Experimental Investigation of the Phase Equilibria in the Al-Mn-Zn System at 400 ° C

Abstract

Al-Mn-Zn ternary system is experimentally investigated at 400°C using diffusion couples and key alloys. Phase relationships and homogeneity ranges are determined for binary and ternary compounds using EPMA, SEM/EDS, and XRD. Reported ternary compound T3 (Al 11 Mn 3 Zn 2 ) is confirmed in this study and is denoted as τ 2 in this paper. Two new ternary compounds ( τ 1 and τ 3 ) are observed in this system at 400°C. τ 1 is determined as a stoichiometric compound with the composition of Al 31 Mn 8 Zn 11 . τ 3 has been found to have homogeneity range of Al x Mn y Zn z ( x = 9 – 13 at%; y = 11 – 15 at%; z = 75 – 77 at%). The binary compounds Al 4 Mn and Al 11 Mn 4 exhibit limited solid solubility of around 6 at% and 4 at% Zn, respectively. Terminal solid solution Al 8 Mn 5 is found to have maximum ternary solubility of about 10 at% Zn. In addition, ternary solubility of Al-rich β -Mn′ at 400°C is determined as 4 at% Zn. Zn-rich β -Mn′′ has a ternary solubility of 3 at% Al. The solubility of Al in Mn 5 Zn 21 is measured as 5 at%. Based on the current experimental results, the isothermal section of Al-Mn-Zn ternary system at 400°C has been constructed.