Effect of precipitate shape on slip and twinning in magnesium alloys

Robson, James; Stanford, Nicole; Barnett, Matthew

doi:10.1016/j.actamat.2010.11.060

Cited by 376 publications

(161 citation statements)

References 20 publications

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“…The precipitate-twin interactions in the Mg-Al alloys and effects of precipitate shape on twinning have been studied. [246][247][248] In the current review and for simplicity, the propagation of twins is considered to involve the motion of twinning dislocations, and only 10 " 12 È É a twins are considered in the plastic deformation process. In addition, the lattice parameters of Mg are taken as a = 0.5200 nm, c = 0.3203 nm (c/a = 1.6235).…”

Section: Mg Alloys Containing Shear-resistant Particlesmentioning

confidence: 99%

Precipitation and Hardening in Magnesium Alloys

Nie

2012

Metall Mater Trans A

1,394

519

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Magnesium alloys have received an increasing interest in the past 12 years for potential applications in the automotive, aircraft, aerospace, and electronic industries. Many of these alloys are strong because of solid-state precipitates that are produced by an age-hardening process. Although some strength improvements of existing magnesium alloys have been made and some novel alloys with improved strength have been developed, the strength level that has been achieved so far is still substantially lower than that obtained in counterpart aluminum alloys. Further improvements in the alloy strength require a better understanding of the structure, morphology, orientation of precipitates, effects of precipitate morphology, and orientation on the strengthening and microstructural factors that are important in controlling the nucleation and growth of these precipitates. In this review, precipitation in most precipitation-hardenable magnesium alloys is reviewed, and its relationship with strengthening is examined. It is demonstrated that the precipitation phenomena in these alloys, especially in the very early stage of the precipitation process, are still far from being well understood, and many fundamental issues remain unsolved even after some extensive and concerted efforts made in the past 12 years. The challenges associated with precipitation hardening and age hardening are identified and discussed, and guidelines are outlined for the rational design and development of higher strength, and ultimately ultrahigh strength, magnesium alloys via precipitation hardening.

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Section: Mg Alloys Containing Shear-resistant Particlesmentioning

confidence: 99%

Precipitation and Hardening in Magnesium Alloys

Nie

2012

Metall Mater Trans A

1,394

519

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“…In a previous study, the authors have discussed the interaction between precipitates and f10 " 12g and suggested a simple semi-quantitative model for determining the effectiveness of a precipitate distribution in preventing twin growth. [8,9] This model suggests that precipitate's shape and habit will also have a strong effect on the resistance that a precipitate distribution provides to twinning.…”

Section: Introductionmentioning

confidence: 99%

“…One potential route to provide this differential strengthening is to take advantage of the fact that precipitation in magnesium alloys is also highly anisotropic, and precipitate's shape and habit are expected to have a large effect on the strengthening of any given slip system. [7][8][9] However, to reduce anisotropy and asymmetry, it is not sufficient to provide differential strengthening against slip alone because magnesium also deforms by twinning, and the f10 " 12g twinning mode in particular requires strong suppression to prevent its dominating yield behavior for loading conditions that produce c-axis tension. In a previous study, the authors have discussed the interaction between precipitates and f10 " 12g and suggested a simple semi-quantitative model for determining the effectiveness of a precipitate distribution in preventing twin growth.…”

Section: Introductionmentioning

confidence: 99%

Effect of Precipitate Shape and Habit on Mechanical Asymmetry in Magnesium Alloys

Robson

Stanford

Barnett

2012

Metall Mater Trans A

104

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Asymmetric yield behavior in tension and compression is a common and usually undesirable feature of wrought magnesium alloys. To prevent yield asymmetry, it is necessary to favor slip over twinning, as it is the unidirectional nature of twinning combined with the strong textures produced in wrought magnesium alloys that produce yield asymmetry. In this article, the potential to use precipitates to strengthen selectively against twin growth is discussed. The effect of precipitate's shape and habit on strengthening of slip and twinning is calculated using simple Orowan-based models. It is shown that basal plate precipitates, although being poor strengtheners against basal slip, are good strengtheners against twin growth. This is because they produce the maximum unrelaxed back-stress when they remain unsheared inside the twin. The predictions of the model have been validated against experiments for two alloys that form different precipitate types: AZ91 (basal plates). and Z5 (c-axis rods). Crystal plasticity modeling has been used to predict that an optimized distribution of basal plate precipitates is expected to strongly reduce yield asymmetry, even in strongly textured magnesium alloy.

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“…For example, basal plate shaped precipitates, such as formed in MgAl-Zn (AZ) alloys strengthen strongly against f10-12g twinning but only weakly against prismatic slip, and can almost completely eliminate mechanical asymmetry if a sufficient volume fraction is formed. 31,32 Prismatic plates, of the type formed in WE43, are also predicted to lead to a strong reduction in asymmetry as well as providing the maximum overall strengthening effect, as discussed in the section on strengthening.…”

Section: Effect Of Solute and Precipitates On Anisotropymentioning

confidence: 99%

“…30 As a result, the strengthening provided by precipitates is itself highly anisotropic. 30,31 This anisotropy can either enhance or reduce the inherent anisotropy of the magnesium matrix. To reduce anisotropy and asymmetry most effectively, it is desirable to form a precipitate that increases the strength of weak modes more than strong modes, leading to a convergence of CRSS values.…”

Section: Effect Of Solute and Precipitates On Anisotropymentioning

confidence: 99%

Critical Assessment 9: Wrought magnesium alloys

Robson¹

2015

Materials Science and Technology

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This assessment is focussed on wrought magnesium alloys for lightweight applications, particularly in the transport sector. The challenges to their wider use are summarised, including poor low temperature formability, corrosion issues, dissimilar metal joining, and limited precipitation strengthening. The fundamental origins of these challenges, and current research to address them, are highlighted. Key developments such as the use of dilute rare earth additions to manipulate texture for improved formability are discussed. Opportunities to exploit the unique properties of wrought magnesium alloys where further research is required are identified.

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Effect of precipitate shape on slip and twinning in magnesium alloys

Cited by 376 publications

References 20 publications

Precipitation and Hardening in Magnesium Alloys

Precipitation and Hardening in Magnesium Alloys

Effect of Precipitate Shape and Habit on Mechanical Asymmetry in Magnesium Alloys

Critical Assessment 9: Wrought magnesium alloys

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