In-situ fabrication of compositionally gradient interfaces via programmable powder deposition in multi-material laser powder bed fusion

Multi-material additive manufacturing enables the integration of dissimilar materials within a single component, yet achieving a compositionally gradient interface within individual layers remains challenging. This study presents a novel approach using a self-developed ultrasonic nozzle system for programmable, high-precision powder deposition. Using an interdigitated interface design with a layer-wise offset arrangement between 316L stainless steel and IN718 superalloy, we demonstrate that the alternating powder layout, together with intense melt-pool stirring during laser powder bed fusion, promotes thorough material intermixing and creates ∼1 mm wide compositionally gradient interface. The interface exhibits continuous transitions in grain growth, elemental distribution, and microhardness, confirming the formation of a continuous gradient between materials. Notably, the width of the gradient interface is tailorable through deposition control. This work demonstrates the feasibility of fabricating compositionally gradient interfaces via designed layer-wise powder deposition, providing a controllable approach for manufacturing functionally gradient components.