Analytical computation and experimental assessment of the effect of the plunger speed on tensile properties in high-pressure die casting

In high-pressure die casting, the plunger motion profile plays a prominent role in determining the quality of components and the speed is often adopted to estimate the mechanical strength. However, the investigation of just the effect of the instantaneous maximum speed during the die cavity filling is not exhaustive to obtain reliable correlations between the process and the quality of castings. As a matter of fact, the final quality is affected by the whole process or at least by some meaningful parts having finite durations. To this purpose, this paper accounts for the effect of the plunger speed through a prediction metamodel based on the estimation of the energy associated to the flow forces over the whole cycle. Additionally, the analytical computation of such a parameter is proposed, to be used also in the a priori process optimization and to show how the proposed parameter is related to those usually adopted in literature and by practitioners. The resulting metamodelling approach differs from the typical ones adopted and allows for the development of effective models with low-order response surface. The model proposed has been then validated through a wide experimental campaign. The quality of the castings obtained has been evaluated by measuring the tensile properties. Moreover, some metallographic and fractographic analyses have been carried out in order to investigate the microstructural features of selected castings. The experimental evidence demonstrates the effectiveness of the analytical model proposed and of the energy associated to the flow forces as an influential factor.