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Unveiling the growth and morphological transition mechanisms of Al2Cu intermetallic compounds quantified by synchrotron X-ray tomography

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材料科学技术（英文版） 2025年第6期209卷 43-54页

作者： Zongye Ding Liao Yu Naifang Zhang Wenquan Lu Jianguo Li Qiaodan Hu Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China School of Mechatronic Engineering and Automation Foshan UniversityGuangdong 528225China Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong UniversityShanghai 200240China

Controlling the morphology of Al2Cu intermetallic compounds(IMCs)has been of importance to enhance the properties of Al-based ***,the quantification of Al2Cu IMCs with diversified morphologies is still lacking,and the morphological evolution of Al2Cu dendrites remains poorly *** synchrotron X-ray tomography,we have directly quantified the morphological evolution of proeutectic Al2Cu IMCs in directionally solidified Al-Cu *** three-dimensional(3D)morphologies of Al2Cu IMCs under different growth rates were quantified using volume,specific surface area,interconnectivity,tortuosity,and Gaussian *** faceted morphology under slow growth rate was divided into three different types,including single hollow prism,irregular prism lacking partial faces,and coalesced prism consisting of two adjacent *** morphological transition from faceted prism to non-faceted algae-like,irregular tree-like,and typically dendritic shapes with increasing growth rates was determined,reflecting the growth modes varied from lateral mode to intermediary and continuous *** non-faceted Al2Cu dendrite had one primary stem,three groups of secondary arms,and a faceted *** angles between secondary arms were 120°,and the tip consisted of(011)and(01(1))*** work provides a deep understanding of the formation and growth of complex IMCs in metallic alloys.

关键词： Proeutectic Al2Cu intermetallic Synchrotron tomography Directional solidification 3-D morphology

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Robust interfacial bonding achieved via phase separation induced by enhanced Al diffusion during AZ31/high-entropy alloy friction stir welding

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Journal of Magnesium and Alloys 2025年第3期13卷 1012-1019页

作者： Gaohui Li Haining Yao Boyuan Fu Ke Chen Katsuyoshi Kondoh Nannan Chen Min Wang School of Materials Science and Engineering Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Key Laboratory of Materials Laser Processing and Modification Shanghai Jiao Tong UniversityShanghai 200240China Joining and Welding Research Institute Osaka UniversityIbarakiOsaka 567-0047Japan

Welding high-entropy alloy(HEA)to Mg alloy has gained increasing attention for multi-metal structure design,while intrinsic sluggish diffusion kinetics of HEA conﬁnes diffusion-controlled interfacial reactions and makes it challenging to establish robust metallurgical *** study investigated welding of FeCoCrNiMn HEA to commercial AZ31 as a model combination to pioneer thisﬁ*** phase separation phenomenon was observed,with the diffusion accelerated by in-situ engineering a submicron-scale thick(∼400–500 nm)HEA nearby the interface into nanocrystalline-structure during friction stir *** grain boundaries generated in this nanocrystalline-interlayer serve as diffusion short-circuits and energetically preferred nucleation-sites,which promoted Al in AZ31 to diffuse into HEA and triggered quick separation into body-centered cubic AlNi-type and tetragonal FeCr-type *** and AZ31 were thus metallurgically bonded by these interfacial *** joint shows exceptional strength in tensile lap-shear testing with fracture largely occurred within AZ31 rather than right along interface as commonly reported previously for dissimilar joints.

关键词： High-entropy alloy Mg alloy Friction stir welding Diffusion Phase separation

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The precipitated phase regulation and performance optimization of laser cladding WC-modified Inconel 625 composite coatings

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International Journal of Advanced Manufacturing Technology 2025年第3期138卷 1477-1490页

作者： Liu, Tongtong Qu, Xiaoguang Zheng, Yi Lu, Hao Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai200240 China School of Materials Science and Engineering Shanghai University of Engineering Science Shanghai201602 China

In order to quantify the effect of WC-reinforced particles on phase transformation and performance modification of laser cladding IN625 coatings, in this study, the mechanical performance and phase transformation of laser cladding IN625/WC composite coatings with different WC contents were comprehensively and quantitatively analyzed via characterization and CALPHAD, respectively. Results demonstrated that the grain characteristics (i.e., size and texture) and mechanical properties (i.e., microhardness and wear resistance) of the composite coatings were synergistically improved with the increase of WC content. XRD and EDS analysis showed that the coatings were comprised of γ phase, Laves phase, carbide particles, and δ phase. Additionally, the variations of γ phase, δ phase, σ phase, Laves, M23C6, M12C, and M6C with temperature and WC content were calculated through the secondary development of Thermo-Calc software. The research revealed that as WC content increased, the mole fraction of carbides in the coating increased, while the mole fraction of δ phase slightly decreased. The mole fraction of σ phase initially increased and then decreased, reaching a peak when the WC content was 8%. Higher carbide content resulted in increased hardness and wear resistance. The γ′, γ″, and δ phases generally enhance the strength and hardness of the coating, while the σ phase and Laves phase seriously impair its plasticity. According to performance requirements, the content of reinforcing particles can be adjusted to effectively control the precipitation of strengthening phase and detrimental phase between dendrites via CALPHAD. © The Author(s), under exclusive licence to Springer-Verlag London Ltd., part of Springer Nature 2025.

