Cold swaging, recovery and recrystallization of oligocrystalline INCOLOY MA 956-part I: Deformed state

Abstract

Oxide dispersion strengthened (ODS) superalloys combine high temperature strength and excellent corrosion and oxidation resistances. INCOLOY MA 956 is an iron-based ODS superalloy containing about 1 % (volume) of fine and uniformly dispersed Y2O3 particles in a ferritic matrix. In the present work a coarse-grained (oligocrystalline) bar of MA 956 alloy was cold deformed by rotary swaging to reductions in area of 20, 47, 61, and 72%. Microstructural characterization of deformed samples was performed using light optical microscopy (LOM), X-ray diffraction (XRD), electron backscatter diffraction (EBSD), and Vickers micro-hardness testing. The microstructure in the deformed state was found to be very inhomogeneous. Deformation bands were observed in all grains. The extent of deformation banding varies from grain to grain in terms of morphology and spacing. The deformation substructures were found to be very different in each grain. A sharp 〈110〉-fiber texture was developed during plastic deformation becoming more pronounced with increasing strain.