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Author

Angelo Fernando Padilha

Other affiliations: Swansea University
Bio: Angelo Fernando Padilha is an academic researcher from University of São Paulo. The author has contributed to research in topics: Recrystallization (metallurgy) & Austenite. The author has an hindex of 27, co-authored 153 publications receiving 2876 citations. Previous affiliations of Angelo Fernando Padilha include Swansea University.


Papers
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Journal ArticleDOI
TL;DR: In this article, the decomposition of austenite in austenitic stainless steels is reviewed in detail including nucleation sites and orientation relationships and the influence of several factors such as composition, previous deformation and solution annealing temperature.
Abstract: Austenitic stainless steels are probably the most important class of corrosion resistant metallic materials. In order to attain their good corrosion properties they rely essentially on two factors: a high chromium content that is responsible for the protective oxide film layer and a high nickel content that is responsible for the steel to remain austenitic. Thus the base composition is normally a Fe-Cr-Ni alloy. In practice the situation is much more complex with several other elements being present, such as, Mo, Mn, C, N among others. In such a complex situation one almost never has a single austenite phase but other phases invariably form. Those phases are, with few exceptions, undesirable and they can be detrimental to the corrosion and mechanical properties. It is therefore of considerable importance to study the formation of such phases. In this work the decomposition of austenite in austenitic stainless steels is reviewed in detail. First the binary equilibrium diagrams relevant to the system Fe-Cr-Ni are briefly presented as well as other diagrams, such as the Schaeffler diagram, that traditionally have been used to predict the phases present in these steels as a function of composition. Secondly the precipitation of carbides and intermetallic phases is presented in detail including nucleation sites and orientation relationships and the influence of several factors such as composition, previous deformation and solution annealing temperature. Next, the occurrence of other constituents such as nitrides, sulfides and borides is discussed. TTT diagrams are also briefly presented. Finally the formation of martensite in these steels is discussed.

378 citations

Journal ArticleDOI
TL;DR: The evolution in the understanding of the recrystallization phenomena is summarized in this article, where the main developments concerning recrestallization are presented from a historical perspective, as well as definitions and concepts involving recrasing are presented regarding it as a solid-state reaction that occurs by nucleation and growth.
Abstract: The evolution in the understanding of the recrystallization phenomena is summarized in this paper. Initially the main developments concerning recrystallization are presented from a historical perspective. Definitions and concepts involving recrystallization are presented regarding it as a solid-state reaction that occurs by nucleation and growth. The recrystallization nucleation mechanisms are subsequently discussed. Finally, the growth step is highlighted, emphasizing boundary and sub-boundary mobilities and the forces acting on the high angle grain boundaries that sweep the microstructure during recrystallization.

244 citations

Journal ArticleDOI
TL;DR: In this paper, the authors reviewed the phenomena involved during the annealing of cold worked austenitic stainless steels, with special emphasis on the formation of deformation induced martensites.
Abstract: This article reviews the phenomena involved during the annealing of cold worked austenitic stainless steels Initially the cold worked state is discussed, with special emphasis on the formation of deformation induced martensites Following, the phenomena of martensite reversion, recovery, recrystallization and grain growth are discussed The interactions between primary recrystallization and precipitation and between precipitate dissolution and secondary recrystallization are dealt with in detail Finally, the textures resulting from hot and cold working, and from primary and secondary recrystallization, are presented

241 citations

Journal ArticleDOI
TL;DR: In this paper, the authors investigated the precipitation of intermetallic phases, especially the chi-phase, in a 45N (type UNS S31803) duplex stainless steel through aging heat-treatments carried out at 700 and 750°C.

