scholarly journals Cyclic deformation behaviour and stability of grain-refined 301LN austenitic stainless structure

2018 ◽  
Vol 165 ◽  
pp. 06005 ◽  
Author(s):  
Jiří Man ◽  
Antti Järvenpää ◽  
Matias Jaskari ◽  
Ivo Kuběna ◽  
Stanislava Fintová ◽  
...  
Keyword(s):  
Strain Rate ◽  
Volume Fraction ◽  
Early Stage ◽  
Low Cycle Fatigue ◽  
Deformation Behaviour ◽  
Polarized Light ◽  
Constant Strain Rate ◽  
Coarse Grained ◽  
Grain Sizes ◽  
Cyclic Straining

Low cycle fatigue (LCF) behaviour of metastable austenitic 301LN stainless steel with different grain sizes – coarse-grained (13 μm), fine-grained (1.4 μm) and ultrafine-grained (0.6 μm) – produced by reversion annealing after prior cold rolling was investigated. Fully symmetrical LCF tests with constant total strain amplitudes of 0.5% and 0.6% were performed at room temperature with a low constant strain rate of 2×10-3 s-1. Microstructural changes in different positions within the gauge part of the specimens were examined by optical microscopy (polarized light) and electron backscatter diffraction (EBSD) technique; for quantitative assessment of the volume fraction of deformation induced martensite (DIM) a Feritscope FMP 30 was adopted. The cyclic stress-strain response and specific changes of hysteresis loop shapes in the very early stage of cycling are confronted with the character of DIM formation and its distribution in the whole volume of the material. A possible effect of strain rate (frequency of cycling) on the destabilization of austenitic structure during cyclic straining of materials with different grain sizes is highlighted.

Effect of Severe Caliber Rolling on Superplastic Properties of Mg-3Al-1Zn (AZ31) Alloy

2012 ◽  
Vol 735 ◽  
pp. 327-331 ◽  
Author(s):  
Rajendra Doiphode ◽  
Rahul Ramesh Kulkarni ◽  
S.V.S. Narayana Murty ◽  
Nityanand Prabhu ◽  
Bhagwati Prasad Kashyap
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Material Constant ◽  
Az31 Alloy ◽  
Strain Rate Range ◽  
Constitutive Relationship ◽  
Grain Sizes ◽  
Different Temperatures ◽  
Rate Test ◽  
Superplastic Properties

Fine grains were developed in Mg-3Al-1Zn (AZ31) alloy by isothermal caliber rolling at five different temperatures in the range of 250-450°C. The samples of different grain sizes were deformed by constant strain rate and differential strain rate test techniques over the temperature range of 220-450 °C and strain rate range of 10-5 to 10-1 s-1. The effects of grain size, test temperature and strain rate on flow stSuperscSuperscript textript textress were analysed to develop the constitutive relationship for supSuperscript texterplastic deformation. The parameters of the constitutive relationship obtained from the constant strain rate tests and differential strain rate tests were used to find out the material constant A of the constitutive relationship.

Strain-Controlled Low Cycle Fatigue of Stainless Steel in PWR Water

2019 ◽  
Author(s):  
Tommi Seppänen ◽  
Jouni Alhainen ◽  
Esko Arilahti ◽  
Jussi Solin
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Degradation Mechanism ◽  
Water Environment ◽  
Constant Strain Rate ◽  
Test Methods ◽  
Primary Circuit ◽  
Limiting Factor ◽  
Draft Model

