Experimental investigation of the Al-Mn-C system: Part I. Phase equilibria at 1200 and 1100 °C

Abstract Phase equilibria in the Al-Mn-C system at 1200 and 1100 °C were studied using DTA, X-ray diffraction, SEM and electron probe microanalysis. Using the results the isothermal sections at 1200 and 1100 °C for this system were constructed covering the whole concentration range. It was shown that the ternary compound Mn 3 AlC (κ-carbide) (antiperovskite structure CaTiO 3 -type, ≿Р 5 -Pm- 3 m ) is stable at these temperatures and has a wide homogeneity range. It co-exists with the majority of solid phases (γMn), eAlMn, Mn 5 C 2 , Mn 7 C 3 , C and Al 4 C 3 at 1200 °C, and at 1100 °C also with the phase eMn 4 С 1-х . In addition to the κ-carbide also (γMn), eAlMn, eMn 4 С 1-х and Mn 5 C 2 show appreciable homogeneity ranges. The Mn 5 C 2 carbide, which in the binary Mn-C system is stable below 1167 °C, participates in equilibria in the ternary system at 1200 and 1100 °C. The character of the phase equilibria at 1100 °C is practically similar to those at 1200 °C. The main difference involves the fact that the equilibrium (γMn) + Mn 5 C 2 which is present in the Al-Mn-C system at 1200 °C, is absent at 1100 °C. Instead, the alternative equilibrium κ + eMn 4 C 1-x is present at 1100 °C.