Influence Of Rare-Earth On Microstructures And Properties Of AZ61 Magnesium Alloy

In this paper, the microstructures and tensile properties of as-cast and solution treated AZ61 magnesium alloys with and without the addition of Ce and Y, as well as as-cast AZ61 magnesium with Nd, were investigated. Moreover, the microstructures and tensile properties of the AZ61+Nd magnesium alloy subjected to hot extrusion were also studied. The ultimate tensile strength σ_b, 0.2% offset yield strength σ_0.2 and elongation to failure 8 of the above-mentioned magnesium alloys with different chemical composition and processing statuses at different test temperatures were determined. The evolution in the microstructure of the AZ61, AZ61+Ce, AZ61+Nd and AZ61+Y magnesium alloys due to either solution treatment and hot extrusion was discussed. And the influence of both solution treatment and hot extrusion on the tensile properties of the AZ61 magnesium alloys with various contents of Ce, Y and Nd at different test temperatures were evaluated.The research results showed that with the addition of rare-earth element Nd in the AZ61 magnesium alloy, the microstructure of the as-cast alloy could be refined, where the microstructural refinement in the AZ61 alloy with 1.5% Nd was the most considerable. The addition of Nd in the AZ61 magnesium alloy could slightly increase the ultimate tensile and yield strengths of the alloy under the cast status while the elongation of the alloy could be significantly improved. After the hot extrusion, the tensile properties of the AZ61+Nd alloy could be greatly enhanced. Adding rare- earth element Ce in the AZ61 magnesium alloy could also refine the microstructure of the alloy under the cast status. At the same time, for the cast AZ61 alloy, the addition of Ce could improve the yield strength at room temperature as well as the tensile properties at the higher test temperatures. The ultimate tensile and yield strengths of various AZ61+Ce alloys subjected to the solution treatment would decrease, but were higher than those of the AZ61 alloy subjected to the same heat treatment. For most of the AZ61+Ce alloys, however, the elongation was lower than that of the AZ61 after solution treatment. With an addition of the rare-earth element Y, the microstructure of the cast alloys could also be refined. Although adding Y in the AZ61 alloy had no significant influence on the yield strength at different test temperatures as well as the ultimate tensile strength at room temperature, it could enhance the ultimate tensilestrength of the cast alloy at the higher test temperatures. After the solution treatment, both elongation at room temperature and yield strength at the higher test temperatures could get increased for various AZ61+Y alloys compared with the solution treated AZ61 alloy.