EVOLUTION OF TEMPERATURE DURING SHAPED METAL DEPOSITION: FINITE ELEMENT PREDICTIONS VS. OBSERVATIONS

摘要

Shaped Metal Deposition (SMD) is a novel technology to build near-net shaped parts by successive weld deposition. The SMD rig consists of a robot with a Tungsten Inert Gas (TIG) welding torch and a manipulator, which are housed inside a sealed chamber. The heat transfer problem is modeled in a series of walls made by SMD of Ti-6Al-4V alloy. The studied specimens have different dimensions and were obtained using a wide range of process parameters (number of layers, layer height, wire feed rate, travel speed, heat input, etc.). The aim is to correlate the temperature field predicted using the finite element model developed by Centro Internacional de Métodos Computacionales en Ingeniería (Santa Fe, Argentina) to macro-, meso- and micrographical observations done at the Department of Metallurgy and Materials Engineering (Katholieke Universiteit Leuven, Belgium), as a way of validating the model of such a complex process. SMD subjects the build part repeatedly to a specific temperature field which results in a unique morphology and in microstructures usually not achievable by conventional fabrication techniques. The appearance of distinct microstructures in the top of the walls, in the substrate and in the intermediate region is explained on the basis of temperature and temperature rate results. Modelling of microstructure evolution in terms of phase kinetics based on phase transformation diagrams is dealt with in a companion paper.