Characterization of a cold-rolled 2101 lean duplex stainless steel.

Duplex stainless steels (DSS) may be defined as a category of steels with a two-phase ferritic-austenitic microstructure, which combines good mechanical and corrosion properties. However, these steels can undergo significant microstructural modification as a consequence of either thermo-mechanical treatments (ferrite decomposition, which causes σ- and χ-phase formation and nitride precipitation) or plastic deformation at room temperature [austenite transformation into strain-induced martensite (SIM)]. These secondary phases noticeably affect the properties of DSS, and therefore are of huge industrial interest. In the present work, SIM formation was investigated in a 2101 lean DSS. The material was subjected to cold rolling at various degrees of deformation (from 10 to 80% thickness reduction) and the microstructure developed after plastic deformation was investigated by electron backscattered diffraction, X-ray diffraction measurements, and hardness and magnetic tests. It was observed that SIM formed as a consequence of deformations higher than ~20% and residual austenite was still observed at 80% of thickness reduction. Furthermore, a direct relationship was found between microstructure and magnetic properties.

Increasing the Corrosion Resistance in the UNS S32750 Super Duplex Steel Welded Joints through Hybrid GTAW-Laser Welding and Nitrogen.

The development of techniques to improve the welding of super duplex steels is necessary in order to ensure that the phase balance and properties of the material are not affected during this process. Hybrid arc-laser welding is a perfect combination of the advantages of both processes, producing deeper weld beads with more balanced phases than the pulsed laser process. Here, the objective was to improve the corrosion resistance of UNS S32750 weld beads by increasing the volumetric austenite percentage in the fusion zone (FZ) with a hybrid process of GTAW (gas tungsten arc welding) and pulsed laser Nd-YAG (neodymium-doped yttrium aluminum garnet). Welds were performed in bead on plate conditions with fixed laser parameters and a varying heat input introduced through the GTAW process. Additionally, welds within a nitrogen atmosphere were performed. After base metal characterization, an analysis of the FZ and heat affected zone were performed with optical microscopy, scanning electron microscopy and critical pitting tests (CPT). The synergy between the thermal input provided by the hybrid process and austenite-promoting characteristic of nitrogen led to a balanced volumetric austenite/ferrite fraction. Consequently, the results obtained in CPT tests were better than conventional welding processes, such as laser or GTAW solely.

Electroplastic Effect during Tension and Bending in Duplex Stainless Steel.

The deformation behavior of duplex stainless steel under tension and bending, accompanied by a pulsed current and when heated by an external source, is investigated. The stress-strain curves are compared at the same temperatures. The contribution to the decrease in flow stresses is greater when using a multi-pulse current at the same temperature, compared to external heating. This confirms the presence of an electroplastic effect. An increase in the strain rate by an order of magnitude reduces the contribution of the electroplastic effect from single pulses to the reduction in flow stresses by 20%. An increase in the strain rate by an order of magnitude reduces the contribution of the electroplastic effect from single pulses to the reduction in flow stresses by 20%. However, in the case of a multi-pulse current, the strain rate effect is not observed. Introducing a multi-pulse current during bending reduces the bending strength by a factor of two and the springback angle to 6.5.

Corrosion Resistance of GMAW Duplex Stainless Steels Welds.

The hydrocarbon industry constantly requires a better understanding of stainless-steel welding metallurgy. Despite the fact that gas metal arc welding (GMAW) is one of the most commonly employed welding processes in the petrochemical industry, the process is characterized by the presence of a high number of variables to control in order to obtain components that are dimensionally repeatable and satisfy the functional requirements. In particular, corrosion is still a phenomenon that highly affects the performance of the exposed materials, and special attention must be paid when welding is applied. In this study, the real operating conditions of petrochemical industry were reproduced through an accelerated test in a corrosion reactor at 70 °C for 600 h, exposing robotic GMAW samples free of defects with suitable geometry. The results show that, even if duplex stainless steels are characterized for being more corrosion resistant than other stainless steels, under these conditions it was possible to identify microstructural damage. In detail was found that the corrosion properties were strongly related to the heat input during welding and that the best corrosion properties can be obtained with the higher heat input.

Cryomilling of Isotope-Enriched Ti Powders for HIVIPP Deposition to Manufacture Targets for Nuclear Cross Section Measurement.

