Please wait a minute...
Acta Metall Sin  2025, Vol. 61 Issue (8): 1141-1152    DOI: 10.11900/0412.1961.2023.00320
Research paper Current Issue | Archive | Adv Search |
Influence of Peak Stress on Room Temperature Dwell Effect in Ti6242 Compressor Disc Forging
XU Xiaoyan1, FANG Chao2,3, QIU Jianke2,3(), ZHANG Mengmeng2,3, SHI Donggang1, MA Yingjie2,3, LEI Jiafeng2,3, YANG Rui2,3()
1.AECC Commercial Aircraft Engine Co. Ltd., Shanghai 200241, China
2.Shi -changxu Innovation Center for Advanced Materials, Institute of Metal Research, Chinese Academy of Sciences, Shenyang 110016, China
3.School of Materials Science and Engineering, University of Science and Technology of China, Shenyang 110016, China
Cite this article: 

XU Xiaoyan, FANG Chao, QIU Jianke, ZHANG Mengmeng, SHI Donggang, MA Yingjie, LEI Jiafeng, YANG Rui. Influence of Peak Stress on Room Temperature Dwell Effect in Ti6242 Compressor Disc Forging. Acta Metall Sin, 2025, 61(8): 1141-1152.

Download:  HTML  PDF(4187KB) 
Export:  BibTeX | EndNote (RIS)      
Abstract  

Cold dwell-fatigue failure in titanium components of gas turbine engines has been a concern for over five decades, posing a continuous threat to the safe operation of aircrafts. Owing to the complexity of influencing factors and mechanisms, there has been a lack of complete understanding and effective prevention of cold dwell effect. In this study, the effects of peak stresses on the dwell effect at room temperature were investigated, focusing on a large compressor disc manufactured from Ti6242 alloy, specifically designed for use in commercial aeroengines in China. The relationships between fatigue life and peak stress were fitted by the Basquin equation, and the stress threshold value of cold dwell effect was obtained. A detailed characterization of the fatigue failure characteristics and microscopic mechanisms was performed using OM, SEM, XCT, EBSD, and TEM techniques. The results revealed a progression of dwell fatigue-fracture characteristics in Ti6242 alloy as the peak stress increased from near-threshold value of the dwell effect to the value exceeding the yield strength. The failure characteristics included initiation of surface crack, mixed surface and subsurface crack, subsurface crack, and mixed subsurface crack and tensile dimples. Initiation facets formed due to dwell fatigue loading exhibited decreasing spatial angles with increasing peak stress levels in the range of ~20o-44o for the stress levels studied. However, the spatial orientations of the propagation facets formed due to dwell fatigue loading were unaffected by the peak stress and remained at less than ~20o. Dwell fatigue stimulated the formation of dense dislocation planar slip bands, facilitating their transfer across the secondary α (αs) lamellae and eventually resulting in long-distance slips. Increasing stress further relaxed the crystallographic conditions necessary for the crack initiation, leading to dislocation sliding and cleavage cracking in unfavorably oriented soft and hard grains. Consequently, at higher stress levels the cleavage facets exhibited a larger spatial orientation range, accompanied by the formation of more fatigue cracks. In the case of dwell fatigue, high-stress levels activated <c + a> dislocations and pyramidal slips. The size and number of fatigue cracks were related to the peak stress. Quantitative characterization of secondary cracks in the dwell fatigue specimens using XCT indirectly showed the average size of macrozones in Ti6242 compressor disc to be approximately 72 μm. The Ti6242 compressor disc exhibited a relatively strong texture, featuring a <112¯0> partial fiber along the axial direction and a <0001> partial fiber aligned with the radial and transverse directions. Based on the spatial orientation of facets on the fracture surface, a method using EBSD data to identify a microstructural feature parameter indicative of dwell fatigue performance was proposed, i.e., the cluster size of α grains with the c-axes inclined within ~30° to the loading direction.

