Single Crystal-like Microstructure Formation in Ni-25at.Mo Alloy Fabricated by Selective Laser Melting

摘要

The Ni-Mo alloys containing 8-33at% Mo exhibit ordering transformation from short range order (SRO) structure to long range order (LRO) structures when annealed at appropriate temperatures, which will change the alloy mechanical property significantly. Besides controlling the ordering transformation, for the application at elevated temperature, it is very necessary to obtain the single crystal microstructure or the directional solidification microstructure, which can improve the creep resistance for absence of grain boundary. Recently, additive manufacturing (AM) technology has been reported to be able to obtain single crystal-like microstructure in numerous materials, such as Nickel based alloys, Cobalt based alloy, Titanium alloys and so on. However, the formation mechanism of single crystal-like microstructure is not very clear because there are numerical influence factors i.e., material thermodynamic property and variable parameters such as power, scanning speed, pitch, scanning strategy and so on. In this study, the effect of scanning strategy on single crystal-like microstructure formation in Ni-25at.%Mo alloy fabricated by selective laser melting was investigated because of its close connection to the grain growth direction..