Impact of ECAP processing on dislocation density and subgrain size in a ti6al4V alloy prepared by direct energy deposition

Abstract

Ti6Al4V alloy billets were additively manufactured by direct energy deposition and then equal channel angularly pressed (ECAPed) at 700 °C. The originally prepared α′ martensite microstructure was completely converted to an equiaxed fine grain structure during ECAP processing. The α′ martensite decomposed into α + β dual phase structure. The dislocation density in the deposited and ECAPed samples was measured by X-ray profile analysis in samples of two orientations. The dislocation density estimated in the deposition plane was found to be higher than that estimated perpendicularly. This difference is probably a consequence of the internal stresses generated in the samples during the deposition process. A similar anisotropy in dislocation density and crystallite size was found in the ECAPed samples. Lattice constants were measured for the α′ martensite and α phase of the ECAPed alloy. The crystallite size distribution was found to be moderately different for samples cut parallel and perpendicular to the extrusion direction.