Understanding the Effect of Surface Machining on the YSZ/Ti6Al4V Joint via Image Based Modelling

Abstract

A method to improve the brazing between YSZ and Ti6Al4V by femtosecond laser surface machining is introduced. The highest strength of ~150 MPa (which is 95.2% higher than that of the flat YSZ/Ti6Al4V joint) is achieved when the processing speed is 200 μm/s. To understand the strengthen mechanism of the surface machining on the joint strength, image based models, based on the observed microstructure, have been used to probe the stress distribution in the joint. It is found that through surface machining on the ceramic, the residual stress distribution in ceramic becomes nonlinear. Upon shear testing, for the joint with a flat interface, the failure happens in the reaction layer and the out of plane stress in this layer is found to be tensile, which acts as the driving force for the crack generation and propagation. But for the joint with a rumpled interface, the compressive out of plane stress at the boundary of the grooves in the reaction layer could inhibit the propagation of the cracks. Finally, by surface machining on the ceramic, the maximum shear stress in the reaction layer is decreased, which could also help to improve the reliability of the joint.

Tailoring an Interface Microstructure for High-Performance Reversible Protonic Ceramic Electrochemical Cells via Soft Lithography

“…Especially, because the majority of electrochemical reactions of SOFCs preferentially take place near the electrolyte/electrode interfaces despite the use of MIECs, the application of a micropatterned interface can also be one of the direct strategies to improve the performance of PCECs by increasing the effective reaction area along with the micropatterned interface. − Despite the significant potential of the micropatterned interface, it is extremely challenging to achieve it in multilayered ceramic cells through conventional micropatterning methods such as selective etching and micromachining. Because all components in ceramic cells are too fragile to be mechanically machined and too vulnerable to be chemically etched, the material integrity of the treated ceramic surface can be severely damaged after typical patterning processes, − deteriorating the mechanical stability of ceramic cells. These unfavorable material properties of ceramic components indicate a great need for a new micropatterning technology designed specially for ceramic cells.…”

Vacuum brazing of titanium alloy to stainless steel enhance by fiber laser surface texturing

“…As a result, it is expected that a well-designed dishevelled interface for a brazing joint will be ready to optimise residual stress distribution and bonding quality. Laser surface processing has emerged as a cutting-edge and promising technique or process for pattering ceramics and metals [23,24]. Y. Zhang et al conducted research to modify the surface morphology of ceramic for dissimilar brazing [18], surface processing on an alumina surface with a femtosecond laser yielded grooves less than 100m deep.…”