Development of Magnesium Alloys with High Performance

Abstract

In Mg-Al-Zn and Mg-Al-Mn alloys containing 2.0~6.0mass%Al and 0~1.5mass%Zn, grain refinement in the as-rolled (F) specimens containing large amount of Al and Zn are achieved by both dynamic recrystallization and dynamic precipitation during hot rolling and leads to high strength and high ductility at room temperature. At high temperatures, the tensile strength of the investigated alloys is almost the same, while the elongation of the F-specimens increases with increasing Al and Zn contents, leading to 150% in Mg-4.5%Al-1.5%Zn alloy. High Al and Zn contents alloys significantly accumulate large working strain in grain interiors, and involve large amounts of high angle grain boundaries and fine spherical precipitates, which can become the nucleation sites for recrystallization. Therefore, dynamic recrystallization in such alloys occurs at small strain region during tensile test. This dynamic recrystallization causes reduction of flow stress and large elongation by grain boundary sliding at high temperatures. Furthermore, .fine recrystallized grains contributes to deformation in normal direction, resulting in isotropic deformation behavior. Authors attempt to improve proof stress and its anisotropic property of Mg-Al-Zn wrought alloys by grain size and precipitates controls utilizing dynamic recrystallization and dynamic precipitation during hot extrusion. In the alloy specimens extruded at lower temperatures increasing Al and Zn contents enhance dynamic recrystallization and dynamic precipitation, resulting in grain refinement and large amount of Mg17Al12 precipitates. As a result, the extruded Mg-9%Al-1%Zn alloy specimen shows high tensile strength of 370MPa, 0.2% tensile proof stress of 240MPa and moderate elongation of 20%, which are almost same as standard values of tensile properties of T5-treated 6N01 Al extruded alloy. Furthermore, a ratio of compressive proof stress to tensile proof stress of the as-extruded specimen improves up to a higher ratio of 0.9 than that of Mg-3%Al-1%Zn alloy specimen with no precipitation, 0.5, due to prevention of tensile twin, which easily occurs during compressive deformation even under a low applied stress perpendicular to the extrusion direction, by dynamic precipitation of Mg17Al12 phase.

Microstructure and tensile property of the ECAPed pure magnesium

“…Magnesium offers a large potential in weight reduction usages because of its low density of about 1.73 g cm −3 [1,2]. However, the relatively low strength and plasticity greatly hinder its wide applications.…”

Microstructure and mechanical property of the ECAPed Mg2Si/Mg composite

“…Small numbers of Mg 2 Si particles with an average size of <20 m are observed which should come from the coarse Type-I Mg 2 Si polygonal particles. Accumulation of the Type-I Mg 2 Si with an angle about 45 • to ECAP direction is obtained. Regular distribution of the dendritic Type-II Mg 2 Si is destroyed.…”

“…Magnesium has a great potential application on the lightweight components of transportation vehicles because of its low density [1,2]. While Mg and its alloys exhibit low mechanical property which greatly limits their high performance applications, such as on aviation and aircraft.…”

Microstructure Evolution of Mg-2Y-0.6Nd-0.6Zr Alloy Rolled at Room and Liquid Nitrogen Temperature

“…Magnesium (Mg) alloys are currently the lightest commercial metal structural material. At the same time, it has high specific strength, good damping and vibration reduction, good thermal conductivity and good electronic shielding effects [1][2][3][4]. Therefore, Mg alloys have attracted increasing attention in aerospace, pharmaceutical, chemical and automotive fields in recent years [5][6][7].…”