Influence of Inclusions on the Mechanical Properties of RAFM Steels Via Y and Ti Addition

Abstract

The effects of the Y- and Ti-containing inclusions on the tensile and impact properties of reduced activation ferritic martensitic (RAFM) steels were evaluated. Four steels with different Y and Ti contents were produced via vacuum induction melting. The size and quantity of inclusions in the steels were analyzed using scanning electron microscopy, and the oxide particle formation mechanism was clarified. These inclusions helped to enhance the pinning effect of the austenite grain boundaries based on the Zener pinning force. The average prior austenite grain sizes, measured via the linear intercept method, were 12.34 (0 wt.% Ti), 9.35 (0.010 wt.% Ti), 10.22 (0.030 wt.% Ti), and 11.83 (0.050 wt.% Ti) μm for the four steels, in order of increasing Ti content, respectively. Transmission electron microscopy was conducted to observe the fine carbides. The strength and impact properties of the steel containing 0.010 wt.% Ti were improved, and the ductile-to-brittle-transition temperature was reduced to −70.5 °C. The tensile strength and impact toughness of the steel with 0.050 wt.% Ti were significantly reduced due to the coarsening of both the inclusions and grain size, as well as the precipitation of large TiN inclusions. The RAFM steel with approximately 0.015 wt.% Y and 0.010 wt.% Ti exhibited an optimized combination of microstructures, tensile properties, and impact properties among the four steels.

The effect of TiN inclusions on the fracture mechanism of 20CrMnTi steel with lath martensite

“…Thus, when the ingot solidifies, a large number of high-temperature large particles such as stable TiN precipitates exist in the matrix [4,5]. The tensile strength and impact toughness of the steel were significantly reduced due to the precipitation of large TiN inclusions [6]. TiN particles with a size larger than 1 μm reduce the toughness of steel, resulting in cleavage and brittle fracture and serious reductions in the impact toughness and fracture toughness of the material [7].…”

The Microstructure and Mechanical Properties of Ferritic-Martensitic Steel EP-823 after High-Temperature Thermomechanical Treatment

“…The efficiency of a nuclear reactor and the possibility of increasing its operating temperature are determined, among other things, by the long-term strength properties of its structural materials. Both long-term and short-term strength properties of ferritic-martensitic steels are controlled by the elemental composition, microstructure features (dimensions of tempered martensite packets, volume fraction of ferrite, dislocation density), composition, dimensions and spatial distribution of carbide (carbonitride) phases [4][5][6][7][8][9][10][11]. Steels of this class are most thoroughly investigated in the structural state after normalization and tempering; this processing is referred to here as a traditional heat treatment (THT).…”

Role of Non-Metallic Inclusions in the Fracture Behavior of Cold Drawn Pearlitic Steel

“…Recent references about inclusions in steel deal with modeling inclusion formation [43], effect of sulfur content [44], the effect of different non-metallic inclusions on the machinability of steels [45], quality control of steel wires [46], micromechanical modeling of fatigue crack nucleation around non-metallic inclusions [47], MnS inclusions formation in resulfu-2 of 15 rised steel [48], influence of inclusions on the mechanical properties [49] or their effect on deformation and fracture [50].…”