TENSILE PROPERTIES OF MECHANICALLY ALLOYED MILLED ODS-NI-BASED ALLOYS

Oxide dispersion strengthened (ODS) NiCr20 alloys were produced by bal l milling blends of either prealloyed NiCr20 and yttria powders or ele mental Ni and Cr powders and yttria powder. After milling, the powders were degassed in a vacuum furnace, sealed in steel cans, and consolid ated by hot extrusion. The mechanical alloying process, which occurs d uring ball milling of elemental Ni and Cr powders, as well as the chan ges of microstructure, which occur during milling and extrusion, were characterized by X-ray diffraction (XRD) techniques. Measurements of m icrohardness, tensile strength, and elongation of extruded bars were d one to gain information about the dispersoid partitioning and about th e relation between milling parameters, microstructure, and tensile pro perties. These investigations showed that the attainable quality of OD S NiCr20 alloys is higher if they are produced by milling elemental Ni and Cr powders and yttria powders. Besides the dispersoid partitionin g, the homogeneity of the mechanically alloyed powder strongly affects the quality. High-quality materials are only produced if the ball mil ling process yields a homogeneous dispersoid partitioning and a comple tely mechanically alloyed NiCr20 solid solution.