Tensile mechanical properties, deformation mechanisms, fatigue behaviour and fatigue life of 316H austenitic stainless steel: Effects of grain size

Abstract

To explore the effect of grain size on the tensile behaviour, symmetrical strain control fatigue behaviour and ratcheting fatigue behaviour of the new austenitic steel 316H, a series of tensile tests, symmetrical strain control fatigue tests and ratcheting fatigue tests were conducted at 25°C within an average grain size range from 14 to 122 μm. The average dislocation free path, forest dislocation density and mobile dislocation density of 316H steel with different grain sizes under tension were obtained. Moreover, the decrease of grain size led to saturation of mobile dislocations at lower strains. The decrease of grain size led to the increase of the cyclic stress and affected softening and secondary hardening process. In addition, under the same stress control conditions, the reduction in grain size caused a reduction in ratcheting strain under the same cycle. The grain refinement of 316H steel contributed to the improvement of ratcheting fatigue life.

Study of Quenching and Partitioning (Q&P) and Ultrasonic Surface Rolling (USR) Process on Microstructure and Mechanical Property of a High-Strength Martensitic Steel

“…Q&P370 N has a rich content of small blocky RA with high stability and refined M/A islands and martensite. The smaller component size with good plasticity in Q&P370 N retards crack propagation, and the total elongation is close to that of Q&P370 W, but the specimen with no filmy RA shows a noticeable decrease in tensile strength [ 40 ]. Q&P370 Oil performs the worst in tensile strength due to the coarse component size and low stability of blocky RA; also, the high content of brittle M/A islands and martensite leads to poor total elongation.…”

Hierarchical Multiple Precursors Induced Heterogeneous Structures in Super Austenitic Stainless Steels by Cryogenic Rolling and Annealing

“…According to the statistics, the average thickness of T/M lamellae was ~24.64 nm. With strain progressing to 50%, the further evolution of dislocation walls and cells not only inhibited dislocation slip, but also promoted an effective grain refinement [ 26 ]. More importantly, the enhanced nucleation driving force led to a significantly increased number density of NTs ( Figure 2 d), and the average size of T/M lamellar thickness was reduced to ~16.43 nm.…”