关键词： Microhardness

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laser-solid interaction and energy accumulation in melt ejection formation during T2 copper oscillation laser welding

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Journal of materials processing Technology 2025年 340卷

作者： Dong, Hao Cai, Yan Li, Wucheng Mu, Weidong Shanghai Key Laboratory of Materials Laser Processing and Modification Shanghai Jiao Tong University Shanghai200240 China

The phenomenon of melt ejection during pure copper laser welding exhibits the characteristics of randomness, accidentality, and abruptness. However, the current understanding of this mechanism cannot be used to conduct a detailed analysis of its random and sudden occurrence. laser oscillations create a constantly changing environment for the laser, keyhole, and molten pool. In this study, a detailed analysis of the formation and development mechanisms of melt ejection was conducted under different laser-oscillation profiles and frequencies. Based on process observations and a self-designed energy and keyhole distortion calculation model, it was found that the random interaction between the laser and solid base metal contributed significantly to the sudden formation of the molten pool by transferring the heat accumulation zone to the rear bottom of the keyhole, which created an abnormal keyhole bulge. This was caused by the very low absorption rate of the solid surface of the T2 copper. The oscillation trajectory of the laser spot changed the frequency and time span when the laser moved near the liquid–solid boundary, as well as the heat input rate at different positions in the molten pool, resulting in a difference in stability with different oscillation strategies. Based on these results, we hypothesized that the formation of melt ejections is closely related to the random contact of a fluctuating keyhole with a highly reflective solid interface. Severe melt ejection was caused by the continuous accumulation of laser energy. This hypothesis led to a better understanding of the instabilities during the laser welding of highly reflective materials and can be applied to analyze most cases where melt ejection occurs. © 2025

关键词： Copper laser welding Energy computational model Mechanism analysis Melt ejection Process observation

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Achieving balanced strength and ductility in a Fe64(CoCrNi)36 ferrous medium-entropy alloy via W addition

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materials and Design 2025年 254卷

作者： Liao, Yu Li, Chuanwei Cheng, Luyao Wang, Yiwei Zhang, Hao Song, Yisi Ye, Zhenhua Gu, Jianfeng School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Shanghai Key Laboratory of Materials Laser Processing and Modification Shanghai Jiao Tong University Shanghai200240 China

The relatively low strength of ferrous medium-entropy alloys (Fe-MEAs) at room temperature has limited their widespread structural applications. In this study, a balanced strength and ductility were achieved in non-equiatomic [Fe64(CoCrNi)36]100−xWx (x = 0, 1, 2.5, and 4, at.%) Fe-MEAs via refractory tungsten (W) alloying and a single-step hot-rolling process. Increasing W content reduces the fraction of the body-centered cubic phase while promoting the formation of W-rich μ and minor Laves phases. The 4W alloy exhibits a yield strength of 810 MPa, an ultimate tensile strength of 891 MPa, and an elongation-to-failure of 26.3%. The improved yield strength is attributed to the combined effects of solid solution strengthening, grain boundary strengthening, dislocation strengthening, and precipitation strengthening. Detailed analysis revealed that the ductile face-centered cubic matrix effectively suppresses the propagation of microcracks originating from the hard and brittle precipitates. Furthermore, dislocation-precipitate/grain boundary interactions, nanoscale deformation twins, and deformation-induced martensitic transformation collectively improve the work-hardening capacity. These findings offer valuable insights into the design and development of cost-effective, high-performance Fe-MEAs for advanced structural applications. © 2025 The Author(s)

关键词： Tensile strength

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Helium bubbles evolution mechanism of SA508-3/52 joint and its effect on nanoindentation hardness and swelling

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Heat Treatment and Surface Engineering 2025年第1期7卷

作者： Qian, Xusheng Li, Chuanzong Li, Ruoyu Zhang, Kejin Tian, Ziyu Chen, Junmei Yu, Chun Lu, Hao Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai China

