Online Martensite Measurement During Tensile Tests of Metastable Austenitic Steels

2006 ◽  
pp. 166-170
Author(s):  
Tobias Balmer ◽  
Markus Pfister
Keyword(s):  
Tensile Tests ◽  
Austenitic Steels

scholarly journals Stacking Fault Energy in Relation to Hydrogen Environment Embrittlement of Metastable Austenitic Stainless CrNi-Steels

Metals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 1170
Author(s):  
Robert Fussik ◽  
Gero Egels ◽  
Werner Theisen ◽  
Sebastian Weber
Keyword(s):  
Phase Transformation ◽  
Intermediate Stage ◽  
Tensile Tests ◽  
Stacking Fault ◽  
Hydrogen Gas ◽  
Stacking Fault Energy ◽  
Austenitic Steels ◽  
Aisi 304L ◽  
Hydrogen Environment ◽  
Gas Atmosphere

Metastable austenitic steels react to plastic deformation with a thermally and/or mechanically induced martensitic phase transformation. The martensitic transformation to α’-martensite can take place directly or indirectly via the intermediate stage of ε-martensite from the single-phase austenite. This effect is influenced by the stacking fault energy (SFE) of austenitic steels. An SFE < 20 mJ/m2 is known to promote indirect conversion, while an SFE > 20 mJ/m2 promotes the direct conversion of austenite into α’-martensite. This relationship has thus far not been considered in relation to the hydrogen environment embrittlement (HEE) of metastable austenitic CrNi steels. To gain new insights into HEE under consideration of the SFE and martensite formation of metastable CrNi steels, tensile tests were carried out in this study at room temperature in an air environment and in a hydrogen gas atmosphere with a pressure of p = 10 MPa. These tests were conducted on a conventionally produced alloy AISI 304L and a laboratory-scale modification of this alloy. In terms of metal physics, the steels under consideration differed in the value of the experimentally determined SFE. The SFE of the AISI 304L was 22.7 ± 0.8 mJ/m2 and the SFE of the 304 mod alloy was 18.7 ± 0.4 mJ/m2. The tensile specimens tested in air revealed a direct γàα’ conversion for AISI 304L and an indirect γàεàα’ conversion for 304mod. From the results it could be deduced that the indirect phase transformation is responsible for a significant increase in the content of deformation-induced α’-martensite due to a reduction of the SFE value below 20 mJ/m2 in hydrogen gas atmosphere.

The Change of the Structure and Mechanical Properties of the Austenitic Steels after Exposure at the Critical Temperature

2017 ◽  
Vol 891 ◽  
pp. 330-334 ◽  
Author(s):  
Šárka Stejskalová ◽  
Ladislav Kander ◽  
Šárka Hermanová
Keyword(s):  
Mechanical Properties ◽  
Critical Temperature ◽  
Thermal Exposure ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
Small Punch Test ◽  
Bend Radius ◽  
Small Punch ◽  
Σ Phase ◽  
Punch Test

The paper deals with the change of the structure and mechanical properties of the austenitic steels after the exposure at the critical temperature. The effects of the bend radius of tubes including effect of solution annealing on the mechanical properties and the structure were studied. The mechanical properties were studied using small punch test (SPT) and miniaturized tensile tests. From the results can be concluded that the mechanical properties and the structure have been influenced due to one year exposure at the working temperature significantly. Various amounts of σ-phase were found in the pulled part of the bend side of the tubes even after only thermal exposure without any loading. The effect of the heat treatment and the bend radius on the mechanical properties and the structure was also evident. Drop in fracture energy due to the presence of the σ-phase in the structure was clearly detected from force - displacement record of the small punch test. Keywords: Austenitic steels, bends, σ-phase, small punch test

Embrittlement of a High Manganese TWIP Steel in the Presence of Liquid Zinc

2012 ◽  
Vol 706-709 ◽  
pp. 2041-2046 ◽  
Author(s):  
Coline Beal ◽  
Xavier Kleber ◽  
Damien Fabrègue ◽  
Mohamed Bouzekri
Keyword(s):  
Strain Rate ◽  
Twip Steel ◽  
Deformation Mode ◽  
Tensile Tests ◽  
Limited Range ◽  
Austenitic Steels ◽  
Liquid Zinc ◽  
High Manganese ◽  
Environmental Requirements ◽  
Classical Mechanism

