Low Cycle Fatigue of Cast γ-TiAl Based Alloys at High Temperature

2010 ◽  
Vol 452-453 ◽  
pp. 421-424 ◽  
Author(s):  
Martin Petrenec ◽  
Miroslav Šmíd ◽  
Tomáš Kruml ◽  
Karel Obrtlík ◽  
Jaroslav Polák
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Surface Region ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Nb Content ◽  
Cyclic Straining

The low-cycle fatigue properties of cast nearly lamellar TiAl alloys with diverse Nb content at room temperature and 750°C were compared. Monotonic tensile curves, cyclic stress-strain curves (CSSC) and combined fatigue life curves were obtained at both temperatures. After cyclic straining the surface relief and the fracture surfaces were observed using scanning electron microscopy. The increase in Nb content significantly improves tensile properties and CSSCs at both temperatures. The combined fatigue life curves especially at 750 °C are shifted to higher fatigue lives. The effect o Nb content on the tensile and cyclic strength is discussed in relation to the thickness of the lamellae. Persistent slip markings formed along interlamellar interfaces were predominant locations for fatigue cracks. At both temperatures and materials showed similar crack initiation and propagation behavior. The cracks initiated at surface or in sub-surface region creating smooth flat areas corresponding to the persistent slip bands.

scholarly journals Evaluation of Low Cycle Fatigue Performance of Selective Laser Melted Titanium Alloy Ti–6Al–4V

Metals ◽  
2019 ◽  
Vol 9 (10) ◽  
pp. 1041 ◽  
Author(s):  
Peng Zhang ◽  
Allen Naihui He ◽  
Fei Liu ◽  
Kaifei Zhang ◽  
Junjie Jiang ◽  
...  
Keyword(s):  
Low Cycle Fatigue ◽  
Fatigue Cracks ◽  
Cyclic Stress ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Low Carbon ◽  
Specific Strength ◽  
Material Fatigue ◽  
Lower Strain ◽  
High Degree

The material of Ti–6Al–4V has been widely applied in various industries, such as automobile, aerospace, and medical due to its high specific strength, superior thermal stability and strong corrosion resistance. In the recent decades, selective laser melting (SLM) has become an attractive method to fabricate Ti–6Al–4V parts, thanks to its significant advantages in low material consumption, the high degree of freedom in design, low carbon footprint, etc. Predictability of SLM material fatigue properties is especially important for the safety-critical structures under dynamic load cases. The present research is aimed at evaluating the low cycle fatigue (LCF) performance of SLM Ti–6Al–4V under high loading states. LCF tests were performed for as-built and annealed SLM Ti–6Al–4V. Comparison between LCF properties of SLM Ti–6Al–4V and the wrought Ti–6Al–4V was also made. It was found that as-built SLM Ti–6Al–4V demonstrated a comparable LCF performance with the wrought material. The LCF life of as-built SLM Ti–6Al–4V was longer than that of wrought Ti–6Al–4V at lower strain amplitudes. However, the wrought Ti–6Al–4V had better LCF performance at higher strain amplitudes. The results revealed that the porosity in the as-built SLM material exerted much more impact on the degradation of the material at high strain amplitudes. Annealing deteriorated the LCF performance of SLM Ti–6Al–4V material due to the formation of coarser grains. The cyclic Ramberg–Osgood and the Basquin–Coffin–Manson models were fitted to depict the cyclic stress–strain and the strain–life curves for the SLM Ti–6Al–4V, based on which the LCF performance parameters were determined. In addition, the fatigue fracture surfaces were observed by using scanning electron microscopy (SEM), and the results indicated that fatigue cracks originated from the surface or subsurface defects.

Effect of T6 Treatment on Low-Cycle Fatigue Properties of Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc Alloy

2014 ◽  
Vol 664 ◽  
pp. 28-33
Author(s):  
Ying Lan ◽  
Li Jia Chen ◽  
Xin Che ◽  
Feng Li
Keyword(s):  
Strain Hardening ◽  
Low Cycle Fatigue ◽  
Aging Treatment ◽  
Cyclic Strain ◽  
Cyclic Stress ◽  
Cyclic Strength ◽  
Fatigue Properties ◽  
Strain Hardening Exponent ◽  
Cycle Fatigue ◽  
Linear Behavior

The low-cycle fatigue behaviors of as-extruded and T6 treated Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloys at room temperature have been investigated under those total-strain amplitudes ranged from 0.3% to 1.0%, and the influence of T6 treatment on the low-cycle fatigue properties of Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy was clarified. The experimental results show that during fatigue deformation, the significant cyclic strain hardening and stable cyclic stress response can be noted for both as-extruded and T6 treated Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloys. The fatigue life of as-extruded Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy at all strain amplitudes is longer than that of the alloy subjected to T6 aging treatment. The relationship between both elastic and plastic strain amplitudes with reversals to failure shows a monotonic linear behavior, and can be described by the Basquin and Coffin-Manson equations, respectively. The T6 treatment can significantly increase the cyclic strain hardening exponent and cyclic strength coefficient of extruded Al-6Zn-2.5Mg-2Cu-0.1Zr-0.1Sc alloy.