Key words:  Ti6242 alloy      dwell fatigue      peak stress      quasi-cleavage facet      microtexture     
Received:  10 August 2023     
ZTFLH:  TG146.23  
Fund: National Natural Science Foundation of China(91960202);National Natural Science Foundation of China(51701219);National Key Research and Development Program of China(2021YFC2800503);National Key Research and Development Program of China(2022YFB3708300);CAS Project for Young Scientists in Basic Research(YSBR-025);Youth Innovation Promotion Association, CAS(2022188)
Corresponding Authors:  QIU Jianke, professor, Tel: (024)83970131, E-mail: jkqiu@imr.ac.cn;

URL: 

https://www.ams.org.cn/EN/10.11900/0412.1961.2023.00320     OR     https://www.ams.org.cn/EN/Y2025/V61/I8/1141

Fig.1  Schematic of sampling in the AD-RD section plane (AD—axial direction, RD—radial direction, TD—transverse direction) (a) and typical OM image (b) of Ti6242 compressor disc; loading waveforms for normal fatigue (NF) (c1) and dwell fatigue (DF) (c2) with test parameters indicated (σ0.2—yield strength, σmax—peak stress, R—stress ratio); and dimensions of fatigue (d) and tensile (e) specimens (unit: mm)
Fig.2  Fatigue lives (Nf) of Ti6242 alloy plotted as a function of the σmax (R = 0.05)
Fig.3  OM images illustrating NF (a1-a3) and DF (b, b1-b3) fracture surfaces of Ti6242 alloy at peak stresses of 0.85σ0.2 (b), 0.94σ0.2 (a1, b1), 0.98σ0.2 (a2, b2), and 1.05σ0.2 (a3, b3) with the faceted initiation sites circumscribed by elliptical circles
Fig.4  SEM images of DF fracture surfaces of Ti6242 alloy at peak stresses of 0.85σ0.2 (a1, b1), 0.94σ0.2 (a2, b2), 0.98σ0.2 (a3, b3), and 1.05σ0.2 (a4, b4), showing low magnification of the crack initiation zones (a1-a4) and high magnification images of quasi-cleavage facets and dimples in the region outlined by the elliptical circles in Figs.4a1-a4 (b1-b4)
Fig.5  Distributions of spatial orientations of the quasi-cleavage facets on NF (a) and DF (b) fractures of Ti6242 alloy at various peak stresses (θ—angle between the facet normal and stress axis)
Fig.6  Three-dimensional rendering of Ti6242 alloy NF fractures with XCT showing subsidiary cracks below the main fracture surface from front (a1-a3) and top (b1-b3) views at peak stresses of 0.94σ0.2 (a1, b1), 0.98σ0.2 (a2, b2), and 1.05σ0.2 (a3, b3)
Fig.7  Three-dimensional rendering of Ti6242 alloy DF fractures with XCT showing subsidiary cracks below the main fracture surface from front (a1-a4) and top (b1-b4) views at peak stresses of 0.85σ0.2 (a1, b1), 0.94σ0.2 (a2, b2), 0.98σ0.2 (a3, b3), and 1.05σ0.2 (a4, b4)

