Papers by Author: Rainer Schmid-Fetzer

Abstract: When trying to calculate the approximate constitution of as-cast tin containing aluminium alloys one has to cope with a combination of intricacies: (i) Scheil solidification simulation may reflect strong enrichment of alloying components, especially in multicomponent alloys, thus leaving the safe ground of the underlying thermodynamic database. (ii) Liquid demixing often intensifies by addition of many components to Al-Sn alloys, thus forming monotectic reactions, boosting the segregation and aggravating the first effect. (iii) Scheil simulation in multicomponent Al-x-y-z-Sn alloys not only combines the first two problems, moreover, the current versions of major thermodynamic software packages are not able to perform the Scheil simulation if liquid demixing and monotectic reactions occur. These intricacies are worked out and the development of a dedicated Al-Si-Cu-Mg-Sn thermodynamic database for large composition ranges is presented. Calculations are compared to experimental data of an Al-7.5Si-3.5Cu-0.3Mg-0.1Sn alloy and the need for specific follow-up work is identified.

Abstract: The growing importance of Al-Sn based alloys for producing self lubricating bearing materials in automotive industries necessitates the development of new alloys for improved performance. The recent thermodynamic work by Schmid-Fetzer at Clausthal University of Technology predicted that the addition of Cu to the binary Al-Sn system makes the miscibility gap stable. With the guidance of the calculated phase diagram, experimental investigations were conducted on the ternary Al-Sn-Cu system to understand the solidification behaviour of this immiscible system under intensive forced convection. The experimental focus was to investigate the effects of shear rate, shearing temperature and cooling rate on the solidified microstructure.