The isothermal section of the Al-Cr-Si system at 800 °C and the crystal structure of τ2 (Cr3Al9Si)

The system Al-Cr-Si at 800 degrees C is investigated using XRD and SEM/EDX on equilibrated alloys. Three ternary phases are found: tau(1)-Cr4Al13Si4 (F43m,Cr4Al13Si4-type, a= 1.09270(2)nm),tau(2)-Cr3Al9Si(P6(3)/mmc,Mn3Al9Si-type, a= 0.75346(3)nm,c=0.78393(4)nm)and tau(3)-Cr-4(AI,Si) I I (P-11 Mn4Al11 -type, a= 0.51260(2)nm, b=0.89802(4)nm, c=0.50472(3)nm, alpha=89.775(4)degrees, beta= 100.711(4)degrees and gamma=106.605(3)degrees for Cr27Al63Si10). Extended homogeneity ranges for tau(3) and several solid binary phases into the ternary are observed. The tie-lines between these phases are determined and the isothermal section at 800 degrees C over the entire composition range is presented. (C) 2006 Elsevier B.V. All rights reserved.