In the past decade, new steels have been developed for the automotive industry in the framework of environmental requirements. Among them, high manganese austenitic steels combining exceptional properties of strength and ductility are particularly promising. These exceptional properties stem from a fully austenitic structure at room temperature and a twinning deformation mode in addition to the classical mechanism of dislocation gliding, known as the TWinning Induced Plasticity (TWIP) effect. In this study, the cracking resistance of the Fe22Mn0.6C TWIP steel was investigated in relation to the liquid metal embrittlement (LME) phenomenon. Indeed, liquid zinc has been found to have an embrittling effect on such steels. Electro-galvanized specimens were subjected to hot tensile tests using Gleeble® thermo-mechanical simulator. The influence of different parameters such as temperature and strain rate on embrittlement was studied. The results show that this steel can be embrittled by liquid zinc within a limited range of temperature depending on strain rate. A critical stress for cracking has been defined for each embrittlement condition.

Laser Welded Joints of High-Nitrogen Austenitic Steels: Microstructure and Properties

2018 ◽  
Vol 284 ◽  
pp. 344-350 ◽  
Author(s):  
Vera V. Berezovskaya ◽  
A.V. Berezovskiy ◽  
D.H. Hilfi
Keyword(s):  
Welded Joints ◽  
Carbon Dioxide Laser ◽  
Continuous Wave ◽  
High Strength ◽  
Tensile Tests ◽  
Wave Mode ◽  
Austenitic Steels ◽  
Maximum Output ◽  
High Nitrogen ◽  
Corrosion Properties

High nitrogen austenitic steels are used as structural materials required possessing high strength and fracture toughness. The present study is concerned with the characteristic features (shape, size, properties and structure) of the laser welded joints in Cr-Mn-, Cr-Mn-Mo-high nitrogen steels compared to the ones of Cr-Ni-steel joint. Butt welded joints were made using carbon dioxide laser with a maximum output of 5 kW in the continuous wave mode. The hardness and tensile tests of welded joints in the air and 3.5 vol.%-solution of NaCl, as well as the theoretical studies were carried out by optical and transmission electron microscopy (TEM). The results are achieved by testing that the welded joints of HNS had satisfactory weldability, adequately high mechanical and corrosion properties. The austenite of the investigated HNS retains high stability throughout the welding cycle.

On the Influence of Cold Rolling Parameters for 14CrW-ODS Ferritic Steel Claddings

2013 ◽  
Vol 554-557 ◽  
pp. 118-126 ◽  
Author(s):  
Toualbi Louise ◽  
Olier Patrick ◽  
Rouesne Elodie ◽  
Didier Bossu ◽  
Yann de Carlan
Keyword(s):  
Cold Rolling ◽  
Annealing Temperature ◽  
Uniform Elongation ◽  
Longitudinal Direction ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
External Diameter ◽  
Intermediate Annealing ◽  
Ods Steels ◽  
Mother Tube

