（1. School of Materials Engineering, Shanghai University of Engineering Science, Shanghai 201620, China) （2. State Key Laboratory of Advanced Welding and Joining, Harbin Institute of Technology, Harbin 150001, China) （3. SANY HEAVY Machine Co, Ltd, Kunshan 215300, China)
Additive manufacturing technology is able to manufacture the complex parts rapidly, which can greatly improve production efficiency, reduce material loss, and reduce production costs. Compared with arc and laser additive manufacturing technology, electron beam freeform fabrication has gradually become a research hotspot due to its features such as low manufacturing cost, high processing efficiency and high material utilization. This review summarizes the research status and main problem of electron beam freeform fabrication in forming precision and defect control, structure and performance characteristics, as well as forming and control mechanism. On this basis, outstanding challenges and research opportunities for electron beam freeform fabrication are identified and discussed, which is (i)research on realizing wire feeding stability and optimizing method of electron beam path for large complex structure parts, (ii)improvement of forming accuracy and reduce internal stress, (iii)research on heat distribution and microstructure transformation, (iv)development of realtime monitoring device for additive manufacturing process.