Mg-Bi-X (X = Ca, Mn, Zn) Alloys Microstructure in the As-Solidified Condition

Magnesium alloys are promising candidates for many structural applications in automotive and aerospace industry. However, due to the low service temperature of the majority of magnesium alloys, huge efforts are made in order to develop the high temperature systems with maximum exploitation temperature of up to 300 degrees C. Nevertheless, the increase of high temperature properties of magnesium alloys is connected with application of expensive rare earth elements (RE). In the paper the microstructure of Mg-XBi (X = 2, 5, 10) alloys has been investigated. The Mg-Bi system may be an effective substitute of Mg-RE alloys, due to the ability of formation of fine precipitates, strengthening the alloy, resulting from the limited solid solubility of Bi in Mg. Moreover the influence of ternary additions of Ca, Mn, and Zn on the microstructure and morphology of eutectic compound has been analysed. It has been found that Ca and Mn alters the microstructure of Mg-Bi alloys, resulting in refinement of eutectic compound precipitates, when Zn addition has no influence on the microstructure of investigated alloys.