Maria J. R. Sandim

• PhD
• Professor (Assistant) at University of São Paulo

We followed the microstructural evolution of UNS S32205 duplex stainless steel during cold rolling up to 79% reduction in thickness and at early stages of isothermal annealing at 1080ºC. Qualitative analysis of peak broadening and kernel average misorientation (KAM) parameter obtained by X-ray diffraction (XRD) and electron backscatter diffraction...

AISI 317 L stainless steel replaces 316 L grade in some applications due to its superior mechanical strength and corrosion resistance. Aiming at expanding its applicability to structural applications, ongoing studies are dedicated to overcoming the trade-off between strength and ductility. The stacking fault energy decreases with deformation temper...

A novel additive manufacturing approach is proposed to produce an electrical steel (Fe-3.5%Si) by laser powder bed fusion (LPBF) followed by conventional thermomechanical processing. The aim of this proof-of-concept study is to develop a new processing route for grain-oriented electrical steels from LPBF-processed plates with strong texture and SiO...

Austenite reversion, i.e., a’-martensite → γ phase transformation in UNS S32304 lean duplex steel was investigated. The material was cold rolled to a true strain (e) of 1.61 and subjected to a continuous annealing up to 1000 °C with a heating rate of 3 °C/min. From the dilatometric curve, an unexpected thermal expansion at around 545 °C was found w...

The annealing behavior of cold-rolled 317L austenitic stainless steel was investigated. The material was rolled to a true strain (ε) of 2.04 and subjected to both stepwise and continuous annealing up to 1000°C, the latter conducted in the presence of an external magnetic field. Electron backscatter diffraction, dilatometry, thermodynamic calculatio...

A R T I C L E I N F O Keywords: Lean duplex steel Strain-induced martensite Austenite reversion Magnetic properties Microstructural evolution A B S T R A C T Strain-induced α′-martensite and austenite reversion in a cold rolled UNS S32304 lean duplex steel were tracked by means of magnetic measurements, with emphasis on both M s (saturation magneti...

Strain partitioning and localization were investigated in a high-Mn steel (17.1 wt.% Mn) during tensile testing by a correlative probing approach including in-situ synchrotron X-ray diffraction, micro- digital image correlation (μ-DIC) and electron microscopy. By combining Warren's theory with the μ-DIC analysis, we monitored the formation of plana...

The presence of δ-ferrite in 316L stainless steel powder reused several times contributes to structural defect formation in selective laser melted parts built using the pin support structure. The virgin 316L stainless steel powder is fully austenitic. After several powder reuse cycles, reused powder has a finer particle size and about 6 vol. % of δ...

In situ synchrotron X-ray diffraction was used to track real-time austenite reversion in AISI 201 austenitic stainless steel deformed to a true strain of 0.34 under tensile testing. The deformed material was continuously annealed from 100 °C up to 800 °C at a heating rate of 0.05 °C s −1. Phase changes and microstrain partitioning were evaluated by...

The formation of submicron structural defects within austenite (γ), ε-and α′-martensite during cold rolling was followed in a 17.6 wt.% Mn steel. Several probes, including XRD, EBSD, and ECCI-imaging, were used to reveal the complex superposition of the strain hardening mechanisms of these phases. The maximum amount of ε-martensite is observed at a...

Austenite (g) reversion in a cold-rolled 17.6 wt.% Mn steel was tracked by means of dilatometry and in-situ magnetic measurements during slow continuous annealing. A splitting of the g-reversion into two stages was observed to be a result of strong elemental partitioning between g and a 0-martensite during the low temperature stage between 390 and...

Austenite (g) reversion in a cold-rolled 17.6 wt.% Mn steel was tracked by means of dilatometry and in-situ magnetic measurements during slow continuous annealing. A splitting of the g-reversion into two stages was observed to be a result of strong elemental partitioning between g and a 0-martensite during the low temperature stage between 390 and...

Strain-induced martensite (SIM) formation was evaluated upon cold-rolling of a 17.6 wt.%Mn-TRIP steel by means of magnetic measurements, X-ray diffraction, and high-resolution electron backscatter diffraction (EBSD). α′-martensite formation was observed to be dependent on the presence of prior ε-martensite. Upon deformation, the coercivity of the f...