Uniaxial Ratcheting and Low-Cycle Fatigue Failure of U75V Rail Steel

2016 ◽  
Vol 853 ◽  
pp. 246-250 ◽  
Author(s):  
Tao Fang ◽  
Qian Hua Kan ◽  
Guo Zheng Kang ◽  
Wen Yi Yan
Keyword(s):  
Fatigue Life ◽  
Strain Amplitude ◽  
Stress Ratio ◽  
Stress Amplitude ◽  
Rail Steel ◽  
Low Cycle Fatigue ◽  
Mean Stress ◽  
Cycle Fatigue ◽  
Ratcheting Strain ◽  
Cyclic Straining

Experiments on U75V rail steel were carried out to investigate the cyclic feature, ratcheting behavior and low-cycle fatigue under both strain- and stress-controlled loadings at room temperature. It was found that U75V rail steel shows strain amplitude dependent cyclic softening feature, i.e., the responded stress amplitude under strain-controlled decreases with the increasing number of cycles and reaches a stable value after about 20th cycle. Ratcheting strain increases with an increasing stress amplitude and mean stress, except for stress ratio, and the ratcheting strain in failure also increases with an increasing stress amplitude, mean stress and stress ratio. The low-cycle fatigue lives under cyclic straining decrease linearly with an increasing strain amplitude, the fatigue lives under cyclic stressing decrease with an increasing mean stress except for zero mean stress, and decrease with an increasing stress amplitude. Ratcheting behavior with a high mean stress reduces fatigue life of rail steel by comparing fatigue lives under stress cycling with those under strain cycling. Research findings are helpful to evaluate fatigue life of U75V rail steel in the railways with passenger and freight traffic.

Low Cycle Fatigue Properties of FGH720Li Superalloy

2021 ◽  
Vol 1035 ◽  
pp. 292-296
Author(s):  
Zi Chao Peng ◽  
Jun Ying Sheng ◽  
Xu Qing Wang ◽  
Yue Tang
Keyword(s):  
Fatigue Life ◽  
Powder Metallurgy ◽  
Applied Stress ◽  
Low Cycle Fatigue ◽  
Influencing Factor ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Nickel Base Superalloy ◽  
Loading Frequency ◽  
Cycle Fatigue

Low cycle fatigue (LCF) properties of a powder metallurgy(PM) nickel base superalloy FGH720Li were systematically studied in this work, including smooth LCF and notched LCF tested at various temperatures and different stress. The relationship between the fatigue life and applied stress was analyzed both for smooth fatigue and notch fatigue tests. The effects of loading frequency and stress ratio on LCF behavior were also studied. As an important influencing factor of the fatigue life in powder metallurgy superalloy, the effect of inclusions on LCF life was also investigated. The results showed that the fatigue properties of FGH720Li alloy was excellent, when tested at the temperature of 450°C and applied stress of 1230MPa, the fatigue life could exceed 5×104 cycles. When tested at 650°C and 1150MPa, the average fatigue life was still beyond 2×105 cycles.

On cyclic stress–strain behaviour and low cycle fatigue life

2002 ◽  
Vol 23 (3) ◽  
pp. 249-254 ◽  
Author(s):  
S. Ganesh Sundara Raman ◽  
V.M. Radhakrishnan
Keyword(s):  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Cyclic Stress ◽  
Cycle Fatigue ◽  
Stress Strain ◽  
Strain Behaviour

Effect of Fiber Volume Fraction on Low Cycle Fatigue Behavior of Al2O3f/Al-Si Composites

2012 ◽  
Vol 268-270 ◽  
pp. 87-91
Author(s):  
Jian Jun Cui ◽  
Bing Chao Li ◽  
Guo Hua Zhang ◽  
Jian Xin Zhang ◽  
Zuo Shan Wei ◽  
...  
Keyword(s):  
Volume Fraction ◽  
Low Cycle Fatigue ◽  
Fatigue Behavior ◽  
Fatigue Cracks ◽  
Fatigue Tests ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Short Fibers ◽  
Fiber Volume ◽  
Large Size

The tensile and low cycle fatigue tests were carried out on alumina short fibers reinforced Al-Si piston alloy composites (Al-Si MMCs). Three Al-Si MMCs reinforced with 10, 17 and 25 vol.% of alumina short fibers were prepared to investigate the effects of volume fraction on tensile and low cycle fatigue properties at room temperature (RT) and 350°C. The results showed that the tensile strength decreased with the increasing of volume fraction of fibers at RT and was slight different at 350°C. Among the three MMCs, the 17%-MMCs showed highest stress level under the low cycle fatigue tests. The fatigue cracks were usually initiated from the clustered and large size fibers near the surface of specimen, propagated along the fiber/matrix interface at RT and grew rapidly by means of broken the fibers at 350°C.