Fatigue

waveform

Peak stress

MPa

Number of

secondary crack

Maximum individual size

μm

Average individual size

μm

NF0.94σ0.242114862
1.05σ0.210138692
DF0.85σ0.2256641
0.94σ0.23626694
0.98σ0.228264767
1.05σ0.2372043955
Table 1  Statistics on the number and size of internal secondary cracks in NF and DF fractures from XCT datasets
Fig.8  Microtexture analyses in the AD-RD plane of the Ti6242 compressor disc
(a) crystallographic orientation map
(b) pole figures of α phase in Fig.8a
(c) α phase with c-axis deviation from TD less than 30° (The black and green lines represent the grain boundaries> 10° and subgrain boundaries 2°-10°, respectively)
(d) pole figures of α phase in Fig.8c
Fig.9  Bright-field TEM images showing typical dislocation activities in the primary α (αp) (a1-a3) and β transformed regions containing secondary α (αs) (b1-b3) of NF specimens of Ti6242 alloy at peak stresses of 0.94σ0.2 (a1, b1), 0.98σ0.2 (a2, b2), and 1.05σ0.2 (a3, b3)
Fig.10  Bright-field TEM images showing typical dislocation activities in the αp (a1-a4, b2, b4) and β transformed regions containing αs (b1, b3) of DF samples of Ti6242 alloy at peak stresses of 0.85σ0.2 (a1, b1), 0.94σ0.2 (a2, b2), 0.98σ0.2 (a3, b3), and 1.05σ0.2 (a4, b4)
[1] Bache M R. A review of dwell sensitive fatigue in titanium alloys: The role of microstructure, texture and operating conditions [J]. Int. J. Fatigue, 2003, 25: 1079
[2] Garvey J F. National Transportation Safety Board Safety Recommendation [R]. Washington, D. C.: National Transportation Safety Board, 2000
[3] BEA. Accident to the AIRBUS A380-861 equipped with Engine Alliance GP7270 engines registered F-HPJE operated by Air France on 30 September 2017 in cruise over Greenland (Denmark) [R]. France: French Civil Aviation Safety Investigation Authority, 2020
[4] Evans W J. Dwell-sensitive fatigue in a near alpha-titanium alloy [J]. J. Mater. Sci. Lett., 1987, 6: 571
[5] Evans W J, Bache M R. Dwell-sensitive fatigue under biaxial loads in the near-alpha titanium alloy IMI685 [J]. Int. J. Fatigue, 1994, 16: 443
[6] Bache M R, Cope M, Davies H M, et al. Dwell sensitive fatigue in a near alpha titanium alloy at ambient temperature [J]. Int. J. Fatigue, 1997, 19: S83
[7] Woodfield A P, Gorman M D, Sutliff J A, et al. Effect of microstructure on dwell fatigue behavior of Ti-6242 [A]. Proceedings of the International Symposium on Fatigue Behavior of Titanium Alloys [C]. Chicago: TMS, 1999: 111
[8] Lavogiez C, Dureau C, Nadot Y, et al. Crack initiation mechanisms in Ti-6Al-4V subjected to cold dwell-fatigue, low-cycle fatigue and high-cycle fatigue loadings [J]. Acta Mater., 2023, 244: 118560
[9] Hémery S, Stinville J C. Microstructural and load hold effects on small fatigue crack growth in α + β dual phase Ti alloys [J]. Int. J. Fatigue, 2022, 156: 106699
[10] Sinha V, Mills M J, Williams J C. Crystallography of fracture facets in a near-alpha titanium alloy [J]. Metall. Mater. Trans., 2006, 37A: 2015
[11] Sinha V, Mills M J, Williams J C, et al. Observations on the faceted initiation site in the dwell-fatigue tested Ti-6242 alloy: Crystallographic orientation and size effects [J]. Metall. Mater. Trans., 2006, 37A: 1507
[12] Uta E, Gey N, Bocher P, et al. Texture heterogeneities in αP/αS titanium forging analysed by EBSD-relation to fatigue crack propagation [J]. J. Microsc., 2009, 233: 451
