Influence of powder shape on atomic diffusivity and resultant densification mechanisms during spark plasma sintering

Li, X. X.; Chao, Yang; Chen, T.; Zhang, Lai-Chang; Hayat, Muhammad Dilawer; Cao, Peng

doi:10.1016/j.jallcom.2019.06.176

Cited by 32 publications

(9 citation statements)

References 30 publications

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“…In stage I, the temperature is lower than 390 °C, and under the action of thermal expansion, amorphous powders are densified through particle rearrangement or rotation. [ 29 ] Figure 3c,d shows the contact morphology corresponding to point A, the densification starting point. The powders remain roughly spherical and are connected in point contact.…”

Section: Resultsmentioning

confidence: 99%

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Elucidating the Multi‐Scale Temperature Evolution and Densification Mechanisms of Amorphous Powders During Spark Plasma Sintering: Experiments and Modeling

et al. 2022

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With unique atomic stacking structures and outstanding performances, amorphous alloys have been formulated during the past several decades via various solidification techniques. [1,2] The cooling rates required to produce amorphous alloys are generally as high as 10 4 -10 5 °C s À1 . [3,4] This imposes restrictions on manufacturing amorphous alloys into giant-sized and geometrically complex parts. Nevertheless, amorphous alloys exhibit viscous-like behavior in the supercooled liquid region (SLR). Micron-sized amorphous powders can be fabricated from most alloy systems, even those having low glass-forming ability. [4] These provide a practical approach to densifying amorphous powders via powder metallurgy (P/M) processes. [5,6] Among the various P/M techniques available, spark plasma sintering (SPS) is promising for consolidating amorphous powders due to its fast heating rate and short cycle time. [5] In the past decade, consolidation of amorphous powders using the SPS process has been reported for Zr-based, [7,8] Ti-based, [9][10][11] Fe-based, [12] and Cu-based [13] alloys.The amorphous powders are heated to the SLR and densified by viscous flow. [10] However, the crystallization tendency is more intense with the increased temperature. [14] Therefore, the research focuses on fast densification while maintaining the amorphous structure. Amorphous powders' densification and crystallization dynamics race each other. Temperature is the key factor affecting this competitive process. Local overheating can lead to partial crystallization, resulting in severe embrittlement. For example, Nowak et al. reported that excessive overheating is generated in the vicinity of particle necks during the initial stages and is responsible for partial devitrification. [15] Similar phenomena have been widely observed in Fe-based [16] and Al-based amorphous alloys. [17] Despite the significant advantages of SPS, its further popularization is hindered by severe temperature and stress gradients, [18] especially for complex-shaped and large-sized parts. Therefore, it is of great concern to figure out the temperature field evolution in the amorphous alloys prepared by SPS. However, to the authors' knowledge, the current understanding of the temperature distribution in amorphous alloys prepared by SPS is limited.The temperature gradients in the sintering molds and samples can be divided into inhomogeneity at the macro and particle scales. In terms of the macroscopic temperature field, Song et al. developed a coupled thermal-electric-mechanical model to simulate the SPS process of Fe powders, [19] which concerns

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Section: Resultsmentioning

confidence: 99%

“…Typically, the instantaneous high temperature is generated due to the highly concentrated pulsed current. [ 7,29 ] Meanwhile, local plastic deformation occurs under the action of applied external pressure. [ 30 ]…”

Section: Resultsmentioning

confidence: 99%

Elucidating the Multi‐Scale Temperature Evolution and Densification Mechanisms of Amorphous Powders During Spark Plasma Sintering: Experiments and Modeling

et al. 2022

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“…Afterward, various conventional surface-modification technologies are introduced because these technologies had played a decisive role in further utilizations of Ti and Ti alloys in the past. Third, many new preparation technologies of Ti and Ti alloys, such as additive manufacturing [65,[166][167][168][169][170][171] and powder metallurgy (for porous structures) [172][173][174][175] were developed in the recent decades. Many Ti products may have complex shapes.…”

Section: Need Of Surface Modifications For Ti and Ti Alloysmentioning

confidence: 99%

Surface Modification of Titanium and Titanium Alloys: Technologies, Developments, and Future Interests

2020

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Thanks to a considerable number of fascinating properties, titanium (Ti) and Ti alloys play important roles in a variety of industrial sectors. However, Ti and Ti alloys could not satisfy all industrial requirements; the degradation of Ti and Ti alloys always commences on their surfaces in service, which declines the performances of Ti workpieces. Therefore, with aim to further improve their mechanical, corrosion and biological properties, surface modification is often required for Ti and Ti alloys. This article reviews the technologies and recent developments of surface-modification methods with respect to Ti and Ti alloys, including mechanical, physical, chemical, and biochemical technologies. Conventional methods have limited improvement in the properties and/or restriction on the geometry of workpieces. Therefore, many advanced surfacemodification technologies have emerged in recent decades. New methods make Ti and Ti alloys have better performance and extended applications. With requirement of high surface properties in future. Understanding the mechanism in various surface-modification methods, combining the advantages of current technologies and developing new coating materials with high performance are required urgently. As such, incorporation of different surface-modification technologies with high-performance modified layers may be the mainstream of surface modifications for Ti and Ti alloys. . His current research interests focus on the metal additive manufacturing (e.g., selective laser melting, electron beam melting), titanium alloys and composites, and processing-microstructureproperties in high-performance materials.

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“…Compared with the "no pulse current" condition, under the SPS pulse current, atomic diffusion was accelerated, and the growth rate constants of Al 13 Fe 4 and Al 5 Fe 2 significantly increased. Li et al 20,21 established a theoretical framework for determining atomic diffusion coefficient D by considering the contribution of powder properties and applied pressure in the process of SPS. The results show that the higher the D value is, the higher the instantaneous densification rate is.…”

Section: Introductionmentioning

confidence: 99%

Performance gradient distribution of (Ti,W)C cermet by skin effects of high‐frequency spark plasma sintering

Wang

Song

et al. 2022

J Am Ceram Soc.

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A (Ti,W)C cermet with graded properties was prepared using high‐frequency spark plasma sintering (HF‐SPS). The effects of the sintering process on the microstructure and mechanical properties of the prepared cermet material were studied, and the densification behavior of the material was analyzed using scanning electron microscopy and energy‐dispersive X‐ray spectroscopy. Owing to the skin effect and pulse current discharge in HF‐SPS, the experimental results showed different sintering effects, as indicated by the current density difference between the surface layer and bulk. On one hand, the surface‐layer grains were larger, the metal phase was concentrated, and the hardness was high; however, the bulk grains were smaller, the metal phase was uniformly distributed, and the strength and toughness were high, causing the material to account for the higher hardness of the surface layer and the bulk strength and toughness. The skin effect of pulse direct current was key for the performance gradient distribution, whereas increases in the current density and sintering temperature decreased the skin effect. In general, the Joule heat effect was more significant, leading to abnormal grain growth.

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Influence of powder shape on atomic diffusivity and resultant densification mechanisms during spark plasma sintering

Cited by 32 publications

References 30 publications

Elucidating the Multi‐Scale Temperature Evolution and Densification Mechanisms of Amorphous Powders During Spark Plasma Sintering: Experiments and Modeling

Elucidating the Multi‐Scale Temperature Evolution and Densification Mechanisms of Amorphous Powders During Spark Plasma Sintering: Experiments and Modeling

Surface Modification of Titanium and Titanium Alloys: Technologies, Developments, and Future Interests

Performance gradient distribution of (Ti,W)C cermet by skin effects of high‐frequency spark plasma sintering

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