173 citations

Journal ArticleDOI
TL;DR: In this article, the sigma phase precipitation of three stainless steels: austenitic type 316L (17Cr−12Ni−2·5Mo, wt-%), superferritic type DIN W. Nr. 1·4575 (Nb−28Cr−4Ni-2Mo, Wt-%) and duplex type Din W.Nr.1·4462 or UNS S31803 (22Cr−5·5Ni-3Mo-0·14N, wT-%).
Abstract: The present work studies, in a comparative manner, the sigma phase precipitation of three stainless steels: austenitic type 316L (17Cr–12Ni–2·5Mo, wt-%), superferritic type DIN W. Nr. 1·4575 (Nb–28Cr–4Ni–2Mo, wt-%) and duplex type DIN W. Nr. 1·4462 or UNS S31803 (22Cr–5·5Ni–3Mo–0·14N, wt-%). In austenitic stainless steel, the formation of sigma phase occurred both at austenite grain boundaries and inside delta ferrite islands. In superferritic stainless steel, sigma phase occurred both at grain boundaries and in the grain interior. In the ferrites, both in the duplex and in the austenitic steel, sigma phase formation occurred by eutectoid reaction ferrite→sigma + austenite. The tendency towards precipitation of the sigma phase in the three types of steel investigated can be placed in the following sequence: duplex>superferritic>austenitic.

167 citations


Cited by
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Journal ArticleDOI
01 Apr 1988-Nature
TL;DR: In this paper, a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) is presented.
Abstract: Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

9,929 citations

Journal ArticleDOI
Abstract: This article presents an overview of the developments in stainless steels made since the 1990s. Some of the new applications that involve the use of stainless steel are also introduced. A brief introduction to the various classes of stainless steels, their precipitate phases and the status quo of their production around the globe is given first. The advances in a variety of subject areas that have been made recently will then be presented. These recent advances include (1) new findings on the various precipitate phases (the new J phase, new orientation relationships, new phase diagram for the Fe–Cr system, etc.); (2) new suggestions for the prevention/mitigation of the different problems and new methods for their detection/measurement and (3) new techniques for surface/bulk property enhancement (such as laser shot peening, grain boundary engineering and grain refinement). Recent developments in topics like phase prediction, stacking fault energy, superplasticity, metadynamic recrystallisation and the calculation of mechanical properties are introduced, too. In the end of this article, several new applications that involve the use of stainless steels are presented. Some of these are the use of austenitic stainless steels for signature authentication (magnetic recording), the utilisation of the cryogenic magnetic transition of the sigma phase for hot spot detection (the Sigmaplugs), the new Pt-enhanced radiopaque stainless steel (PERSS) coronary stents and stainless steel stents that may be used for magnetic drug targeting. Besides recent developments in conventional stainless steels, those in the high-nitrogen, low-Ni (or Ni-free) varieties are also introduced. These recent developments include new methods for attaining very high nitrogen contents, new guidelines for alloy design, the merits/demerits associated with high nitrogen contents, etc.

1,668 citations

01 Jan 2016

1,664 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarized recent research dealing with development of titanium dioxide (TiO2) used for environmental applications and suggested new research directions, including preparation aspects for the development of this promising material.
Abstract: This paper summarizes recent research dealing with development of titanium dioxide (TiO2) used for environmental applications. TiO2 plays the most important role owing to its excellent chemical and physical properties. However, the TiO2 band edge lies in the UV region that makes them inactive under visible irradiation. In this regard, considerable efforts have been made to increase the visible light activity of TiO2 via the modification of its electronic and optical properties. Doping TiO2 using either anions or cations is one of the typical approaches that has been largely applied. Coupling TiO2 with a narrow bad gap semiconductor (MxOy/TiO2 or MxSy/TiO2) represents another approach. This work aims to encompass the new progress of TiO2 for an efficient application in water and wastewater treatment under visible light, emphasizes the future trends of TiO2 in the environment, and suggests new research directions, including preparation aspects for the development of this promising material.

1,281 citations

Journal ArticleDOI
TL;DR: The dynamic recrystallization (DRX) phenomena occurring in different thermo-mechanical processing (TMP) conditions for various metallic materials are reviewed in this article.

1,177 citations