Interfacial bonding mechanisms between aluminum and titanium during cold gas spraying followed by friction-stir modification

Abstract

This paper closely evaluates the interfacial bonding mechanism between titanium particles deposited on an aluminum alloy substrate by cold gas spraying followed by friction-stir processing (FSP). After cold spraying and FSP modification, the produced Al/Ti interface was studied using focus ion beam-transmission electron microscopy (FIB-TEM) analysis and auger electron spectroscopy. Formation of a well-bonded titanium aluminide reaction layer was observed at the interface with a thickness in the range of 10-20 nm and a coherent interface associated with an inter-diffusion distance of about 600 nm. The results of this study showed that the physical bonding phenomenon during cold spraying according to the wellknown adiabatic shear instability at the interface can be associated with chemical bonding and formation of an intermetallic layer at the interface during FSP modification. This is aided by the induced thermo-mechanical processing and deformation-assisted solid-state diffusionbased reactions. Also, these possible interfacial bonding and intermetallic layer formation mechanisms were discussed based on the inter-diffusion of elements at the Al/Ti interface based on the well-established Boltzmann-Matano theory and kinetics models correlated with experimental observations. The main findings of this research highlight the role of FSP on the performance of cold spray coatings as a post-processing technique to promote densification and homogenization during processing by promoting nano-scale interfacial mechanisms and chemical bonding at the interface.

Al matrix composites fabricated by solid-state cold spray deposition: A critical review

“…Owing to these advantages, many attempts have been made to modify CS deposits, such as Ti [160], CuZn alloy [161], 7075Al alloy [162], NiTi alloy, and MMCs [149,150,163,164]. A hybrid AM technique combined with CS and FSP post-processing has been developed for component manufacturing and repairing (Fig.…”

Physically Based Finite Element Modeling Method to Predict Metallic Bonding in Cold Spray

“…The necessity of removing the native oxide layer on particle-substrate surfaces for the creation of metallurgical bonding is widely acknowledged in the CS literature but the details of the in situ oxide layer removal process is still a point of contention. Numerous studies have indicated that adiabatic shear instability is the main mechanism responsible for the oxide layer breakup and cleaning away (removal) (Ref 18,19,22,23,(31)(32)(33)(34), while some have elaborated that metallurgical bonding in CS is not related to the occurrence of adiabatic shear instability (Ref 24,35). In addition, partial melting in the contact region has also been deemed responsible for the localized oxide layer removal and chemical bonding upon solidification (Ref 36,37).…”

Research Status and Prospect of Friction Stir Processing Technology

“…However, the particles added in this way are easy to slip and splash during the FSP process; hence, there is an inhomogeneous distribution of the strengthening phases and a loss of material. Based on this method, pre-fabricated surface composites can be fabricated by cold spraying [44,45] or laser melting [46] with further processing of the coating via FSP. This can improve the microstructure and the distribution of the reinforced particles to obtain surface composites with better properties.…”