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

Ti6Al4V alloy billets were additively manufactured by direct energy deposition and then equal channel angularly pressed (ECAPed) at 700(degrees)C. The originally prepared alpha' martensite microstructure was completely converted to an equiaxed fine grain structure during ECAP processing. The alpha' martensite decomposed into alpha + beta 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 alpha ' martensite and alpha 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.