Thermal behaviors simulation for laser metal deposition of TiAl powders

Due to its high melting point and low weight, TiAl alloys have been developed as the promising high temperature structural materials for future transportation applications, especially suitable for structural parts with complex geometry in aircraft. However, lacking of ductility at room temperature makes it a typical difficult-to-cut material by conventional material-removal manufacturing methods. Additive manufacturing (AM), which has completely different materials incremental manufacturing philosophy and could produce parts layer by layer via consolidation/deposition of powder or wire feedstock, offers a brand new and convenient means to manufacture complex structural components for hard materials. Currently, one the main applications of AM is to design and manufacture critical functional metallic components with complicated geometry for metals, alloys and even metal matrix composites (MMCs), to satisfy the ever-improving requirements in the aerospace, automotive and biomedical industries.
Laser engineering net-shaping (LENS), based on a kind of directed energy deposition (DED), is one of the popular AM technologies for complex metal structural component production. It could fabricate complex, fully dense metal components from CAD files directly without using dies, tooling or machining, which greatly reduce the lead-time and production cost. However, accurate numerical modelling of LENS process is a real challenge due to the involvement of multiple physical processes as well as accompanied mass and heat flows. In this paper, the deposition process of TiAL alloys with LENS is reported. The thermal behaviours of substrate and as-deposited layer/track during the LENS process are investigated by using FEM and phase field modelling. Temperature field distributions caused by the moving laser beam and the resultant molten pool on the substrate, are simulated and compared. Interaction between the laser and the powder particles, which make the powder particles temperature raise and the laser power irradiating to the substrate partially reduced, are also considered. The research offers a more accurate and practical thermal behavior model for LENS of TiAl; it will be particularly useful for key components manufacturing in the field of aerospace which has more demanding requirement on their functional performance.