Oxide dispersion strengthened ODS-Eurofer steel is a promising candidate for structural applications in future nuclear fusion reactors. Samples of 9Cr-ODS-Eurofer steel were cold rolled up to 80% thickness reduction and annealed up to 1350 °C for 1 h. The microstructural changes of the annealed samples were followed by magnetic measurements taken a...

Strain partitioning and texture evolution of AISI 201 austenitic stainless steel were investigated upon cold rolling up to a true strain of ε = 0.92. ε-martensite formation is the main work hardening mechanism at low strains (ε = 0.11). With increasing strain, the volume fraction of α’-martensite increases with a sigmoidal-like behavior. Remaining...

The AISI 317L stainless steel is an austenitic grade with at least 3%Mo. Recently, this steel has replaced AISI 316L in many applications in chemical and petrochemical industries, due to its higher pitting corrosion resistance. The microstructure of the hot rolled and annealed material studied in this work consists of austenitic grains and 4.0% of...

Oxide-dispersion strengthened (ODS) Eurofer steel is targeted for structural applications in future fusion nuclear reactors. Samples were cold rolled down to 80% reduction in thickness and annealed at 1350 C up to 8 h. The microstructural characterization was performed using Vickers microhardness testing, electron backscatter diffraction, scanning...

In situ neutron diffraction experiments were performed to follow the annealing behavior of iron deformed by equal-channel angular pressing at room temperature using route B c to a total von Mises strain of ε vM = 9.2. The temperature was varied from room temperature to 1223 K (950 °C), while neutron diffraction data for quantitative texture analysi...

In recent years the microstructure, mechanical and magnetic properties of Eurofer-97 steel are studied intensively due to its application in nuclear fusion power plants. Its microstructure is usually accessed by means of electron microscopy. Here we present an alternative approach utilizing Atomic Force Microscopy (AFM) to study as-received Eurofer...

O bom desempenho mecânico do aço inoxidável supermartensítico (AISM) depende fortemente da fração volumétrica de austenita retida a temperatura ambiente. Este trabalho visou analisar o efeito da variação das temperaturas de revenimento secundário em um AISM na quantificação das fases por difração de Raios X (método de Rietveld) e magnetização de sa...

Reduced-activation ferritic–martensitic steels are promising candidates for structural applications in future nuclear fusion power plants. Oxide dispersion strengthened ODS-Eurofer and Eurofer 97 steels were cold rolled to 80% reduction in thickness and annealed in vacuum for 1 h from 200 to 1350 °C to evaluate both their thermal stability and magn...

Atom probe tomography was used to characterize the A15 phase in a bronze-route Nb3Sn superconducting wire with a bronze matrix composition of Cu–8Sn–0.3Ti (in at.%). We observed depletion of niobium and segregation of Cu and Ti atoms at Nb3Sn grain boundaries. While the Nb depletion is about 15% relative to the grain interior, the average ratio bet...

High-resolution electron backscatter diffraction (EBSD) technique and DC magnetization were used to characterize a Cu-Nb reinforced bronze route Nb3Sn superconducting multifilamentary wire. The results of DC-magnetization show an extended regime of magnetic reversibility in the operational magnetic field-temperature phase diagram. This observation...

Oxide dispersion strengthened reduced-activation ferritic-martensitic steels are promising candidates for applications in future fusion power plants. Samples of a reduced activation ferritic-martensitic 9 wt.%Cr-oxide dispersion strengthened Eurofer steel were cold rolled to 80% reduction in thickness and annealed in vacuum for 1 h from 200 to 1350...

The paramagnetic Meissner effect (PME) is related to the appearance of a positive magnetization when a superconducting specimen is field cooled through its critical temperature. In this work we report on the PME and ac magnetization in roll-bonded Cu–Nb (RB/Cu–Nb) layered composites. We present typical DC magnetization loops obtained in the normal...

High-resolution electron backscatter diffraction was used to characterize a Nb3Sn-based superconducting multifilamentary wire produced by the bronze method. The niobium core has a clear <1 1 0> fiber texture in the wire axis direction. The Nb3Sn crystals also show a slight preference for the <1 1 0> direction parallel to the wire axis. The misorien...

Polycrystalline iron was deformed by eight ECAE passes using the route Bc to a total strain of 9.2. After deformation the material was annealed at temperatures up to 800oC. Scanning electron microscopy (SEM) and high-resolution electron backscatter diffraction (EBSD) were used to characterize both deformed and annealed structures. In the as-deforme...

