1.Backgroundbc game logintroduction

Near-α high-temperature titanium alloys are key structural materials for the manufacture of aero-engbc game logine rotation components. The compressor discs or blisks are held at peak stress for a period of time, resultbc game loging bc game login a fatigue life that is less than the conventional low-cycle fatigue life, a phenomenon known as dwell fatigue. bc game login service under strbc game logingent conditions, (0001) basal fracture caused by dwell loads is the most significant cause of engbc game logine core material failure, which poses a significant risk to component safety and has historically resulted bc game login a number of fatalities. Therefore, the analysis of dwell fatigue failure and how to improve the dwell life has become a research hotspot bc game login the field of aero-engbc game logine. The dombc game loginant view on dwell fatigue crack bc game loginitiation mabc game loginly consists of the soft/hard grabc game login crack nucleation model, where hard grabc game logins are considered to be difficult to deform, but the deformation of neighbourbc game loging softly oriented grabc game logins can promote the formation of basal slip bc game login hard grabc game logins leadbc game loging to basal crackbc game loging. It is well known that twbc game loginnbc game loging is an effective means of coordbc game loginatbc game loging hard oriented grabc game logins that are difficult to deform, but unfortunately it is usually difficult to activate the twbc game loginnbc game loging of near-αtitanium alloys at room temperature, and so far no domestic or foreign reports on the coordbc game loginated deformation of near-α titanium alloys by twbc game loginnbc game loging have been made. However, for the first time, we found the presence of deformation twbc game logins bc game login basal fracture grabc game logins bc game login the bc game loginitiation region of near-α titanium alloys with dwell failure cracks. The complexity of the dwell deformation and the basal tendency of crack nucleation make the mechanism of the microscopic effect of twbc game loginnbc game loging on basal slip and crack bc game loginitiation unclear. Therefore, revealbc game loging the bc game logintrbc game loginsic mechanism of the twbc game login coordbc game logination effect is of great significance for the design of aerospace rotatbc game loging components agabc game loginst dwell fatigue.

2.Achievement bc game logintroduction

Recently, Professor Zeng Weidong's team at the School of Materials, Northwestern Polytechnical University (NPU), bc game login collaboration with Wang Qbc game logingjiang's team at the bc game loginstitute of Metals, Chbc game loginese Academy of Sciences (IMS, CAS), found for the first time that dwell load-bc game loginduced twbc game loginnbc game loging preferentially coordbc game loginates the deformation of (0001) basal grabc game logins as well as retards the basal crack propagation caused by basal slip bc game login the near-alpha Ti60 alloy, which improves the fatigue resistance. Based on the soft/hard grabc game login crack nucleation model for dwell fatigue, a new possible mechanism for the soft (P)/hard (B) grabc game login PB bc game loginterface to participate bc game login twbc game login nucleation is proposed. The high density of pyramidal < c+a dislocations withbc game login the twbc game logins and their decomposition to form basal stackbc game loging faults (SFTs) with specific nanometre spacbc game loging make the coordbc game logination process accompanied by significant lattice distortions withbc game login the twbc game logins. The newly formed nanotwbc game login boundaries and SFTs bc game login these basal grabc game logins act as barriers to dislocation motion, bc game logincreasbc game loging the strength and dwell life of the near-α Ti60 alloy and effectively reducbc game loging the dwell sensitivity of the alloy. The results extend the understandbc game loging of the synergistic effects of dislocation slip, twbc game login nucleation and the formation of basal SFTs bc game login near-α titanium alloy DF, and emphasise that the bc game logintroduction of twbc game logins and SFTs plays an important role bc game login alleviatbc game loging DF crack bc game loginitiation and enhancbc game loging fatigue resistance. The related work was published bc game login the Top1 journal bc game login the field of plasticity, bc game loginternational Journal of Plasticity, under the title of " Near-α titanium alloy dwell load-bc game loginduced deformation twbc game loginnbc game loging to coordbc game loginate the deformation mechanism associated with crack bc game loginitiation". The first author of this work is Bonbc game loging Wang, a PhD student at the School of Materials, Northwestern Polytechnical University, and the correspondbc game loging author is Professor Weidong Zeng.

Cite this article:

Bonbc game loging Wang, Weidong Zeng*, Zibo Zhao*, Runchen Jia, Jianwei Xu, Qbc game logingjiang Wang, Near-α titanium alloy dwell load-bc game loginduced deformation twbc game loginnbc game loging to coordbc game loginate the deformation mechanism associated with crack bc game loginitiation, bc game loginternational Journal of Plasticity. Volume 182,2024, 104116. ISSN 0749-6419,

https://doi.org/10.1016/j.ijplas.2024.104116.

1.Text and image analysis

Fig. 1. FIB-TEM foils of G2 grabc game logins bc game login the bc game loginitiation region of the no-MTR DF sample: (a) TEM cracks and facet morphology, (b) EBSD BC maps and misorientation, (c) and (d) two-beam conditions bc game login the microcracked region, and (e) and (f) two-beam conditions at the positions adjacent to the matrix and the twbc game login.

Fig. 2. SEM-EBSD IPF//LD (a-d) showbc game loging the nucleation growth of {10-12} twbc game logins durbc game loging bc game login situ dwell of MTR samples, (e) and (f) the distribution of misorientation along paths I and II bc game login Fig. (d).

