Mechanistic origin and prediction of enhanced ductility in magnesium alloys

Abstract

Pure magnesium exhibits poor ductility owing to pyramidal [Formula: see text] dislocation transformations to immobile structures, making this lowest-density structural metal unusable for many applications where it could enhance energy efficiency. We show why magnesium can be made ductile by specific dilute solute additions, which increase the [Formula: see text] cross-slip and multiplication rates to levels much faster than the deleterious [Formula: see text] transformation, enabling both favorable texture during processing and continued plastic straining during deformation. A quantitative theory establishes the conditions for ductility as a function of alloy composition in very good agreement with experiments on many existing magnesium alloys, and the solute-enhanced cross-slip mechanism is confirmed by transmission electron microscopy observations in magnesium-yttrium. The mechanistic theory can quickly screen for alloy compositions favoring conditions for high ductility and may help in the development of high-formability magnesium alloys.

Hierarchical Twinning Induced Texture Weakening in Lean Magnesium Alloys

“…However, it must be understood that the aforementioned shear incompatibility and generation of non-deformable orientations during twinning is primarily as a result of the highly anisotropic dislocation slip prevalent in pure Mg, wherein pyramidal <c+a> slip modes require extremely high stresses (nearly 100 times the critical resolved shear stress of basal <a> slip) to activate (Yoo, 1981;Tonda and Ando, 2002;Wu and Curtin, 2015;Wu et al, 2018). In other words, the main reason behind the poor ductility response of twinned Mg alloys is the lack of homogeneity of slip deformation.…”

“…) are larger than those for the basal planes (γ GSFE(Bas.) ), whereby dislocation nucleation on pyramidal planes becomes energetically unfavorable (Wu and Curtin, 2015;Wu et al, 2018). Moreover, even if they nucleate the high γ stable values ensures that the glissile pyramidal dislocations immediately cross-slip to the basal planes thereby dissociating into a sessile <c> and <a>-type dislocations (Ahmad et al, 2018(Ahmad et al, , 2019.…”

Atomic Scale Investigation on Precipitates and Defects of Mg–RE Alloys: A Review

“…Among these attractive Mg–RE alloys, one important improvement in mechanical properties is increasing of ductility, which is characterized by Wu et al that dilute solute RE elements additions increase cross‐slip and multiplication rate. Another significant improvement of mechanical properties is increasing in strength, which is mainly owing to the presence of various precipitate either in as‐cast state or after heat treatment especially aging.…”

Study on corrosion behavior of as‐extruded AZ80 magnesium alloy sheet in wet hydrogen sulfide atmosphere

“…Magnesium and its alloys as structural materials have great potential for applications in the automotive, aerospace, military, rail transportation and electronic industries due to their low density, high specific strength and stiffness, good castability, excellent damping capacity and good electromagnetic shielding property . However, these materials’ low corrosion resistance has largely restricted their wider use in many application fields .…”

“…Magnesium and its alloys as structural materials have great potential for applications in the automotive, aerospace, military, rail transportation and electronic industries due to their low density, high specific strength and stiffness, good castability, excellent damping capacity and good electromagnetic shielding property. [1][2][3] However, these materials' low corrosion resistance has largely restricted their wider use in many application fields. [4,5] Although much effort has been devoted to the corrosion problem of magnesium and its alloys, it still remains a great obstacle for widening the application of these materials and is related to the highly reactive nature of magnesium.…”