Enhancing the solid-state joinability of A5052 and CFRTP via an additively manufactured micro-structure

Abstract

An Al alloy (A5052) sheet was joined with a carbon fiber-reinforced thermoplastic (CFRTP) sheet by hot pressing without melting the CFRTP sheet (that is, solid-state joining). A micro-structure was manufactured via laser irradiation of Al-Ti-C powders bedded on the A5052 sheet. The laser irradiation to Al-Ti-C powders generates numerous particle-shaped protrusions additively on the A5052 sheet, which facilitate the infiltration of CFRTP and mechanically interlock with the CFRTP sheet. To determine the optimal conditions for joining A5052 and CFRTP consisting of a polyamide 6 (PA6) matrix, the effects of joining temperature during hot pressing on the interfacial structure and joint strength were investigated. The maximum joint strength was attained at the joining temperature of 210 °C. At lower temperatures, PA6 was not sufficiently softened to infiltrate the micro-structure, resulting in lower joint strengths. At higher temperatures, carbon fibers (CFs) were exposed on the CFRTP surface and inhibited the penetration of PA6 and CFs into the micro-structure, thereby lowering the joint strength. To infiltrate PA6 and CFs into the micro-structure, hot pressing was performed in a gradient temperature field. The proposed process enabled appropriate infiltration of CFs and PA6 into the micro-structure and led to high and stable joint strength. It is expected that using the additively manufactured micro-structure approach proposed herein, the operating windows of various cutting-edge joining processes can be expanded to more moderate and lower energy conditions. • A5052 and CFRTP sheets were joined by hot pressing without melting the CFRTP sheet. • CFRTP sheet and additively manufactured micro-structure were mechanically interlocked. • Maximum infiltrations of PA6 and CFs into the micro-structure occurred at 210 °C. • At higher temperatures, CFs were exposed on the CFRTP surface and inhibited the infiltration of PA6 into the micro-structure. • The joint constructed under a gradient temperature field had high strength.