scholarly journals Microstructural Features and Ductile-Brittle Transition Behavior in Hot-Rolled Lean Duplex Stainless Steels

2020 ◽  
Vol 4 (1) ◽  
pp. 16 ◽  
Author(s):  
O. Takahashi ◽  
Y. Shibui ◽  
P.G. Xu ◽  
S. Harjo ◽  
T. Suzuki ◽  
...  
Keyword(s):  
Stainless Steels ◽  
Electron Backscatter Diffraction ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Duplex Stainless Steels ◽  
Brittle Transition ◽  
Ni Content ◽  
Microstructural Morphology ◽  
Hot Rolled ◽  
Backscatter Diffraction

The characteristics of texture and microstructure of lean duplex stainless steels with low Ni content produced through hot rolling followed by annealing were investigated locally with electron backscatter diffraction and globally with neutron diffraction. Then, the ductile–brittle transition (DBT) behavior was studied by Charpy impact test. It is found that the DBT temperature (DBTT) is strongly affected by the direction of crack propagation, depending on crystallographic texture and microstructural morphology; the DBTT becomes extremely low in the case of fracture accompanying delamination. A high Ni duplex stainless steel examined for comparison, shows a lower DBTT compared with the lean steel in the same crack propagating direction. The obtained results were also discussed through comparing with those of cast duplex stainless steels reported previously (Takahashi et al., Tetsu-to-Hagané, 100(2014), 1150).

Examination of the Orientation Relationships between the Main Phases of Duplex Stainless Steel by EBSD

2007 ◽  
Vol 537-538 ◽  
pp. 297-302
Author(s):  
Tibor Berecz ◽  
Péter János Szabó
Keyword(s):  
Stainless Steel ◽  
Duplex Stainless Steel ◽  
Stainless Steels ◽  
Electron Backscatter Diffraction ◽  
Duplex Stainless Steels ◽  
Alloying Elements ◽  
Orientation Relationships ◽  
Σ Phase ◽  
Electron Backscatter ◽  
Backscatter Diffraction

Duplex stainless steels are a famous group of the stainless steels. Duplex stainless steels consist of mainly austenitic and ferritic phases, which is resulted by high content of different alloying elements and low content of carbon. These alloying elements can effect a number of precipitations at high temperatures. The most important phase of these precipitation is the σ-phase, what cause rigidity and reduced resistance aganist the corrosion. Several orientation relationships have been determined between the austenitic, ferritic and σ-phase in duplex stainless steels. In this paper we tried to verify them by EBSD (electron backscatter diffraction).

Stainless Steels Sintered Form the Mixture of Prealloyed Stainless Steel and Alloying Element Powders

2011 ◽  
Vol 672 ◽  
pp. 165-170 ◽  
Author(s):  
Zbigniew Brytan ◽  
Marco Actis Grande ◽  
Mario Rosso ◽  
Róbert Bidulský ◽  
L.A. Dobrzański
Keyword(s):  
Mechanical Properties ◽  
Impact Energy ◽  
Stainless Steels ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Duplex Stainless Steels ◽  
Vacuum Furnace ◽  
Slow Cooling ◽  
Rapid Cooling ◽  
Plastic Properties

The aim of the presented paper is to describe the sintered duplex stainless steels manufactured in sinter-hardening process and their structural and mechanical properties. Duplex stainless steels were obtained through powder metallurgy starting from austenitic 316L or ferritic 410L prealloyed base powders by controlled addition of alloying elements powder. Prepared mixes were compacted at 700MPa and sintered in a vacuum furnace with argon backfilling at temperature of 1240°C for 1h. After sintering different cooling cycles were applied: rapid cooling (6°C/s) using nitrogen under pressure and slow cooling (0.1°C/s) with furnace in argon atmosphere. Produced sintered duplex stainless steels were studied by scanning and optical microscopy and EDS chemical analysis of microstructure components as well as X-ray analysis. Mechanical properties were studied through tensile and three-point bending tests and Charpy impact test. It was demonstrated that austenitic-ferritic microstructures with regular arrangement of both phases and absence of precipitates can be obtained with properly designed powder mix composition as well as sintering cycle with rapid cooling rate. Produced sintered duplex steels show good mechanical properties which depend on austenite/ferrite ratio in the microstructure and elements partitioning (Cr/Ni) between phases. The optimal mechanical properties were obtained for compositions based on ferritic 410L powder where the balanced distribution of α and γ is present and the tensile strength can reach value about 500MPa with 16% of elongation and impact energy about 120J. The precipitations of hard intermetallic σ-FeCr phase take place when sintering with slow cooling cycle what cause substantial decrease of plastic properties, including reduce of elongation to 7% and in particular decrease of impact energy to 68 J.

