THE EFFECTS OF PRE-STRAINING CONDITIONS ON AUSTENITE STABILITY DURING FATIGUE OF MULTIPHASE TRIP STEELS

摘要

A multiphase TRIP780 steel was subjected to tensile pre-strains of 0, 5, and 15% at room temperature and at -20°C. The pre-strained specimens were subjected to strain-controlled, fully-reversed, axial fatigue testing at strain amplitudes ranging from 0.2 to 0.6%. The low-cycle fatigue life was largely independent of the pre-strain history. Pre-strained specimens had lower plastic strain amplitudes and higher stress ranges in the initial fatigue cycles before converging towards the same values as the specimens with zero pre-strain, due to cyclic strain softening. This suggests that the effects of pre-strain are eventually overcome by accumulated plastic deformation during fatigue cycling.