Phase relationships in the fe-cr-mn-ni-c system at solidification temperatures

Abstract

The phase relationships between the liquid phase and the primary solid phases were investigated in the iron-rich corner of the quinary system Fe-Cr-Mn-Ni-C. Of the five quaternary systems that comprise the quinary system, this study was limited to the three quaternary systems which contain both carbon and iron as two of the components;viz.: Fe-Cr-Mn-C, Fe-Cr-Ni-C, and Fe-Mn-Ni-C, as well as all of the binary and ternary subsystems that have iron as a component. This paper discusses the modeling efforts for these systems, with particular emphasis on the ternary systems Fe-Cr-Mn and Fe-Mn-Ni and the quaternary systems Fe-Cr-Mn-C and Fe-Mn-Ni-C. The experimental investigation consisted of measurements of tie-lines for the liquid-delta (bcc) and the liquid-gamma (fcc) equilibria in the iron-rich corner of the Gibbs simplex bounded by 0 to 25 wt pct Cr, 0 to 12 wt pct Mn, 0 to 25 wt pct Ni, and 0 to 1.2 wt pct C (bal. Fe). The temperature ranged from 1811 to about 1750 K. Compositions for the tie-lines were obtained from liquid-solid equilibrium couples, and the temperatures for the equilibrium by differential thermal analysis (DTA). Parameters were selected in a thermodynamic model of the alloy system to minimize the square of the difference between experimentally and calculated tie-lines, the latter being implicitly a function of the derived parameters in the model. Binary and higher-order parameters were generally required. Ternary parameters were obtained on ironcarbon base alloys Fe-Cr-C, Fe-Mn-C, and Fe-Ni-C, and for the Fe-Cr-Ni system, but not for the Fe-Cr-Mn and Fe-Mn-Ni systems. Of the quaternary systems investigated, quaternary parameters were required only for theL/δ equilibrium in the Fe-Cr-Ni-C system; the Fe-Cr-Mn-C and Fe-Mn-Ni-C systems were found to be represented adequately by employing only binary and ternary parameters.