Deformation behavior of an ultrafine-grained Al?Mg alloy at different strain rates

Fan, G. J.; Wang, G.Y.; Choo, Hahn; Liaw, Peter K.; Park, Y.S.; Han, Bing; Lavernia, Enrique J.

doi:10.1016/j.scriptamat.2004.12.028

Cited by 61 publications

(21 citation statements)

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“…Fig. 10 compares the compressive yield strength plotted as a function of plastic strain to failure of various nanocrystalline and amorphous/nanocrystalline Al-based alloys processed by powder metallurgy routes [8,11,[30][31][32][33][34][35][36][37][38]. The general trend is high strength and low plasticity, even in the case of nanostructured Al alloys produced by cold compaction and hot extrusion or low strength and high plasticity.…”

Section: Discussionmentioning

confidence: 99%

Microstructure and mechanical properties of bulk nanocrystalline Al–Fe alloy processed by mechanical alloying and spark plasma sintering

2009

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Section: Discussionmentioning

confidence: 99%

Microstructure and mechanical properties of bulk nanocrystalline Al–Fe alloy processed by mechanical alloying and spark plasma sintering

2009

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“…For instance, Schwaiger et al [31] found that nanocrystalline pure Ni exhibited a positive SRS in flow stress, an effect that was not found in ultrafine and microcrystalline Ni. Fan et al [33] and Joshi et al [34] observed the PLC effect in ultrafine-grained Al-alloys only over a small strain range immediately following yield, while the coarse-grained alloy exhibited serrated flow over nearly the entire plastic strain range for the same applied displacement rate. Del Valle and Ruano [35] reported that SRS strongly increases by decreasing grain size below 15 μm in a Mg-AlZn alloy at moderate temperatures.…”

Section: Contents Lists Available At Sciencedirectmentioning

confidence: 98%

Serrated flow in nanostructured binary Mg-Al alloys

et al. 2017

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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...

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“…The strain rate sensitivity m is defined by [7] m ∂ logr ∂ log _ e e;T 1 m can be obtained by the power law of Equation 1, yielding a small negative strain rate sensitivity with m = -0.016. The negative strain rate sensitivity is often associated with a dynamic strain aging (DSA) in Al alloys, [8][9] which is caused by the interactions of the dislocations with the solute atoms. [9][10][11] During DSA, a lower strain rate allows fast diffusing solute atoms to diffuse to the dislocations in motion, which exerts a dragging force on moving dislocations and raises the flow stress.…”

Section: Methodsmentioning

confidence: 99%

Effect of Nano‐Scale Precipitates Growth on the Deformation Behavior of the Cast Coarse‐Grained Al‐Cu Alloy

Zhao

Wang

et al. 2008

Adv Eng Mater

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Al alloys are becoming increasingly significant as lightweight metal structural materials in many industries, such as aircraft construction, space technology, military field and automobile manufacturing. Therefore, it is necessary to reveal the deformation mechanisms of Al alloys to magnify their further application field.Deformation at higher strain rates is considered as a method of enhancing the ductility of nanostructured metals and alloys. [1] Higher strain rates generate crystalline defects to compete with dynamic recovery at a higher rate and therefore increase the work hardening rate, which leads to higher ductility of the nanostructured metals and alloys. [2][3][4] Despite the above reports, there are some results revealing the contradictory behavior. Cheng reported that a nanostructured Cu had higher ductility at lower strain rates. [5] The abnormal strain rates effect cannot be explained by the above deformation mechanism at higher strain rates. Recently, it is observed the similar phenomenon in the present cast coarsegrained (CG) Al-Cu alloy. So far, very little work on the higher ductility at the lower strain rates for the coarse-grained metals and alloys has been published, especially for the cast Al-Cu alloy. Therefore, the objective of this study is to investigate the reason for higher ductility at lower strain rates of 10 -4 s -1 and 10 -3 s -1 , and strain rate sensitivity at strain rates of 10 -2 s -1 and 10 -1 s -1 in the cast Al-Cu alloy modified by nano-scale Pr x O y . ExperimentalThe compositions (measured by an ARL 4460 Metals Analyzer) of the cast Al-Cu alloy were (in wt.%) 6.0 Cu, 0.15 Mn, 0.25 Ti, 0.13 V, 0.13 Zr, 0.001 B and balance Al. Details of the fabrication process for the present Al-Cu alloys are described elsewhere. [6] The heat-treated cast Al-Cu alloys were cut into tensile dog-bone shaped specimens with a gauge cross-section of 2.5 mm × 2.0 mm and a gauge length of 8.0 mm. Specimen surfaces were polished to a mirror-like finish surface. The uniaxial tensile tests at room temperature were carried out on an MTS-810 tester (U.S.A.) at the strain rate (e) ranging from 1 × 10 -4 s -1 to 1 × 10 -1 s -1 . The tensile ductility in this study was measured by calculating the gauge length change of the specimen before and after the tensile test. The mechanical property data (with a typical uncertainty of ± 1 %) in this study are the mean value of at least two specimens. Fracture morphologies and microstructures were examined with a scanning electron microscope (SEM) (Model JSM-5310, Japan) and the transmission electron microscope (TEM) (JEM-2000FX, Japan), respectively. Figure 1 shows the typical TEM microstructures of the present Al-Cu alloy after the tensile test at e of (a) 1 × 10 -4 s -1 , (b) 1 × 10 -2 s -1 , (c) 1 × 10 -3 s -1 and (d) 1 × 10 -4 s -1 , respectively. As shown in Figure 1(a), some dislocations are tangled around the nano-scale needle-like precipitates. The nanoscale needle-like precipitates were identified as the h′ phase precipitates with a composition of Al 2 Cu ...

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Deformation behavior of an ultrafine-grained Al?Mg alloy at different strain rates

Cited by 61 publications

References 22 publications

Microstructure and mechanical properties of bulk nanocrystalline Al–Fe alloy processed by mechanical alloying and spark plasma sintering

Microstructure and mechanical properties of bulk nanocrystalline Al–Fe alloy processed by mechanical alloying and spark plasma sintering

Serrated flow in nanostructured binary Mg-Al alloys

Effect of Nano‐Scale Precipitates Growth on the Deformation Behavior of the Cast Coarse‐Grained Al‐Cu Alloy

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