Effect of Carbon on Spinodal Decomposition in Fe-26Mn-20Al-C Alloys

Abstract

The supersaturated austenite (gamma) phase decomposed into fine C-rich ordered k' particles and C-depleted gamma(0) phase during quenching in alloys with 5.5 <= C <= 8.0 at%. The misfit between k' particles and gamma(0) phase decreased with increasing carbon content. The strain energy increased dramatically as carbon content approached slightly below 5.5 at%. Undercooling may be insufficient to overcome the strain energy effects, thus leading to the absence of spinodal decomposition and k' particles in the present and prior austemtic FeMnAlC alloys with 3.1 <= C <= 5.2 at% under the as-quenched condition. Additionally, both the amount of ordered k' particles and the carbon concentration in the k' particles increased with increasing carbon content of the alloy. These results revealed that a higher degree of carbon supersaturation in the initial gamma phase might promote a tendency toward C-rich k' particle formation during quenching. [doi:10.2320/matertrans.M2010255]