Additive manufacturing of strong and ductile Ti–6Al–4V by selective laser melting via in situ martensite decomposition. (15th February 2015)

• Record Type: Journal Article
• Authors: Xu, W.; Brandt, M.; Sun, S.; Elambasseril, J.; Liu, Q.; Latham, K.; Xia, K.; Qian, M.
• Is Part Of: Acta materialia. Volume 85(2015)
• Page Start: 74
• Page End: 84
• Publication Date: 2015-02-15
• Subjects: Titanium alloy -- Selective laser melting -- Phase transformation -- Microstructure -- Mechanical properties; Materials -- Periodicals; Materials science -- Periodicals; Materials -- Mechanical properties -- Periodicals; Metallurgy -- Periodicals; Chemistry, Inorganic -- Periodicals; 620.112
• DOI: 10.1016/j.actamat.2014.11.028
• Languages: English
• ISSNs: 1359-6454

Abstract

Abstract: Novel ultrafine lamellar (α + β) microstructures comprising ultrafine (∼200–300 nm) α-laths and retained β phases were created via promoting in situ decomposition of a near α′ martensitic structure in Ti–6Al–4V additively manufactured by selective laser melting (SLM). As a consequence, the total tensile elongation to failure reached 11.4% while maintaining high yield strength above 1100 MPa, superior to both conventional SLM-fabricated Ti–6Al–4V containing non-equilibrium acicular α′ martensite and conventional mill-annealed Ti–6Al–4V. The formation and decomposition of α′ martensite in additively manufactured Ti–6Al–4V was studied via specially designed experiments including single-track deposition, multi-layer deposition and post-SLM heat treatment. The essential SLM additive manufacturing conditions for Ti–6Al–4V including layer thickness, focal offset distance and energy density, under which a near α′ martensitic structure forms in each layer and then in situ transforms into ultrafine lamellar (α + β) structures, were determined. This is the first fundamental effort that has realized complete in situ martensite decomposition in SLM-fabricated Ti–6Al–4V for outstanding mechanical properties.