Influence of Annealing Microstructure on the Low-cycle Fatigue Properties and Fatigue Microstructure of a Fe-15Mn-10Cr-8Ni-4Si Seismic Damping Alloy

摘要

We investigate the effects of the annealing microstructure on the low-cycle fatigue (LCF) life (Ni), cyclic stress behaviour and fatigue microstructure of a Fe-15Mn-10Cr-8Ni-4Si alloy that exhibits a deformation-induced transformation of austenite (gamma-phase) into epsilon-martensite (epsilon-phase). The alloy rolled at 800 degrees C was annealed at 600 degrees C, 700 degrees C, 800 degrees C and 900 degrees C to vary the grain size, the fraction of recrystallised grains and the texture intensity. Fully reversed axial strain-controlled LCF tests were conducted at total strain amplitudes, Delta epsilon(t)/2, ranging from 0.007 to 0.02. The alloy showed a higher N-f than common steels and ferrous high-Mn alloys in this strain range. This type of annealing microstructure was found to impact the N-f,N- fatigue behaviour and deformation-induced epsilon-martensitic transformation (epsilon-MT) in the studied alloy. The fully recrystallised and weakly textured austenite formed at T >= 800 degrees C facilitated the uniform development of epsilon-martensite under cyclic deformation and led to an increased N-f. The partially recrystallised and textured austenite-containing substructure with high dislocation density formed at T <= 700 degrees C suppressed the epsilon-MT, retarded reversible dislocation motions in the un-recrystallised regions and moderately decreased N-f. Moreover, N-f and the deformation-induced epsilon-MT were observed to be less sensitive to variations in grain size.