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245 results on '"Dong, Longlong"'

32. Microstructural Evolution and Deformation Mechanisms of In Situ TiC Reinforced Ti‐6Al‐4V Composites during High‐Temperature Hot Compression.

Author

Dong, Longlong, Zheng, Zekun, Tuo, Jingpeng, Li, Xiang, Tang, Yan, Fu, Yongqing, Elmarakbi, Ahmed, Cui, Wenfang, Zhou, Lian, and Zhang, Yusheng

Subjects
STRAIN rate, FLOW instability, GRAPHENE oxide, DEFORMATIONS (Mechanics), MICROSTRUCTURE
Abstract

Deformation processing is a key strategy to improve the strength‐ductility of metal matrixcomposites. Herein, TiC/TC4 composites are spark plasma sintered usingreinforcement precursors of reduced graphene oxide to reinforce TC4 matrix. Inorder to investigate the hot deformation behaviors and mechanisms of TiC/TC4 composites, the composites are hot compressed over temperature range of 870–1070 °C and strain range of 0.001–10 s−1. The results indicate that the optimal processing window of hot deformation ismainly within the temperature range of 890–970 °C and the strain rate range of 0.01–0.1 s−1. The flow instability of TiC/TC4 composites occurs in the temperature range of 890–930 and 1000–1060 °C at the strain rate range from 0.1 to 10 s−1. The thermal deformation mechanism of TiC/TC4 composites in the processingwindow region involves continuous dynamic recrystallization and discontinuous dynamic recrystallization. TiC can effectively hinder thedislocation motion, leading to the generation of high‐density dislocationsaround TiC. Consequently, this promotes sub‐grains formation and rotation,facilitating CDRX. Meanwhile, TiC particle induces high‐angle grain boundarymigration and provides more nucleation sites for recrystallized grains. These findings enhance understanding the role of hot deformation behaviors of Ti compositesand provide insights into their deformation processing. [ABSTRACT FROM AUTHOR]

Published
2024
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33. Impact of induced shock waves on cavitation bubble collapse dynamics and load characteristics.

Author

Deng, Yuxuan, Gao, Wenrui, Liu, Xiaohui, Dong, Longlong, and Wang, Yanru

Subjects
SHOCK waves, BUBBLE dynamics, COMPUTER simulation, VELOCITY, CAVITATION
Abstract

Induced shock waves significantly influence cavitation evolution and load characteristics, offering a feasible means to control cavitation. However, the complex coupling mechanism between shock waves and cavitation remains to be fully elucidated. This study uses numerical simulations to investigate the effects of shock wave characteristics on cavitation dynamics and load characteristics under free field, near-rigid wall, and near-elastic–plastic wall conditions. Results show that the increased shock wave intensity accelerates cavitation collapses, increases collapse loads, and enhances the peak velocities of collapsing water jets, exacerbating damage to elastic–plastic structures. Reflection waves from rigid walls enhance the nonlinear characteristics of the cavitation collapses, leading to different collapse modes. Elastic–plastic thin walls, with limited reflection capability, exert a weaker influence on the dynamics of primary cavitation collapses but significantly alter the evolution of secondary collapses and their load intensities. The study provides a fitting formula for the relationship between burst distance, peak jet velocity, and corresponding time, which predicts the parameters of water jets from cavitation collapses within a specific range. These findings deepen the understanding of the interactions between cavitation and induced shock waves, significantly aiding in controlling and utilizing cavitation effects. [ABSTRACT FROM AUTHOR]

Published
2024
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40. Achieving High Strength and Superior Wear‐Resistant Properties in TiH2 Matrix Reinforced with Graphene Nanoplates.

Author

Yao, Fusheng, Xu, Kaixuan, Liu, Le, Zheng, Zekun, Chen, Anqi, Guo, Pingyi, Sun, Guodong, and Dong, Longlong

Subjects
TENSILE strength, HOT rolling, MECHANICAL wear, WEAR resistance, RAW materials, TITANIUM alloys
Abstract

In this work, low‐cost TiC/Ti composites with high strength‐ductility and superior abrasive resistance are fabricated using hydrogenation‐dehydrogenation powder and graphene nanoplates as raw materials via spark plasma sintering (SPS) and hot rolling (HR) processes. Effects of in situ TiC contents on the microstructure, mechanical properties and wear behavior of the TiC/Ti composites are investigated. The results indicate that the microstructure after HR is equiaxial α‐Ti grain with random orientation. The TiC/Ti composite exhibits higher strength compared to pure Ti matrix after HR. The ultimate tensile strength of the 1.82 vol% TiC/Ti composite is 1059 MPa, which represents a 49.3% increase compared to pure Ti. The coefficient of friction of the TiC/Ti composite decreases from 0.51 to 0.43 with an increase in TiC contents. The improvement of strength is attributed to refinement strengthening, dislocation strengthening and TiC load transfer. In addition, the increase of TiC contents will reduce the friction coefficient of the composites, thereby improving the wear resistance of the composites. The article proposes a cost‐effective method with good prospects for industrial applications to improve the mechanical properties and wear‐resistant properties of the titanium alloys. [ABSTRACT FROM AUTHOR]

Published
2024
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50. Design strategy of TiC reinforced heterogeneous Ti-composites with an induced <c + a> slip system for achieving high strength-ductility.

Author

Dong, Longlong, Tang, Yan, Fan, Wendian, Li, Xiang, Xu, Junjie, Sun, Guodong, Li, Mingjia, Fu, Yongqing, Elmarakbi, Ahmed, Wang, Lianwen, and Zhang, Yusheng

Subjects
TITANIUM composites, DUCTILITY, BIONICS
Abstract

Achieving high strength and ductility for Ti alloys and their composites has been a key objective and also a great challenge for their engineering applications. Herein, we designed TiC/(TC18 + TC4) composites with bionic and heterogeneously lamella structures, achieving an exceptional combination of high strength and ductility. This is attributed to the formation of alternative layers of TC18-coarse grains and TC4-fine grains with TiC precipitated at their interfaces. Plastic incompatibility of these three-phases produces significant hetero-deformation-induced hardening, induced by mutual interactions of heterogeneous grains and TiC precipitates, as well as activation of extensive < c + a > slip groups. An optimal yield strength of ∼ 1168 MPa and a uniform elongation of ∼ 6% have been achieved, which are much higher than those of the TC4 matrix (i.e. ∼919 MPa and ∼2%). This study provides a new strategy for composite designs to overcome the trade-off dilemma for strength-ductility. [ABSTRACT FROM AUTHOR]

Published
2024
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