Enhancing high-cycle fatigue properties of cold-drawn Fe–Mn–C TWIP steels

• Published in: International journal of fatigue Vol. 85; pp. 57 - 64
• Main Authors: Song, Seok Weon, Lee, Jeong Hun, Lee, Hyong Jik, Bae, Chul Min, Lee, Chong Soo
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01.04.2016
• Subjects: Cold-drawing; Crack initiation and propagation; Fatigue (materials); Fatigue failure; Fatigue properties; Fatigue strength; Filled plastics; High cycle fatigue; Pearlitic steel; Steels; Tensile strength; TWIP steel; TWIP steels; Crack initiation and propagation; TWIP steel; Pearlitic steel; Cold-drawing; Fatigue properties
• ISSN: 0142-1123; 1879-3452
• DOI: 10.1016/j.ijfatigue.2015.12.007

•Fatigue properties of cold-drawn TWIP and pearlitic steels were investigated.•Low fatigue strength was observed in severely cold-drawn TWIP sample.•Grain boundary weakness lead to early intergranular fatigue cracking.•Adequate annealing increased both fatigue strength and fatigue ratio. High-cycle fatigue properties of cold-drawn twinning-induced plasticity (TWIP) steel, a favored candidate for replacing fully pearlitic (FP) steels in wire applications, were investigated. The high-cycle fatigue tests were conducted on cold-drawn TWIP and FP steels that had comparable ultimate tensile strength for comparison. Fatigue strength of both TWIP and FP steels increased with the tensile strength, but the TWIP steel cold-drawn to a tensile strength of 1.5GPa exhibited a very low fatigue ratio (a ratio of fatigue strength to tensile strength) which deviated far from the predicted linear relationship. Fracture surface analysis showed that crack initiation mainly occurred at the ferrite matrix in FP steels, while either at grain or twin boundaries in TWIP steels where a large density of dislocations piled up during cold drawing. In the case of TWIP steels, the presence of inclusions at grain boundaries led to high local stress concentration and caused early intergranular fatigue cracking as notch sensitivity increased with tensile strength. Subsequent annealing after cold-drawing effectively increased fatigue strength of TWIP steels. It was suggested that TWIP steel revealing both high tensile strength and excellent high cycle fatigue strength could be a promising alternative for replacing conventional FP steels.