Abstract Fatigue is a major degradation mechanism and life-limiting factor for primary circuit piping. High temperature, pressurized reactor coolant aggravates fatigue damage with a suitable combination of loading parameters. Nonstandard test methods, incompatible with design codes and the peculiar material behaviour of austenitic stainless steel have been widely used. This complicates quantification of the effect of water environment, commonly referred to as the Fen factor. Four test series in simulated PWR coolant were completed over four years with stainless steel alloys 347 and 304L, hypothesizing that Fen=f⁡ε.pl. Linear strain waveforms were used with non-constant strain rate to represent simplified plant transients and non-realistic mirrored strain waveforms for comparison purposes. Applying multiple strain rates allows identifying potentially non-damaging effects of effectively elastic strain near the valley of a strain cycle and on the other hand the damaging effect of effectively plastic strain. Results generated within this project were used to draft a replacement to the Fen methodology presented in NRC report NUREG/CR-6909. Initially, this model remains based on total strain rate and is presently limited to the narrow parameter window in which valid experiments were performed. It does however reduce the scatter and unnecessarily high conservatism associated with the NUREG Fen by a factor of approximately two. This paper presents new results for 304L and an outline of the draft model proposal for Fen evaluation in PWR water.

Evaluation of the Effect of Dynamic Sodium on the Low Cycle Fatigue Properties of 316L(N) Stainless Steel Base and Weld Joints

2012 ◽  
Vol 31 (3) ◽  
Author(s):  
V. Ganesan ◽  
R. Kannan ◽  
K. Mariappan ◽  
G. Sukumaran ◽  
R. Sandhya ◽  
...  
Keyword(s):  
Stainless Steel ◽  
Austenitic Stainless Steel ◽  
Strain Rate ◽  
Low Cycle Fatigue ◽  
Constant Strain Rate ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Weld Joints ◽  
Steel Base

AbstractLow cycle fatigue (LCF) tests on 316L(N) austenitic stainless steel base and weld joints were at 823 K and 873 K at a constant strain rate of 3

SUPERPLASTIC BEHAVIOR OF COARSE-GRAINED Al-Mg ALLOY

2012 ◽  
Vol 06 ◽  
pp. 401-406 ◽  
Author(s):  
HAOYAN DIAO ◽  
REHAN QAYYUME ◽  
TINGTING WANG ◽  
SHASHA ZHAO ◽  
CHAOLI MA
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Superplastic Forming ◽  
Mg Alloy ◽  
Coarse Grained ◽  
Sensitivity Index ◽  
Maximum Elongation ◽  
Dislocation Glide ◽  
Elongation To Failure

This paper concentrates on the study of the superplastic response of coarse-grained Al - Mg alloys under uniaxial tension at different temperatures (ranging from 400°C to 525°C) and strain rates (10-2 S-1, 10-3 S-1 & 10-4 S-1). The microstructures have been analyzed using optical (OM) and transmission electron microscopy (TEM). It has been observed that continuous re-crystallization occurs during hot deformation of the alloy at the temperature of 425°C and strain rate of 10-2S-1. At the temperature of 425°C and strain rate of 3.78×10-3S-1, this Al - Mg alloy has the maximum elongation to failure of 181%, which is sufficient for manufacturing of extremely complex shapes using superplastic forming technology. The constant strain rate sensitivity index m and TEM observations show that in this case deformation mechanism involved is dislocation glide. Recrystallization during the hot tension greatly enhanced the plasticity of the coarse-grained material at a strain rate of about 10-2S-1 and the maximum elongation changes as a function of the strain rate.

Investigation of Nickel Aluminum Bronze Alloy under Hot Compression Test

2014 ◽  
Vol 931-932 ◽  
pp. 365-369
Author(s):  
Jutamas Anantapong ◽  
Surasak Suranuntchai ◽  
Anchalee Manonukul ◽  
Vitoon Uthaisangsuk
Keyword(s):  
Strain Rate ◽  
Cooling Rate ◽  
Hot Deformation ◽  
Deformation Temperature ◽  
Volume Fraction ◽  
Constant Strain Rate ◽  
Aluminum Bronze ◽  
Nickel Aluminum ◽  
Bronze Alloy ◽  
Nickel Aluminum Bronze

