Abstract:The rheological behavior of the semi-solid TiB₂ reinforced Al-Mg alloy composite slurry was investigated, which is required for the mould filling simulations during the semi-solid processing. TiB₂ reinforced in-situ Al-Mg alloy composite samples were remelted and subsequently brought to the semi-solid temperature regime within the heating chamber of a Searle type rheometer. In order to understand the rheological behavior of composites, three different types of experiment were carried out, namely, steady state test, continuous cooling test and isothermal test. Apart from that, the thixotropic nature of the slurry was confirmed from the obtained hysteresis loops during the experimentation. The results indicate that when isothermally held, the composite slurry exhibits pseudo-plasticity and shows shear-thinning behavior up to the shear rate of 1300 s^-1, and at higher shear rates (>1300 s^-1), it shows a shear thickening tendency, which is probably due to the agglomeration of non-deformable nano-TiB₂ particles. The pseudo-plastic behavior of the slurry was also estimated employing intermittent step changes of shear rate (shear jump test).

Key words: rheology; shear thinning; in-situ nano-TiB₂; thixotropy; shear thickening