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Inconel alloys are one of the materials of choice for high temperature applications whether it is aerospace, nuclear or gas turbine. This is due to their excellent mechanical and non-corrosion properties even under harsh environments at elevated temperatures. Joining Inconel alloys through conventional fusion welding techniques have posed many different problems and hence, solid state joining processes could well be an alternative welding method for these alloys, wherever the design permits. Friction welding being a solid state welding process, is well established for its capability of producing high quality welds and joining dissimilar metals. In this paper, Inconel alloys are introduced initially, and then friction welding in general has been discussed. Thereafter, the published works on the friction welding of Inconel alloys are reviewed with an emphasis on microstructural and mechanical properties of similar and dissimilar Inconel weld joints.

In the present business climate as it is evident with high occupation misfortunes because of cutback and conservation to make a lean association, it is likewise essential for associations to stop loses of performing workers because of diminishing position fulfillment and absence of inspiration to proceed with the association for long. Propelled and fulfilled workers will have submitted approach towards authoritative goal; thusly associations will likewise need to show comparative responsibility towards representative targets. Here the part of HR is to consistently pursue arrangement of desires of the worker with the objectives of the association. This goal can be accomplished by establishing rousing workplace which advances and addresses representative requirement for development and improvement. These elements albeit complex in nature and as they couldn't be tended to for singular worker premise as it might fluctuate case to case it is significant for HR to investigate the regular spaces of crossing point. Occupation fulfillment or representative inspiration is contemplated to deal with the turnover as well as there are other antagonistic impacts of disappointment like truancy, low execution, lower spirit, low commitment to the group, less coordination, less direction towards hierarchical target these could influence the association ability to contend in the exceptionally aggressive business climate. Henceforth the HR needs to prompt a hierarchical climate and advance authoritative culture which takes in to thought of the overall need.

Job satisfaction is a complex concept that is influenced by many factors. The aim of this paper is to analyze the impact of working conditions to job satisfaction. For that purpose, the empirical research has been conducted in select banks. The study has analyzed the various reasons for choosing select public sector banks among the various banks, the working condition of the select bank employees with the level of job satisfaction among the various group of respondents. The study has tested the with the help of Percentage analysis, Chi-square, ANOVA, and Multiple Regression. All the chi-square, ANOVA, and Multiple Regression tested at 5% level of significance. This paper is focused on the observation of the importance of working conditions to employees’ job satisfaction KEYWORDS: Employees, Banks, Working Conditions, Job Satisfaction, Need, Objectives, Methodology, Analysis, Findings and Suggestions.

In this work, the effect of addition of TiB2, SiC as secondary particles on the microstructure, mechanical and tribological properties of the Al6061 MMC has been studied. The wear rate of the composite specimens has been tested using a pin on disc configuration under normal loads of 10, 20 & 30 N. Microstructural characterization was carried out for the above prepared composites to ensure homogeneous distribution of particles. The images of scanning electron microscopy reveal a uniform distribution of TiB2 particles in the Al MMC. The X-ray diffraction analysis reveal the dispersal of SiC particles and Mg2Si inter metallic compound phases in the aluminum matrix. The hardness and tribological properties of cast Al alloy with TiB2 were compared with Al alloy with SiC addition.

Metastable beta (β) titanium alloy welds typically exhibit low strength and hardness due to their coarse fusion zone (FZ) microstructure. Efforts to improve the mechanical properties of these alloys have been confined to the use of various heat treatment processes as the means to promote α precipitation in the β matrix. The present study employs a novel method of using boron-added commercial pure-Ti fillers in gas tungsten arc welding (GTAW) of the Ti-15V-3Cr-3Sn-3Al metastable β titanium alloy. Microstructural analysis of boron-added welds showed refined prior-β grains and equiaxed dendritic grains with nonlinear grain boundaries. The formation of TiB and consequent microstructural modification of the FZ in the welds prepared using 0.5 wt% boron-added CP-Ti filler contribute to the improvement in the mechanical properties.

Near net shaped metal matrix composites were fabricated using high energy cube milling and hot pressing process. Cube milling was up to six times faster than commercially available planetary ball mill in dispersing up to 1 vol.% of Al 2 O 3 nanoparticles in AlMg5 alloy. Combined yield strength of 530 MPa and elongation at rupture of 4% exceed the values of commercially available wrought 5xxx series alloys. Thorough microstructure characterisation of composites revealed bimodal grain structure with an increasing content of finer grains and high angle grain boundaries with higher reinforcement content. The main contributing strengthening mechanisms for achieving high strength were solid solution strengthening, Orowan strengthening and grain boundary strengthening. Coarse grained regions in the bimodal structure, together with low angle grain boundaries were assumed to be the main source of retained ductility.

