The Research On The Microstructure And Mechanical Properties Of Spray Co-deposited 7090/SiC_p Composites

The ultra high strength 7090/SiCp composite reinforced was prepared by spray co-deposition process. The extrusion and rolling technical, heat treatment technology, microstructure and mechanical properties of the heat-treated extruded composite were tested and analyzed.(1) The influence of extrusion and rolling technical of the 7090/SiCp composite was analyzed. After extrusion, and arrayed on the orientation of extrusion directionally and orderly, resulting in the feature of an obvious stripe microstructure. The rolling process improves the SiC particles stripe to some extent.(2) The heat treatment technology, microstructure and mechanical properties of the heat-treated extruded composite were tested and analyzed. The result shows that the 7090/SiCp composite exhibited good mechanical property after 470℃/1h+490℃/1h+120℃/28h heat treatments.The strength of the composite treated with 470℃/1h+490℃/1h+120℃/28h exhibited ultra high strength above785MPa,which was 30MPa higher than that of the 490℃/1h+120℃/28h-treated composite. The modulus of the two heat-treated composites was both improved above 100GPa. And the fracture toughness is the best, about 39.49 MPa·m1/2. The grain size of the composites is bigger prepared by two-stage solution than by single-stage solution. The little fine phase appears in the grain and the grain boundary isη(MgZn2),T(Al2Mg3Zn3)and Cu-rich phase. While after two-stage solution and aging treatment, an amorphous Si-Cu-Al-O(5nm)layer occurs at the interface.(3) The microstructure and mechanical properties of rolled plates of spray co-deposited 7090/SiCp composites were tested and analyed. The results also shows that the peak-aged high strength could reach 700MPa after 470℃/1h+ 490℃/1h+ 120℃/28h heat treatments. The precipitates are MgZn,Cu-rich phase,Al3Zr phase and FeAl3 impurity phase.(4) The fracture mode of the 7090/SiCp composite was analyzed. The results shows that the fracture was the intra-intergranular and intergranular fracture. The tensile fracture is resulted from M/SiC interracial debonding and SiC particles'fracture for the extruded composite,but from A1/SiC interfaeial debonding and matrix failure for the rolled composite.