The realization of isotopically enriched Ti targets for nuclear cross-section measurements requires particular attention, from the starting material preparation up to the deposition technique. In this work, a cryomilling process was developed and optimized, aimed at reducing the size of 49,50Ti metal sponge as provided by the supplier (size up to 3 mm), to the optimal size of 10 µm, to fit the High Energy Vibrational Powder Plating technique used for target manufacturing. The optimization of the cryomilling protocol and the HIVIPP deposition using natTi material was thus performed. The scarce amount of the enriched material to be treated (about 150 mg), the need to obtain a non-contaminated final powder and a uniform target thickness of about 500 µg/cm2 were taken into account. The 49,50Ti materials were then processed and 20 targets of each isotope were manufactured. Both powders and the final Ti targets produced were characterized by SEM-EDS analysis. The amount of Ti deposited was measured by weighing, indicating reproducible and homogeneous targets, with an areal density of 468 ± 110 µg/cm2 for 49Ti (n = 20) and 638 ± 200 µg/cm2 for 50Ti (n = 20). The uniformity of the deposited layer was also confirmed by the metallurgical interface analysis. The final targets were used for the cross section measurements of the 49Ti(p,x)47Sc and 50Ti(p,x)47Sc nuclear reaction routes aimed at the production of the theranostic radionuclide 47Sc.

Advances in Duplex Stainless Steels.

Duplex stainless steels (DSSs) are a group of stainless steels characterized by a biphasic microstructure consisting of ferrite and austenite [...].

Three-dimensional modeling using x-ray shape-from-silhouette.

We present the application of the shape-from-silhouette technique to reconstruct the three-dimensional profile of ancient handworks from their x-ray absorption images. The acquisition technique is similar to tomography, since the images are taken all around the object while it is rotated. Some reference points are placed on a small and light structure corotating with the object, and are acquired on the images for calibration and registration. The reconstruction algorithm gives finally the three-dimensional appearance of the handwork. We present the analysis of a bronze pendant of VI-VII century B.C. (Venetic area, Italy) completely hidden by corrosion products. The three-dimensional reconstruction shows that the pendant is a very elaborated piece, with two embraced figures that were completely invisible at the excavation.

Influence of Electropulsing Treatments on Mechanical Properties of UNS S32750 Duplex Stainless Steel.

Prestrained at 5% and 15% duplex stainless steel UNS S32750 specimens have been subjected to electropulsing treatments with current density of 100 A/mm2 and 200 A/mm2 and 100 and 500 pulses for each current density value. Corrosion tests, X-ray diffraction, microhardness and residual stresses were collected before and after the electropulsing treatments. Tensile tests were performed after the electropulsing treatments in order to compare the mechanical response to reference tensile tests performed before pulsing treatments. Increase in fracture strain was observed after pulsing treatment in comparison to the reference tensile tests. A decrease in microhardness was also observed after electropulsing treatments for both degrees of prestrain. Electropulsing treatment almost eliminates the work-hardened state in the 5% prestrained specimens while partially recovered the 15% prestrained material increasing both uniform and fracture strain. Bulk temperature of the samples remained the same for all treatments duration. The effect are to be addressed to a combined effect of increase in atomic flux due to the electrical current and local joule heating in correspondence of crystal defects. Electropulsing treatment applied to metallic alloys is a promising technique to reduce the work hardening state without the need of annealing treatments in a dedicated furnace.

Investigation of Electroplastic Effect on Four Grades of Duplex Stainless Steels.

Since the late 1950s, an effect of electrical current in addition to joule heating on the deformation of metals called the Electroplastic Effect (EPE) has been known. It is used nowadays in the so-called Electrically Assisted Forming (EAF) processes, but the understanding of the phenomenon is not very clear yet. It has been found that EPE increases the formability of high stacking fault energy (SFE) materials, while low SFE materials reach fracture prematurely. Since Duplex Stainless Steels (DSSs) possess a microstructure consisting of two phases with very different SFE (low SFE austenite and high SFE ferrite) and they are widely used in industry, we investigated EPE on those alloys. Tensile tests at 5 A/mm2, 10 A/mm2 and 15 A/mm2 current densities along with thermal counterparts were conducted on UNS S32101, UNS S32205, UNS S32304 and UNS S32750. The DSS grades were characterized by means of optical microscopy, X-ray diffraction and their mechanical properties (ultimate tensile strength, total elongation, uniform elongation and yield stress). An increase in uniform elongation for the electrical tests compared to the thermal counterparts as well as an increase in total elongation was found. No differences were observed on the yield stress and on the ultimate tensile strength. Un uneven distribution of the current because of the different resistivity and work hardening of the two phases has been hypothesized as the explanation for the positive effect of EPE.

Nd: YAG Pulsed Laser Dissimilar Welding of UNS S32750 Duplex with 316L Austenitic Stainless Steel.

