Characterisation of semi-solid material mechanical behaviour by indentation test

In many metal-forming processes, materials are loaded at high strains, high strain rates and high temperatures. Many experimental tests such as tensile, compressive or torque tests exist to determine the material rheology but are not well appropriate to achieve experiments on semi-solid alloys containing both solid and liquid. They fail due to disturbances such as necking, strain localisation, frictional effects or deformation heating in the material. In the first part of this paper, we propose a new mixed numerical-experimental methodology based on indentation tests and FEM simulations to determine the material rheology. This methodology is first applied to visco-plastic materials and then on semi-solid materials displaying a thixotropic behaviour. In particular, the influence of the microstructure and the strain rate on the semi-solid mechanical response has been studied on Sn-15% Pb alloys. It is shown that the globular morphology of the primary solid phase is really important to benefit from the thixotropic properties of the material during forming processes. In that case, the load level is lower than the one required for semi-solid materials having a dendritric primary solid phase.