surface and are used as an alternative means to avoid heavy use of agrochemicals. In the past few years, the use of nanotechnology has also brought a revolution in agriculture due to the application of various nanomaterials (NMs) or nano-based fertilizers to increase crop productivity. Given the beneficial properties of PPs and NMs, these two can be used in tandem to maximize benefits. However, the use of combinations of NMs and PPs, or their synergistic use, is in its infancy but has exhibited better crop-modulating effects in terms of improvement in crop productivity, mitigation of environmental stress (drought, salinity, etc.), restoration of soil fertility, and strengthening of the bioeconomy. In addition, a proper assessment of nanomaterials is necessary before their application, and a safer dose of NMs should be applicable without showing any toxic impact on the environment and soil microbial communities. The combo of NMs and PPs can also be encapsulated within a suitable carrier, and this method aids in the controlled and targeted delivery of entrapped components and also increases the shelf life of PPs. However, this review highlights the functional annotation of the combined impact of NMs and PPs on sustainable agricultural production in an eco-friendly manner.
This investigation deals with laser remelting of plasma sprayed alumina and chromia coatings. The time-temperature history of the laser remelted zone was recorded using an infrared pyrometer during ...the remelting operation. Cooling rates, under varying scanning speed, were determined from the time temperature curve. Surface morphology, microstructure, and phases of the laser treated and as-sprayed coatings were characterized using scanning electron microscopy, optical microscopy, X-ray diffraction, respectively. X-ray diffraction was also employed to measure the surface residual stress of the coatings. Inherent features of plasma sprayed coatings like porosity and inter-lamellar boundary were obliterated upon laser remelting. A columnar grain growth perpendicular to the laser scanning direction was observed. The range of roughness of the as-sprayed coatings reduced from 6 to 8 µm to 1–2 µm in the remelted layers. For both coatings, more than 90% reduction in porosity was found upon laser remelting. Surface residual stress of the as-sprayed alumina and chromia coatings was found to be tensile and compressive, respectively. Within the limits of the testing condition the tensile residual stress of the remelted layers increased by up to around 500% in the alumina coatings. In the chromia coating a decrease of compressive stress by up to around 80% was recorded. In the remelted layer the tensile nature of the stress showed a tendency to increase with an increase in the cooling rate. However, the state of stress of the as-sprayed layer, i.e., tensile or compressive, was retained in the remelted layer. The residual stress was found to decrease in the remelted layer with an increase in the degree of overlap of the remelted tracks.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
In today's era of modern manufacturing, selective laser melting is getting increasingly popular due to its capability of producing geometrically complex parts directly from CAD model in a single ...step. Few papers have reported the fatigue behaviour of selective laser sintered stainless steel specimens. In the present study, effect of tensile, zero and compressive mean stresses on mode of failures and fatigue strength of laser sintered 15-5 precipitation hardened stainless steel specimens have been investigated. Presence of compressive mean stress is found to improve the fatigue life while tensile mean stress is found to be detrimental. For tensile and compressive mean stresses, fracture surfaces show four distinct regions: crack initiation site, stable crack growth region, unstable crack growth region and fracture region. However, under zero mean stress fracture surfaces do not show any unstable crack growth region. Unstable crack growth region could be attributed to presence of mean stresses. Predominant mode of failure for compressive mean stress is brittle. Presence of tensile mean stress leads to fracture surface having brittle and mixed-rupture characteristics of quasi-cleavage and dimples respectively; whereas under zero mean stress fracture surface shows ductile-brittle mixed mode of failure.
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•An improved 3-D FEM model including keyhole mechanism is developed to simulate L-PBF.•The predicted geometry of the fused layers agrees well with the experiment results.•The ...variation trend of dendrite arm spacing with process parameters was revealed by PF and experiment.•Dendrite arm spacing of AlSi10Mg alloys depends mainly on the temperature gradient.•The columnar/ equiaxed boundary is a eutectic mixture of Al and Si and α −Al increases with increasing line energies.
