Improving ductility in ultrafine grained nickel with porosity and segregation via deformation

Zhao, Yaohua; Zhan, Qian; Topping, Troy D.; Li, Y.; Liu, Wei; Lavernia, Enrique J.

doi:10.1016/j.msea.2009.10.064

Cited by 7 publications

(4 citation statements)

References 38 publications

(50 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A review of the published literature reveals that the reasons for the low ductility of NS materials can be classified into two groups: extrinsic processing artifacts and intrinsic microstructures/deformation mechanisms. The processing flaws, when present, become the controlling factor that prematurely causes the failure during tensile tests before any significant plastic deformation occurs, sometimes even prior to the onset of yielding 5, 10, 18. A number of studies confirm this trend; that the low ductility that is frequently reported for NS materials processed via two‐step approaches can be attributed to the presence of processing flaws.…”

Section: Reasons For Low Ductility In Ns Materialsmentioning

confidence: 91%

“…and then consolidated using cold/hot isostatic pressing (CIP/HIP),3, 5 quasi‐isostatic Ceracon forging6 and spark plasma sintering (SPS),7 or a “one‐step” approach such as electrodeposition8 and severe plastic deformation (SPD) 9. Bulk NS materials produced by the “two‐step” approach frequently have flaws such as porosity, insufficient bonding and impurities 5, 10. The “one‐step” approach encompasses a number of techniques, such as SPD which usually can produce dense and flaw‐free NS materials.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Strategies for Improving Tensile Ductility of Bulk Nanostructured Materials

2010

View full text Add to dashboard Cite

Strength and ductility are two of the most important mechanical properties of structural materials. High strength is desired for structural components so that they can carry high loads. Good ductility is essential to avoid catastrophic failure in load-bearing applications and is also very important for many shaping and forming operations. The ductility of materials is defined as the extent to which a material can be plastically deformed. Usually, ductility is measured as the elongation to failure in uniaxial tension. It has been a long-standing goal for materials scientists to synthesize structural materials with balanced combinations of high strength and high ductility. However, strength and ductility usually exhibit an inverse relationship; i.e., increasing the strength sacrifices the ductility, and vice versa. This longstanding, strength-ductility empiric conundrum has been partially addressed, for example, by the development of solid solute and dispersion (2nd-phase particles) hardened alloys which have widespread engineering applications but have a lower ductility in comparison with their pure metallic matrix.Since 1980s, bulk nanostructured (NS) materials have emerged as a new class of materials with unusual physical and mechanical behavior and as a result, have attracted considerable attention in recent years. [1] The terminology ''nanostructured'' is generally defined as structural features smaller than 100 nm. [2] Bulk NS materials are single or multi-phase polycrystals with nanoscale grain/subgrain sizes, which are distinct from low-dimensional NS materials such as nanotubes, -wires, -films, and -clusters. Bulk NS materials are structurally characterized by a large volume fraction of grain boundaries (50% for 5 nm grains, 30% for 10 nm grains), which may significantly alter their physical, mechanical, and chemical properties in comparison with those of conventional coarse-grained (CG) materials. The relatively high strength of bulk NS materials, typically 5-10 times of conventional materials of similar composition, offers COMMUNICATIONThe low ductility that is consistently associated with bulk nanostructured (NS) materials has been identified as perhaps the single most critical issue that must be resolved before this novel class of materials can be used in a wide variety of applications. Not surprisingly, a number of published studies, published mostly after 2000, identify the issue of low ductility and describe strategies to improve ductility. Details of these strategies were discussed in review papers published by Ma in 2005 and 2006, respectively. [15,16] In view of continued efforts and recent results, in this paper we describe progress in attempting to address the low ductility of NS materials, after 2006. We first analyze the fundamental reasons for the observed low ductility of bulk NS materials, and summarize early (prior to 2006) attempts to enhance the ductility of bulk NS materials, which often sacrificed the strength. Then, we review recent progress in developing strategies for improving ...

show abstract

Section: Reasons For Low Ductility In Ns Materialsmentioning

confidence: 91%

mentioning

confidence: 99%

Strategies for Improving Tensile Ductility of Bulk Nanostructured Materials

2010

View full text Add to dashboard Cite

show abstract

“…A ''two-step'' approach, in which nanocrystalline (nc) powders are first prepared and then consolidated via various techniques, is widely used to produce bulk nanostructured (NS) metals [1][2][3]. Mechanical milling, especially cryomilling (milling in a cryogenic liquid such as liquid nitrogen), represents an approach that can be used to generate a large quantity of nc metallic powders in a single batch [4,5].…”

Section: Introductionmentioning

confidence: 99%

The influence of oxygen and nitrogen contamination on the densification behavior of cryomilled copper powders during spark plasma sintering

et al. 2010

View full text Add to dashboard Cite

It has been found difficult to fully densify some mechanically milled pure metal powders by spark plasma sintering (SPS). In this study, the densification behavior of cryomilled, nanostructured (NS) Cu powders during SPS was related to changes to the chemistry of the powders. The results showed that the presence of very small amounts of O and N in the powders, which were introduced during cryomilling and handling, significantly influenced the densification response. Moreover, reduction/removal of O/N via thermal annealing of the powders before SPS led to complete densification of the powders during subsequent SPS. The mechanisms responsible for this behavior were ascertained: O and N existed in the cryomilled powders in the form of thermally unstable compounds, and the subsequent thermal decomposition of these compounds during SPS generated the gaseous species, leading to porosity formation and incomplete densification; annealing of the powders before SPS removed the gases which resulted from thermal decomposition, thereby facilitating complete consolidation during subsequent SPS.

show abstract

“…Also there is published evidence on grain boundary segregation for other cryomilled material metal systems [19,27]. Recent work by Zhao et al [28] indicates that the grain boundary segregation of nitrogen in nanostructured Ni prepared by cryomilling and QI forging caused an evident embrittlement. Addition to embrittlement via initiating crack growth, grain boundary segregation will suppress grain boundary sliding [25,29], which is widely known to be a dominant deformation mechanism in nanocrystalline and ultrafine grained materials [30,31].…”

Section: Resultsmentioning

confidence: 99%

Strategies for Improving Ductility of Cryomilled Nanostructured Titanium

Ertörer

Topping

Liu

et al. 2009

MSF

View full text Add to dashboard Cite

The room temperature tensile behavior of commercially pure titanium (CP-Ti), cryomilled under different conditions and forged quasi-isostatically into bulk form, was studied in detail. The results demonstrate that the ductility of cryomilled titanium can be improved, and that the mechanical properties can be tailored using three specific strategies: the use of liquid argon as cryomilling media, introduction of coarse grained regions, and low temperature heat treatment. Cryomilling in a liquid argon environment, which differs from the widely used nitrogen cryogenic environment, was found to have a particularly strong influence on ductility, as it prevents nitrogen embrittlement. The contribution of coarse grains and heat treatment to ductility are also introduced and discussed using a comparative approach.

show abstract

Improving ductility in ultrafine grained nickel with porosity and segregation via deformation

Cited by 7 publications

References 38 publications

Strategies for Improving Tensile Ductility of Bulk Nanostructured Materials

Strategies for Improving Tensile Ductility of Bulk Nanostructured Materials

The influence of oxygen and nitrogen contamination on the densification behavior of cryomilled copper powders during spark plasma sintering

Strategies for Improving Ductility of Cryomilled Nanostructured Titanium

Contact Info

Product

Resources

About