Modeling of porosity during spray forming: Part II. Effects of atomization gas chemistry and alloy compositions

In this article, the effects of gas chemistry and alloy composition on the level of porosity in deposited materials are investigated by using a porosity model established in Part I of this article. The calculated results reveal that atomization gas chemistry has a significant influence on the level of porosity during spray forming, which can be rationalized on the basis of the influence of gas properties such as gas density, viscosity, and gas constant on the melt flow rate. The alloy properties that predominantly affect the variation of porosity with melt flow rate include melt viscosity, density, surface tension, solvent melting point, liquidus temperature, and equilibrium partition coefficient. A material property factor, mu(m)gamma(m)/rho(m)(2), plays an important role in determining the processing conditions required to attain a minimum amount of porosity in deposited materials.