Effect of phase proportions on deformation and cavitation of superplastic ?/? brass

Abstract

Studies have been made, using metallographic and precision density techniques, of the deformation and cavitation behaviour during superplastic tensile straining at 873 K of three microduplexα/β brasses which, as a consequence of varying composition, contained varying proportions ofα andβ phases. It was observed that both strain-rate sensitivity and elongation-to-failure passed through a maximum when approximately equivolume proportions of the two phases were present. Cavitation, on the other hand, decreased rapidly as the volume fraction ofβ phase was increased. The cavitation behaviour was attributed to the relative abilities of the phases to accommodate grain boundary sliding. When a high proportion ofα phase is present accommodation is minimal and cavity nucleation. occurs readily. Evidence is presented to show that grain-boundary sliding plays a predominant role in cavity growth. When a high proportion ofβ phase is present accommodation is almost complete and cavity nucleation is minimal.