Tensile properties of mechanically alloyed/milled Ods-Ni-Based alloys

Abstract

Oxide dispersion strengthened (ODS) NiCr20 alloys were produced by ball milling blends of either prealloyed NiCr20 and yttria powders or elemental Ni and Cr powders and yttria powder. After milling, the powders were degassed in a vacuum furnace, sealed in steel cans, and consolidated by hot extrusion. The mechanical alloying process, which occurs during ball milling of elemental Ni and Cr powders, as well as the changes of microstructure, which occur during milling and extrusion, were characterized by X-ray diffraction (XRD) techniques. Measurements of microhardness, tensile strength, and elongation of extruded bars were done to gain information about the dispersoid partitioning and about the relation between milling parameters, microstructure, and tensile properties. These investigations showed that the attainable quality of ODS NiCr20 alloys is higher if they are produced by milling elemental Ni and Cr powders and yttria powders. Besides the dispersoid partitioning, the homogeneity of the mechanically alloyed powder strongly affects the quality. High-quality materials are only produced if the ball milling process yields a homogeneous dispersoid partitioning and a completely mechanically alloyed NiCr20 solid solution.