In this work, the morphology, phase composition, and corrosion properties of microarc oxidized (MAO) gas tungsten arc (GTA) weldments of AZ31 alloy were investigated. Autogenous gas tungsten arc welds were made as full penetration bead-on-plate welding under the alternating-current mode. A uniform oxide layer was developed on the surface of the specimens with MAO treatment in silicate-based alkaline electrolytes for different oxidation times. The corrosion behavior of the samples was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy. The oxide film improved the corrosion resistance substantially compared to the uncoated specimens. The sample coated for 10 min exhibited better corrosion properties. The corrosion resistance of the coatings was concluded to strongly depend on the morphology, whereas the phase composition and thickness were concluded to only slightly affect the corrosion resistance.

Semantic segmentation is pixel-wise labeling of the image. Recently deep convolutional neural network (DCNN) providing progressive results in semantic segmentation. However, in remote sensing multispectral imagery very limited work has been done due to lack of training dataset. In this paper, a Res-Seg-net model is proposed for the semantic segmentation which is motivated by the existing Resnet and Segnet models. This model consists of encoder-decoder parts in which residual mapping is followed. For validation and testing of the proposed model, the RIT-18 dataset of multispectral imagery is used. The comparison results of the experiment on a multispectral imagery dataset have demonstrated the effectiveness of the proposed model.

The investigation of the microstructural development during solidification as well as wear performance of Nb and Mo added hypereutectic WCI hardface deposits with W and V as minor additives was aimed during the study. This would enable the development of the hardface deposits with superior abrasive performance for severe wear applications. The hardfacing alloys were deposited on carbon steel using self-shielded flux cored arc welding (FCAW) technique. Phase formation, microstructural and mechanical properties of hardface deposits were investigated in the as-deposited condition. The microstructural examination showed that the addition of alloying elements to the high-Cr WCI resulted in grain refinement of the primary proeutectic M7C3 (M = Cr and Fe) carbide phase. EDX analysis revealed that the addition of Nb and Mo resulted in the formation of MC (M = Mo and Nb) carbides which resulted in grain refinement and higher wear resistance. Phase investigation of the deposits using XRD analysis shows the existence of M7C3 for all alloys and MC carbides for alloy B, C and D along with the ferrite phase. The main wear mechanism observed for the base high-Cr WCI is abrasive wear, while hardface alloys with alloying addition showed surface delamination which was attributed to the presence of soft phase adjacent to the M7C3 carbides in the microstructure. Among all the alloys, hardface deposits prepared using a filler with 5.5 -Mo, 6 - Nb, 2 - W and 1 - V (wt%) addition showed highest wear resistance due to grain refinement, MC carbide formation and solid solution strengthening by W and V.

Strength and ductility of fusion zone of metastable β titanium alloy welds can be improved by choosing suitable fillers. This paper reports the effects of using CP-Ti filler on the microstructural and mechanical properties of Ti-15-3 weldments. Full penetration autogenous and CP-Ti filler welds were produced by pulsed gas tungsten arc welding. X-ray diffraction analysis revealed small amounts of α-Ti phase in the diffraction pattern obtained for welds prepared using CP-Ti filler. Transmission electron microscopy analysis showed presence of grain boundary and intragranular α in the fusion zone of the welds prepared using CP-Ti filler. The welds prepared with CP-Ti filler showed higher hardness, higher UTS and lower % strain compared to autogenous welds.

Mechanical properties of as-cast beta titanium (β-Ti) alloy can be improved by grain refinement and formation of insoluble precipitate. This paper reports the effect of carbon (C) addition on microstructure and hardness of cast Ti–15V–3Cr–3Sn–3Al (Ti-15-3) samples prepared by argon arc melting. X-ray diffraction analysis of C added as cast Ti-15-3 samples revealed the presence of β-Ti and TiC phases. Scanning electron microscope analysis revealed eutectic TiC precipitates in C added Ti-15-3 samples while a reduction in grain size was observed with increasing carbon addition. Inoculation effect due to TiC and growth restriction by C for β phase resulted in decreased grain size. Hardness of C added Ti-15-3 alloys increased with the increased carbon content of the sample. The improvement in hardness was contributed by grain refinement and the formation of TiC precipitates in the samples.

