Low-Cycle Fatigue Behavior of an Al-Mg-Si Alloy with and without a Small Addition of Sc

2010 ◽  
Vol 654-656 ◽  
pp. 938-941 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Strengthening Effect ◽  
Cycle Fatigue ◽  
Slip Bands ◽  
Transmission Electron ◽  
Peak Aging ◽  
Bearing Alloy

Low-cycle fatigue behavior of a wrought Al-0.8wt%Mg-0.7wt%Si alloy with and without 0.27wt%Sc has been investigated at room temperature under constant plastic-strain amplitudes. After peak-aging treatments, both the alloys had fine lath-shaped β' precipitates. In the Sc-containing alloy, spherical Al3Sc precipitates of about 11 nm in diameter were co-existed. The alloy with Sc exhibited cyclic hardening to saturation, while the alloy without Sc showed clear cyclic softening after initial hardening. Transmission electron microscopy observation revealed that slip band structures were developed in the Sc-free alloy. Within the slip bands, shearing of the β' precipitates by moving dislocations was often observed. The cyclic softening in the alloy without Sc can then be explained by a loss of precipitation strengthening effect through the precipitation destruction within strongly-strained slip bands. In the Sc-bearing alloy, owing to the existence of non-shearable Al3Sc precipitates, dislocations were uniformly distributed, resulting in the absence of the cyclic softening.

Cyclic Softening Effect on Design Margin of JLF-1 Steel

2013 ◽  
Author(s):  
Huailin Li
Keyword(s):  
Elevated Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Softening ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Softening Effect ◽  
As Stress ◽  
Supercritical Water Cooled Reactor ◽  
Design Margin

A reduced-activation ferritic/martensitic (RAF/M) steel, JLF-1, is considered as one of the candidate structure material of the fusion reactors and supercritical water-cooled reactor (SCWR). Low cycle fatigue properties of JLF-1 steel at elevated temperature are the design base to provide adequate design margin against postulated mechanism that could experience during its design life, such as stress range, plastic deformation, and cyclic softening etc. However, the reduction in design margin is significant when the cyclic softening happens in cyclic deformation at RT, 673K, 873K. Thus, for the application as the structural materials, it is necessary to evaluate low cycle fatigue behavior and cyclic softening of JLF-1 steel at elevated temperature since those properties of material at elevated temperature are the key issue for design.

High-Temperature Low-Cycle Fatigue Behavior of MarBN at 600 °C

2016 ◽  
Vol 138 (4) ◽  
Author(s):  
Richard A. Barrett ◽  
Eimear M. O'Hara ◽  
Padraic E. O'Donoghue ◽  
Sean B. Leen
Keyword(s):  
High Temperature ◽  
Low Cycle Fatigue ◽  
Kinematic Hardening ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Material Model ◽  
Cyclic Softening ◽  
Cyclic Strength ◽  
Cycle Fatigue ◽  
Viscoplastic Material

This paper presents the high-temperature low-cycle fatigue (HTLCF) behavior of a precipitate strengthened 9Cr martensitic steel, MarBN, designed to provide enhanced creep strength and precipitate stability at high temperature. The strain-controlled test program addresses the cyclic effects of strain-rate and strain-range at 600 °C, as well as tensile stress-relaxation response. A recently developed unified cyclic viscoplastic material model is implemented to characterize the complex cyclic and relaxation plasticity response, including cyclic softening and kinematic hardening effects. The measured response is compared to that of P91 steel, a current power plant material, and shows enhanced cyclic strength relative to P91.

Low Cycle Fatigue Behavior of a New Type of Zircaloy Material

2011 ◽  
Vol 80-81 ◽  
pp. 788-791
Author(s):  
Wei Wei Yu ◽  
Fei Xue ◽  
Xin Ming Meng ◽  
Lei Lin
Keyword(s):  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Strain Range ◽  
Cyclic Hardening ◽  
Cycle Fatigue ◽  
Fatigue Lifetime ◽  
Softening Behavior ◽  
New Type

To investigate the property of a new type of Zircaloy material, a low cycle fatigue (LCF) test has been performed at room temperature (RT) and 375°C. Results show that the new alloy generally displays cyclic hardening followed by a continuous softening behavior. Fatigue lifetime curves as a function of strain range imply that the new alloy has a nearly same lifetime than that of Zr-4 at RT, and superior than that at 375°C.