The characteristics of Nickel Aluminum Bronze alloy (NAB) after hot deformation were investigated. The NAB alloy have been studied by dilatometer according to study the influence of hot deformation on microstructure of NAB alloy by dilatometer in the temperature range 800 - 950 °C, strain rate 10s-1 and cooling rate 40 and 100 °C/s. The experimental results showed that peak stress in relation to the involved deformation temperature, peak stresses at a constant strain rate decreased with an increase of deformation temperature. It was found that volume fraction of the β phase significantly increased with increasing temperature and cooling rate. The variation of this phase affected macro hardness of the investigated alloy. By higher temperatures, amount of β phase increased as well as the macro hardness of the NAB alloy.

scholarly journals Hot Deformation Behaviour of Mn–Cr–Mo Low-Alloy Steel in Various Phase Regions

Metals ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1255 ◽  
Author(s):  
Ivo Schindler ◽  
Petr Opěla ◽  
Petr Kawulok ◽  
Jaroslav Sojka ◽  
Kateřina Konečná ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Hot Deformation ◽  
Deformation Behaviour ◽  
True Strain ◽  
Coarse Grained ◽  
Peak Strain ◽  
Compression Tests ◽  
Wide Range ◽  
Hot Deformation Behaviour

The deformation behaviour of a coarse-grained as-cast medium-carbon steel, alloyed with 1.2% Mn, 0.8% Cr and 0.2% Mo, was studied by uniaxial compression tests for the strain rates of 0.02 s−1–20 s−1 in the unusually wide range of temperatures (650–1280 °C), i.e., in various phase regions including the region with predominant bainite content (up to the temperature of 757 °C). At temperatures above 820 °C, the structure was fully austenitic. The hot deformation activation energies of 648 kJ·mol−1 and 364 kJ·mol−1 have been calculated for the temperatures ≤770 °C and ≥770 °C, respectively. This corresponds to the significant increase of flow stress in the low-temperature bainitic region. Unique information on the hot deformation behaviour of bainite was obtained. The shape of the stress-strain curves was influenced by the dynamic recrystallization of ferrite or austenite. Dynamically recrystallized austenitic grains were strongly coarsened with decreasing strain rate and growing temperature. For the austenitic region, the relationship between the peak strain and the Zener–Hollomon parameter has been derived, and the phenomenological constitutive model describing the flow stress depending on temperature, true strain rate and true strain was developed. The model can be used to predict the forming forces in the seamless tubes production of the given steel.

scholarly journals Effects of strain rate on tensile deformation behaviour in Ti-6Al-4V at cryogenic temperature

2020 ◽  
Vol 321 ◽  
pp. 06010
Author(s):  
Min-Ki Ji ◽  
Min-Su Lee ◽  
Yong-Taek Hyun ◽  
Tea-Sung Jun
Keyword(s):  
Strain Rate ◽  
Liquid Nitrogen ◽  
Cryogenic Temperature ◽  
Tensile Deformation ◽  
Electron Backscatter Diffraction ◽  
Deformation Behaviour ◽  
Constant Strain Rate ◽  
Tensile Tests ◽  
Local Deformation ◽  
Deformation Twinning

In this study, we investigated the effects of strain rate on tensile deformation behaviour in Ti-6Al-4V sheet at cryogenic temperature. X-ray diffraction (XRD) was used to identify the crystallographic orientation of rolled Ti-6Al-4V. A series of tensile tests were performed by constant strain rate method (CRS) with variable strain rates (i.e., on the order of 1x10-2 to 10-4•s-1). Liquid nitrogen (LN2) was used to mimic cryogenic environment, and for the thermal equilibrium the specimens were immersed in the vessel containing liquid nitrogen for ~10 minutes before tensile testing, and the temperature condition was continuously maintained during the testing. Microstructure and fracture surface was analysed by polarised light microscopy and scanning electron microscope (SEM). Electron backscatter diffraction (EBSD) was further used to characterise local deformation behaviour. Deformation twinning is occurred at cryogenic tempearture, which is rather different to the deformation at room temperature. It is thought that the twinning induced deformation behaviour may lead to a strength enhancement and a rate dependent ductility improvement. Key words: Ti-6Al-4V, cryogenic, microstructure, deformation twinning, EBSD