The present study has investigated the influence of calcium process control agent on the microstructure and mechanical properties of powder metallurgy processed samples fabricated by milling and spark plasma sintering technique. The microstructure of spark plasma sintered Ti-6Al-4V with 0.3 wt% Ca (Ti-6Al-4V-0.3Ca-M) samples revealed fine grain structure compared to sintered unmilled (Ti-6Al-4V-UM) samples. The average grain size values of sintered Ti-6Al-4V-0.3Ca-M and Ti-6Al-4V-UM samples are 8 and 60 μm, respectively. The spark plasma sintered Ti-6Al-4V-UM exhibited a yield strength (YS) of 875 ± 10 MPa, ultimate tensile strength (UTS) of 1057 ± 2 MPa, and % elongation (% El) of 15 ± 2. The spark plasma sintered Ti-6Al-4V-0.3Ca-M exhibited higher YS of 964 ± 9 MPa, UTS of 1153 ± 7 MPa, and lower % El of 6 ± 1 when compared to mill annealed Ti-6Al-4V alloy (YS 899 MPa, UTS 978 MPa and %El 15). The higher strength of Ti-6Al-4V-0.3Ca-M sintered samples could be attributed to the fine grain structure and the presence of interstitial elements in the matrix. In contrast, the lower strength of Ti-6Al-4V-UM can be ascribed to its coarse grains.

Bosentan is a non-peptidic endothelin receptor antagonist used for the treatment of pulmonary artery hypertension (PAH), congestive heart failure and cardiovascular pathology.1,2 Bosentan monohydra...

Microstructural and impression creep properties of hot pressed bulks made from unmilled AlMg5 powders, milled AlMg5, and AlMg5 powders milled with 0.5 vol% of Al2O3 nanoparticles are investigated. Microstructural, high-temperature impression creep, and high-temperature tensile properties investigation is carried out. Activation energies and stress exponent values are determined from the steady state creep rate obtained at different temperatures and creep stresses. AlMg5–0.5 vol% Al2O3 samples display superior strength values at 298 K compared to unmilled AlMg5 and milled AlMg5 samples. However, AlMg5–0.5 vol% Al2O3 nanocomposite exhibits higher creep rate and tensile elongation with a decrease in strength at 473 K due to activation of grain boundary sliding mechanism.

In the present study, powder metallurgy processed unmilled AlMg5 (AlMg5-UM), milled AlMg5 (AlMg5-M), and milled AlMg5–0.4 vol.% Al2O3 (AlMg5–0.4Al2O3) nanocomposite were successfully spark plasma sintered at 550 °C. The microstructural analysis of spark plasma sintered AlMg5-UM revealed equi-axed grains with average size of 20 ± 5 μm. The microstructural analysis of spark plasma sintered AlMg5-M and AlMg5–0.4Al2O3 revealed a bimodal grain structure with both fine-coarse grains of size 700 nm–8 μm and 300 nm–8 μm, respectively. The spark plasma sintered AlMg5-UM exhibited a yield strength (YS) of 132 ± 3 MPa, ultimate tensile strength (UTS) of 296 ± 2 MPa and % elongation (% El) of 22 ± 2 comparable to the conventional Al 5083 alloy — O temper (YS of 145 MPa, UTS of 281 MPa and % El of 16). The spark plasma sintered AlMg5-M and AlMg5–0.4Al2O3 exhibited YS of 242 ± 9 MPa and 274 ± 5 MPa, UTS of 376 ± 4 MPa and 417 ± 8 MPa and % El of 19 ± 1 and 10 ± 1, respectively. The lower strength (YS and UTS) of AlMg5-UM can be ascribed to its coarse grains. Among the milled samples, the AlMg5–0.4Al2O3 composite exhibited high strength and it can be ascribed to its fine grain size (Hall–Petch effect), higher dislocation density and Orowan strengthening effect due to Al2O3 reinforcements. Keywords: Spark plasma sintering, Nano-composites, Microstructure, Hardness, Mechanical properties

In the present study, powder metallurgy processed unmilled AlMg5, milled AlMg5 and milled AlMg5-0.5 vol% Al2O3 nanocomposite have been successfully friction stir welded (FSW). The effect of friction stir welding on the evolution of weld microstructures; hardness and tensile properties were studied and discussed in detail. FSW of unmilled AlMg5 resulted in significant grain refinement and strain hardening in the nugget zone induced by the thermo-mechanical processing, thereby increasing the stir zone hardness and tensile strengths to 100 HV and 324 MPa when compared to 80 HV and 300 MPa of base metal, respectively. In contrast, the FSW of milled AlMg5 and milled AlMg5-0.5 vol% Al2O3 samples showed a reduction in UTS values to 375 MPa and 401 MPa in the stir zone compared to 401 MPa and 483 MPa of respective base metal values. Transmission electron microscopic (TEM) investigation of weld stir zones revealed the homogenous distribution of Al4C3 nanophases in milled AlMg5 and Al2O3 nanoparticles in milled AlMg5-0.5 vol% Al2O3 samples throughout the aluminium matrix. It was revealed that the pre-stored energy from the prior ball milling and hot pressing processes, higher deformation energy and grain boundary pinning effect due to the presence of reinforcement particles has resulted in a higher recrystallization tendency and retarded grain growth during FSW of milled samples. The welds prepared with milled AlMg5-0.5 vol% Al2O3 exhibited higher hardness and tensile strength in the stir zone when compared to all other conditions which was attributed to Hall Petch effect due to fine grain size and Orowan strengthening effect due to Al2O3 reinforcements.

