Effect of Oxygen Content on Microstructure and Tensile Properties of a 22Cr-5Al ODS Steel.

Yukun Zhang,Yazhong Zhai,Yingjie Yan,Wei Qin,Hongyan Che,Tiejun Wang,Rui Cao

doi:10.3390/ma14092241

Abstract

The high tensile strength and irradiation resistance of oxide dispersion strengthened (ODS) ferritic steels is attributed to the ultrafine and dispersed oxides within the matrix. The high content of oxygen and yttrium is critical for the formation of dense Y-rich oxides. However, only few studies have reported the effect of oxygen content on the microstructure and mechanical properties of ODS steels. Herein, we employed gas atomization reactive synthesis to prepare pre-alloy powders and then hot isostatic pressing (HIP) to consolidate two 22Cr-5Al ODS steels with different oxygen content. Our results showed Y-rich precipitates at and near grain boundaries of the as-HIPed alloys. Moreover, with the oxygen content increasing from 0.04 to 0.16 wt%, more precipitates precipitated in the as-HIPed alloy, and the ultimate tensile strength of the alloy was improved. However, increasing the oxygen content to 0.16 wt% led to formation of stripe and chain precipitates at and near grain boundaries, which caused a partial intergranular fracture of the as-HIPed alloy.

Highlights

Oxide dispersion strengthened (ODS) steels are key candidate structural materials for advanced nuclear systems [1,2,3,4]
We observed the microstructure of the as-HIPed samples using a 2 shows the X-ray Diffraction (XRD)(SEM, profiles of the as-HIPed alloys A and
The results showed that increasing the oxygen content increased the ultimate tensile strength and yield strength of the as-HIPed alloy B by 10.7% and

Summary

Introduction

Oxide dispersion strengthened (ODS) steels are key candidate structural materials for advanced nuclear systems [1,2,3,4]. The high density of nanoscale oxides provides ODS steels with excellent mechanical performance by blocking dislocation slipping and hindering grain boundaries movement [5,6,7,8,9]. The common processes to fabricate ODS steels are powder metallurgy (PM) with mechanical alloying (MA) and heat consolidation [14], including hot isostatic pressure (HIP) [9], hot extrusion (HE) [15,16], and spark plasma sintering (SPS) [17], and ODS steels have a high density and an excellent tensile strength. In contrast to HIP and HE, laser additive manufacturing (LAM) [18,19] without the MA process is a method used to manufacture the ODS Fe-matrix alloys because of its low cost and flexibility [18]. Yingnan Shi et al fabricated a Zrcontaining ODS-FeCrAl alloy by LAM, which presented anisotropic tensile properties [18]

Results

Discussion

Conclusion