Fine-Grained Structure Formation in 7475 Al Alloy during Hot Multidirectional Forging

2006 ◽  
Vol 512 ◽  
pp. 79-84
Author(s):  
Alexandre Goloborodko ◽  
Oleg Sitdikov ◽  
Hiromi Miura ◽  
Taku Sakai
Keyword(s):  
Steady State ◽  
Strain Rate ◽  
Grain Refinement ◽  
High Strain ◽  
Volume Fraction ◽  
Coarse Grained ◽  
Al Alloy ◽  
Steady State Flow ◽  
Multidirectional Forging ◽  
State Flow

Effect of strain rate on grain refinement was studied in multidirectional forging (MDF) of a coarse-grained 7475 Al alloy at 490oC under strain rates of 3 × 10-4 s-1 and 3 × 10-2 s-1. At a strain rate of 3 × 10-4 s-1, the stress – strain ( σ - ε) behavior shows significant work softening just after yielding and a steady-state flow at higher strains. The structural changes are characterized by development of deformation bands at early stages of deformation, followed by formation of a fine grain structure in high strain in the whole material. The volume fraction of new grains increases with strain and approaches a value of about 0.85 over a strain of 3. At a higher strain rate of 3 × 10-2 s-1, in contrast, a steady-state flow following small flow softening appears at a relatively low strain. New grains are formed during steady state flow along original grain boundaries and the volume fraction reaches below 0.2 even in high strain. The occurrence conditions and the mechanisms of grain refinement are discussed in detail.

Determination of superplastic constitutive equations and strain rate sensitivities for aerospace alloys

1997 ◽  
Vol 211 (6) ◽  
pp. 367-380 ◽  
Author(s):  
T W Kim ◽  
F P E Dunne
Keyword(s):  
Strain Rate ◽  
Grain Growth ◽  
Strain Rate Sensitivity ◽  
Constitutive Equations ◽  
Experimental Testing ◽  
Deformation Behaviour ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Aerospace Alloys

Constitutive equations for the superplastic behaviour of titanium and aluminium aerospace alloys have been presented and computational procedures developed for the determination of the material parameters arising in the equations. The equations include a description of grain growth kinetics with deformation enabling the influence of microstructure on superplastic deformation behaviour to be modelled. Three predictive methods have been developed for the determination of strain rate sensitivity. The models represent the dependence of the strain rate sensitivity on strain, strain rate, and grain growth, and therefore, provide useful information for process design and optimization. The models are validated by comparison of predictions with experimental data reported in the literature and obtained in this work. Finally, two conventional experimental testing methods for the determination of strain rate sensitivity, namely the constant strain rate and strain rate jump methods are appraised using the methods developed.

Numerical Simulation of Hot Forging for the Disc of Superalloy GH4169

2011 ◽  
Vol 328-330 ◽  
pp. 1598-1601
Author(s):  
Yan Shu Zhang ◽  
Xiao Fei Liu
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Volume Fraction ◽  
Hot Forging ◽  
Pure Titanium ◽  
Constant Strain Rate ◽  
High Temperature Deformation ◽  
Temperature Deformation ◽  
Stress Strain ◽  
Average Grain Size

In this paper, the hot deformation behavior of GH4169 superalloy were investigated at temperature of 900-1020°C and at strain rate of 0.001-0.1up to a 60% height reduction of the sample using isothermal constant strain rate compression tests on process annealed material. The high temperature deformation behaviour of pure titanium was characterized based on an analysis of the stress–strain curves The proposed constitutive equation and the stress-strain curves were implanted into DEFORM2D, a hot forging process for the disc of GH4169 was simulated, and the micro-variable, recrystallized volume fraction, average grain size, recrystallized grain size and etc., were plotted with a contoured figure. According to the comparision between the experimental and predicted result, the absolute error between them is acceptable. The method for microstructure prediction will be significant to the engineering.

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