Friction Stir Welding Dissimilar Layers Gradient Interface

The patent removes the pin component from the rotating tool, extracting the source of pin damage and void formation. The tool consists only of a rotating cylinder that applies friction heat and pressure to the interface, eliminating the mechanical mixing action that causes voids while maintaining the ability to join layers through controlled melting and bonding

The pin in conventional FSLW tools is substantially damaged during the process and requires replacement. By eliminating the pin entirely and using only a rotating cylinder, the tool becomes simpler, more durable, and less costly to maintain, as the cylinder does not suffer from the same wear and damage mechanisms

The patent eliminates the braze layer from the joining process. By using a rotating tool without pin that applies friction heat directly to the interface between layers, the method achieves direct bonding without requiring any intermediate brazing material, thereby reducing cost and preventing contamination

Instead of using a braze layer as an intermediary material to join layers, the patent uses friction heat as the mediator. The rotating tool generates heat at the interface that enables direct bonding between layers without requiring any intermediate substance, simplifying the overall structure

The patent changes the fundamental parameter of the joining process from solid-state mechanical mixing to a process involving controlled melting and bonding. The rotating tool generates sufficient heat to melt the materials at the interface, creating a gradient in properties that transitions smoothly from one layer to the other, eliminating sharp discontinuities

The joining process creates a composite structure at the interface with a gradient composition. The melted and bonded region forms an intermediate zone with properties that gradually transition between the two layers, resulting in improved property continuity and reduced sharp discontinuities