The isothermal section of the La–Si–Mg system at 500  ∘C

• Published in: Calphad Vol. 33; no. 1; pp. 44 - 49
• Main Authors: De Negri, S., Saccone, A., Delfino, S.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.03.2009
• Subjects: Phase diagrams; Rare earth metals intermetallics; Silicides; Rare earth metals intermetallics; Silicides; Phase diagrams
• ISSN: 0364-5916
• DOI: 10.1016/j.calphad.2008.07.012

The isothermal section of the La–Si–Mg system at 500  ∘C was constructed in the whole concentration range by means of the SEM-EDXS and XRPD characterization of about forty alloys prepared by induction melting and then annealed. Phase equilibria are characterized by the following ternary phases: τ 1-La 2+ x Si 2Mg 1− x  (0≤ x≤0.35,tP10-Mo 2FeB 2), τ 2-LaSi 2Mg 2 (tP5-CeSi 2Mg 2), τ 3-LaSi 2Mg (structure still unknown) and τ 4-La 6SiMg 23 (cF120-Zr 6SiZn 23). The high temperature binary phase LaMg 2 (cF24-MgCu 2) has been found to be stabilized at 500  ∘C probably by a small amount of Si. Phases in binary subsystems do not generally form extended ternary solid solutions except for (La 1− x Mg x ) 3Si 2 (0≤ x≤0.167,tP10-U 3Si 2). Crystal structures of phases τ 1-La 2+ x Si 2Mg 1− x and (La 1− x Mg x ) 3Si 2 are correlated, the former being a substitution derivative of the latter.