Effects of Microstructural Anisotropy on the Dwell Fatigue Life of Ti-6Al-4V Bar

2021 ◽  
Author(s):  
Kenichi Mori ◽  
Shohtaroh Hashimoto ◽  
Mitsuo Miyahara
Keyword(s):  
Fatigue Life ◽  
Dwell Fatigue ◽  
Microstructural Anisotropy

scholarly journals PRELIMINARY INVESTIGATION OF BILLET PROCESSING ROUTE ON MICROSTRUCTURE, TEXTURE AND FATIGUE RESPONSE OF Ti834 FORGED DISC PRODUCTS

2020 ◽  
Vol 321 ◽  
pp. 11031
Author(s):  
B. Fernandez-Silva ◽  
B. P. Wynne ◽  
M. Jackson ◽  
M. Bodie ◽  
K. Fox
Keyword(s):  
Fatigue Life ◽  
Texture Analysis ◽  
Fatigue Fracture ◽  
Thermomechanical Processing ◽  
Preliminary Investigation ◽  
Processing Route ◽  
Bimodal Microstructure ◽  
Primary Alpha ◽  
Dwell Fatigue ◽  
Beta Matrix

Non-standard processing routes for the manufacture of industrial scale Ti834 billet have been undertaken to investigate their effect on macrozones in final forged product. Microstructure, texture and dwell fatigue fracture surfaces were characterised from forged disc samples fabricated from these new billets. All processing routes showed a bimodal microstructure consisting of 25pct of primary alpha grains in a transformed beta matrix. Texture analysis has revealed variations in the presence and size of macrozones with relatively weak textures. Quasi-cleavage facets were present in all dwell fatigue samples although the fatigue life was doubled for the sample whose thermomechanical processing has the highest imposed strain.

scholarly journals Effect of Rise and Fall Time on Dwell Fatigue Behavior of a High Strength Titanium Alloy

Metals ◽  
2019 ◽  
Vol 9 (8) ◽  
pp. 914 ◽  
Author(s):  
Qingyuan Song ◽  
Yanqing Li ◽  
Lei Wang ◽  
Ruxu Huang ◽  
Chengqi Sun
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Crack Initiation ◽  
Cross Section ◽  
Fatigue Behavior ◽  
Circular Cross Section ◽  
High Strength ◽  
Initiation Mechanism ◽  
Fall Time ◽  
Dwell Fatigue

Frequency is an important factor influencing the fatigue behavior. Regarding to the dwell fatigue, it corresponds to the effect of rise and fall time, which is also an important issue especially for the safety evaluation of structure parts under dwell fatigue loading, such as the engines of aircrafts and the pressure hulls of deep-sea submersibles. In this paper, the effect of rise and fall time (2 s, 20 s, 110 s, and 200 s) on the dwell fatigue behavior is investigated for a high strength titanium alloy Ti-6Al-2Sn-2Zr-3Mo-X with basket-weave microstructure. It is shown that the dwell fatigue life decreases with increasing the rise and fall time, which could be correlated by a linear relation in log–log scale for both the specimen with circular cross section and the specimen with square cross section. The rise and fall time has no influence on the crack initiation mechanism by the scanning electron microscope observation. The cracks initiate from the specimen surface and all the fracture surfaces present multiple crack initiation sites. Moreover, the facet characteristic is observed at some crack initiation sites for both the conventional fatigue and dwell fatigue tests. The paper also indicates that the dwell period of the peak stress reduces the fatigue life and the dwell fatigue life seems to be longer for the specimen with circular cross section than that of the specimen with square cross section.

scholarly journals Dwell-fatigue life dispersion of a near alpha titanium alloy

2009 ◽  
Vol 31 (3) ◽  
pp. 601-605 ◽  
Author(s):  
L TOUBAL ◽  
P BOCHER ◽  
A MOREAU
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Dwell Fatigue ◽  
Alpha Titanium

Factors influencing dwell fatigue life in notches of a powder metallurgy superalloy

2013 ◽  
Vol 48 ◽  
pp. 55-67 ◽  
Author(s):  
T.P. Gabb ◽  
J. Gayda ◽  
J. Telesman ◽  
L.J. Ghosn ◽  
A. Garg
Keyword(s):  
Fatigue Life ◽  
Powder Metallurgy ◽  
Factors Influencing ◽  
Dwell Fatigue

scholarly journals Effects of Notches and Defects on Dwell Fatigue Mechanism and Fatigue Life of Ti-6Al-4V ELI Alloy Used in Deep-Sea Submersibles

2021 ◽  
Vol 9 (8) ◽  
pp. 845
Author(s):  
Jian Sun ◽  
Lei Wu ◽  
Chengqi Sun
Keyword(s):  
Fatigue Life ◽  
Deep Sea ◽  
Maximum Stress ◽  
Fatigue Testing ◽  
Fatigue Behavior ◽  
Local Maximum ◽  
Control Mode ◽  
Notched Specimens ◽  
Dwell Fatigue ◽  
Fatigue Mechanism

The notch (i.e., stress concentration) and defect are important factors influencing the conventional fatigue behavior of metallic materials. What is the influence of notches and defects on the dwell fatigue mechanism and fatigue life? In this paper, the effects of notches and defects on the dwell fatigue behavior of the Ti-6Al-4V ELI alloy used in deep-sea submersibles are investigated under the load control mode. It is shown that the dwell fatigue is insensitive to the defect size (190–438 μm) compared to the conventional fatigue. For notched specimens, they all present fatigue failure mode under dwell fatigue testing, and the dwell fatigue life is higher than that of the smooth specimen at the same local maximum stress. The dwell of the maximum stress has no influence on the fatigue life and failure mechanism for notched specimens. Moreover, the facet feature is observed in the crack initiation region for both the conventional and dwell fatigue of notched specimens. Electron backscatter diffraction observation indicates that the feature of the fine line markings on the facet in the image by scanning electron microscope is due to the steps on the fracture surface of the α grain.