After metallographic corrosion of dissimilar metal welded joints, a distinct uncorroded bright band, referred to as the ‘white bright band’ (WBB), is often observed on the austenite side immediately adjacent to the fusion line. To investigate the evolution mechanism of helium bubbles in the WBB of dissimilar metal welded joints and their effect on hardening and expansion, SA508-3/52 joints were subjected to irradiation with He⁺ at ion fluences of 1, 3, and 5 e¹⁶ ions/cm² at 300°C. Helium bubbles have been identified as the main contributors to the hardening of the WBB, and the degree of hardening increases with increasing ion fluence. At a 3 e¹⁶ ions/cm² ion fluence, helium bubbles exhibit the highest hardness contribution of 82.16%. At a distance of 3 μm from the fusion line in the WBB, where the major elemental composition is Fe₆₅Cr₁₀Ni₂₅, the helium bubble number density peak values under three different ion fluences are 4.14, 13.69, and 17.94 × 10²³/m³, with corresponding size peak values of 1.73, 1.72, and 1.36 nm, respectively, consistently showing the lowest values within the WBB. This results in the smallest swelling rates, with peak swelling rates of 0.011%, 0.037%, and 0.024% at this location. © 2025 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group.

关键词： he+ ion irradiation helium bubble nanoindentation hardness swelling White bright band

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High-temperature tensile and fatigue properties of Ti-48Al-2Cr-2Nb alloy additively manufactured via twin-wire directed energy deposition-arc

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Intermetallics 2025年 184卷

作者： Zhou, Wenlu Shen, Chen Wang, Lin Li, Ying Zhang, Ting Xin, Jianwen Ding, Yuhan Zhang, Danqi Zhang, Yuelong Li, Fang Hua, Xueming Shanghai Key Lab of Materials Laser Processing and Modification School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai 200240 China Department of Discipline Engineering AECC Commercial Aircraft Engine Co. Ltd. Shanghai 200241 China Shanghai Engineering Research Center of Civil Aero Engine Shanghai 200241 China

Recently, additive manufacturing of titanium aluminide has attracted widespread attention. Since titanium aluminide is an ideal structure material for high-temperature, corresponding mechanical properties are of great significance. In present work, tensile properties from 25 °C to 1050 °C and fatigue properties at 650 °C were examined for the first time on twin-wire directed energy deposition-arc (TW-DED-arc) manufactured Ti-48Al-2Cr-2Nb (TiAl-4822) alloy. Importantly, fracture characteristics and deformation mechanisms were systematically investigated. Similar with extensively investigated titanium aluminide, TW-DED-arc manufactured TiAl-4822 alloy generally tends to decrease strength while increase elongation versus temperature during tensile process. Meanwhile, anomalous increase of strength is detected at 750 °C, and brittle-to-ductile transition temperature (BDTT) is around 850 °C. At 25 °C and 550 °C, γ/α2 lamellar interface and lamellar colony boundary as well as special microstructures are weak positions and susceptible to microcracking, and mechanical twining dominates deformation mode. By comparison, in temperature range of 650 °C–950 °C, γ/α2 interface and colony boundary are weaker, while deformation mechanism shifts to mechanical twinning and dislocation slip. Moreover, dynamic recrystallization (DRX) starts at 850 °C and further affects tensile behaviors, especially at 1050 °C. The fatigue limit (107 cycles) at 650 °C is approximately 335 MPa, ratio of which to tensile strength is calculated to be 0.71, indicating good fatigue resistance of as-manufactured TiAl-4822 alloy. Irrespective of stress level, crack prefer to initiate and propagate at γ/α2 interface and colony boundary. Both mechanical twining and dislocation slip are activated during fatigue process, but their morphologies vary with stress level. In sum, these findings provide a valuable reference for mechanical properties of additively manufactured titanium aluminide. © 2025

关键词： Tensile strength

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In-situ observation on bubble evolution during laser powder bed fusion of oxide ceramic

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International Journal of Minerals,Metallurgy and materials 2025年第06期 1451-1460页

作者： Zhun Su Wenquan Lu Zongye Ding Liang Zhao Fan Yang Jianguo Li Qiaodan Hu Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and EngineeringShanghai Jiao Tong University School of Mechanical Engineering Shanghai Jiao Tong University

laser powder bed fusion（LPBF） is used to fabricate complex-shaped, dense, and high-performance oxide ceramics. During LPBF, bubbles form and evolve in the melt pool and ultimately remain in the printed ceramics as pores, which significantly degrade the mechanical properties. Therefore, it is essential to understand the bubble behaviors during LPBF. Herein, we conducted an in-situ investigation of the bubble dynamics in the melt pool of homogeneously mixed Al2O3–Y2O3powders using synchrotron high-speed X-ray imaging. The formation, growth, motion, and evolution of bubbles, as well as the relationship between the instability of melt flow and bubble rupture during LPBF, were elucidated. The findings reveal that bubbles from the interstices within the powder bed grow following three distinct modes, i.e., uplift growth, gas channel attachment, and bubble coalescence. Furthermore, melt flow oscillations caused by the bursting of large bubbles can lead to local instability of the melt pool. Results from this study enhance the understanding of bubble dynamics during LPBF and may provide valuable insights for pore elimination in LPBF-processed oxide ceramics.

