Directionally solidified nickel-based alloys are widely used as structural materials under extreme environments, where high-temperature strength, thermal creep resistance, and anti-oxidation properties are required. Although additive manufacturing (AM) has become more competitive in manufacturing metal components in recent years, the existing AM methods are still inadequate to fabricate directionally solidified alloys because of the obstacles in controlling crystal nucleation and growth orientations. This EArly-concept Grant for Exploratory Research (EAGER) project investigates fundamental research enabling laser metal deposition to produce highly oriented crystal metals with the help of magnetic fields. It effectively pushes the limit of AM methods to manufacturing high-end structural parts for a number of industries including aerospace, power generation, and automotive, with shorter product development times and enhanced performance, and at affordable costs.
The research objective is to investigate the fundamental science of magnetic field effects on crystal orientation of Ni-based alloys in a laser metal deposition process. With the proper design and process parameters, this project's AM method is expected to mitigate or even eliminate the columnar to equiaxed transition phenomenon, and thus it can produce highly oriented crystalline Ni-based alloys with controllable orientation and improved mechanical properties. Crystal orientation control is realized by applying a strong static magnetic field in laser metal deposition, so that the angle between the easy magnetization axis and the preferred growth direction in in line with that between magnetic field and thermal flux. Comprehensive mechanical property measurements and microstructure characterization will be carried out to validate the effectiveness of the method. The crystal orientation control mechanism will provide unprecedented insight on developing a new generation of high performance alloys with controllable microstructure.