Ceramic coatings were produced on AA7075 by plasma electrolytic oxidation (PEO) technique using a pulsed DC power source with different combinations of duty cycle (20% and 80%) and pulse frequency (50 Hz and 1000 Hz). The morphology and phase composition of these coatings were analyzed by a scanning electron microscope (SEM), optical profilometer and X-ray diffraction (XRD) technique. The corrosion behavior of the PEO coatings was evaluated using open circuit potential measurements, potentiodynamic polarization in 3.5% NaCl solution and salt spray test as per the ASTM B117 standard. The adhesion strength between the coatings and substrate was assessed through scratch testing. X-ray diffraction patterns show that the PEO coatings formed on AA7075 substrate are mainly composed of γ-Al2O3. The SEM analysis reveals more pores over the surface of the samples treated at 50 Hz frequency and micro-cracks at 80% duty cycle. The 3D-images and depth profiles as obtained through optical profilometer confirmed that the 1000 Hz frequency and 20% duty cycle produced a smoother coating with fine and shallow pore morphology. Further, the coating thickness as measured by eddy current thickness gauge and SEM coating cross section confirmed that the 1000 Hz frequency and 20% duty cycle produced a thicker coating. Among all the PEO treated samples, because of the thicker coating and fine pore morphology, the sample treated at 1000 Hz frequency and 20% duty cycle demonstrated the highest pitting potential of 440 mV, highest polarization resistance (Rp) of 31 kΩ·cm2 and the highest scratch resistance of 28.1 N.

A simple and green methodology has been developed for the syntheses of some new 2-styrylbenzimidazoles. In this method, 2-styrylbenzimidazoles 6(a–x) were synthesized by the condensation of o-phenylenediamines 4(a–c) with cinnamic acids 3(a–h) using glycerol containing boric acid (10 mol%) as the reaction medium at 180 °C about 3–5 h. The cinnamic acids 3(a–h) were obtained by the condensation between aromatic aldehydes 1(a–h), and malonic acid using a new heterogeneous catalytic system such as alum-Cs2CO3 in water is described. Compounds 6(a–x) were also obtained alternatively by the condensation of 2-methylbenzimidazoles 5(a-c) with 1(a-h) using the same glycerol containing boric acid (10 mol%) as reaction medium at 180 °C for 5–6 h. The catalytic systems mentioned here were found to be highly active, stable, and recyclable under reaction conditions. All the newly synthesized compounds were characterized by IR, Mass, and NMR spectral analyses. All synthesized compounds were screened for their antimicrobial activity against the clinical strains which include gram-positive bacteria (Micrococcus luteus MTCC 2470, Staphylococcus aureus MTCC 96, Staphylococcus aureus MLS-16 MTCC 2940, Bacillus subtilis MTCC 121) and gram-negative bacteria (Escherichia coli MTCC 739, Pseudomonas aeruginosa MTCC 2453, Klebsiella planticola MTCC 530, and Candida albicans MTCC 3017). The results revealed that compounds (6b, 6g, 6h, 6j, 6k, 6n, 6o, 6t) exhibited significant antibacterial activity almost equal to the standard drug, i.e., Ciprofloxacin.

A very simple, mild, efficient, and novel green methodology has been developed for the syntheses of some 2-hetero/styryl-benzimidazoles. Title compounds were synthesized by the condensation of o-phenylenediamine with cinnamic acids at 150–180°C for 5-6 h using glycerol containing triacetylborate (10–20 mol%) as the reaction medium. In an alternative approach, condensation of 2-methylbenzimidazole derivatives with aromatic aldehydes was done using glycerol containing triacetylborate (10–20 mol%) as the reaction medium.

