DISSIMILAR BIMETALLIC STRUCTURES VIA DIRECTED ENERGY DEPOSITION-BASED ADDITIVE MANUFACTURING

Yanning Zhang

doi:10.7273/000002388

Additive manufacturing (AM) or 3D printing has revolutionized the modern metal manufacturing industry. Recent developments in metal AM systems include upgrades in energy source and resolution, which leads to better part quality and improved reliability. Researchers and engineers also have realized the significance of the innovation of novel materials by adapting AM technology. Bimetallic structures combine two types of metallic materials in one structure offering unique properties from both materials. Typically, bimetallic materials are made by joining two different materials via welding or brazing. Although using welding techniques to join two metallic materials is economical, there are still many critical issues, such as managing the heat-affected zone (HAZ) at the joint, cracking, and premature failures due to brittle intermetallic phase formation, especially for joining two dissimilar metals, and reproducibility. In recent years, metal AM is being explored towards processing bimetallic materials. Metal AM systems are designed with multiple feedstock materials, which enable various printing strategies to be applied for processing bimetallic structures. In the first study, Ti6Al4V+Al12Si compositionally graded cylindrical structures were fabricated on a Ti6Al4V substrate using laser engineered net shaping (LENS™) process. LENSTM fabricated materials had two regions of Ti6Al4V+Al12Si compositions, a pure Al12Si, and a pure Ti6Al4V area. Microstructural changes were affected by both laser power and compositional variations. Our results show that compositionally gradient bulk structures of Ti6Al4V and Al12Si can be directly manufactured using additive manufacturing, however, performances can vary significantly based on process parameters and compositional variations. In the second study, 316L stainless steel (SS) to Al12Si aluminum alloy structures were processed, tailoring the compositionally graded interface on a SS 316 substrate using a directed energy deposition (DED)-based AM process. Applying such a compositionally graded transition for joining two dissimilar metals could mitigate the mismatch of mechanical and thermal properties. This study's objective was to understand the processing parameters that influence the properties of AM processed SS 316L to Al12Si bimetallic structures. Two different approaches were used to fabricate these bimetallic structures. The results showed no visible defects on the as-fabricated samples using 4 layers of Al-rich mixed composition as the transition section.

DISSIMILAR BIMETALLIC STRUCTURES VIA DIRECTED ENERGY DEPOSITION-BASED ADDITIVE MANUFACTURING

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