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

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 alpha ' phase, separated by thin interlayers of residual beta 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 alpha and beta 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. Herein, the effect of high-pressure torsion on structural and phase transformations in alloy Ti-6Al-4V manufactured by 3D printing is investigated for the first time. A strong refinement of the grain structure and a significant increase in the microhardness of the alloy are revealed. The nature of the established structural transformation and their effect on the hardening are discussed.image (c) 2023 WILEY-VCH GmbH