| Summary: | A programme of mechanical testing has been carried out to measure the tensile properties of one AA5083 and three AA6061 alloys, all of near as-cast microstructure, at temperatures primarily around and above the respective solidus temperatures, and over a range of strain rates. The testing method used in this work (the Advanced Semi Solid Elongation Test, or 'ASSET') allowed the rapid re-heating of specimens to the test temperature in order to attempt to preserve the as-cast microstructure. Accurate tensile properties data were gained for the four alloys tested. Such data may be useful in the computer modelling of industrial solidification processes, for example the Direct Chill casting of aluminium alloy ingots. The tensile strength and ductility of the alloys tested, and the ways in which these properties were found to vary with temperature and strain rate, were found to be dependent on the alloy. Several theories are suggested for the differences in tensile properties found between the four alloys tested. Considerations include the solid grain morphology, the form and distribution of solute elements in the alloys, the nature of change in fraction liquid with temperature variation, the balance of interfacial energies in the semi solid alloy, the effects of deformation rate and the grain size. Two apparent regimes of hot tearing behaviour were identified in one of the alloys tested. Two such regimes may also exist in the other alloys used in this work. A constitutive equation, based on an exponential relationship between maximum tensile stress and temperature, was developed for each of the four alloys tested in this work.
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