Experimental investigation on microstructure and properties of Al alloy-PEEK joint with different surface structure obtained by hot-pressing

In this study, selective laser melting (SLM) additive manufacturing was used for the fabrication of Al alloy with the surface structure based on the construction of mechanical interlocking mechanism to complete the joining with polyetheretherketone (PEEK). The application of hot-pressing process provided a direct joining between Al alloy-PEEK at 460 °C for 40 min. This work characterized the forming of both cylindrical and trapezoidal structures, indicating that the structures were formed completely, and the gaps were clear. Although some dimples or micropores were generated in the forming solid, these defects in the forming were beneficial for the flowing and filling of PEEK during hot-pressing joint. The microstructure of Al plate fabricated by SLM showed typical parallel columnar grains perpendicular to the deposition direction and stacked and fish scale like feature in the deposition direction, respectively. The microstructure characterizations of Al alloy-PEEK joints showed that both materials were joined without gaps and formed a strong mechanical interlocking, guaranteeing a firm bond with maximal tensile shear strength up to 81 MPa for trapezoidal structure. By comparison, the joint with cylindrical structure possessed a low 65 MPa shear strength due to weak cuneiform anchor interlocking. Fracture surface was investigated in more detail. The result showed that the joint with cylindrical structure mainly showed interfacial failure and pulling-out, tilting deformation and fracture of the supporting, while the joint with trapezoidal structure exhibited a separation between the top surface of the supporting and the PEEK and brittle cohesive fracture of the PEEK between the gaps.