Size-Induced Strengthening in Nanostructured Mg Alloy Micropillars

Chang, Yuan-Hao; Pozuelo, M.; Yang, Jenn‐Ming

doi:10.1080/21663831.2014.924164

Cited by 14 publications

(8 citation statements)

References 24 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…All micropillars are slightly tapered as a result of the annular cutting method by FIB. However, we achieved angles ≤1.5°, which are smaller than the values reported in the literature (2-5°) for typical micropillars machined by FIB [36]. In any case, to avoid any overestimation of the measured stress due to the tapering, the diameter is considered at half-height of the micropillar (∼ 4 μm).…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 41%

“…In any case, to avoid any overestimation of the measured stress due to the tapering, the diameter is considered at half-height of the micropillar (∼ 4 μm). Micropillar size was also carefully selected ∼4 μm to avoid sizeinduced strengthening, as we have demonstrated in previous works [36,37], and to provide results comparable with those from macro scale tests of Mg alloys. The images on the right hand side of Fig.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 93%

See 1 more Smart Citation

Serrated flow in nanostructured binary Mg-Al alloys

et al. 2017

Self Cite

View full text Add to dashboard Cite

Serrated flow, also known as the Portevin-Le Chatelier effect, has been extensively investigated in binary Mg-alloys such as Mg-Ag, Mg-Y and Mg-Li alloys. Interestingly, however, this effect has not been observed in Mg-Al alloys. In this work, we report the appearance of serrations in nanostructured Mg-Al alloys processed by cryomilling and spark-plasma-sintering during in-situ SEM microcompression tests at room temperature and strain rates between 2 × 10 −3 and 10. The observed serrated stress-strain behavior is attributed to the dynamic strain aging by which interstitial O and/or N impurities introduced during cryomilling diffuse and interact with in-grown dislocations during deformation.© 2016 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved. Keywords: Mechanical millingIn-situ SEM micro-compression tests Magnesium alloys Portevin-Le Chetelier effectThe Portevin-Le Chatelier (PLC) effect is one of the best studied plastic instabilities in metallic materials. One of its main manifestations, in the appropriate strain rate and temperature range, is the appearance of "serrated flow" in the stress-strain curve. The PLC effect has been investigated extensively, from both experimental and theoretical points of view, in body and face centered cubic materials. However, the study of this phenomenon in hexagonal close-packed (hcp) materials, particularly in binary Mg-Al alloys, has been limited.Chaturvedi et al.[1] reported serrated flow in a binary Mg-Ag alloy in the 53-124°C temperature range, and attributed the locking of mobile dislocations to the diffusion of silver atoms during deformation. Serrated flow was also observed by Gao et al. [2] in binary Mg-Y alloys during tensile deformation between 150 and 250°C. In contrast, Caceres et al.[3] investigated the serrated behavior of as-cast binary Mg-Al alloys and did not observe serrations. Interestingly, Standford et al. [4] reported flow serrations during deformation of a Mg-Gd alloy at 200°C. However, they could not observe serrations in a Mg-Al alloy processed under the same conditions to obtain a similar extrusion texture and grain size.The PLC effect has also been found in ternary Mg-alloys, such as AZ91 by Corby et al. [5], and in alloys containing rare earth additions such as Mg-Y-Nd by Zhu et al. [6], Mg-Gd-Zn alloys by Wu et al. [7] and Mg-Mn-Nd by Dudamell et al. [8]. In all these systems, serrated flow was attributed to the dynamic interaction between solute atoms and dislocations, a phenomenon known as dynamic strain aging (DSA), first proposed by Cottrell in 1953 [9]. In the case of AZ91 at room temperature, Corby et al. [5] reported that both Al and Zn atoms were involved in the DSA. They suggested that Al might be the dominant solute, while Zn acted as a catalyzer enabling the formation of a forest of dislocations through which Al atoms might pipe diffuse.This study reveals the appearance of serrations at room temperature in a nanostructured binary Mg-10Al (wt.%) alloy processed via cryomilling and spark plasma sintering (SPS). Our p...

show abstract

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 41%

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 93%

Serrated flow in nanostructured binary Mg-Al alloys

et al. 2017

Self Cite

View full text Add to dashboard Cite

show abstract

“…Mechanical tests at the micron or sub-micron scale usually lead to an overestimation of the yield strength as compared with the bulk properties [59][60][61][62][63][64][65][66][67][68]. This "size effect" is related to the limited number of mobile dislocations and/or to the scarcity of dislocation sources in the small volume, and the critical size of the micropillar to determine the bulk properties depend on the particular alloy and microstructure.…”

Section: Effect Of Zn and Ca On The Crsssmentioning

confidence: 99%

Deformation mechanisms of Mg-Ca-Zn alloys studied by means of micropillar compression tests

Wang

Chen

et al. 2021

Acta Materialia

View full text Add to dashboard Cite

“…Strengthening effects in nanocrystalline materials due to sample size have experimentally been found in micropillar tests and a variation of sample size for fixed grain sizes (e.g. [61,62]). With increasing deformation, the stresses show a slight decrease 1 are assumed to be fixed, where the dislocation glide accounts for approximately 75% of the external strain ε = 0.1, see figure 9(a).…”

Section: Fourth-order Strain-gradient Phase Mixture Modelmentioning

confidence: 99%

“…As soon as heterogeneities or incompatibilities are present, this results in gradient effects which can be captured with a non-local extension of such models [48]. Additionally, sample size dependence has been reported for nanocrystalline materials [61,62] which requires the incorporation of a length scale into the model. Stress-strain curves for the phase mixture model augmented with a second-order gradient term with a negative coefficient according to equation (4) are displayed in figure 4.…”

Section: Second-order Strain-gradient Phase Mixture Modelmentioning

confidence: 99%

Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials

Klusemann

Bargmann

Estrin

2016

Modelling Simul. Mater. Sci. Eng.

View full text Add to dashboard Cite

The proposed modeling approach for nanocrystalline materials is an extension of the local phase mixture model introduced by Kim et al (2000 Acta Mater. 48 493–504). Local models cannot account for any non-uniformities or strain patterns, i.e. such models describe the behavior correctly only as long as it is homogeneous. In order to capture heterogeneities, the phase mixture model is augmented with gradient terms of higher order, namely second and fourth order. Different deformation mechanisms are assumed to operate in grain interior and grain boundaries concurrently. The deformation mechanism in grain boundaries is associated with diffusional mass transport along the boundaries, while in the grain interior dislocation glide as well as diffusion controlled mechanisms are considered. In particular, the mechanical response of nanostructured polycrystals is investigated. The model is capable of correctly predicting the transition of flow stress from Hall–Petch behavior in conventional grain size range to an inverse Hall–Petch relation in the nanocrystalline grain size range. The consideration of second- and fourth-order strain gradients allows non-uniformities within the strain field to represent strain patterns in combination with a regularization effect. Details of the numerical implementation are provided.

show abstract

Size-Induced Strengthening in Nanostructured Mg Alloy Micropillars

Cited by 14 publications

References 24 publications

Serrated flow in nanostructured binary Mg-Al alloys

Serrated flow in nanostructured binary Mg-Al alloys

Deformation mechanisms of Mg-Ca-Zn alloys studied by means of micropillar compression tests

Fourth-order strain-gradient phase mixture model for nanocrystalline fcc materials

Contact Info

Product

Resources

About