In this work the recrystallization of the ABNT 1015 steel deformed by equal channel angular extrusion (ECAP) was reported. The corresponding von Mises equivalent strain (?vM) of the material, after one unique ECAP pass was 0.67. After deformation the material was annealed (under vacuum) at several temperatures up to 800°C. The microstructural chara...

The study of deformation properties of low carbon steels is of particular interest because of their many technological applications. Obtaining fine grained Fe based materials can be approached by one of the several available Severe Plastic Deformation (SPD) techniques. The current paper shows experimental data and simulations of the deformation pro...

In this work we focus on the microstructural and magnetic characterization of wires with different architectures (design and reinforcement). The microstructural characterization was performed using scanning electron microscopy. AC magnetic susceptibility was measured with field applied both parallel and perpendicular to the wire axis. The heat trea...

Superconducting Nb–Ti and NbTa–Ti wires produced by solid-state diffusion were studied, correlating microstructural and transport properties. The most interesting result is that the diffusion layer sharp composition variation is an important source of pinning in these materials. Within this scenario, we suggest that the source of pinning centers in...

In this work we report about the temperature dependence of the characteristic supercurrent (I-0) predicted by the two-fluid model for granular superconductors. The results show that I-0 saturates at zero temperature limit and vanishes at the intergranular critical temperature, the temperature below which superconducting clusters are connected via t...

We have measured transport properties at low temperatures for the granular Sm1.82Ce0.18CuO4-d samples belonging to the family of electron-doped superconductors. The effect of applied electrical current on the resistive behavior is investigated. The experimental data are analyzed using a modified form of the theory for a field-tuned superconductor-i...

Six practical composite wires of Nb3Sn (Furukawa Electric Co, Ltd) with different architectures (design and reinforcement) were compared from the normal state resistance R, critical temperatures Tconset, Tcoffset and ΔTc, upper critical field Bc2 (at 4.2 K) and critical current density Jc points of view. Wires were as follows: three of near-the-edg...

We report on the application of the Resistively Shunted Junction (RSJ) model to granular high-TC superconductors. Some derived predictions of the RSJ model are applied to a set of superconducting granular samples which can be considered as a network of Josephson junctions. The investigated samples belong to both hole-doped Y1-xPrxBa2Cu3O7-d (x = 0....

A two-fluid model is proposed to describe the transport properties of granular superconductors. Using the resistively shunted junction model and some aspects of the two-level system theory, a statistical model is developed which takes into account the ratio between the number of normal electrons and Cooper pairs carrying the applied current. The th...

We report on the influence of the microstructure on the AC and DC magnetic properties of Cu–3.5% Nb nanofilamentary wires. Samples obtained from a single Cu–3.5% Nb wire were subsequently submitted to different plastic strain levels via drawing so that their microstructure was altered. Noticeable differences are observed in their isothermal DC magn...

The present work presents the steps for the manufacture of an Nb–Ti artificial pinning centre (APC) multifilament wire for AC applications. The wire production starts from a Ti bar inserted in a Nb tube. The superconductor Nb–Ti alloy was obtained using heat treatments during the wire production steps through the growth of the diffusion layer betwe...

The influence of the structural quality of a normal metal–superconductor interface on the strength of the proximity effect is studied for the cylindrical geometry of bulk Cu–Nb multifilamentary composite samples. In as-drawn Cu–Nb samples the superconducting properties induced to the Cu matrix due to its proximity with Nb filaments are manifested i...

We report on the microstructure evolution in Cu-15% Nb multifilamentary wires upon annealing and the corresponding effects on their electrical and magnetic properties. During annealing at temperatures higher than 800degC thermal instability mechanisms take place in the microstructure of the Cu-15%Nb composite, leading to spheroidization, followed b...

We report on the application of the Resistively Shunted Junction (RSJ) model to granular high-TC superconductors. Some derived predictions of the RSJ model are applied to a set of superconducting granular samples which can be considered as a network of Josephson junctions. The investigated samples belong to both hole-doped Y1-xPrxBa2Cu3O7-d (x = 0....

A two-fluid model is proposed to describe the transport properties of granular superconductors. Using the resistively shunted junction model and some aspects of the two-level system theory, a statistical model is developed which takes into account the ratio between the number of normal and superconducting electrons carrying the applied current. The...

