Al-Mo-Zn (Aluminum-Molybdenum-Zinc)

Recently, [2006Wan] determined an isothermal section for this ternary system at 450 °C.

Binary Systems

The Al-Mo phase diagram [2006Eum] depicts the following intermediate phases: MoAl₁₂ (Al₁₂W-type cubic), MoAl₅(r) (rhombohedral, space group ${R\bar{3}c}$, MoAl₅(h′) (hexagonal, P321), MoAl₅(h) (hexagonal, P6₃22), Mo₅Al₂₂ (orthorhombic, Fdd2), Mo₄Al₁₇ (monoclinic, C2), MoAl₄ (monoclinic, Cm), MoAl₃ (monoclinic, C2/m), Mo₃Al₈ (monoclinic, Cm), Mo₃₇Al₆₃, MoAl (bcc), and Mo₃Al (A15, Cr₃Si-type cubic). In the Al-Zn system [Massaslski2], solidification occurs through a eutectic reaction at 381 °C yielding (Zn) and (Al). On solidification, (Al) has more than 60 at.% of dissolved Zn. At lower temperatures, this solid solution exhibits a miscibility gap, with a monotectoid reaction at 277 °C: (Al)′ ↔ (Al) + (Zn). In the Mo-Zn system [Massalski2], to intermediate phases MoZn₂₂ (orthorhombic) and MoZn₇ (Ca₇Ge-type cubic) are stable below 463 and 575 °C respectively.

Ternary Isothermal Section

With starting metals of 99.99% purity, [2006Wan] melted 23 ternary alloys containing up to 40 at.% Mo in evacuated quartz tubes at 1200 °C. The alloys were given a final anneal at 460 °C for 20 d and quenched in water. The phase equilibria were studied with metallography, x-ray powder diffraction and energy dispersive x-ray analysis attached to the scanning electron microscope. The identified phases and their measured compositions were listed. The isothermal section at 460 °C constructed by [2006Wan] is shown in Fig. 1. The phase MoAl₄ shown by [2006Wan] is presumably Mo₄Al₁₇ [2006Eum]. The equilibria involving Mo₅Al₂₂ are not known. The phases MoAl and Mo₃₇Al₆₃ are not stable at this temperature. The solubility of Mo in liquid (Zn) and solid (Al) is negligible. Mo₃Al and Mo₃Al₈ dissolve up to 11.5 and 13.5 at.% Zn respectively. MoZn₂₂ and MoZn₇ dissolve up to 1 and 7 at.% Al respectively. No ternary phases were found.

Fig. 1

Al-Mo-Zn isothermal section at 450 °C [2006Wan]