Grain Boundary Precipitation and Tensile Ductility of Fe-Mn-Ni Alloys

Abstract

The mechanism of grain boundary embrittlement and the improvement of the tensile ductility afforded by alloy addition or heat treatment was investigated in an Fe-Mn-Ni alloy. The precipitation of θ-MnNi intermetallic particles was observed at the prior austenite or interlath boundaries during the aging treatment and this was believed to be responsible for the grain boundary embrittlement of these alloys. After prolonged aging or aging at higher temperatures above 520°C, these metastable intermetallic particles were transformed into the thermodynamically stable austenite phase, thereby leading to the recovery of the grain boundary strength. The addition of Mo caused the grain boundary precipitate to be changed to austenite and resulted in a significant improvement in the tensile ductility after aging.