Effect of hot rolling and testing temperature on superplastic characteristics of a SiCp/6061 aluminum alloy composite made by a vortex method before squeeze casting and extrusion were investigated in order to make clear the superplastic deformation mechanism. Total rolling strain of about 94% was given to the composites in rolling temperatures from 843 K to 873 K and in the rolling strain per passes of 0.05 to 0.30. Fine grain size of about 1.6 μm was obtained in the composite rolled at temperature of 573 K and at the strain per pass of 0.10. The flow stress was not so effected by rolling strain per passes, and the composite exhibits m-value of 0.33 and the maximum total elongation of about 350% at the strain rate of 0.24 s-1 and at 853 K. Total elongation of more than 100% was obtained in the wide strain rate region from 0.003 to 1.30s-1 and in rolling temperatures of 573 K, 673 K, and 723 K. Relationship between ε1/2 and σ became linear when exponent of n = 2 was selected. Apparent activation energy determined from relationship between strain rate and effective stress (= flow stress minus threshold stress) was higher than that of lattice self diffusion of aluminum so that it is thought that high strain rate superplasticity of the composite could occur by grain boundary sliding, and grain boundary diffusion and liquid phase accommodation mechanisms. On the fracture surface of the composite after superplastic deformation, filaments and cavities in striation structures were observed and it became clear that on the microstructural level superplastic phenomena occur.
|ジャーナル||Keikinzoku/Journal of Japan Institute of Light Metals|
|出版ステータス||出版済み - 1999|
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