Characterization of microstructure and microtexture in longitudinal sections from friction stir processed nickel-aluminum bronze

Abstract

Cast nickel-aluminum bronze (NAB) is the material of choice for propellers in both surface ships and submarines. New designs require a material with improved strength and hardness while retaining NAB's corrosion resistance. Friction stir processing (FSP) represents a new technology for surface hardening of as-cast NAB by means of severe plastic deformation induced by a rotating tool that is traversed across the surface of a material. FSP can convert a microstructure from a cast to a wrought condition without altering the overall shape of the object being worked. The purpose of this study is to apply recently developed orientation imaging microscopy (OIM) methods to evaluate the influence of FSP on microstructure and microtexture of an as-cast NAB material. Processed material was examined in planes having both longitudinal and transverse orientations with respect to tool motion. Shear textures in the thermomechanically-affected zone (TMAZ) were of particular concern. Results of the analysis of this work will be described and the implications to FSP of NAB propeller materials will be delineated.