Microstructural characteristics and mechanical properties of 7075 aluminum alloy foam sandwich panels fabricated via integrated forming and foaming

Abstract

A new integrated forming and foaming method based on friction stir welding (FSW) was proposed for foam sandwich panels. The microstructure characteristics of the precursors and foams with different welding parameters were analyzed using optical microscopy and scanning electron microscope (SEM/EDS). The temperature field and flow field of foam precursor joint in FSW were simulated by Fluent CFD software. The microstructural characteristics of foam precursor after hot forming were analyzed using electron backscattered diffraction (EBSD) and transmission electron microscopy (TEM). The effect of foam precursor deformation on foam evolution was also investigated. The results show that the formability of foam precursor is the same as that of rolled plate. Aluminum foam sandwich panel with homogenous pore structure is prepared at 680 °C for 225 s. After hot forming, the equiaxed recrystallized grain is obtained, and the dislocation and the second phase provide reinforcement. In addition, Rgoss{110}〈110〉 texture component strength increases. When the tensile strain is 0.15, smaller and more uniform pores are produced. Numerical simulations show that the peak temperature gradually decreases with the increase of the distance of the stirring head center. In addition, the temperature on the advancing side (AS) is higher than that on the retreating side (RS). When the tool travel speed is 50 mm/min and rotational speed is 2000 r/min, the maximum material flow velocity at the joint section is 184.2 mm/s and the highest concentration of powder tracing particles is 0.0123 kg/m3. It is proved that the integrated forming and foaming method can solve the problem in manufacturing of complex curved AFS components.