Fracture mechanical investigations on selective laser melted Ti-6Al-4V

Abstract

Additive Manufacturing (AM) techniques such as selective laser melting (SLM) enable material efficient production of individual and complex components in a short period of time. One typical material that is processable by SLM is the titanium alloy Ti-6Al-4V. This alloy is frequently used in medicine technology because of low density, very high strength and biocompatibility. The AM process leads to many advantages like the opportunity to produce complex parts with for instance undercuts or lattice structures. As AM parts are used in various high-quality sectors the material properties are of great interest. Many influencing factors have an impact on the resulting material properties of additively manufactured Ti-6Al-4V products. For a reliable application and a fracture-safe construction the influence of different changes in the production parameters on the material properties have to be known. As Ti-6Al-4V is already processable and the mechanical and fracture mechanical properties for a defined powder particle size distribution are known, the influence of a varied powder particle size, in this case of a significantly smaller, average particle size is investigated in the scope of this paper. In detail, the mechanical and fracture mechanical behavior under different heat treatments is compared to existing data for the higher average particle size. Because of the resulting residual stresses during the building process a heat treatment is always necessary for a reliable structure. To determine the material properties, tensile tests according to DIN EN 10002-1 were conducted. For the fracture mechanical examinations compact tension specimens, according to ASTM 647-08 standard, were used. Fatigue crack growth curves with an R-ratio of 0.1 were investigated.