A series of new N-alkyl-2-(3-methyl-indolyl)benzimidazoles 8(a–c) were synthesized by the condensation of N-alkyl-2-propylbenzimidazole-phenylhydrazone derivatives 7(a–c), in polyphosphoric acid (PPA) underwent cyclization via Fischer-indole synthesis. Alkylation of 8(b–c) with different alkylating agents gave the title compounds 9(a–f). All the synthesized compounds were characterized by spectral data. The newly synthesized compounds 8(a–c) and 9(a–f) which possess a variety of N-substituents in both benzimidazole and indole moieties, were evaluated for their antimicrobial and anticancer activities. The results showed that compounds 9b, 9c, and 9d were active only against Gram-positive bacteria, and selective antibacterial activity was exhibited by compounds 8c and 8e against Staphylococcus aureus MLS-16 and Bacillus subtilis, respectively. Further, compounds 8a, 8b, 8c, 9a, 9e, and 9f showed significant anti-proliferative activity.

Microstructural and mechanical properties beta Titanium (β-Ti) weldments can be improved by grain refinement and formation of insoluble precipitates in the weld. This paper reports the effect of Boron (B) and Carbon (C) addition to Ti-15V-3Cr-3Sn-3Al (Ti-15-3) fillers on the microstructural and mechanical properties of Ti-15-3 gas tungsten arc weldments. X-ray diffraction and scanning electron microscopic analysis revealed the presence of β-Ti phase in the weldments prepared without the filler modification, while additional TiB and TiC phases are observed in the weldments prepared with fillers modified with B and C, respectively. B and C addition to the fillers has resulted in the grain refinement of the weldments and the grain size reduction is seen to be higher with the increasing B and C addition. The formation of TiB, TiC and growth restriction effect due to the presence of B and C in the filler resulted in the decreased grain size of the β-Ti weldments. Mechanical properties such as hardness and tensile strength improved as the amount of B and C addition increased. The improvement of mechanical properties is contributed by the grain refinement and the formation of TiB and TiC precipitates in weldments.

Microstructural development, post-weld ageing response and mechanical properties of gas tungsten arc and CO2 laser welded Al-6 %Cu (AA2219) alloy were investigated in the present study. The fusion zone of laser weld consists of three parts: the fine grains in the middle part, the columnar zone and equiaxed zone adjacent to fusion boundary. In contrast, fusion zone of gas tungsten arc weld consists of two parts: the columnar zone in the middle part and the equiaxed zone adjacent to fusion boundary. The size of the equiaxed grains in the fusion zone was the least in the laser welds when compared to gas tungsten arc welds. Laser welds have exhibited higher hardness, post weld ageing response, yield strength, ductility and fatigue strength when compared with gas tungsten arc welds. Fine equiaxed grain morphology and discontinues eutectic distribution in the laser weld fusion zone could be attributed to the improved tensile and fatigue properties of laser welded samples. ‘Thermal pinning effect’, due to non isothermal conditions, has arrested grain growth in heat affected zone in spite of temperatures close to the melting point of aluminum in heat affected zone.

AA5083 alloy is welded with gas tungsten arc welding using optimized welding parameters. Al-Si-Sc master alloy filler with varying contents of scandium is used for welding. Welding was carried out with and without AC-pulsed current techniques. A narrow heat affected zone with more refined grain structure is observed in the case of the pulsed current technique. Furthermore, it is observed that the columnar solidification structure in the fusion zone was suppressed and fine equiaxed grains were formed in the weld zone with increasing scandium content, which is attributed to the grain refinement effect of scandium with the generation of increased nucleating sites during weld solidification. This effect is reflected in mechanical properties also. An increased hardness of about 10 % results with pulsed current technique compared to about 20 % with an addition of 0.75 % scandium. However, in the case of tensile properties pulsing resulted in about 8 % increase in tensile strength and addition of 0.75 % scandium resulted in about 40 % increase in tensile strength. Both the pulsed current technique and the addition of scandium were observed to be better in increasing not only strength but also elongation due to the refined grain structure in the weld fusion zone.

Wear is one of the major problems faced in industry that reduces the life of industrial components and increases the operating costs. Therefore, hardfacing is widely employed by engineers to minimize components’ wear, in which single or multiple layers of hard material that mainly consists of carbides deposited on the base metal. However, these carbide-based materials suffer from solidification cracking due to lack of ductility. In this study, titanium carbide (TiC) reinforced alloy steel deposited using self-shielded flux cored arc welding technique. The microstructure and phase analysis in the hardfaced deposit by scanning electron microscope, energy dispersive x-ray and X-ray diffractometer revealed that the microstructure consists of finely distributed TiC within matrix of martensite and some retained austenite. Microhardness test and pin-on-disk wear test had shown that the clad deposit posses better hardness and wear resistance. Retained austenite formation and TiC precipitation were discussed in detail and correlated with the mechanical properties.

