Papers by Keyword: Thixo-Co-Extrusion

Abstract: Due to the excellent thermal conductivity and high strength of aluminum alloy and unique advantages containing shock absorbing, vibrations dampening and corrosion resistant of magnesium alloy, Al/Mg double-layer tubes have been widely utilized in household appliances, automobiles, aerospace industries, and high-speed trains in recent years. Conventionally, double-layer tubes are produced by welding, extrusion, hydroforming, magnetic pulse cladding. These processes are either complex or highly energy-consuming. To improve efficiency and reduce energy consumption, a new technology, thixo-co-extrusion (TCE), is put forward for production of double-layer tubes. In this paper, the thixo-co-extrusion of a 7075/AZ91D double-layer tube is investigated by numerical simulation. This study assesses the influences of extrusion velocity, the thickness ratios of two layers, the reheating temperatures of billets and the preheating temperature of die on the flow behaviors. The results show that the extrusion velocity and the thickness ratios significantly influence the contact pressures on the interface as well as the velocity fields. Besides, the reheating temperatures of billets and the preheating temperatures determine the distribution of temperature fields. Under the contact pressures and a certain temperature, atomic diffusion takes place on the interface between inner and outer layer, which leads to metallurgical bonding of the interface. The paper contributes to a better understanding of the thixo-co-extrusion technology for the production of double-layer tubes with desirable mechanical properties.

Abstract: Thixo-forming is in the forefront of metal processing technology in the 21st century. The research on thixo-co-extrusion of multi-layer tube as extension and development of the semi-solid forming technology is a completely new processing method for the composite material forming and is of great significance, in which different semi-solid billets (slurries) are extruded at the same time to form multi-layer tubes. In this study, different sizes of column-shaped and ring-shaped billets of Al/Mg alloys were firstly prepared by using specially designed molds. Then they were reheated by electric-resistance furnace，microstructures from different heating laws were investigated. Lastly, FEM simulation on thixo-co-extrusion of double-layer tube with A356/AZ91 was conducted.