Duplex stainless steels (DSSs), a particular category of stainless steels, are employed in all kinds of industrial applications where excellent corrosion resistance and high strength are necessary. These good properties are provided by their biphasic microstructure, consisting of ferrite and austenite in almost equal volume fractions of phases. In the present work, Nd: YAG pulsed laser dissimilar welding of UNS S32750 super duplex stainless steel (SDSS) with 316L austenitic stainless steel (ASS), with different heat inputs, was investigated. The results showed that the fusion zone microstructure observed consisted of a ferrite matrix with grain boundary austenite (GBA), Widmanstätten austenite (WA) and intragranular austenite (IA), with the same proportion of ferrite and austenite phases. Changes in the heat input (between 45, 90 and 120 J/mm) did not significantly affect the ferrite/austenite phase balance and the microhardness in the fusion zone.

Use of different spectroscopic techniques in the analysis of Roman age wall paintings.

In this paper the analysis of samples of Roman age wall paintings coming from: Pordenone, Vicenza and Verona is carried out by using three different techniques: energy dispersive x-rays spectroscopy (EDS), x-rays fluorescence (XRF) and proton induced x-rays emission (PIXE). The features of the three spectroscopic techniques in the analysis of samples of archaeological interest are discussed. The studied pigments were: cinnabar, yellow ochre, green earth, Egyptian blue and carbon black.

Body fluid distribution in elderly subjects with congestive heart failure.

The aims of this study were to investigate body fluid changes in elderly patients suffering from congestive heart failure (CHF) and to identify the fluid measurement that best characterizes fluid overload states in CHF patients by comparison with normal hydration in the elderly. In a case-controlled experimental design, 72 elderly subjects (65-98 yr), 38 healthy and 34 with CHF, were studied. Total body water (TBW) and extracellular water (ECW) were determined by dilution methods; fat-free mass (FFM) and fat mass (FM) were determined by dual-energy X-ray absorptiometry (DEXA). In healthy subjects, the FFM hydration expressed as TBW% FFM (males 72.0 +/- 4.3 vs females 72.4 +/- 5.0%) and ECW% TBW (males 47.3 +/- 3.4 vs females 47.8 +/- 5.1) were similar in both genders. ECW in liters for FFM and for TBW (ECW% TBW), corrected for body weight, was greater in the group with CHF than in the control group, in both sexes. Among the relative fluid measures, only ECW% TBW [odds ratio (OR) 1.5] independently predicted fluid retention. Having an ECW% TBW greater than 50% corresponded to an OR of about 10. In conclusion, elderly patients suffering from CHF have a characteristic increase in body fluid levels, mainly affecting the extracellular compartment, and ECW% TBW is a useful indicator of fluid retention.

Surface characterization of a decarburized and nitrided steel.

This article describes the effects of surface controlled decarburization on the structure of a nitrided steel. Samples of quenched and tempered 40CrMo4 steel were decarburized by air heat treatment (800-900 degrees C) at different depths and submitted to gaseous nitriding. The microstructure of surface layers after decarburization and nitriding were investigated by optical (OM) and scanning electron microscopy (SEM). The nitrogen and carbon profiles in the diffusion layers were determined by a scanning electron microscope equipped with a wavelength dispersive spectrometer (EPMA-WDS). The effect of nitriding was determined by microhardness measurements. The increasing of time and temperature of decarburization slightly affect the surface hardness values, while case hardness depths decrease. In all the specimens, the nitriding depth, as determined by the WDS nitrogen profile, is larger than the one determined by the hardness profile.

Changes in fluid compartments and body composition in obese women after weight loss induced by gastric banding.

BACKGROUND/AIMS: Surgical gastric banding procedures induce considerable and rapid weight losses in obese subjects. Nevertheless changes in lean mass and body fluids following these surgical treatments are not well known. METHODS: We studied 6 obese women aged 38-42 years, before, and 8 and 24 weeks after laparoscopic adjustable silicone gastric banding (LAP-BAND(TM)). Fat-free mass (FFM) and fat mass (FM) were investigated using dual energy X-ray absorptiometry (DEXA), while total body water (TBW) and extracellular water (ECW) were assessed by dilution methods. RESULTS: The subjects showed a total weight loss of 16% of initial weight; the weight reduction was greater during the first 8 weeks. FFM decrease after 24 weeks was very limited and represented only 14% of the weight loss. The mean FFM changes per week were similar in the two periods of observation (0-8 and 8-24 weeks after LAP-BAND). TBW showed a global reduction of 2.2 +/- 1.8 litres mainly due to a decline in intracellular water (ICW), while ECW remained constant during weight loss. As a consequence, the ECW/ICW ratio increased after LAP-BAND. CONCLUSION: LAP-BAND seems to achieve satisfactory weight losses while sparing FFM and causing only mild body fluid alterations.