The Serrated Flow Behavior of Mg-Gd(-Mn-Sc) Alloys

Fang, Xi‐Ya; Yi, Danqing; Nie, Jian Feng

doi:10.1007/s11661-009-9967-1

Cited by 35 publications

(16 citation statements)

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“…Plastic instability associated with the production of Portevin-Le Chatelier (PLC) bands, which is also know as serrated flow or jerky flow, is a topic of current theoretical and engineering interest. Lots of studies in this area are on aluminum alloys; however, due to soaring research on magnesium alloys, similar results have been reported in Mg-Ag [1], Mg-Gd [2], Mg-Y-Nd [3], Mg-Nd [4], and Mg-Al-Zn [5,6] alloys, respectively.…”

Section: Introductionmentioning

confidence: 60%

Investigations on the Plastic Instability in an HCP Mg-Li Alloy

Wang

Han

2012

Journal of Metallurgy

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Plastic instability is reported in hexagonal close-packed (HCP) LA41 magnesium alloy during tensile tests. Serration amplitude associated with plastic instability is measured to increase with increasing strain and decrease with increasing strain rate. The model of dynamic strain aging (DSA) is proposed to be the controlling mechanism. Moreover, it is reported that annealing could reduce the flow instability, which has potential practical applications.

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Section: Introductionmentioning

confidence: 60%

Investigations on the Plastic Instability in an HCP Mg-Li Alloy

Wang

Han

2012

Journal of Metallurgy

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“…On the other hand, twin boundaries act as additional obstacles to subsequent slip and twinning deformation (Karaman et al, 2000). Recently, El Kadiri and Oppedal (2010) proposed that the hardening is also related to a rapid increase in the dislocation density inside twins.…”

Section: Resultsmentioning

confidence: 99%

“…During plastic deformation at intermediate temperatures (100-250 °C), several binary and ternary magnesium alloys containing RE elements exhibit serrated flow (also known as the Portevin-Le Chatelier effect) (Couling, 1959;Zhu and Nie, 2004;Zhongjun et al, 2007;Fang et al, 2009;Gao et al, 2009;Stanford et al, 2010;Jiang et al, 2011;Wu et al, 2012;Yuan et al, 2013;Cai et al, 2014;Garcés et al, 2015). Different explanations of this have been proposed depending on the strain rate of the mechanical tests.…”

Section: Introductionmentioning

confidence: 99%

Evolución microestructural y envejecimiento dinámico por deformación en la aleación Mg-6%Gd- 1%Zn durante ensayos a tracción y compresión a temperaturas intermedias

et al. 2018

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La aleación Mg-6%Gd-1%Zn muestra el fenómeno de serrado durante la deformación a temperaturas intermedias debido al proceso de envejecimiento dinámico provocado por la presencia de átomos de soluto en solución sólida y dislocaciones móviles. Aunque la aleación tiene una textura al azar, se observa un comportamiento diferente en tracción y en compresión. El límite elástico y el endurecimiento es mayor cuando la aleación se ensaya en compresión. Durante la deformación a temperaturas intermedias se ha observado la activación de dislocaciones tipo < a > y maclas de tensión, independientemente del signo de la carga. Sin embargo, la fracción en volumen de maclas es siempre mayor cuando el material se somete a compresión. A temperaturas intermedias, los átomos de Gd y Zn anclan tanto las dislocaciones como las maclas. Por encima de 250 ºC, el fenómeno de serrado desaparece y la presencia de precipitados g´ y g´´ en el plano basal aumenta el endurecimiento.

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“…Against the alleged efficiency of this mechanism it may be argued that serrated flow is also observed in many other Mg alloys [12,32,[94][95][96], including AZ91 alloy [92,97,98], which, again, hardly qualifies as creep resistant. Along the same lines, it has been suggested [99] that small additions of Zn (0.3at.%) to Mg-Nd-La improves the alloy's creep strength through Cottrell atmospheres of Zn atoms around dislocations.…”

Section: Solute Dragging / Solute Clusteringmentioning

confidence: 99%

Thermodynamics-based design of creep resistant Mg solid solutions using the Miedema scheme

Abaspour¹

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Most current creep resistant alloy design methods for Mg alloys aim at incremental strengthening of existing alloys such as AZ91 thorough addition of ternary and quaternary elements, or alternatively through RE's additions. The most remarkable improvements has been through either Mg-Y or recently developed Mg-Gd-Y-Zr and Mg-Y-Nd-Zr alloys, although still below the strength of MgTh alloys, which are being phase out due to Th's radioactivity.Many micromechanisms proposed to account for the observed improvements in either hardness or creep strength of Mg alloys including solid solution and/or precipitation hardening, dynamic precipitation, solute dragging/solute clustering and more importantly atomic size controlled diffusivity more often than not are little more than ad-hoc, after-the-fact explanations, valid at best for the particular system under consideration. Hence, extrapolation to other alloy-systems is either not possible or contradictory. In practice, a feasible path for systematic, either precipitationhardened or creep-resistant Mg alloys, selection and design is still lacking.The aim of the present work was to use atomic level thermodynamical arguments that suggest that extending the athermal regime through short range order (SRO) is a most feasible path to increasing the creep strength of Mg alloys. Potential solutes were sorted out and ranked based on their tendency to developing SRO using the Miedema's phenomenological scheme. The predictions were corroborated by experiments involving dilute binary alloys as well as through a collection of data from the literature.Monotonic compression and stress relaxation tests were carried out on specimens of 6 cast binary alloys with (at.%) 2.5 Al, 0.6 Sn, 2.2 Zn, 0.8 Gd, 1.3 Y and 0.9 Nd, and of a similarly cast AZ91D alloy for reference. The solute concentration in the binary alloys was kept deliberately low to limit precipitation hardening effects during the testing. Compression testing was carried out at 298K (25°C), 373K (100°C) and 453K (180°C) The relative tendency or lack of it, of most solutes to develop SRO rationalizes a number of observations in current multicomponent Mg alloys while it disputes the viability of several other micromechanisms often considered.The feasibility of strengthening HPDC Mg alloys through a combination of percolating eutectics and residual solute in solution, or, more generally, age hardenable alloys through either homogeneously nucleated, coherent with the Mg matrix, precipitates, or via internally ordered precipitates mimicking Mg-Th alloy system, is also considered by making parallels with either the Al-Zn or the Al-Cu alloy systems. Examples of these approaches were discussed using data from the literature, such as experiments on alloys combining Mn and Sc to introduce order in the soft Mn precipitates, or the use of Na to provide finely dispersed, homogeneously nucleated clusters with the aim of refining the subsequent precipitation in alloys such as Mg-Sn. III Declaration by authorThis thesis is composed of my or...

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The Serrated Flow Behavior of Mg-Gd(-Mn-Sc) Alloys

Cited by 35 publications

References 35 publications

Investigations on the Plastic Instability in an HCP Mg-Li Alloy

Investigations on the Plastic Instability in an HCP Mg-Li Alloy

Evolución microestructural y envejecimiento dinámico por deformación en la aleación Mg-6%Gd- 1%Zn durante ensayos a tracción y compresión a temperaturas intermedias

Thermodynamics-based design of creep resistant Mg solid solutions using the Miedema scheme

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