Crystallographic relations during decomposition of the ferritic phase by isothermal ageing of duplex stainless steel

2012 ◽  
Vol 46 (1) ◽  
pp. 135-141 ◽  
Author(s):  
Tibor Berecz ◽  
Peter J. Szabo
Keyword(s):  
Stainless Steels ◽  
Electron Backscatter Diffraction ◽  
Parent Phase ◽  
Duplex Stainless Steels ◽  
Σ Phase ◽  
Orientation Relations ◽  
Mathematical Expressions ◽  
Duplex Steel ◽  
Isothermal Ageing ◽  
Backscatter Diffraction

In highly alloyed and duplex stainless steels the range of alloying elements leads to many different phases precipitating at higher temperatures. Duplex stainless steels consist of almost equal ratios of austenite and ferrite, and between 923 and 1273 K the ferrite begins decomposing into secondary austenite (γ2) and the σ phase. Several orientation relations between the austenitic, ferritic and σ phases have been determined by other researchers. The calculation and testing of mathematical expressions for these orientations are important for a close understanding of changes in duplex steel hardness, ductility, and other qualitative measures imposed by annealing or heat ageing. The method described in this article also offers an approach for determining parent phase orientations from inherited orientations in other metallic microstructures. When the orientation relations of adjacent grains calculated from mathematical equations and those measured by electron backscatter diffraction were compared, naturally it was found that the average orientation differs less between grains that inherit matrix structure from common parents. However, it was also found that the degree of difference depended on the variants involved in the orientations. This phenomenon can be explained by features of the microstructure and decomposition of the ferritic phase: initially the microstructure contains only primary austenite (γ1) and ferrite, then after a while it contains [beside primary (γ1) austenite] increasing amounts of secondary (γ2) austenite and the σ phase, and decreasing amounts of ferrite. The presence of two variants of austenite makes it difficult to verify parent relations for secondary (γ2) austenites.

Influence of Specimen Geometry and Strain Rate on Ductile-Brittle Transition Characterisation of Reactor Pressure Vessel Steels Using the Small Punch Technique

2015 ◽  
Author(s):  
Jack Adams ◽  
Roger C. Hurst ◽  
J. Bryan Borradaile ◽  
Martin R. Bache
Keyword(s):  
Strain Rate ◽  
Health And Safety ◽  
Charpy Impact ◽  
Charpy Impact Test ◽  
Transition Curve ◽  
Charpy Test ◽  
Small Punch ◽  
Code Of Practice ◽  
Brittle Transition ◽  
Post Test

The small punch (SP) tensile test, originally developed for assessing the integrity of nuclear containments, has seen a renaissance in recent years with the introduction of a Code of Practice and a standardisation proposal. For nuclear applications, the extremely low volumes of material that are required allows specimens to be manufactured from quasi-destructive scoop samples, surveillance specimens or even previously tested Charpy specimens. The low volume of material also alleviates the health and safety requirements and the cost associated with testing active materials. By assessing the energy absorbed before fracture, it is possible to build an entire SP ductile-brittle transition curve using less material than is required for a single Charpy test. Small punch testing has been performed on SA 508-3 NESC-1 spinning cylinder material to establish ductile-brittle transition data, for comparison to that obtained by conventional Charpy impact test techniques. Multiple SP ductile-brittle transition curves have been constructed, building upon the framework of the existing Code of Practice. Novel geometries and associated machining techniques employed to incorporate notches into the surface of the SP specimen, and also the application of relatively high strain rates have been investigated. Post-test fractography illustrates the influence of both stress raising features and strain rate on small punch fracture behaviour.

