On the influence of microstructure on the fracture behaviour of hot extruded ferritic ODS steels

Effect of anisotropic microstructure of ODS steels on small punch test results

“…Fig. 7a, whereas cigar shaped elongated grains were observed in the hot extruded materials ODS-HE-1 and ODS-HE-2 [10] (cf. Fig.…”

“…• ODS-HE-1 is a hot extruded 13% Cr ODS steel round bar also provided KIT. The main fabrication steps include: mechanical alloying in an attritor ball mill, encapsulation of the powder, evacuation of the capsule and hot extrusion at 1100 °C [10,22]. • ODS-HE-2 is a hot extruded 14% Cr ODS steel round bar provided by Centro Sviluppo Materiali, Italy (CSM).…”

“…Gas atomized pre-alloyed steel powder was mixed with 0.3% Y2O3 and dry ball milled in an environment of Ar and H. After canning, direct hot extrusion was performed at 1150 °C with an extrusion ratio of 22.5. A heat treatment at 1050 °C was applied for one hour with subsequent cooling in the furnace [10]. Small punch tests were executed in three orientations for ODS-HR (S -thickness direction, L -rolling direction and T -transverse direction) and in two orientations for ODS-HE-1 and ODS-HE-2 (L -extrusion direction, R/C -radial/circumferential direction).…”

“…(b) Figure 7. EBSD images from [9,10]: (a) pan-cake shaped coarse grains in ODS-HR; (b) Cigar shaped coarse grains in ODS-HE-1.…”

“…Depending on the orientation of the weak planes in the impact specimen, they discriminated a "crack arrester" and a "crack divider" situation. The impact of two different fabrication routes (hot rolling and hot extrusion) on the grain morphology and thereby on the fracture toughness in different orientations was investigated in detail by Das et al [9,10].…”