title: Ductility improvement due to martensite α' decomposition in porous Ti-6Al-4V parts produced by selective laser melting for orthopedic implants.
abstract: Ti-6Al-4V parts obtained by selective laser melting typically have an acicular α' martensitic microstructure whose ductility is low. Thus, post-heat treatments are useful for increasing ductility. In this work, the effects of sub-β-transus heat treatments on the mechanical properties of Ti-6Al-4V parts with porous structures are correlated with martensite α' phase decomposition. The precipitation of β phase and the gradual transformation of α' into α phase by the diffusion of excess vanadium from α' to β phase are proposed to be the main events of martensite α' phase decomposition in parts fabricated by selective laser melting. The heat treatment performed at 650°C for 1h produced no microstructural changes, but the samples treated for at the same temperature 2h showed a fine precipitation of β phase along the α' needle boundaries. The heat treatment performed at 800°C for 1 or 2h produced a fine α+β microstructure, in which β phase are present as particles fewer in number and larger in size, when compared with the ones present in the sample heat-treated at 650°C for 2h. Heat-treatment of the parts at 800°C for 2h proved to be the best condition, which improved the ductility of the samples while only slightly reducing their strength.
authors.affiliation: University of Campinas, School of Mechanical Engineering, RuaMendeleiev 200, 13083-860 Campinas, SP, Brazil.
authors.forename: E
authors.initials: E
authors.lastname: Sallica-Leva
authors.affiliation: University of Campinas, School of Mechanical Engineering, RuaMendeleiev 200, 13083-860 Campinas, SP, Brazil.
authors.forename: R
authors.initials: R
authors.lastname: Caram
authors.affiliation: University of Campinas, School of Chemical Engineering, Av. Albert Einstein 500, 13083-852 Campinas, Brazil.
authors.forename: A L
authors.initials: AL
authors.lastname: Jardini
authors.affiliation: University of Campinas, School of Mechanical Engineering, RuaMendeleiev 200, 13083-860 Campinas, SP, Brazil. Electronic address: fogagnolo@fem.unicamp.br.
authors.forename: J B
authors.initials: JB
authors.lastname: Fogagnolo
mesh_terms: D000497:Alloys; D003722:Dental Alloys / Q000737:chemistry*; D006358:Hot Temperature; D007834:Lasers; D009985:Orthopedics; D044367:Phase Transition; D016062:Porosity; D019736:Prostheses and Implants; D013314:Stress, Mechanical; D013329:Structure-Activity Relationship; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry*
chemical_list: D000497:Alloys; D003722:Dental Alloys; C093824:Martensite; C031462:titanium alloy (TiAl6V4); D014025:Titanium
keywords: Additive manufacturing; Mechanical properties; Thermal analysis; Thermal treatment; Titanium alloys; X-ray analysis