부산대학교 도서관

The effects of Y on microstructure and mechanical properties of as-cast AZ80–2Sn magnesium alloys were investigated by optical microscopy, scanning electron microscopy and X-ray diffraction. Y addition not only changes the as-cast microstructure but also influences the mechanical properties of AZ80–2Sn alloy. Unmodified AZ80–2Sn alloys under casting state show that Mg17Al12 eutectic phase is semicontinuous and reticulated shape and distributes mainly at grain boundaries. Moreover, there are numerous Mg2Sn precipitate particles dispersing in Mg17Al12 eutectic phases. Y addition to as-cast AZ80–2Sn alloys has an important influence on the precipitation phase. But there has no obvious effect on grain refinement with Y addition. The results show that the AZ80–2Sn alloys with variable Y contents all contain Al2Y phase. By adding Y, the amount of Mg17Al12 is decreased and the dimension of that is reduced. Mg17Al12 eutectic phase turns to discontinuous, and the more disperse phases occur with the increase of Y content. The tensile tests indicate that a minor addition of Y can contribute to the formation of the dispersed small polygonal Al2Y particles and the improvement in the room-temperature strength. However, excessive Y addition leads to the coarsening of Al2Y phases, and thus results in the decline of strength and ductility.