Fabrication and Compression Properties of Aluminum Foam-Filled Tubes with Different Tube Wall Materials

Aluminum foam-filled tubes (AFFTs) with different tube wall materials were fabricated via an in situ tube wall forming method based on gravity casting. The effects of key process parameters, including preheating temperature, preheating time, pouring temperature, and holding time, on the filling behavior of tube walls and morphology of the composite structure were systematically investigated by an orthogonal experiment. The axial and radial compression properties of AFFTs with different tube wall materials were analyzed. The results indicated that the key process parameters have significant effects on mold filling behavior and the defects generated during casting. Considering the radial distances of the molten metal infiltrating into the foam core and the area of the blowhole generated during casting, the optimal parameters of preheating temperature, preheating time, pouring temperature, and holding time are 650 °C, 15 min, 750 °C, and 3 min, respectively. Under these conditions, the metals completely filled the tube wall and effectively infiltrated the internal pores of the aluminum foam core, and no obvious cast defects were found. The interface between the aluminum foam core and tube wall is bonded via mechanical interlocking. Aluminum foam-filled pure aluminum tubes (AFFTs-Al) under axial compression exhibit excellent compressive performance and energy absorption capacity, which is mainly attributed to the stable plastic deformation behavior of the specimens. Specifically, the plateau loads, total energy absorption values, and ideal energy absorption efficiency of AFFTs-Al reach 49.13 kN, 841.53 J, and 0.74, respectively. Nevertheless, no distinct plateau stage can be observed for AFFTs-Al under radial compression, and the mean ideal energy absorption efficiency is only 0.54. In addition, the aluminum alloy A356 tube wall provides limited reinforcement. Although aluminum foam-filled aluminum alloy A356 tubes (AFFTs-A356) possesses a high initial peak load of 119.03 kN, their plateau load drops sharply to only 6.3 kN under axial compression. AFFTs-A356 undergo brittle fracture under both axial and radial compression, demonstrating unsatisfactory energy absorption performance.