Comparative Study of Microstructure and High Temperature Low Cycle Fatigue Behaviour of Nickel Base Superalloys Inconel 713LC and MAR-M247

2016 ◽  
Vol 713 ◽  
pp. 86-89 ◽  
Author(s):  
Ivo Šulák ◽  
Karel Obrtlík ◽  
Ladislav Čelko
Keyword(s):  
High Temperature ◽  
Fatigue Life ◽  
Low Cycle Fatigue ◽  
Strain Curve ◽  
Cyclic Stress ◽  
Fatigue Tests ◽  
Casting Defects ◽  
Cycle Fatigue ◽  
Stress Strain Curve ◽  
Nickel Base

The present work is focused on the study of microstructure and low cycle fatigue behavior of the first generation nickel-base superalloy IN 713LC (low carbon) and its promising second generation successor MAR-M247 HIP (hot isostatic pressing) at 900 °C. Microstructure of both alloys was studied by means of scanning electron microscopy (SEM). The microstructure of both materials is characterized by dendritic grains, carbides and casting defects. Size and morphology of precipitates and casting defects were evaluated. Fractographic observations have been made with the aim to reveal the fatigue crack initiation place and relation to the casting defects and material microstructure. Low cycle fatigue tests were conducted on cylindrical specimens in symmetrical push-pull cycle under strain control with constant total strain amplitude and strain rate at 900 °C in air. Hardening/softening curves, cyclic stress-strain curve and fatigue life data of both materials were obtained. Cyclic stress-strain curve of MAR M247 is shifted approximately to 120 MPa higher stress amplitudes in comparison with IN 713LC. Significantly higher fatigue life of MAR-M247 has been observed in Basquin representation. On the other hand IN 713LC shows prolonged lifetime compared with MAR-M247 in the Coffin-Manson representation. Results obtained from high temperature low cycle fatigue tests are discussed.

High-Temperature Fatigue Properties of Single Crystal Superalloys in Air and Hydrogen

2004 ◽  
Vol 126 (3) ◽  
pp. 590-603 ◽  
Author(s):  
N. K. Arakere
Keyword(s):  
Fatigue Life ◽  
Single Crystal ◽  
Room Temperature ◽  
Low Cycle Fatigue ◽  
Turbine Blades ◽  
Fatigue Properties ◽  
Cycle Fatigue ◽  
Fatigue Data ◽  
Blade Tip ◽  
Pressure Hydrogen

Hot section components in high-performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys such as PWA1480, PWA1484, CMSX-4, and Rene N-4 as these materials provide superior creep, stress rupture, melt resistance, and thermomechanical fatigue capabilities over their polycrystalline counterparts. Fatigue failures in PWA1480 single crystal nickel-base superalloy turbine blades used in the space shuttle main engine fuel turbopump are discussed. During testing many turbine blades experienced stage II noncrystallographic fatigue cracks with multiple origins at the core leading edge radius and extending down the airfoil span along the core surface. The longer cracks transitioned from stage II fatigue to crystallographic stage I fatigue propagation, on octahedral planes. An investigation of crack depths on the population of blades as a function of secondary crystallographic orientation (β) revealed that for β=45+/−15 deg tip cracks arrested after some growth or did not initiate at all. Finite element analysis of stress response at the blade tip, as a function of primary and secondary crystal orientation, revealed that there are preferential β orientations for which crack growth is minimized at the blade tip. To assess blade fatigue life and durability extensive testing of uniaxial single crystal specimens with different orientations has been tested over a wide temperature range in air and hydrogen. A detailed analysis of the experimentally determined low cycle fatigue properties for PWA1480 and SC 7-14-6 single crystal materials as a function of specimen crystallographic orientation is presented at high temperature (75°F–1800°F) in high-pressure hydrogen and air. Fatigue failure parameters are investigated for low cycle fatigue data of single crystal material based on the shear stress amplitudes on the 24 octahedral and 6 cube slip systems for FCC single crystals. The max shear stress amplitude [Δτmax] on the slip planes reduces the scatter in the low cycle fatigue data and is found to be a good fatigue damage parameter, especially at elevated temperatures. The parameter Δτmax did not characterize the room temperature low cycle fatigue data in high-pressure hydrogen well because of the noncrystallographic eutectic failure mechanism activated by hydrogen at room temperature. Fatigue life equations are developed for various temperature ranges and environmental conditions based on power-law curve fits of the failure parameter with low cycle fatigue test data. These curve fits can be used for assessing blade fatigue life.

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