Vacuum-assisted rheo-forging process of A356 aluminum alloys

In recent years, various rheo-forming methods have been developed to produce products with improved mechanical properties. To this end, rheo-forging of metal offers not only superior mechanical strength but also requires much lower machine loads than solid forming processes. However, there are many problems, such as air indraft during the stirring of the molten metal as well as the expense of the starting materials. As a result, the commercial availability of products formed through semi-solid processes is still limited. Semi-solid materials with a desired microstructure are produced by stirring during solidification from their molten state. Occasionally, indraft of air has degrades the resultant mechanical properties. This paper presents the results of the influence of air control during stirring and forging. A356 aluminum alloys were prepared by electromagnetic stirring under vacuum in order to prevent the indraft of air and sample parts were subsequently fabricated with hydraulic press machinery. To compare the influence of air control, two type samples were fabricated (I) samples fabricated under vacuum and (2) samples fabricated while open to the free atmosphere. An H-shaped product was formed in order to select and observe the deformation behavior. (C) 2008 Elsevier Ltd. All rights reserved.