The isothermal section of the Al-Cr-Si system at 800 deg C and the crystal structure of t_2 (Cr_3Al_9Si)

摘要

The system Al-Cr-Si at 800 deg C is investigated using XRD and SEM/EDX on equilibrated alloys. Three ternary phases are found: t_1 -Cr_4Al_(33)Si_4 (F-43m, Cr_4Al_(13)Si_4-type, a = 1.09270(2)nm), T_2-Cr_3Al_9Si(P6_3/mmc, Mn3Al9Si-type,a = 0.75346(3) nm, c = 0.78393(4) nm) and T_3-Cr_4(Al,Si)_(11) (P-1, Mn_4Al_(11)-type, a = 0.51260(2) nm, b = 0.89802(4) nm, c = 0.50472(3)nm, a = 89.775(4)deg , 0 = 100.711(4)deg and y = 106.605(3)deg for Cr_(27)Al_(63)Si_(10)). Extended homogeneity ranges for t_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 deg C over the entire composition range is presented.