A hybrid damage model of laminated Ni/Al sheets (LANS) during high-temperature deformation

Utilizing the laminated Ni/Al sheets (LANS) with excellent plastic deformation capability prepared by vacuum hot-pressing and subsequent in-situ reaction, holds significant potential for the fabrication of NiAl complex thin-walled component. In this paper, the GTN damage model was applied to the Ni and Al layers in LANS, while a brittle fracture model was adopted for the Ni-Al intermetallic layer between the Ni and Al layers, thereby establishing a high-temperature deformation damage model for LANS. The initial parameters of the damage model were obtained by high-temperature uniaxial tensile experiments and microstructural characterization. The damage and fracture mechanisms of LANS during high-temperature deformation were investigated through in-situ microstructural observation during tensile tests and simulation, validating the rationality of the model construction. Moreover, through hot gas bulging experiments and simulations, the high-temperature forming limit curve (FLC) of LANS was plotted. The results demonstrated that the hybrid LANS damage model is reasonable, as the fracture strain predicted by the tensile simulation agreed well with experimental results, with an error of less than 5%. During high-temperature deformation of LANS, microcracks initially formed in the Ni-Al intermetallic layer. The number of these microcracks increased explosively within a certain strain range. As the deformation increased, the growth rate of the microcrack number slowed down, while the microcracks propagated and widened along the tensile direction. With further increase in deformation, the microcracks gradually extended in the direction perpendicular to the Ni-Al intermetallic layers. Subsequently, microcracks penetrated the layers and merged into main cracks, ultimately leading to material fracture. The experimental results of hot gas bulging agreed well with the simulation results, indicating that the LANS damage model can accurately predict material damage under different strain states.