Relationship Between Phase Development and Swelling of AISI 316 During Temperature Changes

Abstract

The effect of temperature changes on radiation-induced swelling and phase development of AISI 316 has been examined for specimens irradiated in two different experiments. The formation of radiation-stable phases at low temperature appears to precede swelling but these phases tend to dissolve when subsequently subjected to higher temperature. Phases which develop at high temperature persist when the temperature is subsequently lowered. Once nucleated at low temperatures, voids tend to persist without reduction in density at higher temperatures. However, a new round of void nucleation occurs when the temperature is decreased during irradiation. If the swelling has entered the steady-state swelling regime prior to the temperature change, there is no effect on the subsequent swelling rate. For temperature changes that occur before the end of the transient swelling regime, substantial changes can occur in the swelling behavior, particularly if the changes occur in the range around 500°c. The isothermal swelling behavior of AISI 316 is much less sensitive to irradiation temperature than previously envisioned. While the steady-state swelling rate is relatively insensitive to temperature, the duration of the transient regime can be quite sensitive or not, depending on the particular heat of steel studied.