Abstract:Based on analysis of the main forming methods for double-layer tube, a new short-term forming process called thixo-co-extrusion was put forward in producing double-layer tube by combining the semi-solid forming technology and multi-billet extrusion technology. By means of forward extrusion with shaft, a finite element model of thixo-co-extrusion with A356/AZ91 was constructed by ABAQUS FEM software. The distributions of temperature field and velocity field as well as the contact force during thixo-co-extrusion were studied. The diffusion on the interfaces between inner and outer metals was analyzed. The simulation results show that, in the beginning of thixo-co-extrusion, the uneven wall thickness can appear. To thickness ratio of 5:5, a double layer tube with good inner and outer wall combination can be realized if V_A356 is 0.12 m/s and V_AZ91 is 0.20 m/s.

Key words: semi-solid forming; double-layer tube; thixo-co-extrusion; numerical simulation