Microstructural Transformation and Enhanced Strength of Wire‐Feed Electron‐Beam Additive Manufactured Ti–6Al–4V Alloy Induced by High‐Pressure Torsion

Abstract

For the first time, the present study demonstrates the influence of high‐pressure torsion (HPT) on microstructural refinement and mechanical strength of Ti–6Al–4V titanium alloy produced by wire‐feed electron‐beam additive manufacturing. This technology has attracted an increasing interest presently from manufacturers of products with complex shapes and it allows for producing a titanium alloy with a unique microstructure that consists of martensitic α′ phase, separated by thin interlayers of residual β phase. Further processing of the alloy by HPT results in the formation of an ultrafine‐grained (UFG) structure with an average grain size of about 25 ± 10 nm, significantly increasing its microhardness up to 448 ± 5 HV. Microscopic studies reveal that the attained UFG structure consists predominantly of the grains of α and β phases in the ratio of 92.8% and 7.2%, respectively. This article also considers the nature of the high strength of Ti–6Al–4V subjected to HPT.