[13] Pilchak A L, Williams J C. Observations of facet formation in near-α titanium and comments on the role of hydrogen [J]. Metall. Mater. Trans., 2011, 42A: 1000
[14] Stroh A N. The formation of cracks as a result of plastic flow [J]. Proc. Roy. Soc., 1954, 223A: 404
[15] Qiu J K, Ma Y J, Lei J F, et al. A comparative study on dwell fatigue of Ti-6Al-2Sn-4Zr-xMo (x = 2 to 6) alloys on a microstructure-normalized basis [J]. Metall. Mater. Trans., 2014, 45A: 6075
[16] Pilchak A L. A simple model to account for the role of microtexture on fatigue and dwell fatigue lifetimes of titanium alloys [J]. Scr. Mater., 2014, 74: 68
[17] Kassner M E, Kosaka Y, Hall J S. Low-cycle dwell-time fatigue in Ti-6242 [J]. Metall. Mater. Trans., 1999, 30A: 2383
[18] Mcbagonluri F, Akpan E, Mercer C, et al. An investigation of the effects of microstructure on dwell fatigue crack growth in Ti-6242 [J]. Mater. Sci. Eng., 2005, A405: 111
[19] Zeng W D, Zhou Y G. The influence of microstructure on dwell sensitive fatigue in Ti-6.5Al-3.5Mo-1.5Zr-0.3Si alloy [J]. Mater. Sci. Eng., 2000, A290: 33
[20] Chandravanshi V, Prasad K, Singh V, et al. Effects of α + β phase deformation on microstructure, fatigue and dwell fatigue behavior of a near alpha titanium alloy [J]. Int. J. Fatigue, 2016, 91: 100
[21] Zheng Z B, Balint D S, Dunne F P E. Mechanistic basis of temperature-dependent dwell fatigue in titanium alloys [J]. J. Mech. Phys. Solids, 2017, 107: 185
[22] Harr M E, Daly S, Pilchak A L. The effect of temperature on slip in microtextured Ti-6Al-2Sn-4Zr-2Mo under dwell fatigue [J]. Int. J. Fatigue, 2021, 147: 106173
[23] You R Y, Zhang M M, Qiu J K, et al. Influence of hold time on dwell fatigue behavior in IMI834 disc forging [J]. JOM, 2022, 74: 3733
[24] Liu Y, Dunne F P E. The mechanistic link between macrozones and dwell fatigue in titanium alloys [J]. Int. J. Fatigue, 2021, 142: 105971
[25] Cuddihy M A, Stapleton A, Williams S, et al. On cold dwell facet fatigue in titanium alloy aero-engine components [J]. Int. J. Fatigue, 2017, 97: 177
[26] Dunne F P E, Rugg D. On the mechanisms of fatigue facet nucleation in titanium alloys [J]. Fatigue Fract. Eng. Mater. Struct., 2008, 31: 949
[27] Shen W, Soboyejo W O, Soboyejo A B O. An investigation on fatigue and dwell-fatigue crack growth in Ti-6Al-2Sn-4Zr-2Mo-0.1Si [J]. Mech. Mater., 2004, 36: 117
[28] Sinha V, Mills M J, Williams J C. Determination of crystallographic orientation of dwell-fatigue fracture facets in Ti-6242 alloy [J]. J. Mater. Sci., 2007, 42: 8334
[29] Sinha V, Jha S K, Pilchak A L, et al. Quantitative characterization of microscale fracture features in titanium alloys [J]. Metallogr. Microstruct. Anal., 2017, 6: 261
[30] Sinha V, Pilchak A L, Jha S K, et al. Correlating scatter in fatigue life with fracture mechanisms in forged Ti-6242Si alloy [J]. Metall. Mater. Trans., 2018, 49A: 1061
[31] Themelis G, Chikwembani S, Weertman J. Determination of the orientation of Cu-Bi grain boundary facets using a photogrammetric technique [J]. Mater. Charact., 1990, 24: 27
[32] Ranjan A, Singh A, Jha J S, et al. Effect of the primary alpha fraction on the dwell fatigue behaviour of Ti-6Al-4V alloy [J]. Int. J. Fatigue, 2023, 175: 107745
