Study of helium irradiation induced hardening in MNHS steel

TL;DR

This study investigates how helium ion irradiation causes hardening in MNHS steel, revealing that He bubbles and dislocation loops significantly impede dislocation motion, with bubbles being the stronger obstacle.

Contribution

It provides experimental and modeling insights into helium irradiation hardening mechanisms in MNHS steel, highlighting the roles of He bubbles and dislocation loops.

Findings

He irradiation induces dislocation loops and He bubbles in MNHS steel.

He bubbles act as stronger barriers than dislocation loops.

Predicted hardness increments match nanoindentation measurements.

Abstract

A recently developed reduced activation ferritic/martensitic steel MNHS was irradiated with 200keV He ions to a fluence of 1E21ions/m^2 at 450 celsius degree and 1E20ions/m^2 at 300 celsius degree and 450 celsius degree, respectively. The irradiation hardening of the steel was investigated by nanoindentation measurements combined with transmission electron microscopy (TEM) analysis. Dispersed barrier-hardening (DBH) model was applied to predict the hardness increments based on TEM analysis. The predicted hardness increments are consistent with the values obtained by nanoindentation tests. It is found that dislocation loops and He bubbles are hard barriers against dislocation motion and they are the main contributions to He irradiation-induced hardening of MNHS steel. The obstacle strength of He bubbles is stronger than the obstacle strength of dislocation loops.