Isothermal section of the Cu-Mn-Si ternary system at 700 °C

Isothermal section of the Cu-Mn-Si ternary system at 700 °C was investigated over the whole concentration range by means of X-ray diffraction, scanning electron microscopy equipped with energy dispersive X-ray analysis, and electron probe microanalysis. A new MgZn2-type ternary compound T with an average composition of Cu50.8Mn36.3Si12.9 (in at.%) was observed, while two ternary compounds with approximate formulae of Cu32.5Mn50.2Si17.3 and Cu28.3Mn60.5Si11.2 reported in the literature were not found. The lattice parameters of the T phase were determined to be a = b = 4.83(6) and c = 7.846(7) Å. The binary compound Mn5Si2, the existence of which is controversial in the literature, was observed at 700 °C. Five three-phase equilibria, Mn3Si + T + (Cu), Mn5Si3 + Mn5Si2 + T, Mn5Si3 + MnSi + γ-Cu56Si11, MnSi + Mn11Si19 + η-Cu19Si6, and Mn11Si19 + η-Cu19Si6 + (Si) were well determined. The solubilities of Cu in (βMn), Mn6Si, Mn9Si2, Mn3Si, Mn5Si2, Mn5Si3, MnSi and Mn11Si19 were determined to be 0.6, 0.8, 2.1, 1.5, 2.3, 2.5, 1.6 and 0.8 at.% Cu, respectively. The solubilities of Mn in γ-Cu56Si11 and η-Cu19Si6 were measured to be about 3.7 and 2.7 at.% Mn, respectively.