Oxide dispersion strengthened (ODS) steels, produced by powder metallurgy, are considered as promising material for high burn up cladding tubes for future Sodium Cooled Fast reactors. They present superior radiation resistance compared with austenitic steels and high creep strength due to reinforcement by the homogeneous dispersion of hard nano-sized particles. While the manufacturing route of 9Cr-based martensitic ODS steels are relatively well mastered thanks to the alpha  gamma phase transformation, the cold processing of ferritic ODS steels is more complicated because the material recovery after amounts of cumulative plastic strain is quite difficult. The aim of this study is to investigate several possible cold rolling routes for a Fe-14Cr-1W-0,3Ti-0,3Y2O3 ODS ferritic grade comparing the effects of annealing temperature on cold-workability, microstructure evolution and mechanical properties. A three-roll type HPTR rolling mill was used to manufacture ODS steel claddings. Cold rolling passes and intermediate annealing were repeated until reaching the final geometry: 10.73mm external diameter and 500µm thick. Depending of the cold rolling routes, different annealing temperatures of 1150°C, 1200°C and 1250°C were applied on the mother tube. Each pass was conducted using cross-section reduction ratio varying from at least 15% up to 25%. In each case, intermediate annealing at 1200°C for 1 hour were applied between one or several passes. The optical and SEM observations, hardness measurements, tensile tests were conducted to characterize the manufactured cladding tubes. The highest annealing temperature used on the mother tube enhances the recovery which leads to the lowest hardness level. The intermediate heat treatments applied in the course of the cold processing induces relatively low decrease of hardness. Microstructure characterization of hot extruded mother tubes shows highly anisotropic structures with equiaxed grains in the transverse direction but with significant elongation in the longitudinal direction. The elongated grain structure produced during hot extrusion is retained during cold rolling processes. Tensile tests are carried out on both longitudinal and circumferential directions by mean of respectively tile and ring tensile specimens for temperatures between 20°C and 700°C. The lowest is the annealing temperature applied on the mother tube the highest is the ultimate strength and the lowest is the uniform elongation. For the lowest annealing temperature, the UTS values measured at room temperature are ~1500MPa and ~1300MPa in the longitudinal direction and the circumferential direction, respectively. UTS values around 1000MPa in the both directions are found in case of lower annealing temperature showing a less pronounced anisotropy. For each test temperature, the uniform elongation values are relatively low compared to values obtained by other authors on 12%Cr-ODS ferritic steels. The lowest values of elongation are measured around 400°C.

Semi-Massive Nanocrystallised Composites: From the Process to Mechanical and Microstructural Investigations

2013 ◽  
Vol 762 ◽  
pp. 487-492 ◽  
Author(s):  
Laurent Waltz ◽  
Delphine Retraint ◽  
Arjen Roos
Keyword(s):  
Microstructural Characterization ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
Surface Mechanical Attrition Treatment ◽  
Three Point Bending ◽  
Steel Sheets ◽  
Transmission Electron ◽  
Mechanical Attrition ◽  
Refinement Mechanism ◽  
Duplex Process

The aim of the present study is first to describe an original process, the so called duplex process, whose feature is the coupling between the well-known SMAT (Surface Mechanical Attrition Treatment) and the traditional co-rolling. The first step of this process consists of SMA-Treatment of 316L stainless steel sheets to generate nanocrystalline layers on their top surfaces according to the grain refinement mechanism of austenitic steels which is well described in the literature. During the second step, three treated sheets are co-rolled at 550°C to obtain a semi-massive nanocrystallised multilayer structure with improved mechanical strength alternating nanocrystalline, transition and coarse grain layers. The second part of this work deals with the mechanical and the microstructural characterization of the as-obtained structures. Thus, sharp nanoindentation tests performed over the cross section of the laminates coupled with Transmission Electron Microscopy (TEM) confirm the presence of nanograins after the thermomechanical treatment. In addition, the enhanced yield strength demonstrated by tensile tests correlate well with the theoretical volume fractions of nanoand transition layers. The interface cohesion between the sheets is tested by three-point bending tests and the interface bonding is evaluated by microstructural observations.

Deformation Mechanisms in a Proton-Irradiated Austenitic Stainless Steel

1994 ◽  
Vol 373 ◽  
Author(s):  
R.D. Carter ◽  
M. Atzmon ◽  
G.S. Was ◽  
S.M. Bruemmer
Keyword(s):  
Stainless Steel ◽  
Grain Boundaries ◽  
Tensile Tests ◽  
Dislocation Motion ◽  
Austenitic Steels ◽  
Extension Rate ◽  
304L Stainless Steel ◽  
Dislocation Source ◽  
Transmission Electron ◽  
Core Components

