Calorimetric data for α-AlMnSi and the α-TO-β decomposition

The specific heat of α-AlMnSi crystals precipitated from liquid solutions and separated by dissolution of the aluminium solid solution has been determined as C p = 21.06 + 0.0091 T J mol −1 K −1. The heat of decomposition at 1027 K to a liquid plus β-Al 9Mn 3Si was measured as 3200 ± 200 J mol −1. The reaction products of the α-phase with highest Si content (11.8 wt.% Si) are a liquid of composition Al-7 wt.% Mn-14 wt.% Si and β-AlMnSi with 36.5 wt.% Mn and 11.6 wt.% Si. The phase diagram for Al-Mn-Si has been extended to 18 wt.% Si and 40 wt.% Mn. The extra Si atoms in the β-phase are assigned to the 6-fold sublattice occupied otherwise by aluminium.