Abstract: A metal alloy mass of a defined porosity for forming in the semi-solid state. When the porosity is measured by cooling in ambient air from a temperature corresponding to a liquid fraction ratio between 30 and 70% to the ambient temperature, the mass has a porosity ratio, measured by image analysis, between 2 and 20%, and preferably between 3 and 8%. Alternatively, when the gassing level is measured by a solidification test under 80 hPa, the mass has a volumetric porosity ratio between 3 and 50% and preferably between 4 and 25%.

Abstract: The invention relates to an aluminum alloy for thixoforming with the composition (by weight): Si: 5%-7.2% Cu: 1%-5% Mg<1% Zn<3% Fe<1.5% other elements<1% each and<3% in total, with % Si<7.5-% Cu/3, which, when reheated to the semisolid state to the point at which a liquid fraction ratio between 35 and 55% is obtained, has an absence of non-remelted polyhedral silicon crystals.

Abstract: A blank is prepared of a thixotropic metal material and the blank is reheated to a semi-solid state to obtained a liquid fraction corresponding to a desired viscosity for shaping, while determining the power used in the reheating. The reheated blank is transferred to a forging press including a forging stamp or to a pressure die casting machine including an injection plunger. The resistance of the material to the forging stamp or the injection plunger is determined and defined as a set point value and the blank is shaped by the forging stamp or pressure die casting machine. A subsequent blank of the thixotropic metal material is shaped by the forging press or the pressure die casting machine, and the power used in reheating is regulated to maintain the resistance at the set point value.