Ultrafine Fe-Fe2Ti eutectics produced by laser metal deposition: processing and characterization

Abstract

Additive manufacturing (AM) presents advantages over the traditional production methods such as the ability to produce near net-shape components with reduced material usage and a weight-optimized component design. Laser-based AM process methods, i.e. Laser Metal Deposition (LMD) and Selective Laser Melting (SLM), provide rapid and directional solidification in the melt pool and hence the possibility to produce ultrafine microstructures. These conditions hold great promise for the production of novel eutectic materials with ultrafine microstructural length scales. Eutectics can benefit immediately and dramatically from rapid solidification, since it has been shown [1, 2] that the reduction of the eutectic spacing leads to increasing the materials strength along with increasing ductility and fracture toughness. In this presentation, we describe our research on Fe-Fe2Ti eutectics produced by Laser Metal Deposition (LMD). We will discuss the effect of process parameters such as Laser scanning velocity and Laser power on the microstructure on distinct length scales, encompassing features such as eutectic grain size, interlayer boundary morphology and eutectic spacing. We will show that the lamellar eutectic consisting of hexagonal Laves-phase Fe2Ti and the BCC a(Fe) can be processed to above 99.8 % density, while reaching lamellar spacing in the range of 50 to 200 nm. Furthermore, mechanical properties will be discussed based on microhardness measurements and in-situ micromechanical testing inside an SEM.