scholarly journals The effect of loading direction on the dwell fatigue properties of Ti-6Al-4V forged bar with highly oriented texture

2020 ◽  
Vol 321 ◽  
pp. 11025
Author(s):  
Kenichi Mori ◽  
Shohtaroh Hashimoto ◽  
Toshiyuki Okui ◽  
Yoshihisa Shirai ◽  
Mitsuo Miyahara
Keyword(s):  
Fatigue Life ◽  
Fracture Surface ◽  
Surface Morphology ◽  
Room Temperature ◽  
Fatigue Properties ◽  
Fracture Surface Morphology ◽  
Creep Tests ◽  
Loading Direction ◽  
Dwell Fatigue ◽  
Oriented Texture

The purpose of this study was to improve our understanding of the effect of macro/micro texture on dwell fatigue properties. The Ti-6Al-4V forged bar with highly oriented texture and fine equiaxed microstructure was used. Dwell fatigue, cyclic fatigue and creep tests were conducted at room temperature by using specimens taken in the longitudinal (L) direction and the transverse (T) direction of the bar. The effects of loading direction on dwell fatigue life and fracture surface morphology were examined in detail. The dwell fatigue life in T direction was shorter than that in L direction. The fracture surface morphologies were characteristically varied by loading waveform, amplitude and directions. In the range of 93 - 95% of 0.2%PS, the characteristic large facets were observed in the T direction in dwell fatigue. Detailed analyses revealed that the large facet consists of multiple initiation facets and propagation facets. The propagation facet plane and crack propagation direction appeared to correspond to alpha (0001) <10-10>. Furthermore, the relationship between strain rate and life time was compared to that for room temperature creep. The deviation from the Monkman-Grant relationship corresponded to the change of the fracture surface morphology.

scholarly journals Data Driven Tools and Methods for Microtexture Classification and Dwell Fatigue Life Prediction in Dual Phase Titanium Alloys

2020 ◽  
Vol 321 ◽  
pp. 11091
Author(s):  
V. Venkatesh ◽  
R. Noraas ◽  
A. Pilchak ◽  
S. Tamirisa ◽  
K. Calvert ◽  
...  
Keyword(s):  
Fatigue Life ◽  
Life Prediction ◽  
Fatigue Life Prediction ◽  
Dual Phase ◽  
Modeling Tools ◽  
Dwell Fatigue ◽  
Integrated Computational Materials Engineering ◽  
Computational Materials ◽  
The Ohio State University ◽  
Near Term

Microtexture has been linked to large reductions in cold dwell fatigue (CDF) life of specific dual phase titanium alloy aeroengine components. A recently completed Metals Affordability Initiative (MAI) funded program led by Pratt & Whitney (P&W) and includes ATI Forged Products, Boeing, GE Aviation, Rolls Royce (RR), Arconic, Titanium Metals Corporation (TIMET), PCC-Wyman Gordon (PCC-WG), Scientific Forming Technologies (SFTC), Materials Resources LLC (MRL) and The Ohio State University (OSU) has developed improved techniques for the characterization of microtexured regions (MTR) in titanium billet and forgings, and integrated computational materials engineering (ICME). These methods are aimed at developing and integrating process and property modeling tools for the prediction of microtexture and fatigue life in titanium components. These characterization and fatigue life prediction tools have near-term application off ramps that will enable use for process and product development and quality control. Key results for two widely used alloys, Ti-6242 and Ti-64, will be reviewed in this paper.

scholarly journals Normal and dwell fatigue behavior of a near-alpha titanium alloy - IMI 834

2020 ◽  
Vol 321 ◽  
pp. 04005
Author(s):  
K.U. Yazar ◽  
Anish Karmakar ◽  
Vivek Sahu ◽  
Amit Bhattacharjee ◽  
Satyam Suwas
Keyword(s):  
Titanium Alloy ◽  
Fatigue Life ◽  
Fatigue Behavior ◽  
Fatigue Loading ◽  
Large Plastic Strain ◽  
Dwell Fatigue ◽  
Order Of Magnitude ◽  
Alpha Titanium ◽  
Imi 834 ◽  
Fully Lamellar

Dwell sensitivity of titanium alloys at ambient temperature (~250 C) is a well-known phenomenon, although the question about the exact micromechanical reasons responsible for this still remains open. In this work, the normal and dwell fatigue response of a near-alpha titanium alloy, IMI 834, is studied. Samples with three different microstructures, namely, fully lamellar, fully equiaxed and bimodal, are evaluated for their dwell fatigue behaviors. A reduction in fatigue life by at least an order of magnitude is seen in all the three microstructures. Large plastic strain accumulation (almost equal to the monotonic ductility) was observed during the dwell fatigue loading condition and this is held responsible for this large debit in fatigue life. The normal fatigue lives decreased in the order, bimodal > fully equiaxed > fully lamellar, while the dwell fatigue lives decreased in the order, fully equiaxed > fully lamellar > bimodal. Bimodal microstructure showed a dwell fatigue debit of 17, while fully lamellar and fully equiaxed showed a debit of 9 and 10, respectively.

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