Design Strategies for Laser Additive Manufacturing of High-Performance Alloys With Uniform Mechanical Properties

Additive manufacturing (AM), or 3D printing, enables the fabrication of metallic components layer by layer with enhanced design flexibility and efficiency. However, the layer-wise build fashion of AM, along with the associated high cooling rates, steep thermal gradients, and repeated thermal cycling, often results in microstructural heterogeneities. While such heterogeneities may be beneficial for certain applications, they are often unfavorable because they not only degrade mechanical performance but also lead to highly non-uniform mechanical properties that compromise the reliability of AM components. In this review, we provide an overview of state-of-the-art process and alloy design strategies for developing high-performance alloys with uniform mechanical properties by laser AM. We focus on two typical laser AM processes, that is, laser powder bed fusion and laser directed energy deposition. We discuss the principles and fundamentals of the AM process that can produce microstructural heterogeneities through laser-powder interactions, solidification, and solid-state phase transformations. We survey and analyze the merits of different process and material design strategies aimed at mitigating microstructural heterogeneities. Finally, we articulate the unmet needs and current challenges in the development of metallic alloys for AM with exceptionally uniform mechanical properties.