Hot Deformation Mechanism and Ring Rolling Behavior of Powder Metallurgy Ti2AlNb Intermetallics

Powder metallurgy（PM） Ti–22Al–24Nb–0.5Mo（at.%） alloys were prepared by hot isostatic pressing. In order to study the feasibility of PM + ring rolling combined process for preparing Ti;AlNb rings, thermal mechanical simulation tests of PM Ti;AlNb alloys were conducted and two rectangular PM rings（150 mm in height, 75 mm in thickness,350 mm in external diameter） were rolled as a validation experiment. Experimental results show that the flow stress of Ti;AlNb alloys exhibited a significant drop at the very beginning of the deformation（true strain0.1）, and became stable with the increase in strain. Stress instability phenomenon of PM Ti;AlNb alloys was more obvious than that of wrought alloy. Flow stress fluctuation at the initial stage of deformation is related to phase transition of Ti;AlNb alloys which strongly depends on heat treatment and thermal mechanical deformation process. Processing windows during initial stage of ring rolling process is very crucial. A sound PM Ti;AlNb rectangular ring blank（height = 150 mm, thickness = 30 mm, external diameter = 750 mm） was successfully rolled in two passes by using the improved heat preservation method and optimized rolling parameters. Tensile properties of PM Ti;AlNb alloy were improved, and the porosity was reduced after ring rolling.