Microstructural Evolution and Mechanical Properties of Type 304 L Stainless Steel Processed in Semi-Solid State

Abstract The paper discusses the effect of semi-solid processing on the microstructural evolution and mechanical property of 304L stainless steel. For the study, steel specimens were part ially melted and cooled to room temperatures in different cooling mediu m. The effect of temperature, t ime and cooling mediu m on microstructural evolution was studied by using optical microscopy. It was found that melting begins with the nucleation of liquid phase at the triple junctions and grain boundaries followed by propagation of the liquid phase along grain boundaries. The mechanical behavior of the semi-solid processed material was compared with that of the conventionally processed material with regard to their tensile properties and hardness. The semi-solid processed material shows better ductility and reduced YS and UTS than the conventionally processed counterpart. The correlation of the tensile properties and evolved liquid content shows that the UTS of the material decreases, while the YS increases with liquid fraction. The study also shows that there is a significant effect of cooling med iu m on the microstructural evolution and hence on the mechanical propert ies

Effect of semi-solid heat treatment on elevated temperature plasticity of 304L stainless steel

The present work explores the potential of semi-solid heat treatment technique by elucidating its effect on the plastic behavior of 304L SS in hot working domain. To accomplish this objective, hot isothermal compression tests on 304L SS specimens with semi-solid heat treatment and conventional annealing heat treatment have been carried out within a temperature range of 1273-1473 K and strain rates ranging from 0.01 to 1 s(-1). The dynamic flow behavior of this steel in its conventional heat-treated condition and semi-solid heat-treated condition has been characterized in terms of strain hardening, temperature softening, strain rate hardening, and dynamic flow softening. Extensive microstructural investigation has been carried out to corroborate the results obtained from the analysis of flow behavior. Detailed analysis of the results demonstrates that semi-solid heat treatment moderates work hardening, strain rate hardening, and temperature sensitivity of 304L SS, which is favorable for hot deformation. The post-deformation hardness values of semi-solid heat-treated steel and conventionally heat-treated steel were found to remain similar despite the pre-deformation heat treatment conditions. The results obtained demonstrate the potential of semi-solid heat treatment as a pre-deformation heat treatment step to effectively reduce the strength of the material to facilitate easier deformation without affecting the post-deformation properties of the steel

Role of grain boundary ferrite layer in dynamic recrystallization of semi-solid processed type 304L austenitic stainless steel

A semi-solid processed steel with well arranged delta-ferrite layer around the austenite-solid globules is found to show different dynamic recrystallization (DRX) pattern compared to its conventionally processed counterpart with ferrite stringers across the austenite grains. Analysis of experimental results indicates that the presence of delta-ferrite layer around austenite-globules delays the nucleation of new DRX grains. On the other hand, with increase in temperature, the delta-ferrite layer contributes to increase in DRX fraction by restricting the grain growth of the austenite matrix prior to deformation. (C) 2016 Elsevier B.V. All rights reserved