Search

Microstructures, tensile properties and work-hardening behavior of extruded Mg-1Gd- x Zn (x = 0, 0.5, 1.0, 1.5, wt.%) alloy sheets were investigated in the present work. All the extruded sheets exhibit a fully-recrystallized microstructure and a weak extrusion-direction (ED)-split texture. The average grain sizes of Mg-1Gd sheets slightly decrease with the increase of Zn content up to 1.0 wt%, while a sharp decrease of the grain size occurs in Mg-1Gd-1.5Zn sheet attributed to the existence of abundant fine W-phase precipitates. Zn addition is found to cause a weak ED-split texture and to gradually form new transverse direction (TD)-split texture component. The combination of Zn solute, fine W-phase precipitate and weakening texture induced by Zn addition simultaneously improve the strengths and ductility of Mg-1Gd- x Zn sheets. However, excessive Zn addition leads to larger Mg 5 Gd precipitates and thus decreases the ductility. With the increment of Zn content from 0 to 1.5 wt%, work-hardening exponents of Mg-1Gd- x Zn sheets gradually increase from 0.34 to 0.39 along ED, and from 0.23 to 0.29 along TD, respectively. Meanwhile, hardening capacities increase from 1.73 to 1.84 along ED, and from 0.73 to 1.07 along TD, respectively. • The effect of adding Zn on the microstructures of Mg-1Gd alloy was studied. • The work-hardening mechanism of Zn in Mg-1Gd alloy was analyzed in detail. • Dense W-phase precipitates are homogeneously dispersed in the Mg-1Gd-1.5Zn alloy. [ABSTRACT FROM AUTHOR]

A remarkable yield asymmetry at room temperature (RT), all the time, severely influenced the wide industrial applications of Mg alloys. Here, we report a novel approach entitled as bimetal casting-co-extrusion to reduce the yield asymmetry of Mg–3Al–1Zn (wt.%) alloy. The results show that when casting temperature is set as 760 °C, Mg–3Al–1Zn/Mg–1Y (AZ31/W1, wt.%) alloy with the sleeve-core structure can achieve a well metallurgical bonding. While casting temperature is below 760 °C, the contact surface of AZ31 and W1 billets takes place massive cracks, and even two alloys are unable to well connect. After co-extrusion, the interface zone of AZ31/W1 rod never has any cracks and holes. By TEM observation, the interface zone of ~ 1 μm is composed of only α-Mg. With increasing the proportion of W1 core, the tensile and compressive elongation-to-failure values of AZ31/W1 rod apparently enhance, and the decrease in tensile strength and the consistence in compressive strength give rise to the improved yield asymmetry from 0.57 to 0.84 at RT. This is mainly attributed to the more activity of slip deformation in tension and the restriction of {10 1 ‾ 2 } extension twinning in compression. Therefore, this work offers an insightful opinion to improve the mechanical properties of Mg alloys, especially the yield asymmetry, by bimetal casting-co-extrusion method. [ABSTRACT FROM AUTHOR]