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Influence of the thermal treatment on the deformation-induced precipitation of a hypoeutectic Al-7wt% Si casting alloy deformed by high-pressure torsion
A hypoeutectic Al-7wt%Si alloy was subjected to high-pressure torsion (HPT) at
room temperature using an imposed pressure of 6 GPa and torsional straining through
five revolutions. Different thermal treatments, prior to the HPT processing, resulted in
reducing supersaturated Si concentration in comparison to the as-cast materials.
Microstructural parameters and microhardness were evaluated in the present work.
Processing by HPT produced significant grain refinement with grain sizes of about 200-
400 nm. Furthermore, fine deformation-induced Si precipitates from the supersaturated
solid solution were observed, which are very useful in retaining the fine microstructure
during HPT processing. The microhardness increase was outstanding, with values for
processed samples twice higher (84HV) than that for the as-cast Al-7wt%Si alloy
(44HV). The results demonstrate that the refining and strengthening of the Al matrix by
HPT processing depend on the available supersaturated solid solution during the
processing.Financial support from MICINN (Project MAT2009-14452) is gratefully
acknowledged. C.M.Cepeda-Jiménez. thanks the Spanish National Research Council
(CSIC) for a I3P contract, and A.P. Zhilyaev to the Spanish Ministry of Education and
Science for a RamĂłn y Cajal contract.Peer reviewe