Low Cycle Fatigue Behavior of Original Ferritic P92 Steel at High Temperature: Experiments and Simulations

2015 ◽  
Author(s):  
Xiaowei Wang ◽  
Jianming Gong ◽  
Yong Jiang ◽  
Yanping Zhao
Keyword(s):  
Plastic Material ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Constant Strain Rate ◽  
Cyclic Softening ◽  
Isotropic Hardening ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
P92 Steel ◽  
Softening Behavior

Low cycle fatigue tests of original ferritic P92 steel at high temperatures and different strain amplitudes were conducted to investigate its cyclic softening behavior and fracture behavior. LCF tests of strain amplitudes ranging from ±0.2% to ±0.8% were performed in fully reversed manner with constant strain rate at 600 °C and 650 °C. In order to represent the different hysteresis stress-strain curves and the cyclic softening behavior of P92 steel, a cyclic plastic material model was used. In the model, improved nonlinear isotropic hardening parameter was proposed to make better simulation of the cyclic softening behavior. Based on the simulated stress-strain hysteresis loops, an energy-based life prediction model was used to predict the low cycle fatigue life. When compared with experimental responses, the simulations and predicted life were found to be quite reasonable. Low cycle fatigue fractography of the P92 steel was also observed, and it was found to be associated with the different strain amplitudes imposed on the specimen, the larger strain amplitude the more amounts of crack initiation sites could be found.

Comparative Low-Cycle Fatigue Behavior of HAYNES 244 Alloy and Waspaloy

2021 ◽  
Author(s):  
Michael G. Fahrmann
Keyword(s):  
Thermal Loading ◽  
Coefficient Of Thermal Expansion ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Axial Strain ◽  
Fatigue Crack Initiation ◽  
High Strength ◽  
Cyclic Hardening ◽  
Cycle Fatigue ◽  
Softening Behavior

Abstract HAYNES® 244® alloy was chiefly developed to address the need for high-strength, low coefficient of thermal expansion (CTE) alloys for seal rings and cases in advanced gas turbine engines. In addition to these attributes, adequate resistance to low-cycle fatigue (LCF) due to cyclic thermal and mechanical loading during service is critical for such applications. The isothermal LCF performance of commercially produced 0.5” (12.5 mm) thick, fully heat treated plate products of 244 alloy was evaluated by means of axial strain-controlled (R = −1) LCF tests covering total strain ranges up to 1.25 % (without dwells), at temperatures ranging from 800–1400°F (427–760°C). In addition, the comparative LCF performance of Waspaloy, a well-established alloy for turbine cases, was evaluated under selected, nominally identical test conditions. S-N curves were constructed and fitted by the Coffin-Manson equation, allowing the delineation of regimes controlled by the elastic and plastic response of the material. Fracture surfaces were examined in the scanning electron microscope to identify fatigue crack initiation sites and crack propagation modes. Differences between the alloys are discussed in terms of tensile strength and cyclic hardening/softening behavior. Implications for fatigue performance of these alloys under cyclic thermal loading conditions are discussed as well.

Low-Cycle Fatigue Behavior of Small Slice Specimens of Zircaloy-4 at Elevated Temperature

2006 ◽  
Vol 324-325 ◽  
pp. 1241-1244 ◽  
Author(s):  
Li Xun Cai ◽  
Yu Ming Ye
Keyword(s):  
Elevated Temperature ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Fatigue Tests ◽  
Uniaxial Strain ◽  
Transverse Strain ◽  
Test Results ◽  
Element Analysis

A series of strain fatigue tests were carried out on small bugle-like slice-specimens of Zr-4 alloy at 20 and 400. According to Elastic and Plastic Finite Element Analysis and assumption of local damage equivalence, a strain formula was given to transform transverse strain of the specimen to uniaxial strain. Based on the test results of the alloy and the strain transform formula, M-C (Manson-Coffin) models to be used for estimating uniaxial fatigue life of Zr-4 alloy were obtained. The results show that, the alloy mainly behaves as cyclic softening at 20 and as cyclic hardening at 400, and the elevated temperature can lead serious additional fatigue damage of the alloy and the effect of the elevated temperature impairs gradually with increasing of amplitude strain. A conclusion is helpful that prediction life by using M-C model based on traditional strain transform equation is quite conservative when uniaxial strain amplitude is less than 0.5%.

The Effect of Alloy Elements on Cyclic Fatigue Behavior of Bucket Candidate Materials for USC Power Plants

2007 ◽  
Vol 26-28 ◽  
pp. 1141-1144 ◽  
Author(s):  
Kuk Cheol Kim ◽  
Byung Hoon Kim ◽  
Jin Ik Suk ◽  
Dong Soo Kim ◽  
Jeong Tae Kim
Keyword(s):  
Fatigue Life ◽  
Power Plants ◽  
Boron Content ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Fatigue ◽  
Strengthening Effect ◽  
Cycle Fatigue ◽  
Commercial Steel ◽  
Power Plant Operation

The demand for ultra supercritical (USC) power plants has increased due to the need for high thermal efficiency and reduced CO2 emissions. For turbine materials, high-cycle and lowcycle fatigue life at USC service temperatures are needed to verify material integrity due to the heat-up and cool-down process of power plant operation and due to turbine variations during operation. In this paper, fatigue characteristics for 9~12 Cr steels as candidate USC bucket materials were investigated. First, the fatigue life between DS2B2 and COST B2 steel were compared. COST B2 is the commercial steel with improved high temperature properties by adding boron, and DS2B2 is the new steel developed by Doosan by adding Co and adjusting Mo and W based on the same Mo equivalent value (%wt. Mo + 1/2 %wt. W). DS2B2 steel was found to have longer low cycle fatigue life than COST B2. Second, the effect of boron on fatigue life for bucket materials based on COST B2 steel was investigated. At room temperature, as boron content increased, low cycle fatigue life became superior, whereas, at 593oC the fatigue life was similar. For high cycle fatigue, as boron content increased, fatigue life increased due to the strengthening effect by the addition of boron.

