The Research On 7075/SiCp Composite Sheets' Production Process

The present study covers two main subjects as followes: The influence of extrusion and rolling processing on the formability of spray co-deposited 7075A1/SiCp composite sheets, the distribution of SiC particles and the interface states after extrusion and rolling processing; and the heat-treatment of the 7075Al/SiCp composite sheets.(1) Firstly, hot extrusion processing was carried out to investigate the effect of hot extrusion processing parameters such as the extrusion ratio, temperature and speed on the formability of the spray deposits. The flowing phenomenon and the distribution characteristics of SiC particles, and the distinct interfaces between the particles and the matrix were observed in the extruded bars by optical microscope. Moreover, the large scale planks were also prepared by hot extrusion processing.The results showed that the spray deposits were well formed with the extrusion ratio from 8 to 10 and temperature from 400 to 410. The density of the extruded material was higher than 2.79X 103kg/m3, while that of the spray deposits was 2.54X 103kg/m3. The rearrangement of SiC particles, which were directionally and orderly distributed along the orientation of extrusion and characteristic of an obvious stripe microstructure, was also observed. The interfaces between SiC particles and the metal were distinct and metallurgical bonding was achieved. Thus no detrimental reactions occurred.(2) Secondly, the effect of the rolling manners (such as longitudinal rolling, crossing rolling and bevel rolling), temperature and reduction system on the formability of the spray deposits sheets were investigated.As the results indicated, the planks extracted from the extruded plate parallel to the extrusion direction were liable for rolling, and bevel rolling was superior to other manners. The highest productivity was obtained at 410癈, with the system of higher frequencies and smaller reduction. The non-uniform distribution of SiC particles was eliminated to some extent by rolling. However, many difficulties were faced to completely eliminate the bright stripe microstructure by hot-rolling. The bigger the deformation, the thinner the stripes and the more the SiC particles of cracking. Therefore, the stripes of SiC particles could not be eliminated by rolling.(3) The solution and aging treatment of the as-rolled sheets were studied. The solution temperature and time, and the ageing temperature and time were optimized. The strengthening mechanism of the 7075Al/SiCp composite sheet was discussed andits fracture mechanism were also analysed.