Modelling the anisotropic fracture behaviour of cold spray additive manufactured 6061 aluminium alloy deposits based on the phase field method

Cold spraying has been widely accepted as a promising additive manufacturing technique to produce large metallic structures. The fracture behaviour of cold spray additive manufactured deposits is complex because of their inherent anisotropy. In order to study the anisotropic fracture, a multiple-particle impacting model was established in a Lagrangian frame. Then, an image recognition program was developed to convert the simulated deposit image into a finite element discretisation scheme. In finite element framework, a phase field model was proposed to simulate the fracture process of deposits under tensile loading along (0 degrees) and perpendicular (90 degrees) to the particle impacting direction. The deposit anisotropic fracture behaviour for two impact velocities, at 600 m/s and 800 m/s, was investigated. It is shown that the interfacial fracture toughness is the most important parameter that affects the tensile properties of deposits. The tensile ultimate load of the deposit increases thrice when the interfacial fracture toughness increases by an order of magnitude. For the 800 m/s deposit, the ultimate load and fatigue life in 90 degrees loading direction are about 11.3% and 39.2% higher than those in 0 degrees loading direction, respectively. The fracture anisotropy relates to the degree of flattening of the deformed particles. The higher interfacial fracture toughness of mode II can lead to more transparticular cracks, shorter crack length and smoother crack path. The comparison between simulations and published experimental results suggests that the proposed phase field model can capture the complex anisotropic fracture behaviour of cold sprayed deposits.