Evolution of transverse weld during porthole extrusion of AA7N01 hollow profile

Abstract

This work investigates the transverse weld in 7N01 aluminum alloy hollow profile used in high-speed train by experimental analysis coupled with finite element simulation. The macroscopic morphology and the evolution of transverse weld were obtained by extrusion experiments and the corresponding microstructure and texture were analyzed with EBSD. Significant differences in grain size, grain orientation and texture content on both sides of transverse weld were found. The content of recrystallization texture in the old billet was larger than that in the new billet, and the grain sizes in the old billet were smaller than those in the new billet. In order to analysis the evolution of transverse weld and reduce the length of transverse weld, the numerical model of transverse weld was then built with HyperXtrude and was verified by comparing with experimental observations. The influences of extrusion process parameters and die structure on the length of transverse weld were studied systematically by using the established transverse weld model. The transverse weld length was reduced effectively by adjusting the extrusion ratio, ram speed, height of baffle plate, corner radius of welding chamber and sinking depth of port bridge.