Research progress of typical defects in additive manufactured metallic materials

Additive manufacturing is a near-net shaping technology that builds three-dimensional solid parts by depositing material layer by layer. It offers unique advantages in producing metal parts with complex structures. As a result, it has been widely used in key fields such as aerospace, biomedical and high-end mold manufacturing. However, the unique forming process of additive manufacturing introduces defect characteristics that differ from those in traditional manufacturing methods. These issues severely affect the service reliability of the formed parts and have become a critical challenge for the technology. This paper systematically summarizes the research findings of AECC Additive Manufacturing Technology Innovation Center on defects in additively manufactured metal materials. It focuses on the morphological features, formation mechanisms and effects on mechanical properties of typical defects such as holes, lack of fusion, inclusions and cracks. The paper also analyzes the role of hot isostatic pressing in closing defects and improving mechanical properties. To address current research gaps, it suggests further studies in several areas. These include revealing the relationship between defect formation mechanisms and process parameters, developing metal materials specifically for additive manufacturing, establishing defect acceptance standards based on part service requirements, and advancing intelligent online monitoring and closed-loop control technologies. These efforts aim to promote further progress of additive manufacturing.