[33] Sinha V, Mills M J, Williams J C. Understanding the contributions of normal-fatigue and static loading to the dwell fatigue in a near-alpha titanium alloy [J]. Metall. Mater. Trans., 2004, 35A: 3141
[34] Pilchak A L, Bhattacharjee A, Rosenberger A H, et al. Low ΔK faceted crack growth in titanium alloys [J]. Int. J. Fatigue, 2009, 31: 989
[35] Suresh S, translated by Wang Z G. Fatigue of Materials [M]. 2nd Ed., Beijing: National Defense Industry Press, 1999: 209
Suresh S著, 王中光 译. 材料的疲劳 [M]. 第2版. 北京: 国防工业出版社, 1999: 209
[36] Bridier F, Villechaise P, Mendez J. Slip and fatigue crack formation processes in an α/β titanium alloy in relation to crystallographic texture on different scales [J]. Acta Mater., 2008, 56: 3951
[37] Lavogiez C, Hémery S, Villechaise P. On the mechanism of fatigue and dwell-fatigue crack initiation in Ti-6Al-4V [J]. Scr. Mater., 2020, 183: 117
[38] Hémery S, Stinville J C, Wang F, et al. Strain localization and fatigue crack formation at (0001) twist boundaries in titanium alloys [J]. Acta Mater., 2021, 219: 117227
[39] Germain L, Gey N, Humbert M, et al. Analysis of sharp microtexture heterogeneities in a bimodal IMI 834 billet [J]. Acta Mater., 2005, 53: 3535
[40] Germain L, Gey N, Humbert M, et al. Texture heterogeneities induced by subtransus processing of near α titanium alloys [J]. Acta Mater., 2008, 56: 4298
[41] Gey N, Bocher P, Uta E, et al. Texture and microtexture variations in a near-α titanium forged disk of bimodal microstructure [J]. Acta Mater., 2012, 60: 2647
[42] Germain L, Samih Y, Delaleau P, et al. Analysis of cold dwell fatigue crack initiation site in a β-forged Ti-6242 disk in relation with local texture [J]. Metals, 2020, 10: 951
[43] Kirane K, Ghosh S. A cold dwell fatigue crack nucleation criterion for polycrystalline Ti-6242 using grain-level crystal plasticity FE model [J]. Int. J. Fatigue, 2008, 30: 2127
[1] QI Min, WANG Qian, MA Yingjie, CAO Hemeng, HUANG Sensen, LEI Jiafeng, YANG Riu. Growth Behavior of Grain Boundary α Phase and Its Effect on the Microtexture During βα Phase Transformation in Ti6246 Titanium Alloys[J]. 金属学报, 2025, 61(2): 265-277.
[2] ZHANG Bin, TIAN Da, SONG Zhuman, ZHANG Guangping. Research Progress in Dwell Fatigue Service Reliability of Titanium Alloys for Pressure Shell of Deep-Sea Submersible[J]. 金属学报, 2023, 59(6): 713-726.
[3] SUN Xiurong, WANG Huizhen, YANG Ping, MAO Weimin. MECHANICAL BEHAVIORS AND MICRO-SHEAR STRUCTURES OF METALS WITH DIFFERENT STRUCTURES BY HIGH-SPEED COMPRESSION[J]. 金属学报, 2014, 50(4): 387-394.
[4] YANG Xuyue SUN Huan WU Xinxing MA Jijun QIN Jia HUO Qinghuan. EVOLUTIONS OF MICROSTRUCTURE AND MICROTEXTURE IN AZ21 Mg ALLOY DURING MULTI–DIRECTIONAL FORGING UNDER DECREASING TEMPERATURE CONDITIONS[J]. 金属学报, 2012, 48(2): 129-134.
[5] WU Xinxing YANG Xuyue ZHANG Lei ZHANG Zhiling. EFFECT OF ORIGINAL ORIENTATION ON MICROTEXTURE EVOLUTION OF AZ31 Mg ALLOY[J]. 金属学报, 2011, 47(2): 140-144.
[6] CHEN Lei WANG Longmei DU Xiaojian LIU Xiao. HOT DEFORMATION BEHAVIOR OF 2205 DUPLEX STAINLESS STEEL[J]. 金属学报, 2010, 46(1): 52-56.
[7] XU Yourong;GU Qing;WANG Deying Shanghai University of Science and Technology; GU Jufang;QU Tiancai Shanghai Iron and Steel Research Institute. DYNAMIC MECHANICAL BEHAVIOURS OF HIGH Mo AUSTENITE STAINLESS STEEL DURING HOT DEFORMATION[J]. 金属学报, 1991, 27(4): 134-138.
No Suggested Reading articles found!