THERMAL MODELING OF DEPOSIT SOLIDIFICATION IN UNIFORM DROPLET SPRAY FORMING

In spray forming, the deposit thermal state is a key parameter which i nfluences the microstructural evolution upon and after droplet impact onto the deposit. The uniform droplet spray (UDS) forming process has been developed to enable precise control of the droplet and deposit th ermal state and the resultant material microstructure. By having a uni form droplet size throughout the spray, all the droplets deposited ont o the substrate will have the same thermal state upon impact, allowing for precise control of the solidification process. This paper describ es a one-dimensional, finite difference model that predicts the temper ature and liquid fraction of the deposit during the UDS process. The m odel employs an explicit temperature-enthalpy method to incorporate a variety of solidification models. Experiments were conducted using Sn- 15 wt percent Pb binary alloy. Temperatures were measured in the depos it and acceptable agreement with the simulation was obtained Modeling has shown that the deposit thermal stare is highly dependent on variat ions in spray conditions, which are predicted using droplet trajectory and droplet thermal models. Using the droplet and deposit models, the relationship between UDS process parameters and material microstructu re can be understood.