An experimental study on the optimization of powder forging process parameters for an aluminum-alloy piston

The purpose of this paper is to optimize the powder forging process parameters for an aluminum-alloy piston, namely the composition, mixing time, sintering time, sintering temperature, shape of the preform, etc., through experiments and to develop a high strength aluminum-alloy piston with an optimized process. At the first step, the composition of the material was determined and optimal sintering conditions for the material were examined. Proper mass percentages of Al, Cu, Si, Ni, Mn, Mg powders were added to Alumix 123 (Al–4.5Cu–0.5Mg–0.7Si), manufactured by Eckart (Germany). The number of experimental parameters were totally 27, i.e., Si contents of 1, 1.5, 2.0% (mass), sintering temperatures of 560, 580 and 600°C, and sintering times of 20, 25 and 30 min. From the experiments, a Si content of 1.5% (mass), a sintering temperature of 580°C, and a sintering time of 25 min were determined as the optimal process conditions. At the second step, the shape of preform for a cup-shaped product was determined considering the workability of the material and the effect of density increase in the forging process. Performed for this purpose was the upsetting test for the workability of the sintered specimens. The effect of density increase and strain loci were studied. A preform with a proper wall height was determined as the most effective shape. Finally, an aluminum-alloy piston for a vehicle engine was formed using the process parameters determined previously. After T6 heat-treatment of the formed piston, the hardness and tensile strength of the piston head were examined. The results showed, that compared with the hardness and tensile strength of the forged piston, those of the formed piston increased to 76.4 HRB and 500 MPa.