The Research On Cyclic Pressing Of Large Dimension 7075/SiCp Composite

The large dimension spray deposited billet which is consolidated by extrusion, forging and other technologies does not acquire excellent mechanical properties at present. In order to obtain large dimension billet with high mechanical properties, the large dimension 7075/SiCp composite billet was consolidated by cyclic pressing in this investigation. The deformation behaviour, densification effect and mechanical properties after cyclic pressing are also investigated in this paper.(1) The deformation and densification behaviors of spray co-deposited 7075/SiCp composite billet were investigated.The deformation behaviour of the spray co-deposited 7075/SiCp composite billet was investigated by grid method. The transverse deformation of the billet was divided into four areas. The surface of the billet has the largest deforming quantity at the beginning of the cyclic pressing. When the whole billet compressing degree reach 31%, the highness of the 56.3% from the surface of the billet has the largest deforming quantity. The cyclic pressing with transverse deformation can improve the densification effect of the billet. 7075/SiCp composite has a good workability at the transverse deformation of 10% and 15% after cyclic pressing. 420 ℃ is the suitable for the densification of the 7075/SiCp composite because the closed pores can get to excellent metallurgical binding at this temperature.(2) The deformation of the pores and the distribution behavior of SiC particles at the cyclic pressing of spray co-deposited 7075/SiCp composite were investigated.The deformation behaviour of the pores is different at different stress state and different cyclic pressing stage. The three-dimensional compressive stresses at the middle part of the billet is beneficial to the deformation of the pores. The dimension of pores in the 7075/SiCp composite is minished at the beginning of the cyclic pressing. While at the plastic deformation densification stage, the pores are collapse, elongation and disappearance. At the cyclic pressing of the as-deposited billet and as-extruded billet, the high SiC volume fraction band and the low SiC volume fraction band are both compressed.(3) The workability and the properties of the large dimension spray co-deposited 7075/SiCp composite were investigated.The large dimension as-deposited 7075/SiCp composite was cyclic pressing four passes. After cyclic pressing, the relative density of the large dimension as-deposited billet is up to 96%. The large dimension as-extruded 7075/SiCp composite was cyclic...