AbstractSamples of austenitic 304L stainless steel have been irradiated with 3.4 MeV protons to atotal dose of 1 dpa. The microstructure of the irradiated stainless steel has been quantified by transmission electron microscopy and shown to be similar to that found in neutron-irradiated core components. Constant extension rate tensile tests have been performed at strain rates of 3x10−7 s−1 and 3x10−8 s−1 to strains of up to 27% at 23°C and 288°C. The resulting microstructures were characterized using electron and optical microscopy. Deformation of the unirradiated material is similar to that reported by others in previous work on austenitic steels, consisting of dislocation source activation and formation of dense dislocation networks with increasing strain. In the irradiated samples tested at 288°C, deformation consists of dislocation source activation at grain boundaries punching dislocations through the grain interior to the opposing grain boundaries. The dislocations create channels that are free of radiation-produced defects and on which dislocation motion is concentrated. Dislocations in the channels pile-up at the boundaries, creating regions of highly localized stress concentration at the grain boundary. The mechanism by which this stress is relieved is still unknown. Deformation at 23°C consists of the nucleation and propagation of microtwins across the width of the grains.

Deformation Behavior of Nitrogen Bearing Austenitic Steels with Various Nitrogen Contents

2007 ◽  
Vol 345-346 ◽  
pp. 117-120 ◽  
Author(s):  
Yong Suk Kim ◽  
Seung Man Nam ◽  
Sung Joon Kim
Keyword(s):  
Nitrogen Content ◽  
Deformation Behavior ◽  
Tensile Deformation ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
High Nitrogen ◽  
Tensile Deformation Behavior ◽  
Nitrogen Steel ◽  
Nitrogen Contents

Tensile deformation behavior of the high-nitrogen austenitic Fe-18Cr-14Mn-4Ni-3MoxN steel with various nitrogen contents has been studied. The nitrogen content of the steel varied from 0.28 to 0.88 wt. %. Nitrogen atoms in high nitrogen steel (HNS) make an interstitial solid solution by being scattered in the steel constituting a short-range order. They strengthen the austenite matrix without deteriorating ductility of the steel. The present investigation was carried out to elucidate the hardening and plasticizing role of the nitrogen in the HNS by analyzing tensile deformation behavior of the steel containing various nitrogen contents. Tensile tests of the steel specimens were performed at room temperature with a constant strain rate of 5x10-5/sec. Microstructure of the tested specimens was analyzed to explore the deformation mechanism of the HNS as a function of nitrogen contents. The flow stress of the steel increased with the increase of the nitrogen content; however, the specimen with the highest nitrogen content (0.88 wt. %) showed saturated strength and reduced ductility. The superior mechanical property of the HNS was explained by the low stacking fault energy and the twin-induced plasticity provoked by the nitrogen.

scholarly journals Fatigue life of materials claded with the method of explosive welding

2018 ◽  
Vol 67 (2) ◽  
pp. 109-118
Author(s):  
Grzegorz Kwiatkowski ◽  
Dariusz Rozumek
Keyword(s):  
Fatigue Life ◽  
Explosive Welding ◽  
Base Material ◽  
Tensile Tests ◽  
Austenitic Steels ◽  
Hardness Distribution ◽  
Initiation Point ◽  
Bending Tests ◽  
Static Tests ◽  
Connected Area

This paper describes the comparison of fatigue life on bending of two claded materials with the base material. The base material was the carbon steel P3335NH of the thickness of 10 mm and the clad materials was austenitic steels 254SMO and 316L. As a part of the work, ultrasonic testing of static tests such as tensile tests, shear tests, bending tests and impact tests were performed. The hardness distribution tests in the cross-section of the sample was subsequently carried out. Last tests were the cyclic bending tests at four different loads. Surveys show that the plates are connected to the entire surface with the exclusion of technological margins of approximately 30 mm per side and the detonation initiation point, which, as a rule, is always a non-connected area. Hardness distribution tests shown that the explosive plating process has resulted in an increase in the hardness of materials near the joint line. The bending studies show that the highest fatigue life is the same as the base material compared to the cladding materials. For each sample, the crack initiation always started in the base material. Keywords: explosive welding, fatigue life, bending, austenitic steels

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