2022 Zhongji Sun Thermodynamics guided alloy and process design for additive manufacturing

In conventional processing, metals are typically subjected to multiple manufacturing steps such as casting, plastic deformation, and heat treatment to achieve the desired properties. In contrast, additive manufacturing (AM) requires achieving the same target in a single fabrication process that involves solidification and cyclic remelting. The thermodynamic and kinetic differences between solid and liquid phases lead to constitutional undercooling and variations in the solidification interval, often resulting in defects like hot cracking. This study addresses the hot cracking issue, utilizing the commercially significant IN738LC superalloy as a model material to demonstrate a knowledge-based approach for designing alloys suitable for AM. The findings elucidate how high cooling rates impact the thermodynamic and kinetic nature of phases during rapid solidification and drive the need for tailored alloy compositions. Consequently, this methodology not only solves the specific problem of hot cracking but also holds the potential for adaptation to other alloy systems vulnerable to similar issues in the AM process.