Peter the Great St. Petersburg Polytechnic University, Saint Petersburg, Russia:

V. Sh. Sufiiarov, Leading Researcher, e-mail: vadim.spbstu@ya.ru
A. A. Popovich, Professor, Director of Institute of Metallurgy, Mechanical Engineering and Transport
E. V. Borisov, Researcher, Post-Graduate Student
I. A. Polozov, Engineer, Student

Additive manufacturing (in particular, selective laser melting (SLM)) is a prospective technology for manufacturing of geometrically complex parts. This technology is especially attractive for aircraft industry, where titaniumbased alloys are widely used. This paper shows the results of the study of Ti – 6Al – 4V alloy powder, which was used for manufacturing of bulk specimens and gas-turbine engine workpiece by SLM. There was carried out the investigation of influence of heat treatment on microstructure and mechanical properties of specimens. Initial powder material is characterized by spherical form of particles with some satellites and consists mainly of martensitic α'-phase. Microstructure of bulk specimens after SLM is martensitic α'-phase in the form of fine-dispersed acicular precipitates. Ultimate tensile strength before heat treatment was 1160 MPa, however elongation was 3.8%. As a result of heat treatment, partial deformation of martensitic phase occurred, which led to increasing material elongation (up to 9.9%), keeping ultimate tensile strength at a high level (1090 MPa). Obtained mechanical properties after heat treatment correspond to American additive manufacturing standard ASTM F2924–14 for Ti – 6Al – 4V alloy. Fractography of specimens showed that fracture type may be characterized as ductile with local elements of brittle fracture, since there are dimples on the fracture surface, typical for ductile fracture, however there are micropores with some unmolten powder particles.

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