The Low Cycle Fatigue Behavior of Equal-Channel Angular Pressed Al 5052 Alloy

2008 ◽  
Vol 385-387 ◽  
pp. 725-728 ◽  
Author(s):  
J.H. Cha ◽  
H.H. Cho ◽  
W.H. Kim ◽  
S.I. Kwun ◽  
Dong Hyuk Shin
Keyword(s):  
Tensile Strength ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Subsequent Annealing ◽  
Cycle Fatigue ◽  
Angular Pressing ◽  
In The Beginning ◽  
Al 5052 Alloy ◽  
Slight Amount

The low cycle fatigue(LCF) test was performed to characterize the influences of the equal channel angular pressing(ECAP) and subsequent annealing of Al 5052 alloy. In the present research, one group of Al 5052 alloy specimens was directly subjected to ECAP, while another was subjected to ECAP and subsequent annealing. It was found that the tensile strength of the Al 5052 alloy increased, while its elongation decreased, with increasing number of ECAP passes. The LCF test was conducted at constant total strain amplitudes of 0.5%, 0.7%, 0.9% and 1.1%. Only cyclic hardening was observed as the number of fatigue cycles increased at all strain amplitudes in the specimen without ECAP. However, the ECAPed specimens showed a slight amount of cyclic hardening in the beginning and then saturation until fracture.

Low Cycle Fatigue Behavior of 429EM Ferritic Stainless Steel at Elevated Temperatures

2004 ◽  
Vol 261-263 ◽  
pp. 1135-1140 ◽  
Author(s):  
Keum Oh Lee ◽  
Sam Son Yoon ◽  
Soon Bok Lee ◽  
Bum Shin Kim
Keyword(s):  
Stainless Steel ◽  
Elastic Modulus ◽  
Fatigue Life ◽  
Elevated Temperatures ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Dynamic Strain ◽  
Temperature Structure ◽  
Cycle Fatigue

In recent, ferritic stainless steels are widely used in high temperature structure because of their high resistance in thermal fatigue and low prices. Tensile and low cycle fatigue(LCF) tests on 429EM stainless steel were performed at several temperatures from room temperature to 600°C. Elastic modulus, yield stress and ultimate tensile strength(UTS) decreased with increasing temperature. Considerable cyclic hardening occurred at 200°C and 400°C. 475°C embrittlement observed could not explain this phenomenon but dynamic strain aging(DSA) observed from 200°C to 500°C could explain the hardening mechanism at 200°C and 400°C. And it was observed that plastic strain energy density(PSED) was useful to predict fatigue life when large cyclic hardening occurred. Fatigue life using PSED over elastic modulus could be well predicted within 2X scatter band at various temperatures.

scholarly journals Effects of Microstructures on Fatigue Behavior of an Al-Mg-Sc Alloy at an Elevated Temperature

2012 ◽  
Vol 706-709 ◽  
pp. 426-430 ◽  
Author(s):  
Chihiro Watanabe ◽  
Ryoichi Monzen
Keyword(s):  
Fatigue Life ◽  
Fatigue Behavior ◽  
Cyclic Hardening ◽  
Cyclic Softening ◽  
Small Particles ◽  
Factors Affecting ◽  
Slip Bands ◽  
Large Particles ◽  
Fatigue Characteristics ◽  
The Relationship

Polycrystalline Al-1wt%Mg-0.27wt%Sc alloys bearing Al3Sc particles with different average sizes of 4 and 11nm in diameter have been cyclically deformed at 423K under various constant stress amplitudes, and the relationship between fatigue characteristics and microstructure of the alloy has been investigated. The specimen bearing 11 nm particles exhibited a cyclic hardening to saturation, while in specimens with the small particles a cyclic softening was observed after initial hardening. In the specimen with large particles, dislocations were uniformly distributed under all applied stress amplitudes, whereas the specimens bearing small particles, in which cyclic softening occurred exhibited clearly developed slip bands. The cyclic softening for the latter specimen was explained by particle shearing within the strongly strained slip bands. The width of precipitate free zones (PFZs) has been found to be one of the factors affecting the fatigue life of the specimens at 423K. The two-step aging decreases the width of PFZs, resulting in increase in the fatigue life.

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