| dc.description.abstract | Aluminum alloys have been generally used because of its opposite strength, light weight, high heat and electric conductivity, superior ductility and easily to manufacture. One’’s early years, Soviet bring up that aluminum alloys have perfect mechanical properties when adding scandium into alloys. This approach has more and more emphasis recently and is used for the frame of bicycles, the head of golf club and so on.
The experiment adopts Al-7.9Zn-2.5Mg-2.3Cu alloy and Al-6.0Zn-2.0Mg alloy which are all added about 0.1wt.% scandium and about 0.1wt.% zirconium. Metal plate is processed by rolling and metal bar is processed by equal channel angular extrusion. Metal plate changes the rolling reduction ratio and changes the temperature of elongation. Metal bar changes the direction and the frequency of extrusion. By way of changing these parameters, we aspect this method can promote the strength of materials and improve the breadth of 7XXX series of aluminum alloys which are added scandium.
The experiment result exhibit that the tensile strength can promote about 30 MPa, yield strength can promote about 25MPa and elongation can promote from 5% to 12.3% at room temperature when adding about 0.1wt.% scandium into alloys. The excellent elongation of plate is 353.9% and the excellent elongation of bar is 329.8%. We can know that all of the mechanical properties are obvious be promoted when the temperature is 400℃.
When R=40%, the maximum tensile strength of metal plate is 583Mpa, the maximum yield strength is 474MPa and the material has the best elongation. When R=60%, the tensile strength instead of declining about 80MPa. The temperature of all tensile tests are below 300℃ to 500℃. When R=20％, the excellent elongation is about 395％. When R=40％, the excellent elongation is about 555％. Although R=20％ has better mechanical strength than R=40％, but the elongation is obvious lower 1.4 times than R=40％.
The bar is used by ECAE. When the extrusion coefficient is Rote A, the grain size is about 50μm after C1 extrusion and is about 40μm after C3 extrusion. After that, the grain size can be thinned down about 20％. When the extrusion coefficient is Rote Bc, the grain size is about 50μm after C1 extrusion and is about 15μm after C6 extrusion. After that, the grain size can be thinned down about 70％. | en_US |