A multi-component nanocrystalline AlCrCuFeNiZn high entropy alloy with 12 nm crystallite size was successfully synthesized using high energy ball milling. The progress of solid solution formation during milling was analyzed using XRD. A major portion of the HEA is observed to be BCC in crystal structure after 30 h of milling. Thermal analysis showed that HEA powders exhibited exponential oxidation characteristics. Thermal analysis showed that low activation energy was sufficient to start recrystallization because of high energy stored in the milled powders. The crystallite size after consolidation is in nanocrystalline range due to the sluggish diffusion of atoms and nanotwinning. After consolidation, the crystallite size is around 79 nm. Samples sintered at 850 °C for 2 h exhibited high hardness values of 700 ± 15 HV1.0, major volume fraction of the phases are having FCC crystal structure along with a minor phase having BCC crystal structure. Due to positive enthalpy mixing of Cu with other elements, decomposition of BCC to new FCC phases occurs.

The refinement in weld metal grain size and shape results in both improved mechanical properties (ductility and toughness) as well as a significant improvement in weldability. In the present study, the influence of scandium (Sc) additions to the fillers on the structure and mechanical properties of AA6082 gas tungsten arc (GTA) weldments were investigated. Controlled amounts of scandium as grain refiner were introduced into the molten pool of AA6082 by pre-deposited cast inserts (AA4043 and AA5356) by GTA welding. Full penetration GTA welds were prepared using alternating current (AC). It was observed that grain size decreased with increasing amounts of scandium. The grain refinement is mainly caused by the Al 3 Sc particles, which act as heterogeneous nucleation of α-Al grains. It has been shown that welds prepared with AA5356 cast insert exhibited high strength and ductility when compared with other welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength and ductility. Post-weld aging treatment resulted in improved tensile strength and hardness of the weldments and this aging response could be attributed to the weld dilution from the base metal. The slow diffusion of Sc in Al matrix and stability of Al 3 Sc precipitates at elevated temperatures were suggested to be responsible for the improved high temperature yield strength of welds made from Sc modified fillers.

Dissimilar welds were prepared between 4 mm thick AA5083 and AA6061 sheets using Nd-YAG laser welding with different laser power, beam spot sizes and welding speeds. The results show that the temperature gradient and cooling rates play a major role in resultant microstructures of the weldments. Room temperature hardness and tensile properties of the weldments in the as-welded condition were studied and correlated with the microstructure. The microhardness examination showed that there was significant variation in hardness values at AA6061 side when compared with AA5083 side due to steeper temperature gradient. It has been observed that welds prepared with 3.5kW laser power, 3.5 m/min welding speed and 180 µm beam spot size exhibited highest tensile strength of 241 MPa.

Grain refinement of weld metal plays a vital role in improving mechanical properties (ductility and toughness) as well as weldability. The present study has investigated the influence of Tibor™ additions on the structure and mechanical properties of AA6082 gas tungsten arc (GTA) weldments. Controlled amounts of Tibor™ grain refiner (containing Ti and B in a ratio of 5:1) were introduced into the molten pool of AA6082 by pre-deposited cast inserts (AA4043 and AA5356) under different welding conditions by GTA welding. Full penetration GTA welds were prepared using alternating current (AC). It was observed that grain size was decreased with increasing amounts of Tibor™. The grain refinement is mainly caused grain nucleation associated with constitutional undercooling during solidification. It has been shown that welds prepared with 5356 cast insert exhibited high strength and ductility when compared with other welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength and ductility.

High strength AA2219 aluminum alloys have gathered wide acceptance in aeronautic and aerospace applications mainly due to their excellent mechanical properties, high corrosion resistance and good weldability. However, these alloys have poor as welded joint strength. The loss of strength is due to melting and quick resolidification, which renders all the strengthening precipitates to dissolve. One way of improving strength is through the modification of weld microstructures. The refinement of fusion zone microstructure helps in improving the mechanical properties of weld metal. The present study has investigated the influence of Tibor additions on the structure and mechanical properties of AA2219 gas tungsten arc (GTA) weldments. Full penetration GTA welds were prepared using alternating current (AC). It was observed that grain size was decreased with increasing amounts of Tibor. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness.

The present study has investigated the influence of scandium additions on the structure and mechanical properties of AA2219 gas tungsten arc (GTA) weldments. Controlled amounts of scandium modified AA2319 fillers were introduced into the molten pool of AA2219 by predeposited cast inserts under different welding conditions in GTA welding. Full penetration GTA welds were prepared using alternating current. It was observed that grain size decreased with increasing amounts of scandium and gradual transformation from columnar to equiaxed grain morphology. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, strength, and ductility. Room temperature hardness and tensile properties at different temperatures (room temperature, 100, 150, 200 and 250 °C) of weldments in the as-welded condition were observed and correlated with microstructure. The results show that the welds subjected to post-weld aging treatment have displayed superior hardness and tensile strength.

