κ‐Phase Formation in Fe–Mn–Al–C Austenitic Steels

摘要: In the present work, a combined approach of ab initio theoretical calculations and in situ synchrotron X-ray diffraction is used to investigate κ-phase formation Fe–Mn–Al–C austenitic steels. order understand driving forces for short- long-range ordering steels, fully systematic DFT calculations. A weak Al–Al as well strong Al–C repulsion austenite matrix established which both gradually decrease with increasing interatomic distance. An exception Al–C–Al configuration that also exists identically κ-phases. It found that, an Al contents exceeding 25%, ordered has higher thermodynamic stability than disordered κ-phase. The results further reveal already starts precipitating from within first 15 min during aging at 600 °C Fe-30Mn-8Al-1.2C steel. lattice misfit between expands upon time. Up 9 h aging, however, still maintains being very small (less 2%) leads effective coherent precipitation hardening material.