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

Abstract 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 MgZn 2 -type ternary compound T with an average composition of Cu 50.8 Mn 36.3 Si 12.9 (in at.%) was observed, while two ternary compounds with approximate formulae of Cu 32.5 Mn 50.2 Si 17.3 and Cu 28.3 Mn 60.5 Si 11.2 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) A. The binary compound Mn 5 Si 2 , the existence of which is controversial in the literature, was observed at 700 °C. Five three-phase equilibria, Mn 3 Si + T + (Cu), Mn 5 Si 3  + Mn 5 Si 2  + T, Mn 5 Si 3  + MnSi + γ-Cu 56 Si 11 , MnSi + Mn 11 Si 19  + η-Cu 19 Si 6 , and Mn 11 Si 19  + η-Cu 19 Si 6  + (Si) were well determined. The solubilities of Cu in (βMn), Mn 6 Si, Mn 9 Si 2 , Mn 3 Si, Mn 5 Si 2 , Mn 5 Si 3 , MnSi and Mn 11 Si 19 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-Cu 56 Si 11 and η-Cu 19 Si 6 were measured to be about 3.7 and 2.7 at.% Mn, respectively.