Determining the orientation of parent β grain from one α variant in titanium alloys

2018 ◽  
Vol 51 (4) ◽  
pp. 1125-1132 ◽  
Author(s):  
Z. B. Zhao ◽  
Q. J. Wang ◽  
H. Wang ◽  
J. R. Liu ◽  
R. Yang
Keyword(s):  
Titanium Alloys ◽  
Habit Plane ◽  
Electron Backscatter Diffraction ◽  
Three Dimensional ◽  
Dimensional Structure ◽  
Plane Normal ◽  
Β Phase ◽  
Microstructural Morphology ◽  
Backscatter Diffraction ◽  
The Relationship

The relationship between the crystallographic orientation and habit plane normal of transformed α laths in titanium alloys is discussed according to the Burgers orientation relationship and the three-dimensional structure of the α lath. A new method (orientation–trace method) is developed to determine the orientation of the parent β phase using the orientation of the α lath, which was measured by electron backscatter diffraction, and the microstructural morphology of that α variant. This approach is validated in a near-α titanium alloy. Moreover, the habit plane normal direction of the transformed α lath can be obtained from the crystallographic orientations of the α lath itself and its parent β grain. The verification and the corresponding discussion show the reliability of this approach.

scholarly journals Ductile to Brittle Transition Behavior in Cast Duplex Stainless Steels

2014 ◽  
Vol 100 (9) ◽  
pp. 1150-1157 ◽  
Author(s):  
Osamu Takahashi ◽  
Morio Yabe ◽  
Yohei Shibui ◽  
Yo Tomota
Keyword(s):  
Stainless Steels ◽  
Duplex Stainless Steels ◽  
Brittle Transition ◽  
Transition Behavior ◽  
Ductile To Brittle Transition

Martensite Formation and Recrystallization Behavior in 17Mn0.06C2Si3Al1Ni TRIP/TWIP Steel after Hot and Cold Rolling

2013 ◽  
Vol 753 ◽  
pp. 185-190 ◽  
Author(s):  
Sara Silva Ferreira de Dafé ◽  
Débora Rezende Moreira ◽  
Mariana de Souza Matoso ◽  
Berenice Mendonça Gonzalez ◽  
Dagoberto Brandão Santos
Keyword(s):  
Cold Rolling ◽  
Electron Backscatter Diffraction ◽  
Total Elongation ◽  
Strain Induced Martensite ◽  
Work Hardening Rate ◽  
Rolled Condition ◽  
Hot And Cold Rolling ◽  
Hot Rolled ◽  
Hot Rolled Steel ◽  
Backscatter Diffraction

This work evaluates the evolution of the microstructure and its influence on the mechanical behavior of steel containing 17% Mn, 0.06% C, 2% Si, 3% Al, and 1% Ni after hot rolling at 1070°C, cold rolling with 44% reduction, and annealing at 700°C for different time periods. The resultant athermal, strain-induced martensite and austenite grains were analyzed by optical and scanning electron microscopy (SEM). The volume fractions of the g, e, and α’ phases of martensite were confirmed by X-ray diffraction, dilatometry, and SEM-electron backscatter diffraction (EBSD) techniques. It was found that cold reduction results in the formation of more a’ martensite. The Vickers microhardness values were higher for the cold-rolled condition and lower for recrystallized samples, as expected. However, this reduction is counterbalanced by the formation of athermal e and a’ martensite during the cooling process. The sizes of the recrystallized grains change exponentially during their growth and remain within 1–3 mm. The yield and tensile strength of the hot-rolled steel reach values close to 250 and 800 MPa, respectively, with a total elongation of 40%, which demonstrates the high work-hardening rate of the steel.

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