Fratini L

Influence of Process Parameters for Thixotropic Alloys

With reference to a metallic alloy, the attribute thixotropic is utilized to indicate the behaviour of it in the semi-solid state when its microstructure consists of spheroids in a liquid matrix. Such alloys are characterized by very low values of viscosity under shearing stress in the semi-solid state, while after solidification they show relevant mechanical properties. Actually a structural change from a dendritic structure to a globular one, with the globular grains finely dispersed in a liquid matrix, is observed after particular thermo-mechanical treatments. In the present paper the authors present the results of a wide experimental campaign on the AA 7075 aluminium alloy that shows a large semi-solid window temperature range. In particular, a mechanical device was set up in order to develop a mechanical treatment with the aim to produce thixotropic material to be subsequently forged. The influence of the main operative parameters was taken into account and micrographic analysis and mechanical tests were performed highlighting properties of the obtained structures.