High strain rate mechanical behavior of Ti-6Al-4V octet lattice structures additively manufactured by selective laser melting (SLM)

• Published in: Materials science & engineering. A, Structural materials : properties, microstructure and processing Vol. 745; pp. 231 - 239
• Main Authors: Gangireddy, Sindhura, Komarasamy, Mageshwari, Faierson, Eric J., Mishra, Rajiv S.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 04-02-2019; Elsevier BV
• Subjects: Additive manufacturing; Compressive strength; Deformation mechanisms; Elastic deformation; Elastic recovery; Elastic waves; Energy absorption; High speed cameras; High strain rate; High strain rate testing; Laser beam melting; Lattices; Mechanical analysis; Mechanical properties; Needles; Nodes; Octet lattice; Porosity; Split Hopkinson pressure bars; Split-Hopkinson pressure bar; Ti-6Al-4V; Titanium base alloys; Trusses; Unit cell; Octet lattice; High strain rate testing; Additive manufacturing; Ti-6Al-4V; Split-Hopkinson pressure bar
• ISSN: 0921-5093; 1873-4936
• DOI: 10.1016/j.msea.2018.12.101

Dynamic mechanical response of additively manufactured 12 mm × 8 mm size octet lattice structures of Ti-6Al-4V was investigated. Cylindrical specimens composed of a single unit cell of 36 trusses and 13 nodes sandwiched between two support plates were built using selective laser melting. The radius of the trusses was incrementally varied from 0.1 mm to 0.5 mm. The interior of the trusses and nodes examined using electron microscope was found to be fully densified with no porosity of other defects and demonstrated a uniform microstructure throughout the lattice composed of acicular martensitic needles. High strain rate compression of these lattices was conducted using split-Hopkinson pressure bar at a displacement rate of 7500 mm/s corresponding an effective strain rate of ~ 1000 s−1. The peak compressive strength and energy absorption capacity of the lattices were found to vary almost linearly with relative density of the cell, which increased proportional to the square of the truss radius. Specific strength and absorption however were found to be significantly higher in the lattice with smallest truss radius. The dynamic compression was recorded using a high speed camera at 100,000 fps capture rate and provided insight into the deformation processes: the initial elastic wave loading, the inertia driven continued loading followed by relaxation for elastic strain recovery. These mechanisms which significantly diversified with the truss radius are presented.