The current study has investigated the influence of alternating current pulsing on the structure and mechanical properties of AZ31 magnesium alloy gas tungsten arc (GTA) weldments. Autogenous full penetration bead-on-plate GTA welds were made under a variety of conditions including variable polarity (VP), variable polarity mixed (VPM), alternating current (AC), and alternating current pulsing (ACPC). AC pulsing resulted in significant refinement of weld metal when compared with the unpulsed conditions. AC pulsing leads to relatively finer and more equiaxed grain structure in GTA welds. In contrast, VP, VPM, and AC welding resulted in predominantly columnar grain structures. The reason for this grain refinement may be attributed to the periodic variations in temperature gradient and solidification rate associated with pulsing as well as weld pool oscillation observed in the ACPC welds. The observed grain refinement was shown to result in an appreciable increase in fusion zone hardness, tensile strength, and ductility.

CO2 laser welds were prepared on 3 mm thick sheets of continuous cast and rolled AZ31 magnesium alloy, using different welding speeds (3 m/min, 4 m/min and 5 m/min). The microstructure and composition analysis of weld metal was examined using optical and scanning electron microscopy (HR-SEM, EPMA and EDS/X). Room temperature hardness and tensile properties of the weldments in the as-welded condition were studied and correlated with the microstructure. The microstructure of fusion zone consists of two parts: the equiaxed zone in the middle part and the columnar zone adjacent to fusion boundary. It has been shown that the average width of columnar grains in the fusion zone is increased with decreasing the welding speed. Microstructural examination showed that the equiaxed grain size in the fusion zone was the least in the welds made using 5 m/min welding speed. It has been shown that welds prepared with 5 m/min welding speed exhibited increase in hardness, yield strength and ductility when compared with other welds.

The present study deals with the effect of beam oscillation technique using elliptical waveform on fatigue life of Ti–6Al–4V electron beam weldments. Autogenous full penetration bead-on-plate electron beam welds were made with and without beam oscillation. Some welds were subjected to post-weld heat treatment (PWHT) at two different temperatures (700 and 900 °C). Room temperature hardness, tensile properties and fatigue life of the weldments in the as-welded and PWHT conditions were studied and correlated with the microstructure. The beam oscillated weldments exhibited lower strength (hardness) compared to those made without beam oscillation. This was attributed to wider diffusional α plates in the beam oscillated welds due to lower cooling rates. The beam oscillated weldments exhibited inferior fatigue lives compared with unoscillated weldments owing to the presence of wider α platelets in the former. As the width of α platelets in the weldments subjected to PWHT at 700 °C was smaller than that in the weldments subjected to PWHT at 900 °C, they exhibited longer fatigue lives.

This paper deals with the influence of direct current pulsing on the microstructure, room temperature hardness and tensile properties at four different temperatures of tungsten inert gas (TIG) weldments of Ti–6Al–4V. Autogenous full-penetration bead-on-plate TIG welds were made with and without direct current pulsing. A few coupons were subjected to a post-weld heat treatment (PWHT) at 900 °C. Room temperature hardness and tensile properties at four different temperatures (25, 150, 300 and 450 °C) of the weldments in both as-welded and PWHT conditions were studied and correlated with the microstructure. Current pulsing resulted in slight refinement of prior β grains leading to higher hardness, tensile strength and ductility of weldments in the as-welded condition. The post-weld heat treatment at 900 °C resulted in improvement in ductility and reduction in strength of weldments (both unpulsed and pulsed) owing to more coarsening of α, reduction in defect density and decomposition of martensite to equilibrium α and β. Both pulsed and unpulsed weldments after PWHT exhibited almost the same values of strength and ductility. This may be attributed to the width of the α plates being almost the same in both welds.

The present study has investigated the influence of current pulsing on the structure and mechanical properties of Ti–6Al–4V tungsten inert gas (TIG) weldments. Autogenous full penetration bead on plate TIG welds were made with and without direct current pulsing. Microstructural observations and evaluation of hardness, tensile and fatigue properties of the weldments were made in different conditions: as welded and post-weld heat treatment (PWHT) conditions (PWHT was done at 700 and 900°C). Current pulsing resulted in slight refinement of prior β grains, leading to better tensile strength, ductility and fatigue lives of weldments in the as welded condition. In the case of weldments subjected to PWHTs, the pulsed weldments exhibited inferior fatigue lives compared with the unpulsed weldments. The PWHT done at 900°C resulted in inferior fatigue lives of weldments compared with that done at 700°C.

