New microcrystalline (MC) Al -12%Si and Al -18%Si alloys processed by ECAP (Equal Channel Angular Pressing)
technology have been investigated. The MC alloys have an average grain size of 5-8 microns in the aluminum matrix
after 6 cycles of ECAP treatment. Mechanical tests at room temperature have shown that the elongation to failure
of these alloys attains 20%, which is 4- 5 times higher than the values obtained for cast samples. The effect of superplasticity
in MC Al -12%Si and Al -18%Si alloys has been discovered: the high values of the strain-rate sensitivity
coefficient (of about 0.7), the low values of flow stress (less than 2 MPa) and the record values of elongation to failure
(more than 750%) have been obtained in the strain-rate range of 2?10-4 to 3?10-3 s-1 within the deformation temperature
interval 490-520oC.
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