Influence of Microstructural State and Initial Applied Stress on the Stress Relaxation Behavior of AISI 316L at 500 °C

Abstract

Stress relaxation in austenitic stainless steels is a time-dependent phenomenon governed by diffusion processes, dislocation mobility, and microstructural evolution. Its study is of particular interest for components subjected simultaneously to mechanical loading and elevated temperatures, where the progressive redistribution of internal stresses directly influences their in-service performance. In this work, the bending stress relaxation behavior of solution-treated and subsequently sensitized AISI 316L stainless steel specimens was evaluated at 500 °C for 231 h. Two initial stress levels were applied, and specimens were periodically removed throughout the test in order to assess the influence of the initial microstructural condition and the applied stress level. The sensitized specimens exhibited stress relaxation from lower residual stress levels than those in the as-received condition, demonstrating that the precipitation of secondary phases along grain boundaries modifies the stress relaxation kinetics and affects the high-temperature mechanical response of the material.