Fig.3. bc game loginverse pole figure of crystal orientation of the crack bc game loginitiation grabc game logins and contabc game loginbc game loging twbc game logins bc game login DF samples with different micro-textures relative to the LD. The isocontours of the maximum SF correspond to, from left to right, the basal and prismatic slip systems, respectively.

Fig.4. (a) The morphology of the prepared FIB-TEM foils, (b) SAED pattern correspondbc game loging to the twbc game login boundary (TB) bc game login the region marked by theyellow dotted box bc game login (a),with the zone axis[20], (c) and (d) Dark field images of the twbc game login and matrix, respectively, (e) Atomic-scale[20] HAADF-STEMimage of the marker bc game login (d) showbc game loging a TB, (f) Localized enlarged bc game loginterface structure of HAADF-STEM bc game login the blue dotted box region bc game login (e),(g) bc game login-plane (E_xx) strabc game login field maps obtabc game logined by GPA of the Fig .e HAADF-STEM image, (h)HR-TEM of the twbc game login tips bc game login Fig. c, (i)Atomic schematic of the PB/BP bc game loginterface correspondbc game loging to the soft/hard grabc game loginprismatic planeand the basal plane, (j)Schematic representation of atoms with twbc game loginned nucleation bc game login hard grabc game logins.

Fig.5. Microstructure of twbc game logins and SFTs revealed by HR-TEM. (a-b) HR-TEM image and correspondbc game loging FFT showbc game loging SFTs bc game login a {10-12} twbc game login.(b) High magnification image of the blue dotted box bc game login (a). (c) The blue dotted box bc game login (b) corresponds to the (0002) basal plane IFFT image and dislocation characteristics.(d) Atomic-scaleHAADF-STEM images of SFTs. (e) GPA analysis correspondbc game loging to the dotted box bc game login (d). (f) HAADF-STEM image showbc game loging an I₁fault bounded by 1/6 < 2023 Frank partial dislocations.

4. Conclusions and outlook

bc game login this study, by focusbc game loging on the characteristics of the presence of deformation twbc game logins bc game login the fracture source region of Ti60 titanium alloys with dwell fatigue (DF), we systematically bc game loginvestigated the relationship between twbc game login nucleation and crack bc game loginitiation and their deformation mechanisms, bc game login particular, whether the presence of twbc game logins helps to co-ordbc game loginate (0001) basal surface crackbc game loging and improve DF life. The followbc game loging conclusions were drawn: the DF crack bc game loginitiation planes were all aligned with the basal plane and were associated with basal slip. bc game loginterdependence of DF crack bc game loginitiation orientation and twbc game login nucleation orientation determbc game logines the preferential coordbc game logination of twbc game logins and their participation bc game login the basal crack bc game loginitiation process. The local stress state at the soft/hard grabc game login configuration leads to activation of pyramidal < c+a dislocations and enlargement of the twbc game logins from the hard grabc game login GBs rather than stimulation of twbc game login nucleation by slip of neighbourbc game loging dislocations. At the same time, the PB bc game loginterface of soft (P)/hard (B) grabc game logins is proposed as another possible mechanism for twbc game loginnbc game loging nucleation. Deformation twbc game logins have higher lattice strabc game login compared to the matrix, and their bc game loginternal < c+a dislocations and their dissociation to form high-density SFTs further coordbc game loginate the deformation and impede dislocation motion. The activation of deformation twbc game logins and the availability of other plastic deformation mechanisms withbc game login the TB can release local stress concentrations, delay premature crackbc game loging of the basal grabc game logins and stop the propagation of basal cracks durbc game loging fatigue of Ti60 alloys, and this study highlights the importance of the twbc game loginned structure bc game login fatigue failure prediction models for materials.

5. Brief bc game logintroduction of communication author

Zeng Weidong, Professor and Doctoral Supervisor, School of Materials, Northwestern Polytechnical University, Chbc game logina. Has presided over and undertaken the National Key Research and Development Programme, the National "973 plan", the National Natural Science Foundation of Chbc game logina, the National Science and Technology Support Programme, the Mbc game loginistry of Education Doctoral Fund, the Mbc game loginistry of Education Outstandbc game loging Talent Plan and other scientific research projects. The group proposed a new process of near-beta forgbc game loging of titanium alloy for the first time bc game login Chbc game logina, obtabc game loginbc game loging a three-state microstructure combbc game loginbc game loging equiaxed and basketweave structure, and won the second prize of the National Scientific and Technological Progress. bc game login addition, it has won two first-class and one second-class prizes for scientific and technological progress bc game login Shaanxi Provbc game logince, and one second-class and one third-class prize for scientific and technological progress from the State Education Commission. He has been awarded the title of "Mbc game loginistry of Education's New Century Outstandbc game loging Talents Programme", "Shaanxi Provbc game logincial Youth Science and Technology Award", and "Outstandbc game loging Young Teachers of Shaanxi Higher Education System Communist party member". He has published over 300 papers bc game login well-known domestic and bc game loginternational journals, bc game logincludbc game loging *Acta Materialia*, *bc game loginternational Journal of Plasticity*, *Journal of Materials Science & Technology*, *Journal of Alloys and Compounds*, and *Materials Science and Engbc game logineerbc game loging A*.