A 0.3C-CrMoV(ESR) steel is being developed primarily for making pressure vessels used for aerospace applications. Since it is important to understand the range of microstructures and mechanical properties that will be obtained in the heat affected zone of welds, the steel has been subjected to different austenitizing treatments (temperatures ranging from 925°C to 1250°C) followed by cooling at various rates to room temperature. It has been shown that the austenite grain size increased from about 10 to 250 μm as the austenitizing temperature is increased from 925°C to 1250°C (1 hr) and that the hardness, YS, UTS,% elongation and% reduction in area as well as CVN energy for 450°C tempered condition decrease as the austenitizing temperature is increased for all cooling rates (furnace cooling, air cooling, oil quenching, quenching and tempering at 450°C). This is attributed mainly to the increase in austenitic grain size. The ranges of microstructures that can be obtained in the heat-affected zone are massive ferrite, fine pearlite, upper as well as lower bainite and martensite. The Charpy impact energy for the oil-quenched steel tempered at 200°C, however, did not vary significantly with austenitizing temperature.

The present study investigated the influence of heptane and tin process control agents on cube milled Ti–6Al–4V + 0.5 Vol% TiC (Ti–6Al–4V–0.5TiC) powder. A smaller particle size and nar-row particle distribution was observed for Ti–6Al–4V–0.5TiC powder milled with heptane, while the powder milled with tin showed relatively larger particle size and broader particle distribution due to the cold welding of particles. Hcp phase was observed in the Ti–6Al–4V–0.5TiC powder milled with tin. The formation of fcc Ti(C, H)metastable phase with high lattice strain and interstitial content in Ti–6Al–4V–0.5TiC powder milled with heptane, resulted in higher hardness compared to the powder milled with tin.

Austenitic stainless steel AISI 304 coating was deposited over low carbon steel substrate by means of friction surfacing and the microstructural evolution was studied. The microstructural characterization of the coating was carried out by optical microscopy (OM), electron back scattered diffraction (EBSD), and transmission electron microscopy (TEM). The coating exhibited refined grains (average size of 5 ?m) as compared to the coarse grains (average size of 40 ?m) in as-received consumable rod. The results from the microstructural characterization studies show that discontinuous dynamic recrystallization (DDRX) is the responsible mechanism for grain evolution as a consequence of severe plastic deformation. � 2012 The Minerals, Metals & Materials Society and ASM International.

Resistance spot welds were prepared on 3. mm thick sheets of continuous cast and rolled AZ31 magnesium alloy. The microstructure and composition analysis of weld nugget, heat affected zone (HAZ) and base metal were examined using optical and scanning electron microscopy (HR-SEM and EDS/X). The resistance spot welded magnesium alloy joints consist mainly of weld nugget and HAZ. The nugget contains two different structures, i.e. the cellular-dendritic structure at the edge of the nugget and the equiaxed dendritic structure in the centre of the nugget. The structure transition is attributed to the changes of solidification conditions. In the HAZ, grain boundary melting occurred and grain boundaries became coarse. It has been shown that hardness reduction in the weld nugget and HAZ compared with base metal is evident due to dendritic microstructure and grain growth, respectively. The results showed that spot welded joints have failed in interfacial mode under torsion and te nsile-shear loading conditions. Digital image correlation during tensile-shear testing showed that low surface strains occur in the interfacial failure mode, because fracture and deformation happened primarily in the nugget area.

Vitiligo is an acquired disorder characterized by circumscribed depigmented macules devoid of identifiable melanocytes. Complex genetic, immunological, neural and self destructive mechanisms interplay in its pathogenesis. According to autocytotoxic hypothesis, oxidative stress has been suggested to be the initial pathogenic event in melanocyte degeneration.The aim of our investigation was to evaluate the role of oxidative stress by measuring levels of the antioxidant enzymes superoxide dismutase (SOD) and catalase (CAT) in lesional and normal skin of patients with vitiligo and in the skin of normal controls.We determined the activity of SOD in lesional and non-lesional skin and CAT in lesional skin only of 25 vitiligo patients and 25 controls by using the spectrophotometric assay and Aebi's method, respectively.There was statistically significant increase in the levels of SOD in vitiliginous and non vitiliginous skin of patient group compared to the control group (P0.001). No significant difference was found between the levels of SOD in lesional skin and non-lesional skin of vitiligo patients. The levels of CAT in the skin of patients were found to be significantly lower than those of controls (P0.001).There is increased oxidative stress in vitiligo as is indicated by high levels of SOD and low levels of CAT in the skin of vitiligo patients.