The paper "Advances in Ultrasonic-Assisted Directed Energy Deposition (DED) for Metal Additive Manufacturing" by Wenjun Zhang, Chenguang Xu, Cencheng Li, and Sha Wu reviews the latest advancements in ultrasonic-assisted directed energy deposition (UA-DED) technology. DED is a significant technique for fabricating large metal components in industries such as aerospace, automotive, and healthcare, characterized by its high deposition rate and scalability. However, it faces challenges such as residual stresses, distortion, porosity, and rough surfaces due to rapid melting and solidification. UA-DED integrates ultrasonic oscillations into the DED process to address these issues. The paper critically reviews the current major challenges in DED, including residual stresses, porosity, and crack defects, and details the working principle and system components of UA-DED technology. It also discusses the material improvement achieved by introducing UA into the DED process, focusing on grain refinement, porosity reduction, tensile properties, and deposition defects. The optimization methods for process parameters and the interaction mechanisms between UA and DED processes are identified and discussed in detail. Finally, the paper discusses the research gaps and potential future developments in UA-DED. 1. **Introduction**: The paper introduces the significance of AM in producing complex metal components and the advantages of DED over other AM processes. It highlights the challenges and limitations of DED, such as residual stresses, porosity, and cracking. 2. **Fundamental Mechanisms and Principles of DED**: This section explains the working principles of DED, including the synchronization of heat sources and material feed rates, and the importance of shielded gas environments to prevent oxidation. 3. **Current Challenges of DED Processes**: The paper discusses the primary defects in DED, including residual stresses, porosity, and cracking, and their impacts on material properties. 4. **UA-DED Technology**: This section details the working principles of UA-DED, the system configurations, and the performance enhancement mechanisms. It covers grain refinement, reduced porosity, improved tensile properties, and reduction in deposition defects. 5. **Conclusion**: The paper concludes by emphasizing the potential of UA-DED to enhance the quality and mechanical properties of fabricated parts, making it a promising technique for advanced manufacturing.The paper "Advances in Ultrasonic-Assisted Directed Energy Deposition (DED) for Metal Additive Manufacturing" by Wenjun Zhang, Chenguang Xu, Cencheng Li, and Sha Wu reviews the latest advancements in ultrasonic-assisted directed energy deposition (UA-DED) technology. DED is a significant technique for fabricating large metal components in industries such as aerospace, automotive, and healthcare, characterized by its high deposition rate and scalability. However, it faces challenges such as residual stresses, distortion, porosity, and rough surfaces due to rapid melting and solidification. UA-DED integrates ultrasonic oscillations into the DED process to address these issues. The paper critically reviews the current major challenges in DED, including residual stresses, porosity, and crack defects, and details the working principle and system components of UA-DED technology. It also discusses the material improvement achieved by introducing UA into the DED process, focusing on grain refinement, porosity reduction, tensile properties, and deposition defects. The optimization methods for process parameters and the interaction mechanisms between UA and DED processes are identified and discussed in detail. Finally, the paper discusses the research gaps and potential future developments in UA-DED. 1. **Introduction**: The paper introduces the significance of AM in producing complex metal components and the advantages of DED over other AM processes. It highlights the challenges and limitations of DED, such as residual stresses, porosity, and cracking. 2. **Fundamental Mechanisms and Principles of DED**: This section explains the working principles of DED, including the synchronization of heat sources and material feed rates, and the importance of shielded gas environments to prevent oxidation. 3. **Current Challenges of DED Processes**: The paper discusses the primary defects in DED, including residual stresses, porosity, and cracking, and their impacts on material properties. 4. **UA-DED Technology**: This section details the working principles of UA-DED, the system configurations, and the performance enhancement mechanisms. It covers grain refinement, reduced porosity, improved tensile properties, and reduction in deposition defects. 5. **Conclusion**: The paper concludes by emphasizing the potential of UA-DED to enhance the quality and mechanical properties of fabricated parts, making it a promising technique for advanced manufacturing.