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Effect of building-height-dependent heat accumulation on microstructure and properties of Super Invar alloy fabricated by laser powder bed fusion

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materials Characterization 2025年 224卷

作者： Zhao, Renjie Shi, Lu Liu, Haihui Zhang, Lanting Feng, Kai Li, Zhuguo Xie, Renbiao Shanghai Key Laboratory of Materials Laser Processing and Modification School of Materials Science and Engineering Shanghai Jiao Tong University Shanghai200240 China Co. Ltd Shanghai200120 China Shanghai Aerospace System Engineering Institute Shanghai201108 China Shanghai Zhongchen Tobacco Machinery Spare Parts Co. Ltd Shanghai201206 China Shanghai Key Laboratory of High Temperature Materials and Precision Forming Shanghai Jiao Tong University Shanghai200240 China School of Materials and Energy Engineering Guizhou Institute of Technology Guizhou Guiyang550002 China

The poor thermal conductivity of Super Invar alloy (Fe-32Ni-4Co) further enhances the intrinsic building-height-dependent heat accumulation during its laser powder bed fusion (LPBF) process, resulting in its non-negligible microstructural inhomogeneity and significant property variation. In this paper, a detailed study for the effect of heat accumulation on microstructures, and thermal, mechanical and magnetic properties within a 10 × 10 × 100 mm3 vertically-built Super Invar alloy bar sample was conducted. Overall, LPBF fabricated Super Invar alloy exhibits considerably high degree of deformation and suffers very similar building-height-dependent thermal histories to the typical annealing process. The Curie temperature and Vickers hardness show a negative correlation with the lattice constant but a positive correlation with compressive residual stresses within this LPBF-manufactured Super Invar alloy bar. The vertically-measured coercivity is negatively correlated with the columnar grain size on the side surfaces, notwithstanding the pore-defect-induced coercivity enhancement within first-built layers. The segment of the bar located at a height of 50–75 mm exhibits relatively high bending degrees of magnetic domains, resulting in an extremely low coefficient of thermal expansion (CTE). In contrast, the 75–100 mm segment shows slightly higher CTE values compared to the 0–25 mm and 25–50 mm segments. The first-built segment of the Super Invar alloy bar sample contains coarse grains and significant small pores due to poor melting. This issue gradually diminishes as sufficient heat accumulates. As the building height increases further, a noticeable decline in dislocation density is observed without any change in grain size, indicating the occurrence of recovery at the building height of 30–40 mm. This recovery process causes a decrease in the Curie temperature and a reduction in hardness. Fine columnar grains can be achieved through heat accumulation processing, sugges

关键词： Curie temperature

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A new understanding of micromechanism analysis of gear interference fit failure

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Journal of materials Research and Technology 2025年 36卷 6350-6365页

作者： Chao Wen Zhengminqing Li Hongyan Wu Wanyuan Gui Jianfeng Gu Institute of Materials Modification and Modelling School of Materials Science and Engineering Shanghai Jiao Tong University 200240 China Shanghai Key Laboratory of Materials Laser Processing and Modification Shanghai Jiao Tong University 200240 China CRRC Qishuyan Institute Co. Ltd. Changzhou Jiangsu 213011 China College of Mechanical and Electrical Engineering Nanjing University of Aeronautics and Astronautics Nanjing 210016 China School of Chemistry and Materials Science Nanjing University of Information Science and Technology Nanjing 210044 China National Center for Materials Service Safety University of Science and Technology Beijing Beijing 100083 China

To address the problem of macroscopic gear shaft matching caused by the micro deformation of sprocket hole in high-speed railway during in their service, the microstructure of the gear before and after operation was analyzed in detail by means of electron back scatter diffraction (EBSD) and transmission electron microscopy (TEM). Cyclic stress-induced dislocation motion in martensite triggered the transformation of sub-grain boundaries into high-angle grain boundaries (HAGBs), forming new grains and leading to surface layer grain refinement. Volumetric contraction under compression, driven by grain boundary proliferation, amplified surface defects and reduced interplanar spacing, collectively contributing to gear shrinkage. These findings demonstrate that enhancing external stress resistance can be achieved through grain refinement and increased grain boundary obstruction to dislocation motion.

关键词： Gears Interference fit Hole expansion Dislocations Grain refinement

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