Fracture toughness and tensile strength of 316L stainless steel cellular lattice structures manufactured using the selective laser melting technique

摘要

Selective User Melting (SLM) process is a metallic additive manufacturing technique that directly manufactures strong, lightweight and complex three dimensional parts in a layer-by-layer to scan and melt the metal powder for aerospace applications. However, there are still certain evaluation criteria such as fracture toughness and tensility of cellular structure made by SLM which were not reported before. This study presents new and novel methods in additive manufacturing and evaluates the local failure mechanism of 316L cellular lattice structures made by SLM under uniaxial tension and three point pending load. The effect of different build directions of the 316L lattice structure on the fracture toughness properties are compared to the Ashby and Gibson models. Also, the effect of different build directions on tensile properties of 316L cellular structures has been investigated. Microcomputer tomography (CT) reveals that the cellular structure parts with different build directions were manufactured free of defect by the SLM. The density of the lattice structure samples was found at 1.35 g/cm~3 for both vertical and horizontal building directions while the relative density of solid struts is 96.25%. The tensile and fracture toughness properties in vertical building direction samples are higher than those samples that were built in horizontal building direction. There was no big difference between the Ashby and Gibson micromechanical model to predict fracture toughness and Single Edge Notch Bend (SENB) test results from 0.2 to 0.5 MPa m~(0.5).