Papers by Keyword: Mg-Nd Alloy

Abstract: The creep behavior of two series of magnesium alloys, Mg-4Al based alloys with strontium addition and binary Mg-Nd alloys, has been studied. Results show that the high creep properties achieved by the Mg-Nd alloys are attributed to the precipitation of tiny dispersed β’ particles, which form and effectively restrict the dislocation slipping and climb during creep deformation. In terms of values of the stress exponent and apparent activation energy gained from systematic creep tests, the mechanism responsible for creep deformation of the Mg-Nd alloys is inferred as dislocation climb, which is supported by TEM observations performed on the Mg-2Nd alloy after creep test. For the Mg-4Al based alloys, however, microstructural observations reveal that the significant improvement on creep properties caused by Sr addition is accounted for the formation of an interphase network consisting of Al4Sr and a Mg-Al-Sr ternary compound distributing at grain boundaries. The breakage of the interphase network after extrusion results in a sharp drop of creep properties, indicating the creep deformation of the alloy is controlled mainly by grain boundary sliding, which is in contradiction to the mechanism for creep of the alloys inferred by the classical criterions based on the values of stress exponent and apparent activation energy.

Abstract: Influences of Gd or Y addition on microstructures and tensile properties at room and elevated temperatures were investigated for T6-treated Mg-3%Nd-0.5%Zn-0.4%Zr casting alloys, on the basis of experimental results from X-ray diffractometry, scanning electron microscopy, transmission electron microscopy, energy dispersive spectroscopy, tensile and creep tests. Microstructures of the T6-treated alloys are characterized by recrystallized α-(Mg) grains containing various nano-sized precipitates such as Mg41Nd5, Zn2Zr3 and Zr particles. In T6 condition, most of added Gd and Y elements are dissolved in Mg41Nd5 precipitates rather than formation of new phases. Tensile properties and creep resistance of the Mg-3%Nd-0.5%Zn-0.4%Zr alloy are remarkably increased by the addition of Gd or Y, but their efficiencies are substantially the same.