We report on the influence of the microstructure on the AC and DC magnetic properties of Cu–3.5% Nb nanofilamentary wires. Samples obtained from a single Cu–3.5% Nb wire were subsequently submitted to different plastic strain levels via drawing so that their microstructure was altered. Noticeable differences are observed in their isothermal DC magn...

We report on the microstructural evolution in Cu15%Nb multifilamentary wires upon annealing and the corresponding effects on their magnetic properties. During annealing at temperatures higher than 800 °C thermal instability mechanisms take place in the microstructure of the Cu15%Nb composite, leading to the spheroidization of niobium filaments. Ano...

We report on the annealing effects on the microstructure, electrical, and magnetic properties of jelly-rolled Cu –xvol %Nb (x = 25, 33, 50, 63) composite wires, a promising material to be used in high-field magnets. During annealing at temperatures as high as 850 °C, noticeable changes take place in the microstructure, including recovery and recry...

We report the microstructural evolution of a Cu–15%Nb composite annealed from 100 to 1050 °C. The microstructure was characterized by scanning electron microscopy (SEM) and high-resolution electron backscatter diffraction (EBSD). Boundary splitting is the predominant mechanism to explain the spheroidization of niobium. A simple model describing thi...

We report on transport properties of granular Sm1.83Ce0.17CuO4−y superconductors belonging to the dielectric side of the superconductor–insulator transition. This compound has a small superconducting volume fraction and can be described by a collection of superconducting islands embedded in an insulating matrix. We have performed measurements of ma...

We report on the influence of the filament morphology on the magnetic properties of a multifilamentary Cu 15vol% Nb composite. Vacuum annealing was performed in 0.6-mm diameter conductors in the 300-1050 °C temperature range, for 1-32 h. During annealing at high temperatures, e.g. T>700 °C, noticeable changes take place in the microstructure, inclu...

In this paper, the annealing effects on the microstructure and electrical resistivity of jelly-rolled Cu-x% vol. Nb (x=25, 33, 50, and 63) composite wires were investigated. During annealing, noticeable changes take place in the microstructure, including recovery and recrystallization of copper and niobium, followed by spheroidization and further c...

In this paper, the annealing effects on the magnetic properties of a multifilamentary Cu–15vol%Nb composite were investigated. During vacuum annealing, noticeable changes take place in the microstructure, mostly the partial spheroidization and further coarsening of the niobium filaments. Results show that spheroidization becomes noticeable at about...

In this paper, annealing effects on the electrical and superconducting properties of a multifilamentary Cu-Nb composite were investigated. During annealing, noticeable changes in the microstructure take place, in special those related to recovery and recrystallization of copper and niobium followed by spheroidization and further coarsening of the N...

We have performed measurements of electrical resistance, /R(T), and magnetoresistance, /R(T,H), in applied magnetic fields H up to 18 T in granular samples of the electron-doped superconductor Sm1.83Ce0.17CuO4-y. These samples have a small superconducting volume fraction, bellow the percolation threshold, and can be described by a collection of sup...

We report on intergranular transport properties of polycrystalline samples of Sm1.82Ce0.18CuO4−y exhibiting the double resistive superconducting transition. These samples are comprised of small islands which undergo a superconducting transition at a higher temperature Tci∼21 K and the long-range phase coherence is achieved through Josephson couplin...

We have studied the magnetic and transport properties of granular samples of the electron-doped superconductor Sm1.83Ce0.17CuO4-y prepared under certain conditions. Measurements of magnetic susceptibility, electrical resistance and magnetoresistance in applied magnetic fields up to 8.8 T reveal that superconductivity develops below Tci ~ 17.5 K in...

This paper presents the main results and the stage of some projects related to superconductor magnets that employs Niobium and its alloys, developed at the Department of Materials Engineering, Faculty of Chemical Engineering at Lorena - SP (FAENQUIL). Analytical and numerical methods used for magnetic fields and mechanical stresses calculations in...

Neste trabalho foram realizadas medidas de transporte em campos magnéticos aplicados no intervalo 0 '<OU =' H '<OU =' 18 T em supercondutores granulares 'Sm IND. 2-X''Ce IND. X''CuO IND. 4-Y', X = 0.17 e 0.18, constituídos de ilhas supercondutorasembutidas em uma matriz isolante e pertencentes a uma transição do tipo supercondutor-isolante (SI). Am...