Laser powder bed fusion (L-PBF) process is an additive manufacturing process, in which rapid heating and cooling takes place. The microstructure and the solidification behaviour of L-PBF components have significant impacts on their mechanical properties. The solidification takes place in a very short duration which is difficult to capture experimentally, therefore the finite-element (FE) simulation is the best feasible solution. In this paper, to study the evolution of the AlSi10Mg alloy’s microstructure during the L-PBF process, a model composed of macroscopic finite element (FE) model and microscopic phase field (PF) model was built. This model is suitable to predict a more realistic thermal behaviour involving the possible physical phenomena and the thermal behaviour for various heat inputs was calculated. The PF model was then updated with these results in order to simulate the chemical compositions’ concentration field and solidified microstructure. According to the simulation’s results, the primary dendrite arm spacing (PDAS) is significantly influenced by the laser line energy. To validate the FE model along with the Phase field (PF) model, the results were compared with the analytical and experimental findings; and the FE model and PF results exhibited good agreement with the experimental results. Additionally, the solute distribution analysis demonstrated that during the solidification process, micro-segregation developed and the process parameters affected the micro-segregation. Finally, the specimens were subjected to metallographic and element distribution analyses using an energy-dispersive spectrometer (EDS) to compare the results with those from the PF simulation and establish the relationship between the process parameters.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Multidrug-resistant (MDR)
(
) is one of the major pathogens present in burn wound infections. Biofilm formation makes it further challenging to treat with clinically available antibiotics. In the ...current work, we isolated the
-specific bacteriophages (BPABΦ1), loaded into the chitosan microparticles followed by dispersion in gel, and evaluated therapeutic efficacy against MDR
clinical strains. Isolated BPABΦ1 were found to belong to the
family, with burst size 102.12 ± 2.65 PFUs per infected host cell. The BPABΦ1 loaded chitosan microparticles were evaluated for quality attributes viz. size, PDI, surface morphology, in vitro release, etc. The developed formulation exhibited excellent antibiofilm eradication potential in vitro and effective wound healing after topical application.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
"This reference is a compilation of holistic responses of cyanobacteria ranging from ecology and physiology to modem aspects of molecular biology and biochemistry. It presents research in ...cyanobacterial stress biologies, from classical to the most modern, and provides a holistic view of cyanobacterial bioenergetics under different abiotic stresses. Authors focus on topics ranging from evolution, ecophysiology, biochemistry, and molecular biology and discuss genomics and proteomics of cyanobacteria under abiotic stresses. Written by a team of global experts from 12 countries, this reference was created for phycologists, marine biologists, chemists, limnologists, botanists, and students of related fields"--
•Experiment and simulation on laser forming of pre-bent steel plates are presented.•Change in bent angle was more for laser scan on the convex side.•For higher punch radius bent angle changed more ...for laser scan on concave side.•Bent angle changed more for laser scan on convex side in case of higher bent angle.•Bent angle did not change with Fourier number but increased with laser spot diameter.
Laser forming, being a flexible non-contact forming technique, is an attractive tool for the correction of spring back, over-bending or distortion of sheets formed mechanically or by other means. However, literatures are scarce on this topic. This work investigates the modification of bent angle of mechanically formed stainless steel blanks by laser forming using experiments and finite element (FE) simulations. Changes in angle imparted by laser forming, in specimens bent with the help of different die-punch combinations, have been studied for different Fourier numbers and laser spot diameters. Laser parameters were decided with the help of an analytical model so as to keep the peak surface temperature due to laser scan nearly constant for all the laser scan parameter combinations. Laser forming was carried out by scanning laser beam on both concave and convex sides of the mechanically bent specimens. The change in bent angle was found to be significantly larger when laser was scanned on convex side than on concave side. Further, for laser scanning on convex side, the change in bent angle increased with initial bent angle. Opposite trend was observed for laser scan on the concave side of the bending edge. However, for the similar mechanically bent angle, change in bent angle increased for laser scan on the concave side with increasing punch radius. For laser scan on the convex side the trend was just the opposite. Laser scans corresponding to different Fourier numbers did not significantly affect the change in bent angle. However, increase in laser spot diameter increased the change in bent angle. These observations were explained with the help of FE simulations considering temperature dependent material properties and multimode intensity distribution of the laser beam. Simulation results matched fairly well with their experimental counterparts in most of the cases.
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